CN115587399A - Project progress management system and application based on BIM - Google Patents

Abstract

The invention relates to a project progress management system and application based on BIM, wherein a data model is generated by combining a three-dimensional data model expression method and a method for carrying out shielding inquiry with a plurality of viewpoints to identify hidden pieces in an assembly body, a progress management model establishes a real-time model and generates a corresponding calculation model according to the analysis of a data model structure, and a comparison model superposes and compares the real-time model with a plan model to provide a scheme for deviation correction and adjustment of construction progress. The invention needs to continuously adjust the target in the project process and adopts proper measures to solve the problems, the project often has the phenomenon that the completion time, the total cost or the resource distribution deviates from the original planned track, corresponding measures need to be adopted to lead the project development to be consistent with the plan, if the project has larger change or seriously deviates from the project process, the project schedule needs to be rearranged, the target plan is determined, the resource distribution and the budget cost are adjusted, thereby realizing the schedule balance.

Description

Project progress management system and application based on BIM

Technical Field

The invention relates to the field of management systems, in particular to a project progress management system based on BIM and application thereof.

Background

The national power grid infrastructure requirements are in fact promoting standardized application of three-dimensional design in links of construction management, construction organization, file transfer and the like, information transmission and data sharing modes based on the three-dimensional design application are established, management requirements of each stage of engineering construction are met, process standardized management is explored and carried out by utilizing three-dimensional design results, the traditional construction planning and progress management modes are gradually difficult to meet the existing business requirements, and the visual simulation means is mainly shown in the situation that progress of a construction site is remotely controlled by an owner and a construction manager and lacks;

the foreign research on the 4D simulation of the engineering progress is mainly based on the application of the BIM technology, and the important aspect of the application of the foreign BIM technology in progress management is to explore how to realize the 4D simulation of the engineering progress on the basis of a three-dimensional building model and a time dimension.

The prior art has the following defects: the existing management system has many limitations, one is that the system mainly focuses on the dynamic management of the progress of the engineering construction stage, does not relate to other engineering stages such as engineering design and the like, and cannot participate in the project initial stage; secondly, the three-dimensional composite model established by the system is only the image size simulation of the building product, does not contain other building product information, and is not a real building information integration model, so a project progress management system based on BIM is needed to solve the problems.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a project progress management system based on BIM aiming at the defects of the prior art, wherein the system comprises a data model, a progress management model and a comparison model;

the data model is generated by combining a three-dimensional data model expression method and a method for carrying out shielding inquiry on a plurality of viewpoints to identify hidden pieces in an assembly body, the progress management model establishes a real-time model and generates a corresponding calculation model according to the analysis of the data model structure, and the comparison model superposes and compares the real-time model and the plan model to provide a scheme for deviation correction and adjustment of the construction progress.

Preferably, the data model includes a power grid three-dimensional information model, the power grid three-dimensional information model is converted into a surface model through a scanning entity, and the specific steps are as follows:

assuming that points before scanning are A (XA, YA, ZA), B (XB, YB, ZB) \8230 \\8230andK (Xk, yk, zk), scanning vectors V (XV, YV, ZV), and scanning the points along the scanning vectors V to obtain An, bn \8230 \8230andKn, and a line-surface net formed by the points is a boundary model of 3 DGIS:

An＝A+V，Bn＝B+V……Kn＝K+V

for the Curve scanning, the tangent vector of the Curve Curve = (M1 (X1, Y1, Z1), M2 (X2, Y2, Z2) \8230;. Mn (Xn, yn, zn)) is selected to be Hn = Xn-Xn-1, yn-Yn-1, zn-Zn-1. If one point is a point A' after A (XA, YA, ZA, 0) scanning, the following formula is calculated, wherein N is the normal of the Curve:

and the conversion from the solid model to the boundary model is realized in the same way.

Preferably, the three-dimensional data model includes a solid model and a mesh model, wherein the solid model is used for describing the geometric and topological information of the component, and the mesh model adopts a polygon patch to form the geometric shape of the object.

Preferably, the method for conducting occlusion query on the plurality of viewpoints to identify the hidden part in the assembly body comprises the following steps:

(1) Generating a query object ID for an object to be queried;

(2) Starting occlusion query;

(3) Rendering an object needing to be subjected to shielding query;

(4) Ending the occlusion query;

(5) Extracting the number of samples queried by occlusion;

(6) And deleting the ID of the query object and recycling resources.

Preferably, in the identification algorithm of the hidden part, the visibility value of the part at a certain viewpoint is calculated as:

wherein: lambda [ alpha ] ₁ +λ ₂ +λ ₃ ＝1；

Wherein λ is ₁ 、λ ₂ And λ ₃ For weighting, the component visibility, the component area contribution and the component volume contribution are initially set to share the same weight, i.e. λ ₁ 、λ ₂ And λ ₃ Are all 1/3;

obtaining the maximum of the part i after the part i completes the occlusion inquiry at all the set viewpointsLarge visibility values, i.e.

Defining a critical parameter F _T (0<F _T <1) When the F value of a certain part in the assembly body is larger than the critical parameter, the part is visible when the part is observed outside the assembly body, otherwise, the part is a hidden part.

Preferably, the recognition algorithm of the hidden element commonly evaluates the priority value C (v) of the vertex by the position of the vertex in the cache and the degree of the vertex, and the priority value C (R) of the triangle ring is the sum of the priority values of the vertices of all the unoutput triangles in the ring

The vertex priority value C (v) may be calculated by the following formula:

C(v)＝C _p (v)+C _a (v)

wherein,

in the above formula, p represents the position of the vertex v in the buffer, s represents the size of the buffer space, a represents the number of non-output triangles adjacent to the vertex v, k ₁ 、k ₂ 、k ₃ Are coefficients.

Preferably, the model primitive data structure of the three-dimensional information model of the power grid comprises basic data and extended data, wherein the basic data comprises geometric data, physical data and functional data, and the extended data comprises technical data, economic data and management data.

Preferably, the real-time model includes statistical distribution of process duration, the statistical distribution includes normal distribution, beta distribution, uniform distribution and triangular distribution, in the normal distribution, the mean, median and mode of the process duration coincide, the probability that the process duration is greater than or less than the mean is equal, the probability that the process is delayed or advanced is equal, in the beta distribution, the distribution range is in [0,1], and the distribution formula of the beta distribution is as follows:

(1) Mean value:

(2) Variance:

the value ranges of alpha and beta are 0:0.1:10000, the value range of the mean value is 0.3:0.05:0.5, the simulation results are stored in the matrix respectively, the first column is alpha value, the second column is beta value, and the third column is variance value.

Preferably, in the beta distribution, the safety time is a difference between a duration at 95% completion probability of the process and a duration at 50% completion probability, and the formula is as follows:

T _k ＝[F(x)I _x＝0.95 -F(x)I _x＝0.5 ]×t _k

wherein F (x) is the distribution function of the beta distribution, T _k Is a safe time of process k, t _k The duration of process k.

The invention also provides an application of the project progress management system based on the BIM, the progress management system is applied to the transformer substation construction simulation project management, the analysis and the visual display of the model are realized based on the D3Station platform, and the attribute of the model is supported to be checked.

Compared with the prior art, the invention has the beneficial effects that:

1. the invention analyzes the characteristics of a GIM three-dimensional product model and the data expression mode of the current three-dimensional model, and provides a three-dimensional data model expression method capable of being rapidly displayed on desktop equipment aiming at the characteristics of mobile equipment, wherein the data model has the advantages of high drawing speed and memory saving, meets the requirement of efficient browsing on a desktop platform, ensures the safety of the model, and meets the requirement of a user in engineering practice because the data model comprises complete geometric information, product structure information and attributes; the small file volume data model filters non-geometric information such as parameters and PMI in an original model, the separation of an assembly file and a part file avoids repeated expression of the same model, the reasonable organization and compression of geometric data greatly reduce the data volume of the model, the efficiency of transmitting the model through a mobile network is greatly improved compared with that of the original model, and more three-dimensional models can be stored on mobile equipment;

2. the characteristics of hardware of the mobile equipment and a three-dimensional graph drawing system are fully considered by quickly reading the data model, reasonable organization and display optimization are carried out on the data in the data model generation stage, time-consuming optimization operation is transferred to a desktop computer with higher computing power to be executed, the weakness of lower hardware performance of part of desktop equipment is avoided, the performance of the mobile terminal can be fully utilized by the generated data model, the loading and drawing speed is accelerated, and demonstration and interaction of the three-dimensional model on the low-performance mobile equipment become possible;

3. the method can automatically judge invisible parts in the assembly model and fine parts with small influence on appearance, and can reduce the drawing quantity of graphics primitives and improve the drawing efficiency by combining a lightweight expression method under the condition of not destroying the structural relationship of a product;

4. through comparative analysis between actual progress and project plans, more deviations can be found, potential problems existing in the projects are pointed out, targets need to be adjusted continuously in the project process in order to avoid the problems caused by the deviations, appropriate measures are taken to solve the problems, the phenomenon that completion time, total cost or resource allocation deviates from original plan tracks often happens to the projects, corresponding measures need to be taken to enable the project development to be consistent with the plans, if the projects change greatly or deviate from the project progress seriously, the project progress needs to be rearranged, the target plans need to be determined, and resource allocation and budget cost need to be adjusted, so that progress balance is achieved.

Drawings

FIG. 1 is a schematic diagram of the technical scheme of the present invention.

Fig. 2 is a data structure diagram of the grid information model of the present invention.

FIG. 3 is a data structure diagram of the data model of the present invention.

FIG. 4 is a flow chart of the generation of the data model of the present invention.

FIG. 5 is a statistical schematic diagram of the occlusion query result of the present invention.

FIG. 6 is a flow chart of the identification of the hidden element according to the present invention.

FIG. 7 is a simplified schematic diagram of an engine model of the present invention.

FIG. 8 is a schematic diagram of a triangle sequence according to the present invention.

FIG. 9 is a flow chart of cache optimization according to the present invention.

FIG. 10 is a diagram of a data structure of a model primitive according to the present invention.

FIG. 11 is a block diagram of an MVC based system architecture according to the present invention.

FIG. 12 is a flow chart of an implementation of the MVC based system architecture of the present invention.

FIG. 13 is a BIM-based progress management application framework diagram of the present invention.

FIG. 14 is a block diagram of the BIM information platform according to the present invention.

FIG. 15 is a schematic diagram of a 4D simulation analysis of the schedule of the present invention.

FIG. 16 is a diagram illustrating a sequence of network graph operations according to the present invention.

FIG. 17 is a progress monitoring view of the present invention.

FIG. 18 is a comparison of a planned progress model and an actual progress model of the present invention.

Fig. 19 is a block diagram of a 4D construction progress management platform of a substation according to the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It will be understood that when an element is referred to as being "secured to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present.

Example 1

Referring to fig. 1, the project schedule management system based on BIM according to the present embodiment includes a data model, a schedule management model and a comparison model, wherein,

and (3) data model: the advantages of the solid model and the grid model are combined, the use requirement of the low-performance desktop end is fully considered, and the method has the following characteristics and advantages in general:

(1) The file volume small data model filters non-geometric information such as parameters and PMI in the original model, the separation of the assembly file and the part file avoids the repeated expression of the same model, the reasonable organization and compression of geometric data greatly reduce the data volume of the model, the efficiency of transmitting the model through a mobile network is greatly improved compared with that of the original model, and the storage of more three-dimensional models on mobile equipment is facilitated;

(2) The characteristics of hardware of the mobile equipment and a three-dimensional graph drawing system are fully considered in the process of quickly reading the data model, reasonable organization and display optimization are carried out on the data in the data model generation stage, time-consuming optimization operation is transferred to a desktop computer with stronger computing power to be executed, the weakness of lower hardware performance of part of desktop equipment is avoided, the performance of the mobile terminal can be fully utilized by the generated data model, the loading and drawing speed is accelerated, and the demonstration and interaction of the three-dimensional model on the low-performance mobile equipment become possible;

(3) The application of memory reference is saved, so that the same part is only stored in the memory, and the other parts are obtained by space transformation matrix, so that the use amount of the memory can be reduced to a great extent, and the harsh requirement of three-dimensional application on the memory is met;

(4) The complete model information data model has complete geometric information and product structure information, has high usability, and meets the use requirement of the three-dimensional model under the mobile network environment;

(5) The data safety data model is guaranteed not to contain information such as characteristic parameters and modeling parameters of the model, the model can not be edited, and the data model can be guaranteed not to be used for other purposes such as reverse engineering and the like.

Firstly, analyzing the characteristics of a GIM three-dimensional product model and the data expression mode of the current existing three-dimensional model, and aiming at the characteristics of mobile equipment, providing a three-dimensional data model expression method capable of being quickly displayed on desktop equipment, wherein the data model has the advantages of high drawing speed and memory saving, meets the requirement of efficient browsing on a desktop platform, ensures the safety of the model, and meets the requirement of a user in engineering practice because the data model comprises complete geometric information, product structure information and attributes;

the method can automatically judge invisible parts in the assembly model and tiny parts with small influence on appearance, and can reduce the drawing quantity of graphic elements and improve the drawing efficiency under the condition of not destroying the structural relationship of a product by combining a lightweight expression method.

The progress management model comprises: by analyzing the content of project progress management and a common progress management technical method, the establishment of a three-dimensional power grid information model and the establishment of construction progress data are explored, the establishment of a four-dimensional power grid information model is analyzed, the implementation mode of fusion of BIM data and construction progress is provided, the structural system of a BIM4D system is formed by combining the system function requirements and the analysis of a three-dimensional model data structure, and the implementation flow of the structural system is designed.

Comparing models: the method for realizing progress information acquisition on a construction site and superposing and comparing a real-time model with a plan model is systematically discussed, so that a solution is provided for deviation correction and adjustment of construction progress, the problem of comparing the real-time model of the construction site with the plan model of which information is well associated in a platform is solved, the specific mode is that the construction site information is acquired by using a camera, the construction site model is reconstructed by technologies such as image registration, characteristic point matching, motion structure, model registration and the like and is overlapped with the plan model, and a real-time data basis is provided for output of a subsequent progress report and three-dimensional progress display;

after the actual progress information is updated in the system, through comparative analysis between the actual progress and the project plan, more deviations can be found, potential problems in the project are pointed out, in order to avoid the problems caused by the deviations, targets need to be continuously adjusted in the project process, appropriate measures are taken to solve the problems, the project often has the phenomenon that the completion time, the total cost or the resource allocation deviates from the original plan track, corresponding measures need to be taken to enable the project development to be consistent with the project plan, if the project has larger changes or seriously deviates from the project progress, the project progress needs to be rearranged, the target plan needs to be determined, the resource allocation and the budget cost need to be adjusted, and therefore the progress balance is achieved.

Example 2

Referring to fig. 2, in the data model, the main idea is to study data organization structures of a general model, a product model, a power transmission and transformation project and the like, extract data commonalities and summarize to form a power grid information model data analysis scheme, establish a detection index according to a three-dimensional design standard of a company, detect data format, content integrity and correctness, study efficient processing and storage of power grid information model data, study a pyramid scheme according to a display scale and data fineness by referring to a geographic information data organization mode, combine data composition structure to study an LOD strategy, simulate data to observe an object from high altitude falling from a fuzzy to a clear process, start from data quantity, study a data geometric texture simplification scheme, and optimize data storage on the premise of ensuring data definition;

referring to fig. 3, the most important influencing factor for the technical framework of the fusion of the Grid Information Model (GIM) and the GIS is often the data format, and since the grid information model and the GIS have respective data formats, how to make these multi-source heterogeneous data formats compatible on one platform becomes a key problem;

data format conversion is a mainstream GIS and three-dimensional model fusion mode at present, conversion research of data formats mostly focuses on conversion from IFC to CityGML, partial research focuses on conversion from CityGML to IFC, conversion from power grid information model data to GIS data is a process of coarsening refined data, and analysis of a power grid information model comprises two aspects of geometry and semantics:

1) Multi-level geometric information extraction and conversion

Most of the three-dimensional information models of the power grid are solid geometric construction methods (CGS), most of the expression formats of the GIS are surface boundary methods, so that the geometric information conversion is needed, a scanning method is needed when one solid is converted into a surface model, and after scanning, triangular grid division needs to be carried out on the scanned model to obtain a surface model of the 3 DGIS;

for the scanning of a straight line edge, the scanning is simple, points before scanning are A (XA, YA, ZA), B (XB, YB, ZB) \8230 \ 8230 \ 8230; (Xk, yk, zk), scanning vectors V (XV, YV, ZV) are set, an, bn \8230; \ 8230; (Kn) is obtained after the points are scanned along the scanning vectors V, and a line-surface net formed by the points is a boundary model of 3 DGIS:

An＝A+V，Bn＝B+V……Kn＝K+V

for the Curve scanning, we select the tangent vector of the Curve Curve = (M1 (X1, Y1, Z1), M2 (X2, Y2, Z2) \8230;. Mn (Xn, yn, zn)) change Curve Hn = Xn-Xn-1, yn-Yn-1, zn-Zn-1. If there is a point A (XA, YA, ZA, 0) after scanning, the point A' is calculated by the following formula, wherein N is the normal of the Curve:

by analogy, the conversion from the solid model to the boundary model can be realized;

2) Mapping of semantic information

Besides pure geometric information conversion, the mapping of semantic information is also important content for the fusion of the GIM and the GIS, the fusion of the GIM and the GIS is not realized through pure data format conversion, the structure of a model is changed, but the semantics of the model is not changed;

the method comprises the following steps that firstly, the difference of geometric expression forms exists, a scanning body formed by boundary description, extension or rotation, a construction entity geometry and other 3 expression forms exist in a power grid information model, only one geometric expression form is described in a data standard supported by a GIS platform, after the GIM model is converted into a format supported by the GIS platform, the geometric information expressed by the scanning body formed by stretching or rotation and the geometric construction entity can only be expressed by a boundary description method, a large amount of coordinate data is needed to express a plurality of patch information, which inevitably causes the loss of the geometric information and the increase of data quantity, and on the other hand, the difference of object semantics exists, because the power grid information model and the 3DGIS are different in expression and understanding of a space object and do not have related object semantics standardization research work, the loss of the semantic information is inevitable in the process of converting the GIM model into the data format supported by the GIS, and semantic geometrical reconstruction of the power grid information model into the 3DGIS model is also needed;

the power grid information model is rich in semantics, mapping can be found in a 3DGISLOD4 level model, and LOD3-LOD0 level semantic information is gradually decreased, so that semantic filtering is required in the conversion process, some information is abstracted and filtered, useful information is reserved, and the semantic information and the geometric information of each component are associated by a unique ID value to provide index information for the management of model data;

3) Spatial scale variation

After the GIM entity model is triangulated into a GIS-supported triangulation network model, because the GIM adopts a local coordinate system, when the model is introduced into a 3D-GIS system, model measurement points and actual measurement point coordinates are used for establishing positioning reference information, a model family coordinate transformation matrix is obtained, the local coordinate system is transformed into a global coordinate system, and the correct positioning of the model in the 3D-GIS system coordinate system is completed, wherein three models which are commonly used for transformation under different coordinate systems are a seven-parameter model of Bolsberg, a Moluggins-based model and a Wu-Measure model;

in order to solve the problem of fast browsing of a three-dimensional product model on mobile equipment with limited performance and resources and enrich channels for product data communication of users, a desktop computer is required to be used for carrying out lightweight processing on an original model to obtain a data model for direct browsing of the mobile equipment;

starting from the problems existing in the current three-dimensional model data sharing, the characteristics of a three-dimensional product model and the defects existing in the current existing model expression method are analyzed, a data model expression method capable of being rapidly displayed on mobile equipment is provided, the expression modes of the three-dimensional model can be generally divided into two types, one type is an entity model, and the other type is a grid model, and the method is as follows;

1) Solid model: the solid model can be divided into three types of representation methods, namely a boundary representation method (B-Rep), a constructive solid geometry method (CSG), and a scanning method, and the three-dimensional models established by most three-dimensional systems (Pro/E, UG, catia, inventor and the like) are solid models;

the solid model can describe the geometric and topological information of the component with high accuracy, but the solid model has the following problems, which limit the application of the solid model in data sharing:

(1) The solid model does not contain any triangular patch information, and a large amount of calculation is usually required to be carried out before the solid model is displayed so as to disperse the solid model into a polygonal mesh, so that the loading time is long, and the long loading display time is more unacceptable for a complex three-dimensional product model;

(2) The data structure of the entity model is complex, the file volume is huge, the information therein is oriented to various purposes, and for users, much information therein is redundant information, such as proofreading and auditors mainly utilize the model to browse and circle, the proofreading and auditors only pay attention to the structural geometric information of parts, analysis engineers only need to utilize simplified product geometric information in the analysis process, and remote clients only need to browse the appearance shape of the model and only need the geometric information;

(3) The browsing entity model must use a three-dimensional system or universal three-dimensional browsing software which is the same as that of a modeler, the universal three-dimensional browsing software is usually developed by a third party, the problems of insufficient hysteresis, stability and the like generally exist, the heterogeneity of three-dimensional product data is caused by the diversity of the three-dimensional system, the data sharing and communication in and among enterprises are influenced, and the production efficiency is reduced;

(4) The confidentiality of the entity model is poor, sensitive design information such as a modeling process and characteristic parameters is contained, and once the entity model is used for other purposes except for collaborative development, such as reverse engineering, great loss is caused to an enterprise;

2) Grid model: the mesh model is a non-precise model expression method which adopts a large number of polygon patches to approximate the geometric shape of an object, the mesh model has a plurality of file formats, such as STL, VRML, PLY, OBJ and the like, wherein the most common is STL file format which is introduced and popularized by 3DSystems, the STL mesh model is widely applied in the manufacturing industry, most three-dimensional systems can output model files in the STL format, the STL file describes the geometric shape of the model in the form of a triangular patch, each triangular patch records the normal vector of a triangle and the position coordinates of a triangle vertex, the STL mesh model has two storage formats, namely ASCII and binary, and the file structure in the ASCII format is as follows:

nx, ny and Nz in the file respectively represent the components of the normal vector of the triangular patch in three directions of xyz, V _1x ，V _1y ， V _1z Respectively representing coordinate values of the vertex in the xyz direction, and the rest are keywords in the file;

as can be seen from the example of the STL, the data structure of the mesh model is simple, and the expression mode of the triangular patch makes it possible to use hardware to accelerate the rendering process, so as to achieve the purpose of rapidly displaying the three-dimensional model, but the mesh model has the following problems:

(1) The grid model only contains the display information of the object, has no assembly structure relationship of the model, cannot express the relationship between parts, and simultaneously lacks key information such as attributes and the like, so that the actual requirements of engineering are difficult to meet;

(2) The grid model is generally not compressed or the compression ratio is not high, the data volume is large, and the network transmission and storage of the model are not facilitated;

because the traditional three-dimensional model has the defects in information transmission, the geometric information of the three-dimensional product model needs to be extracted, compressed and optimized, and the required attribute information, product structure information and the like are simplified and extracted, so that a data model which is small in scale, high in efficiency and convenient to browse quickly is obtained, and the expression method of the data model is introduced below;

the data model is mainly used for fast browsing and interaction of desktop equipment, so that the characteristics of the desktop equipment and an optimization strategy aiming at the performance bottleneck of a desktop graphic system must be fully considered in the design of a data model information storage and expression mechanism, and in order to ensure that the lightweight of a three-dimensional product model can meet the requirements of desktop users, the generated data model must meet the following conditions:

(1) The data model must firstly ensure that the browsing experience on the desktop equipment is due to an embedded system structure, hardware resources and performance of the desktop equipment cannot be compared with a desktop computer all the time, the calculation and graphic rendering capabilities of the data model are relatively limited, in order to ensure good browsing experience, the model must have higher display speed, and can meet the requirement of real-time interaction, data model files should be reasonably organized and cannot be too complex, the performance such as compression ratio and the like can be properly sacrificed on the premise of ensuring the display speed, and meanwhile, certain optimization measures which do not depend on the latest hardware support can be adopted to ensure that the complex model can obtain smoother experience on various desktop equipment;

(2) The usability and lightweight process of the data model in the engineering field is required to be guaranteed, geometric information of the product model is generally simplified and compressed, information such as size, attributes, matching and parameters is simplified and extracted, the data model generated through the process loses a part of information, but the usability of the model cannot be damaged by the process, and the process is represented as follows: in the aspect of geometric appearance, overhanging edges, overhanging surfaces and holes are not allowed to be generated, key features must be reserved and the like, in the aspect of non-geometric information, due to the limitation of screen size and interaction mode, three-dimensional application on desktop equipment is more mainly displayed, so that information such as modeling process, engineering constraint, features and the like can be simplified or exist as optional items, but the information of assembly and product structure of the information must be extracted, otherwise, a data model loses the function of data sharing in the engineering field;

(3) The data model needs to have smaller file volume due to the limitation of the embedded system architecture of the desktop equipment, the storage and memory capacity of the data model is smaller, and the expansion is difficult, so that the reduction of the volume of the model is very necessary, on one hand, the model is favorably transmitted through a network, and simultaneously, the memory can be saved, so that the data demonstration on the desktop equipment with low performance is possible;

according to the above requirements, the following design scheme of the three-dimensional data model file is proposed:

(1) For each part, the triangular mesh data with the same color are organized together, are subjected to geometric compression and are stored into an independent file, the data are organized according to the color instead of the plane as a basic unit, the maximization of the one-time incoming data can be ensured to a greater extent, the complexity of a shader and the state change in the rendering process can be reduced, only one color value needs to be recorded in a color list, the data redundancy is reduced, and the effect of optimizing a rendering pipeline is also achieved;

(2) The XML (ExtensibleMarkupLanguage) format is adopted to describe the structure and attribute data of the model product, the XML has good expansibility and platform independence, simultaneously, the separation of content and form can be realized, and the XML is very suitable for describing the assembly model with strong structure;

(3) The redundancy is reduced by adopting a reference mode, a plurality of parts with the same appearance usually exist in the three-dimensional product model, and the data redundancy can be avoided by reference, so that the volume of a lightweight file is reduced, and the use amount of a memory can be reduced;

(4) Data are managed in a container mode, all data are brought into different container nodes in a lightweight file, and a lightweight assembly file points to a geometric data file of a part through a container, so that the expansion and modification of the data are facilitated;

(5) By adopting a level of detail (LOD) technology, adding multi-resolution expression of parts into geometric data, supporting an LOD model of the parts by a bounding box of the parts, wherein the bounding box of the parts corresponds to a rough model, and an actual part model corresponds to an accurate model, and by sacrificing display quality, the drawing time of the model can be reduced, so that a user can conveniently and rapidly browse and interact the three-dimensional model;

(6) The method mainly comprises the following steps of carrying out display acceleration on geometric data, wherein the display acceleration is mainly embodied in two aspects, on one hand, the visibility of parts is judged in advance in light weight, the visibility of the parts is recorded in an assembly file, invisible parts and fine parts can be prevented from entering a rendering pipeline according to visibility information provided in advance when a model is drawn, and can be manually displayed when needed, so that the better balance is achieved between the drawing speed and the usability, on the other hand, vertex cache optimization is carried out on grid data, and the vertex cache hit rate in the rendering process is improved and the display speed of a data model is accelerated by modifying a triangular sequence of a grid;

referring to fig. 4, the data model file adopts a multi-document structure, the assembly file and the part file are stored separately, the assembly file records the product structure and the attribute information, and the part file records the optimized display information;

the assembly file records related information of a lower-level sub-assembly and parts, including part names, relative paths of the lower-level parts, visibility of the parts, relative transformation matrixes, geometric display attributes and the like, and can perform rapid display and interaction of a product model by combining with the geometric information of the parts;

the part file is used for recording display information of the part under a self object coordinate system, and comprises triangular grid data for quick display and point and edge information for representing contour points and contour edges, because most models adopt surface coloring, the report organizes the grid data according to colors, when the colors of a plurality of surfaces are the same, only one color value needs to be recorded in a color list, the grid data is firstly optimized through vertex cache and then stored in an index mode, namely, the part display information is stored as a unique vertex and a triangular sequence arranged according to the vertex index, for a three-dimensional product model, the topological relation is complex, and meanwhile, the lower computing performance of mobile equipment is considered, so that the model is not subjected to topological compression in the part file, and only the geometric compression is carried out to reduce the precision of the vertex data;

when a user views a data model file, firstly, whether the data model file is a model expected to be browsed or not can be judged with the help of thumbnails, then, whether the model file is opened or not is selected, loading of the data model file is firstly traversed from the total product structure to obtain all the lightweight sub-assemblies and parts, then, a whole scene is constructed and drawn, in the lightweight assembly file, matrixes of all parts are transformation matrixes relative to positions of parts at the upper stage, therefore, absolute positions of the parts in a total assembly body can be obtained by multiplying transformation matrixes of all upper-stage nodes of the parts, in the display process of the file, the parts with invisible visibility attributes can be cut off at first, the parts are not sent to a rendering pipeline, and when the internal structure of the assembly body needs to be viewed, the parts of geometric data are sent to the rendering pipeline for rendering;

the method comprises the steps that the main bottleneck of drawing three-dimensional graphics of the current platform is the contradiction between huge model data volume and limited hardware performance of a terminal, model simplification and model data arrangement optimization are two feasible methods for solving the bottleneck, the model is simplified to reduce primitive data volume needing drawing, the data arrangement optimization of the model can increase the reuse rate of hardware cache, and the purpose of display acceleration is achieved;

in a complex three-dimensional product model, the number of part models is huge, the hierarchical structure is deep, the structural relationship is complex, the display speed is slow, and in order to meet the requirement of rapidly browsing the three-dimensional product model on different hardware, a multi-level data model expression method is provided, the data model needs to extract geometric information, topology information and corresponding assembly information from an original model and reasonably organize the information, so that a corresponding data model export interface program is developed by using secondary development tools provided by a common three-dimensional system, the required effect can be achieved according to the actual engineering, the efficiency and the flexibility are higher, the development tools are all downward compatible, the stability of the export interface program is better, and frequent change is not needed;

referring to fig. 5, three-dimensional product models in various file formats are input in the process of weight reduction, and after the following weight reduction operations are performed on a desktop computer, a data model capable of being directly and rapidly displayed on terminal desktop equipment can be obtained;

1) Extracting product structure and attribute information, namely extracting product structures of all parts of an assembly body, names and attribute information of the parts, and non-geometric information such as a transformation matrix of each part relative to a superior assembly body, wherein the structure of the assembly body is an obvious tree structure, in the information extraction process, required information can be obtained in a recursion mode, when the model is of the assembly body, the information is extracted and the next recursion operation is carried out, if the model is a part, the recursion is carried out after the information extraction is finished, and the accurate display and attribute query of a data model can be carried out only when the structure and the attribute information are possessed under the environment of being separated from a three-dimensional system;

2) Triangularization is carried out on the geometric data, and triangularization is carried out on each part in the assembly body to obtain a triangular grid supporting rapid display;

3) Extracting key geometric information, namely extracting information of key edges and points in the model to support certain special display requirements;

4) Hiding part identification and recording, carrying out shielding query on the whole assembly model from a plurality of viewpoints, judging the visibility of parts in advance according to a plurality of results, and recording the results in a lightweight assembly file, wherein the content of the parts is described in detail in the next section;

5) Vertex cache optimization, which is to modify a triangular sequence of a three-dimensional model to increase the hit rate of the vertex cache, reduce the memory bandwidth requirement and accelerate the drawing speed of the model, and is described in detail below;

6) Coding and compressing, namely geometrically coding the geometric information of the part file through three steps of quantizing vertex position, predicting and entropy coding, storing the file in a binary mode, and compressing the assembled file by Huffiman coding;

because the number of parts contained in the three-dimensional product model is huge, the structural relationship is also complex, invisible parts in the model and tiny parts with small influence on appearance generally exist in the whole assembly body, the parts are generally called hidden parts, and the hidden parts in the assembly body can be eliminated to reduce the number of picture elements sent to a drawing pipeline by analyzing in the second chapter, so that in the process of exporting the data model, an automatic mode is needed to judge the visibility condition of the parts to obtain whether the parts are hidden parts or not, the visibility of the parts is recorded in a generated lightweight assembly file, when the data model is displayed, the hidden parts can be selected not to be drawn, and the parts can be manually displayed under necessary conditions, thereby achieving the aim of simplification and keeping the complete product structure of the model;

the basic idea of hidden part identification is to perform shielding query on an assembly body from multiple viewpoints to obtain visible areas of the assembly body and each part, and then synthesize all query results and volume information of the parts to obtain all hidden parts;

in order to judge the visibility of the part, the shielding query technology of OpenGL is utilized, the number of pixels of the model passing the depth test can be obtained by performing shielding query on the model, and then whether the object is rendered or not can be determined according to a query result;

in order to use occlusion queries, the following steps need to be performed:

step1: generating a query object ID for an object to be queried;

step2: starting occlusion query;

step3: rendering an object needing to be subjected to shielding query;

step4: ending the occlusion query;

step5: extracting the number of samples queried by occlusion;

step6: deleting the ID of the query object and recycling resources;

the method has the advantages that the number of primitives to be drawn can be reduced by using the shielding query technology, the drawing frame rate can be greatly improved, but the cost for executing shielding query is very high, and the method is mainly represented in two aspects, namely, each query is additionally added with one drawing call, so that the cost of the method is high, in addition, the waiting query result causes large delay, and the performance of a CPU (Central processing Unit) and a GPU (graphics processing Unit) is influenced;

in order to comprehensively understand the model, a user needs to observe the model from multiple angles, and for this purpose, multiple viewpoints are set to comprehensively judge whether the part is visible, so that the simplified three-dimensional model can still correctly reflect the appearance of the part and meet the aim of three-dimensional model data communication, the viewpoints are uniformly distributed on a sphere with the radius being three times that of the sphere surrounded by the assembly body, the whole assembly body can be just in a viewing cone, in order to achieve a balanced effect on algorithm complexity and result accuracy, the number of the viewpoints is set to be 12, the directions of the viewpoints are the vertexes pointing to the center of the sphere surrounded by the three-dimensional model, shielding inquiry tests are respectively carried out from the viewpoints, the number of pixels on a screen after the part is rendered is obtained, rendering results are comprehensively analyzed, and whether the part is a hidden part can be finally determined;

to be able to describe the algorithm more clearly, the following variables are defined:

(1)

representing the number of pixels which pass a depth test and are obtained by independently conducting shielding query on the part i at a viewpoint j when the assembly body is rendered;

(2)

representing the number of pixels which pass the depth test and are obtained by carrying out shielding query on the part i at a viewpoint j when the part i is independently rendered;

(3)

representing the number of pixels which pass a depth test and are obtained by carrying out shielding query on the whole assembly at a viewpoint j when the assembly is rendered;

(4)V _i represents the volume of part i;

(5)V _T represents the volume of the whole assembly;

(6)

a visibility value representing the part i at a viewpoint j for measuring whether the part can be considered as a hidden part;

in the hidden piece recognition algorithm, the visibility value of the part at a certain viewpoint is calculated by the following expression:

wherein: lambda ₁ +λ ₂ +λ ₃ ＝1；

In the above formula, λ ₁ 、λ ₂ And λ ₃ For weighting, the expression can better identify near-invisible parts and fine parts which do not influence the appearance of the assembly model, and the initially set part visibility rate, the part area contribution rate and the part volume contribution rate occupy the same weight, namely lambda ₁ 、λ ₂ And lambda ₃ All are 1/3, and in actual operation, corresponding adjustment can be carried out according to specific effects so as to obtain more satisfactory effects;

when the part i completes occlusion inquiry at all set viewpoints, the maximum visibility value of the part i can be obtained, namely

Defining a critical parameter F according to the actual demand _T (0<F _T <1) When the F value of a certain component in the assembly body is greater than the critical parameter, the component can be considered to be visible when being observed from the outside of the assembly body, otherwise, the component is considered to be a hidden component;

referring to fig. 6, for the assembly model, the above-mentioned component visibility determination algorithm is used to perform a process of automatically identifying the hidden component in the assembly body;

it should be noted that in the hidden part identification process, traversal of a part is a recursive process, and when a selected part is a sub-assembly, on one hand, the sub-assembly is required to be used as a whole to perform multi-view occlusion query testing, and on the other hand, the sub-assembly model is also required to be read, and the sub-assembly is used as a new whole to perform hidden part identification to obtain visibility information of the part in the sub-assembly;

for a more complex three-dimensional model, the cost for carrying out shielding query is high, in order to improve the identification efficiency, the surrounding box of an object can be adopted to replace the object for carrying out shielding query, in the process of light weight, the surrounding box information of the object can be obtained through a development interface of a three-dimensional system, and the surrounding box does not need to be calculated independently;

the grid model generated in the light-weight process is input in the process, and when parts in the assembly body are subjected to concealed part identification work, corresponding visibility information can be recorded into a light-weight assembly file of the assembly body;

as shown in fig. 7, after the hidden part of the assembled body model is simplified, the number of primitives to be drawn can be reduced, and the drawing speed is increased;

specific information before and after simplification of the engine model is shown in table 1:

	number of parts	Number of vertices	Number of triangular patches
				Original model	368	404422	424720
After simplification	152	317908	334655

TABLE 1

As can be seen from table 1, the number of parts in the engine is greatly reduced after the hidden parts are identified and simplified, which brings about a great reduction in the number of vertices of the model and the number of triangular patches, of course, the operation effect is closely related to the model itself, if the model is complex in shape, closed in appearance and has many fine parts, etc., the number of the identified hidden parts is large, on the contrary, the obtained simplified model cannot obtain an obvious simplification effect, because most of the parts identified as the hidden parts are inside the assembly or are small in size (such as bolts, nuts, etc.), the appearance of the three-dimensional model without the hidden parts has no obvious change, in addition, the lightweight assembly file only records the visibility of the parts in the assembly, and does not remove the hidden parts from the product structural relationship, therefore, all the parts can be displayed when needed, the correct expression of the product structure of the assembly model cannot be affected at all the time, and the usability of the data model is fully ensured;

the reason for this phenomenon is mainly that the proposed data model is a multi-layer structure, only the information of the next-level sub-assembly and parts is recorded in the total assembly file, and the information of which sub-assemblies are composed of parts and the positions of the part files is generally recorded in the sub-assembly file, the file information organization mode can reduce data redundancy and bring convenience to the use of a user, for example, for a three-dimensional model of a finished automobile, the user wants to check the automobile engine part, the user only needs to open the engine assembly file, but does not need to load a very complicated automobile total assembly file, in order to enable any one-level sub-assembly model to meet the purpose of data communication, during the hidden part identification process, the part must judge the visibility of the previous-level assembly, and cannot only pay attention to whether the part is visible in the total assembly, so that the degree of simplification is further improved;

when the three-dimensional model is rendered, the graphics processing unit needs to read the vertex data of the model from the memory, the memory bandwidth of the mobile device is limited, and the access of the vertex data needs longer time;

in order to alleviate the gap between the data processing speed and the access speed in the process of graphics rendering, a vertex cache (VertexCache) is added in a graphics processor, vertex data subjected to transformation and illumination effect processing is stored in the vertex cache, if a certain vertex is not in the cache, the data needs to be read from a system memory or a graphics processor memory, and for the hit vertex cache content, the data can be directly used in the next stage, so that repeated geometric processing is avoided, the overhead of data reading can be effectively reduced, usually, researchers use an average vertex mismatching rate (ACMR) to describe the vertex cache hit rate of the graphics processor, the ACMR is equal to the number of vertices needing to be read from the memory when drawing a frame, the lower the vertex mismatching rate means that the number of times of accessing the vertex data in the memory by a graphics processing unit is lower, the shorter the time needed for vertex data reading and geometric transformation in the process of the graphics processing is, the maximum value of the vertex mismatching rate is 3, namely, the vertices of all the vertices of the model are not close to the vertex in the vertex, the theoretical number of the vertex of the triangle is two times, the theoretical mismatching rate of the minimum value of the vertex, the maximum value of the vertex of the triangle, the theoretical mismatching rate is only 0, and the theoretical number of the minimum value of the vertex of the triangle surface of the triangular model, and the theoretical mismatching rate is limited to be 0.5;

referring to FIG. 8, the vertex cache hit rate is not only related to the graphics processor hardware itself, but also closely related to the grid data arrangement if the triangular sequence of the model is T ₀ T ₁ T ₂ Then when drawing T ₁ And T ₂ Triangularity, all vertices of the two triangles need to be read from the memory again, if the triangle sequence of the model is T ₀ T ₃ T ₄ Then draw T ₃ When the two vertexes of the triangle are already in the vertex cache, the GPU only needs to read one vertex again to draw the T ₄ The method has the advantages that only one vertex needs to be accessed, so that the cache reuse rate can be improved by modifying the triangular sequence of the model and increasing the locality of the model, the problem of vertex hit rate is not considered in the mesh model obtained by solid model conversion, the average vertex mismatching rate can be further reduced by changing the arrangement sequence of triangles, the vertex cache optimization is carried out on the three-dimensional model, the load of obtaining model data can be reduced, meanwhile, the calculation amount required by rendering operation can be reduced, and the drawing process is accelerated;

in this respect, we do a lot of work to achieve rendering optimization of the mesh, hoppe adopts greedy algorithm to reorder triangle sequence of triangle mesh, triangle strips with very high vertex cache hit rate are generated, a last-in first-out data reference mode is adopted, hoppe method is improved, cache optimized triangle strips with any cache parameter are obtained, ACMR values generated by the two methods are very close to the minimum value, but the number of triangle strips generated by the method is large, because of deep levels and many parts of the data model, if the strip generation mode is adopted, the number of triangle strips of the whole assembly body can reach a very large order of magnitude, excessive drawing function calling can be caused, graphics system overload is caused, rendering speed is affected, bogomjakov and the like propose a general drawing sequence algorithm, so that the obtained triangle drawing sequence can obtain good vertex hit rate in vertex cache with any capacity, but speed is slow, lin and the like carries out global search on mesh based on greedy method, heuristic conditions thereof are obviously optimized, and more ACMR models are obtained, but the ACMR optimization effect is complex;

sander et al propose a cache optimization method based on triangular ring, this method only carries on the heuristic search near the last result, have good vertex cache hit rate while guaranteeing the linear time complexity, but it belongs to known cache parameter (cache-aware) algorithm, when the actual cache is smaller than the ideal cache, the vertex cache hit rate will be seriously reduced;

in practice, vertex cache parameters of the graphics processor are difficult to obtain, and meanwhile, in order to ensure the universality of the optimized model, the cache optimization effect is not influenced by the real vertex cache parameters as much as possible, so that on the basis of documents, a brand-new heuristic search rule is adopted, and on the premise of keeping linear time complexity, the good vertex hit rate in drawing is ensured, and the adaptability to caches with different capacities is realized;

in order to accelerate the algorithm speed and keep a high vertex cache hit rate, the algorithm uses the thought based on triangular ring operation for reference, and continuously searches local optimal vertexes as Fanning vertexes, then outputs adjacent unoutput triangles containing the vertexes to finally obtain a high-hit rate triangular sequence In the vertex cache, the searching is only carried Out In the candidate vertexes, if the searching cannot be found, the searching is carried Out In other vertexes In the vertex cache, if all vertexes In the vertex cache are output, one unoutput vertex is randomly selected as the Fanning vertex to be output, and the searching process is continuously continued until all triangles In the mesh are output;

when the actual cache is smaller than the set simulation cache size, the vertex which is supposed to be hit originally has been replaced in the actual cache, the GPU must access the data in the memory again, and the subsequent vertex in the triangle sequence aggravates the phenomenon, which causes complete out-of-sequence of the triangle sequence and affects the final rendering efficiency;

to overcome this problem, a completely new heuristic search rule is adopted, i.e. the chosen Fanning vertices must satisfy the following two conditions:

(1) After the output of the triangular ring of this vertex, the vertex must remain in the vertex cache;

(2) The Fanning vertex must have the vertex with the highest triangle ring priority value, the priority values C (v) of the vertices are jointly evaluated through the positions of the vertices in the cache and the degrees of the vertices, and the priority value C (R) of the triangle ring is the sum of the priority values of the vertices of all the unoutput triangles in the ring

The vertex priority value C (v) may be calculated by the following formula:

C(v)＝C _p (v)+C _a (v)

wherein,

in the above formula, p represents the position of the vertex v in the buffer, s represents the size of the buffer space, a represents the number of non-output triangles adjacent to the vertex v, and k ₁ 、k ₂ 、k ₃ Is a coefficient;

in the calculation of the vertex priority value, the vertex priority value entering the vertex cache later is higher, so that even if the space capacity difference between the simulation cache and the real cache is larger, the vertex can still hit the vertex cache really, however, if only the factor of the vertex position is considered, a long and narrow triangle strip can be generated, and the vertex in the vertex cache is difficult to reuse by the subsequent triangles, therefore, the evaluation on the vertex degree is also added in the searching and selecting process, and the number of the adjacent triangle which contains the vertex and is not output is less, and the triangle strip is preferentially used as a Fanning vertex, so that the locality of the triangle sequence can be increased, the vertex of the triangle which is output before can be reused fully by the triangle which is output subsequently, and the possibility of generating the long and narrow triangle strip is reduced;

referring to fig. 9, the input data of the vertex cache optimization operation is a mesh model obtained by entity model conversion, and after an optimization process, a triangular mesh model subjected to cache optimization is obtained, and after coding compression, a final data model is obtained:

step1: establishing an adjacency relation between a mesh vertex and a triangle, and initializing a vertex priority value;

step2: selecting any vertex as a Fanning vertex;

step3: outputting triangles which are adjacent to the Fanning vertexes and are not output, taking the vertexes of the triangles as candidate for next selection, updating the content in the vertex cache, and updating the priority values of the vertexes;

step4: performing heuristic search on vertexes in the candidate, firstly, judging whether the vertexes are still in a vertex cache after the triangular rings are output, if a plurality of vertexes meet the condition, calculating the priority values of the triangular rings of the vertexes, selecting the vertexes with high priority values as next Fanning vertexes, if the vertexes in the candidate do not meet the condition, performing the same search operation on the other vertexes in the vertex cache, and if the Fanning vertexes are not found, indicating that the triangles including the vertexes in the vertex cache are completely output, so that one vertex is selected as the next Fanning vertex;

step5: when the number of the output triangles is smaller than the total number of the triangles of the model, turning to Step3: otherwise, the algorithm ends.

The process of establishing the adjacency relation in the algorithm does not need to record the information of the edges, the time consumption of the step is in direct proportion to the number of triangles of the grid, each vertex is a Fanning point at most once in the output process of the triangles, each triangle is accessed at most three times, and the cache updating operation is only related to the size s of the cache, so that the operation process consumes constant time, the time consumed by calculating the priority value of the triangular ring is related to the average degree of the model, and for a common model, the time consumed by calculating the priority value of the triangular ring is a small constant, so that the time consumption of the step is a constant, and in total, the time complexity of the algorithm is kept at O (t), which is proved by the following experimental results;

the test platform used in the experiment is IntelCorei32.13GHzCPU,2.0GBRAM, and a coefficient k is set in the experiment ₁ ＝0.3， k ₁ ＝0.9，k ₁ The comparison vertex cache optimization algorithm is a triangle fan method (FanSort) and a general drawing sequence construction algorithm (Bog), the vertex cache size of both the triangle fan method and the triangle fan algorithm is set to be 32, the two algorithms are selected for comparison, the triangle fan method is high in speed and good in optimization effect, the algorithm is improved aiming at the problem that the algorithm is difficult to adapt to caches with different capacities, and the general drawing sequence construction algorithm can obtain a good vertex hit rate in a vertex cache with any capacity;

the model a is a gear model, the number of triangular patches is 13884, the model b is a sphere generated by modeling software, the number of the triangular patches is 20480, the models c and d are from a Stanford university three-dimensional scanning database, the number of the triangular patches of the model c is 49954, the number of the triangular patches of the model d is 69451, the model e is a motor model, the number of the triangular patches is 91948, the model f is a plate-shaped part in a rear axle of an automobile, and the number of the triangular patches is 180311;

from the data in table 2, it can be seen that FanSort has the fastest processing speed, the processing time of the algorithm is in direct proportion to the number of triangles of the model, and is slightly longer than the consumption time of FanSort, mainly because the algorithm needs to calculate the priority value of the triangular ring in order to ensure better adaptability to vertex caches with different capacities, but still is many times faster than the BoG algorithm;

TABLE 2

The average vertex mismatching rate changes when the actual drawing runs at different cache capacities are compared, the ACMR value is increased sharply when the actual vertex cache capacity is smaller than the ideal vertex cache capacity by the Fansort algorithm, the cache mismatching rates of the algorithm and the BoG algorithm are stable under different cache capacities, the severe change is not caused, and the optimization effect of the algorithm is slightly worse than that of the BoG algorithm;

in summary, the algorithm has a faster processing speed and a better vertex cache hit rate under any cache capacity, and can improve rendering efficiency.

Example 3

In the progress management model, engineering project management, operational research and systematics are used as guidance to establish an engineering progress 4D simulation management system and a progress simulation model, the management system is used as an application frame, the progress management is used as drive, combinable points between the engineering progress management and BIM visualization are developed more on the basis of realizing the integration of engineering progress, time, manpower and materials, the process control of an engineering construction stage is enhanced, and accordingly, a 4D digital progress management model for establishing BIM three-dimensional integration time and resources is formed;

the basic content of project schedule management comprises project schedule planning and project schedule control, wherein the project schedule planning refers to the establishment of a reasonable and economic schedule within a specified time, the project schedule control refers to the checking of whether the actual schedule is carried out according to the schedule requirement in the process of executing the schedule, if deviation occurs, the reason is found out in time, necessary remedial measures are taken or the original schedule is adjusted and modified until the project is finished;

1) The project schedule management process mainly comprises the steps of activity definition, activity sequencing, activity resource estimation, activity time estimation, schedule planning, schedule control and the like, wherein the activity definition is generally established on the basis of project range determination and work decomposition structures to determine each specific activity included in deliverable results, the activity sequencing needs to refer to a project range description, an activity list and attributes, a milestone list, is completed by methods such as a front guide graph, an arrow graph, a condition graph and the like, and finally the dependence and restriction relation among activities is obtained, the activity resource estimation is to calculate the number of hours and the number of shifts required by each activity on the basis of determining the engineering quantity, so that the activity resource demand is obtained;

the activity time estimation estimates the construction period required by each activity on the basis of activity resource estimation and logic relationship determination, further determines the start time and the end time of the activity, can compile a project schedule plan on the basis of finishing the work, and utilizes a target plan to perform project schedule control, the work of each process of project schedule management is performed after a project team determines a primary plan, in the project schedule management practice, each work room has no boundary but overlaps and influences each other, and the schedule management process is clearly defined so as to facilitate theoretical analysis;

2) After the activity definition, the activity sequencing and the time estimation are finished, project resources and other restriction factors are comprehensively considered, so that the starting and ending time, the implementation scheme and measures of project activities are determined, the compilation of the whole project schedule and the compilation of the project schedule are finished, the time of a project can be reasonably arranged, the achievement of project day marks is ensured, the project schedule is a basis for project schedule control in the construction process, and a basis can be provided for resource allocation and time allocation;

3) The project schedule planning finishes the schedule arrangement of each activity, however, the unforeseeable problems in the construction process are many, deviation often occurs in the schedule execution process, project managers are required to correct deviation in time, and the schedule is adjusted, so that the project is finished according to the requirements of contracts, the control of the project schedule refers to that after the project schedule planning is finished, in the project implementation process, the implementation progress condition is checked, compared, analyzed and adjusted, so as to ensure the achievement of the total goal of the project schedule, the project schedule control is a cyclic routine activity, and mainly comprises the following steps: determining a fixed report period, controlling the whole execution process of the project, comparing the actual process with the planned process, if the project is delayed, exceeds the budget or does not meet the technical specification, taking measures to make the project return to a normal track, and if the plan is revised according to the change, establishing a new reference plan;

the dynamic monitoring of project progress mainly includes the tracking inspection that the progress was carried out, the data of arrangement, statistics and analysis collection, three works of actual progress of contrast and planned progress, the contrast of actual progress and planned progress, forms such as usable Gantt chart, network map, s curve, progress table directly perceived reflection disparity between the two, through the contrast, the actual progress that can find out is more advanced than the planned progress, still keeps unanimous after dragging, the process of project progress adjustment includes: analyzing the reason of the progress deviation, analyzing the influence of the deviation on subsequent work, determining the limiting conditions influencing the total construction period and the subsequent work, taking corresponding progress adjustment measures and implementing an adjusted progress plan;

with the continuous deepening of project management concepts, progress planning technologies are rapidly developed, project progress management is supported, and great benefits are brought to projects;

gantt chart, namely cross-road chart, is widely applied to project period plan and schedule, in Gantt chart, project activity is arranged longitudinally on the left side, display the work content, the cross axis represents the time of progress, the horizontal bar represents the time of project activity, the cross-road chart can display the start time, end time and duration of each work, gantt chart has the characteristics of simplicity, clearness and easy reading, can express the activity time difference and logic relation of the work task clearly, can be used for any level of WBS, the time unit can be from year to day or even to time, gantt chart can be used for making the schedule plan, besides being used for making the schedule plan, the Gantt chart can also be used as the tool of schedule control, express the actual schedule condition in the form of bar chart, compare the amount deviation between the actual schedule and the schedule plan intuitively, as the basis of schedule plan adjustment, in addition, gantt chart can be used for resource optimization, make up resource plan and expense plan, gantt chart is the construction schedule management method that is most frequently used in the electric transformation project at present;

the construction progress management system takes a time plan as a starting point, integrates a network planning technology, realizes the comprehensive management of progress and resources, and comprises project range planning and responsibility distribution, comprehensive plan compiling and optimizing, target management, plan feedback, analysis and updating, report and information publishing functions and the like;

project scope planning and responsibility allocation, project scope definition and control enabling project participants to agree on what a project should do and not, scope definition enabling further breakdown of deliverables into smaller, easily manageable work packages;

the comprehensive plan is compiled and optimized, the project schedule is compiled, the construction progress plan is taken as a leading factor, and related functional departments formulate respective business plans, so that a comprehensive progress plan comprising most contents of project management such as a financial capital plan, a design plan, a marketing plan, a purchasing plan and the like is formed, after the dominant plan compilation of the construction and installation is completed, a project department or a contracting unit can compile a quality certification work plan of construction work in combination with project schedule in schedule management professional software, a design and review department can also formulate a corresponding demand plan, a purchasing department can formulate a drawing on a sleeve, in addition, a quality inspection department or personnel can compile quality class files to deliver and review/report and verify the work plan in combination with the purchasing plan, and a contracting unit quality inspection department or personnel can also formulate quality inspection and related work plans in a matched manner according to the arrangement of the whole construction plan, and a safety department can compile a site construction safety environment plan;

the method comprises the steps of target management, establishing of an engineering project target plan to facilitate tracking and control of project progress, comparing progress performance with the target plan, analyzing progress conditions, finding deviation, taking measures to correct deviation in time or updating the target plan, wherein the progress management professional software has the functions of target establishment and maintenance, retaining the current plan as a target, and has the functions of combining main targets (progress, resources and cost) with the project plan;

plan feedback, analysis and updating, wherein the analysis is the basis of control decision and optimization management, the target and actual feedback are the basis of analysis, the content and the depth of progress analysis have different requirements on different management layers, and the progress analysis required by the engineering construction project comprises the following steps: the summary of responsibility items, the recent schedule and the summary of the completion condition of the engineering quantity comprise: the completion of the current period, the completion of accumulation, the completion of plan requirements, the difference value with a target plan and the progress trend, and the resource analysis comprises the following steps: the period, accumulated value, planned value, difference, labor productivity, resource use condition and cost condition, because of the diversity of the target, the operation feedback confirmation time limit is different, and different analysis period control measures can be adopted for different types of targets;

the report and information release function is used for reflecting a standard report of planned arrangement, a standard report of actual progress and a standard report of comparison of the planned arrangement and the actual progress, providing Web release and releasing the standard report or a graph into a webpage;

the creation of Project progress data is important preparation work for realizing progress management based on BIM, project management software such as Project integrates functions such as Gantt chart and network plan, a power grid information model based on GIM standard is used for bearing a large amount of available information of a transformer substation, the creation of construction progress data can be carried out based on a three-dimensional data platform and on the basis of decomposing a Project work structure by applying WBS technology, the Project management software such as Project is used as a tool;

firstly, basic information of a project is collected, then task details of the project are determined, after a project file is established, a task can be prepared to be input, and the stage of inputting the task is generally called as activity definition in the process of project management;

the activity definition is usually completed under the guidance of scope declaration and work breakdown structure WBS, according to the condition of the Project, the WBS can be established first, then the task list can be established, the WBS and the task list can also be established simultaneously, the method for inputting the tasks into Project software has a plurality of methods, the thought tasks can be directly added without considering whether the sequence and the related task group are met, then the adjustment and organization are carried out, the Project can be considered from head to tail in the sequence, the Project can be input in the sequence, the whole stage of the Project can be considered first, and then the tasks and the subtasks are added;

and also can consider which works are to be implemented by the project according to the milestones and the deliverable results, and the works are taken as task input, so that a task list is established;

developing a task list, sequencing tasks, establishing a task outline, possibly customizing a work breakdown structure WBS code, and making a task progress plan, wherein the project progress plan is a route map for completing the tasks, submitting deliverables, passing milestones, and finally completing a project target on time, making a progress plan which is accurate, feasible and truly reflects the operation condition of the project, inputting the task duration in software, determining the relationship and the dependency among the tasks, and arranging individual task progress to meet specific time requirements if necessary, so that an outline of a real project progress plan is obtained, and the task duration and the duration of the whole project can be known from the software;

the completion of Project tasks requires resource allocation, resources must be actually pointed out in the Project plan along with the definition of the tasks and the scheduling of the Project plan, the accuracy of the Project plan is improved by adding the resources to the Project, whether the resources are overloaded and allocated too much work is known in advance in the allocated time, the progress of the Project is tracked according to resource working hours, the use, cost and consumption of raw materials in the Project are tracked, the responsible and reliable resources are confirmed to be allocated to all the tasks, the tasks and the resources are arranged in the Project plan, the tasks and the resources need to be matched together, and the 'allocation' is created, and after personnel, equipment and material resources are allocated to the tasks, project can create a Project schedule which not only reflects Project calendars, task periods, dependencies and limitations, but also reflects the calendars and availability of the allocated resources;

after a project scope is defined, a task schedule is arranged, resources are allocated, a project planning phase is not finished, in a general case, a result needs to be checked to determine whether the project plan meets expectations and requirements, if the project cannot be completed on time according to the plan, the project plan needs to be adjusted until the expectations and requirements are met, after the adjustment is made, the project plan needs to be rechecked, resources are added for the tasks, the time of ending the tasks can be shortened, but the cost can be increased, if more tasks are allocated to the existing resources, the resources can be over-allocated, the time and the cost can be saved, individual tasks, deliveries or phases can be abandoned, and the project plan can enter an execution phase after balance is made according to project requirements;

referring to fig. 10, the analysis model primitive is a material basis of the entire 3D information model, and all the component objects, attributes and operations thereof are defined herein, that is, the model core data is concentrated on the model primitive, and the model primitive is a final carrier of the 3D information model data, so that the data structure of the 3D information model to be researched is also summarized as the data structure of the research model primitive;

in the power grid information model, the data structure of a model primitive comprises basic data and extended data;

basic data comprises geometric data, physical data, functional data and the like, the data describe the self characteristics and attributes of a model component, the basic data are inherent to the component, the basic data can not change along with the change of time and environment, extended data comprise technical data, economic data, management data and the like, the data are mostly information or data which are generated in the project management process and are associated with model primitives, the data are limited by project specific stages and specific environments, the characteristics of the model primitives are not described, the extended data have certain independence, a power grid information model can integrate the extended data to enable BIM technology and function to be expanded, a large amount of indirect various data which are associated with model elements are integrated into the information model to form a complete and unique power grid information model, so that BIM functions and application can be greatly expanded, BIM technical value maximization is realized, time data are integrated into the power grid information model, and progress management based on the BIM technology is also realized;

through the structural analysis of the three-dimensional model based on the BIM technology, the following results can be obtained: the model primitive extension data is the basis for realizing the power grid information model function, and if the power grid information model is integrated with other extension functions, for example: the method comprises the following steps that corresponding expansion data are integrated into model primitives in progress simulation, cost calculation and the like, a 3D model architecture is still used for building a 4D model, the difference between the model primitives and the model primitives is mainly the difference of the data structure of the model primitives, and on the basis of a 3D power grid information model, construction plan data, 3D geometric data and associated data of the model primitives are integrated, so that the 4D power grid information model can be built, and functions of 4D simulation and the like are achieved;

the application program designed by applying the MVC structure is provided to the same database, the function range of a plurality of views can be displayed, the structure is mainly used for designing a distributed application system, the separation of a data layer and a table small layer can be well realized, the application program developed based on the MVC is divided into a model layer, a view layer and a control layer, the separation of the three modules enables the same model to be displayed in multiple views, a user changes model data through the control layer of a certain view, other views depending on the model can be subjected to associated change, as long as the data is changed, the control layer can inform all views of the change, and therefore the display is updated immediately, the 4D system based on the BIM can be designed in the MVC mode by combining with the function requirements of the system;

referring to fig. 11, a system model layer can implement business logic in a system, after a GIM three-dimensional information model is analyzed through a three-dimensional platform, model component spatial data is exported to a DWF three-dimensional model library, construction attribute data of a model component is exported to an SQL database, construction progress data is created through a similar Project platform and stored in an SQL database, then association between a three-dimensional component and a two-dimensional WBS element is established through a model component ID number, so that integration of the spatial data and the progress data is implemented, a system view layer displays model information in different views or display forms, a construction progress is displayed based on design review, construction simulation is implemented, display of specific information such as component construction start time, end time, engineering quantity, materials and the like is implemented through an attribute table control, a system control layer handles interaction between a user and the system, so that the model and the views work in a coordinated manner, an independent progress control module is provided, so that comparison control is performed on construction start time and end time of the component, and a system structure based on MVC;

referring to fig. 12, the BIM-based 4D system needs to be built on the basis of Project planning technology and three-dimensional power grid information model technology, and is implemented by comprehensively applying database technology and system development technology, and after analyzing a three-dimensional platform and Project software, an MVC-based system architecture implementation process can be constructed;

the application of the prior related technology in the progress management is isolated, although a certain technology is independently applied to project management, the application is far lower than the benefit of integrated application between technologies, the BIM and the related technology bring great value and convenience to the project management, especially the creation, sharing and transmission of information in the whole life cycle of a project, the effective communication of the information can be ensured, only the related information technology is integrated, and a progress management system based on the BIM is constructed, so that the defects of the traditional information creation, management and sharing can be eliminated, the progress management informatization of the project can be better realized, and the efficiency of the project management is improved;

referring to fig. 12, the timeliness, accuracy and acquirability of the progress information provided by the system are not high, the information requirements of each stage of project participation cannot be met, the efficiency is low, the advantages and derivative functions of the progress management system are integrated into the progress management through analysis of relevant theories and technologies of project progress management and combination of technical characteristics of BIM, a progress management framework system based on a BIM technology platform is constructed, the defects of a traditional management mode are tried to be made up, and an application framework system is managed based on the progress of the BIM;

the BIM-based progress management application framework system can visually display the promotion and the improvement of a progress management method tool after the BIM technology is introduced, the BIM technology is introduced into the existing progress management system based on the BIM, the BIM technology is aimed at comprehensively exerting the values of the BIM technology and the existing progress management theory and method, and because the BIM technology model can bear information required in the project whole life cycle management, a BIM information platform and functions generated by the BIM technology are beneficial to the whole process of project progress management, and the benefits of the BIM information platform and the functions penetrate into each link of progress planning and control;

on the basis of the existing progress management system, the project takes a BIM information platform as a core, and establishes the association between BIM and WBS network plans, so that various methods and tools are comprehensively utilized, the progress management flow is improved, and the project benefit is increased;

referring to fig. 13, the core of the BIM-based progress management system is a BIM information platform, which can be divided into three subsystems, namely, an information acquisition system, an information organization system and an information processing system, the three subsystems are in a progressive relationship, and the work of the subsequent system can be continued only after the work of the preorder system is completed, the project information mainly comes from project participants such as owners, designers, construction parties, materials and equipment suppliers, and includes all information related to progress management in the whole life cycle of the project, after the information acquisition system completes the collection of the project information, the information processing system performs the work of encoding, classifying, storing and modeling the information according to industry standards, specific rules and related requirements, and the information processing system can support the project progress management by using the system-structured information, and provide the functions of construction process simulation, construction scheme analysis, dynamic resource management, site management and the like, and the overall framework of the BIM information platform.

Example 4

In the comparison model, research methods such as analysis and investigation, experimental verification and the like are applied, and the construction progress control method based on the BIM is provided by analyzing the real-time performance of the information acquisition technology on construction site information collection and the integration performance of the BIM on engineering information, aiming at the management requirements and the faced problems of the power transmission and transformation engineering on the construction side, researching the collection means of the construction progress data on the site and the reconstruction method of the real-time model;

after the key chain is identified, the size of the buffer area needs to be calculated, and the size of the buffer area is set by taking the safe time of the process as a reference, so that the next step needs to determine a method for determining the safe time of the process adopted by the model;

the determination method of the safe time is various, the following two methods are applied more and have advantages and disadvantages, and parameters in the two methods can be adjusted to achieve the purpose of adapting to the actual construction situation:

the method comprises the following steps: establishing an uncertain index system of a project construction period, dividing the project into four time periods including a project planning and decision making period, a project preparation period, a project implementation period and a project completion acceptance, wherein uncertain index numbers of projects in different periods are different, the influence on the progress is different, comprehensively evaluating uncertain indexes of different periods in the whole construction period of the project, calculating the uncertainty of each construction period through the index system, and extracting safety time from the procedures of each construction period according to a certain proportion;

the second method comprises the following steps: assuming that the time required for completing a process follows Gaussian distribution or lognormal distribution, the longer the time allocated to the process, the higher the probability of completion, and if the completion of the activity is estimated at 95% probability, the time appears to be particularly long, and the more time the completion of the activity is at 95% probability than at 50% probability is often used as the safe time for the project task;

the first method is more complex than the second method, an uncertain index system needs to be constructed according to the characteristics of the project, if the actual project is adopted, more management cost and time cost are inevitably increased, but the uncertainty of the actual project is calculated according to the system, the method for extracting the safe time is more scientific and has higher reliability, the second method is simpler, the actual operation is easier and basically accords with the actual construction, but the methods have certain limitations because the working procedures are different and mutually influence,

due to the simple and easy-to-use property of the second method, the method for selecting the safe time of the process by the second method is determined, and on the basis, statistical distribution conforming to the process duration characteristics of the project is selected;

the statistical distribution of the process duration can mainly adopt normal distribution and beta distribution, but uniform distribution, triangular distribution and the like are less applicable, and the distributions exist with certain possibility although the normal distribution and the beta distribution are not universal;

when the statistical distribution is adopted to carry out construction period simulation, construction periods generated by different distribution simulations can generate larger influence on the result, therefore, each procedure should select statistical distribution which accords with the reality as much as possible, MATLAB is adopted to carry out simulation analysis on the engineering progress, and the characteristics of the four statistical distributions are introduced respectively, and the characteristics are as follows:

(1) Normal distribution, which has very important status in theory and reality and is the basis for analyzing other distributions, wherein under the condition that the process duration distribution is normal distribution, the mean value, the median and the mode of the process duration distribution coincide, the probabilities that the process duration is greater than the mean value or less than the mean value are completely equal, and the probabilities that the process is delayed or advanced are completely equal;

(2) The beta distribution, which is generally an asymmetric unimodal distribution with well-defined end points, has four variations in distribution morphology according to the values of its parameters α, β: left deviation distribution and right deviation distribution, wherein the distribution range is in [0,1], the distribution value is stable, and the method is suitable for simulation estimation of the working procedure duration;

(3) The uniform distribution, also called rectangular distribution, is symmetrical probability distribution, the distribution probability at intervals of the same length is equally possible, when the process duration is uniformly distributed, the time for completing the process is equally possible within a certain range, and the probability of occurrence in the construction process is lower;

(4) The method is characterized by comprising the following steps of triangular distribution, wherein the triangular distribution is determined by three parameters, namely a distribution lower limit, a mode and a distribution upper limit, has both discrete distribution and continuous distribution, and is often used for business decision-making, particularly in the field of computer simulation;

in actual field construction, the estimation of the process duration is quite abundant, because multiple layers of upper and lower organization relations exist in each construction subject, each time when an upper level assigns a task to a lower level, various uncertainties existing in the tasks are considered, a certain safety time is added to the tasks, when the multiple layers of safety time are overlapped, the safety time is quite considerable, however, even if the safety time is given, the duration of most processes in actual construction still has the characteristic of left biased distribution, people often use the planning time to finish the work just before the planning time is used up or the planning time is used up after the planning time is finished, and then report the process results, in short, the safety time in the process is wasted, according to the idea of key chain project management, the process time is expanded automatically until all available time is occupied, the time is more abundant, the time required for completing one task is more, and the view explains the phenomenon;

therefore, under the condition that the influence of psychological and adverse behavior factors of people is not considered and the safe time of the process is reduced, the distribution of the process duration time is subject to right bias distribution, assuming that the total time of one process is marked as ' 1 ' day, the time for the process to be completed in the actual construction is roughly biased to ' 0.7-0.9 ' day, and the beta left bias distribution is subject, under the condition that the influence of the factors of people is not considered, the process execution completion time is biased to ' 0.5-0.7 ' day, and the beta right bias distribution is subject, according to the idea of key chain project management, in order to eliminate the influence of the factors of people, the safe time of the process is removed, so when the process duration time is simulated, the statistical distribution of the process duration time is subject to right bias distribution, the safe time reserved by a layer is taken as buffer centralized processing, however, the safe time cannot be completed by ' 0 ' time, the safe time occupies half of one work, and the whole right-biased beta distribution graph is moved to the coordinate axis, so that the process can be completed within the average time of the process within ' 0.5-0 day, and the process can be completed within a certain time;

based on the above contents, it is considered that the process duration should be simulated and estimated by adopting beta right-bias distribution whose initial value is not zero, and at the same time, the selection of parameters of beta distribution should require one, and the beta distribution is ensured to be right-bias distribution, and secondly, because the processes have characteristics, the uncertainty of different degrees is provided, and the estimation of the process duration can also be distinguished by selecting the beta distribution parameters;

as can be seen from the above, the beta distribution has four kinds of pattern distributions, namely a downward sliding type waveform curve, an upward type waveform curve, a left deviation type curve and a right deviation type curve;

in probability theory, a beta distribution, also called beta distribution, refers to a set of continuous probability distributions defined in intervals, with two parameters α, β >0, the important properties of which are shown in the following formula,

(1) Mean value:

(2) Variance:

it can be seen that the above two equations are simultaneous binary quadratic equations, and have infinite solutions, where α and β are known, the mean and the variance can be obtained separately, but α and β values are difficult to obtain with known mean and variance, and by MATLAB design simulation, the value range of α and β is specified to be 0:0.1:10000, since the required distribution pattern is a right-bias pattern, the value range of the specified mean value is 0.3:0.05:0.5, respectively calculating the variance values, respectively storing simulation results into A11-A51 matrixes, selecting proper mean values and variances according to needs through data of the A11-A51 matrixes, and selecting corresponding parameter combinations to simulate the process duration, wherein the selected parameter combinations are simulated through MATLAB to draw distribution patterns and are applied under the condition of confirming right-handed distribution because conditions of the occurrence of a beta distribution downward sliding waveform curve and an upward rising waveform curve are not clear;

it can be known from MATLAB design simulation that the downslide waveform curve and the ascent waveform curve appear only under the condition of large variance: when the mean value is less than 0.5 and the variance is large, a downward sliding type waveform curve appears, and when the variance is small, a right deviation type waveform curve appears, when the mean value is more than 0.5 and the variance is large, an upward type waveform curve appears, and when the variance is small, a left deviation type waveform curve appears, and the variance is large, the curve fluctuation is large, so that the peaks of the downward sliding type waveform curve and the upward type waveform curve appear in the curve fluctuation range, the deviation state is difficult to see, the exact form is not researched any more, the right deviation type beta distribution with the small variance is mainly applied, and meanwhile, if the variance is too large, the right deviation type beta distribution is not suitable for being applied to the simulation of the process duration, and the stability is difficult to meet the actual requirement;

according to engineering practice, the larger the duration of one process is, the larger the uncertainty degree of the process is, and the more delay is, three kinds of parameter combination selection are given through division of the process duration, and the detail is shown in table 3, wherein the three kinds of parameter combination selection correspond to the uncertainty degree of the process respectively so that the beta distribution fits the actual situation better;

degree of process uncertainty	Duration of the procedure	(α，β)	Mean value	Variance value
					Big (a)	t>80 days	(3，3)	0.5	0.0357
In	T is more than or equal to 40 days>10 days	(2，3)	0.4	0.04
					Small	t is less than or equal to 10 days.	(1.5，3.5)	0.3	0.035

TABLE 3

Corresponding to the three conditions, when the process in the project network is respectively matched with the beta distribution of different parameters for simulation, in order to avoid that the process simulation time is too short and is not accordant with actual field construction, the beta graphs of the three parameters are shifted to the right by 0.3 unit, and the number of the random distribution of the beta is set to be not less than 0.15, so that the minimum duration of each process is ensured to be at least 45% of the original duration, under the condition, the completion time of the process is between 60% and 80% of the original duration, certain probability exceeds the original duration, the process is relatively accordant with the actual condition, and uncertainty is large;

in summary, the processes in the project are considered to be all subjected to the right-biased beta distribution and independent of each other, and the safety time is the difference between the duration at 95% completion probability and the duration at 50% completion probability of the process, and the formula is as follows:

T _k ＝[F(x)I _x＝0.95 -F(x)I _x＝0.5 ]×t _k

wherein F (x) is the distribution function of the beta distribution, T _k Is a safe time of process k, t _k Duration of process k;

the BIM-based progress plan and control comprehensive application technology of BIM, WBS, network plan and the like, the progress plan is compiled on the basis of BIM model information, a traditional progress management software interface is applied, and the steps of work decomposition structure establishment, construction period estimation, work logic relationship arrangement and the like are carried out;

before the project schedule is compiled, the scope management and work definition of the project are firstly completed, WBS is considered as one of the most main tools for planning and controlling the project work content and scope at present, and similarly, the first step of project schedule based on BIM is to establish a work decomposition structure, which is generally completed by assistance of related software or systems;

WBS establishment and encoding are the key for linking BIM model component primitive information with information such as operation progress, resources, cost and the like, so that direct application of the BIM model information in progress management is realized;

the project work decomposition structure is to decompose project targets, tasks, work ranges and contract requirements into mutually independent, mutually influenced and interconnected project units according to system principles and requirements, use the project units as a series of project management work objects of project planning, implementation, control, information transmission and the like, and merge all the project units into a whole through project management so as to achieve comprehensive planning and control requirements, wherein the project work decomposition structure is a top-down layer-by-layer decomposition expression mode of the project tasks, so that each task is arranged at a proper position of the whole project structure;

WBS is the foundation of compiling time plan in project management, the work decomposition structure method decomposes projects by using the system idea, prevents project network plan from lacking, carries out man-hour estimation, construction period estimation, resource allocation, lap joint relation establishment and time optimization on each decomposed unit so as to achieve the optimal management of the time plan of the project, and carries out time control in the project implementation process based on each decomposed unit;

WBS has created the condition for computer-aided project management, the computer is a mark of the modern project management applied to project management, in the course of implementing and controlling the project, collect classification resource, progress information through WBS coding system, guarantee the information is annotated out through the unified and unanimous annotation method, through inputting name and overlap joint relation of every hierarchical work unit by the computer, can produce the cross-road picture, network map, 4D model automatically, can look over the progress state of the project at any time in the course of implementing the project, produce the periodic report of the progress automatically by the computer;

from the creation process, the Work Breakdown Structure (WBS) is to break down a functional entity (project) into sub-projects according to a tree diagram, then break down the sub-projects into a plurality of relatively independent work units step by step, and determine the task of each work unit and the work (or called activity) subordinate to the work unit, so as to organize the progress of the project more effectively;

in the progress management system based on the BIM, WBS establishment is realized through a computer, and for obvious work required by a project, information in the BIM model can be directly utilized to check the model or derive a detailed list for determination;

for work with certain concealment, the work necessary for a complete project is listed on the basis of experience or by referring to the prior project practice, the input and the coding of WBS elements are completed through a computer software system, and the relation between project work and BIM model components is constructed;

a BIM-based progress system that can add an unlimited number of WBS milestones that can also be used to calculate earned value, the milestones assigned at the WBS level, each assigned a weight to indicate its importance to project progress, when a certain WBS milestone is marked as completed, the module will use its weight to calculate the completion percentage of all jobs contained at the WBS level, apply the completion percentage to all jobs at the WBS level, and then roll up to the WBS, e.g., if a certain WBS level contains 10 jobs, and enter actual completion dates for 5 of the jobs therein, the WBS level will also be assigned 4 WBS milestones of the same weight, but only one of them is marked as completed, the module will use the completed WBS milestone to calculate the completion percentage of the WBS level, i.e., 25%, even if the jobs contained at the WBS level have completed 50%;

if a WBS element has a total of 4 weighted milestones and all milestones have a weight value of 1.0, then marking one of them as "completed" means that the WBS element has been 25% completed, and if the milestone has a weight of 9.0 and the other 3 have a weight of 1.0, then marking the milestone as "completed" means that the WBS element has been 75% completed, and the module can calculate the completion percentage from the weighted milestones using the following formula: actual weight of completed milestone/total weight of all milestones, applying the above formula to the above example, the weight of completed milestone is 9.0, divided by the total weight of all milestones is 12.0, resulting in a percentage of completion of 75%;

the WBS earner value BIM based system can define earner value settings for specific WBS elements, thereby implementing WBS earner value analysis, which is a method for measuring project execution according to project cost and progress, and compares budget cost of work with actual cost, and earner value analysis is generally used for WBS elements, and can also be performed for jobs or job groups;

using the earned value function of the work breakdown structure, it may be specified to calculate the earned value setting for the selected WBS element, with "earned value" cost referring to the total budget cost for jobs that have actually completed since the start of the project data date, calculated as follows: earned value = budget at completion x execution completion percentage, the calculation method of completion percentage depending on the earned value method selected for the WBS of the job;

the project schedule plan is a route map for completing tasks, submitting deliverables, passing milestones, and finally completing project targets on time, the project schedule plan is made to be most relevant to time management, the schedule plan which is accurate and feasible and truly reflects the project operation condition is made, the work period and the logic relation among the works need to be determined, resources are distributed, the cost is estimated, and the budget is set;

after the work decomposition structure defines the project operation, the operation time is required to be estimated one by one, the operation time refers to the operation duration, the estimated operation time is the core of a time plan, the estimation of the operation time does not simply depend on mathematical operation, but also needs to be adjusted according to the capability of a project team and available professionals, equipment and funds, the operation time is estimated, internal and external factors influencing the construction period need to be considered, and the estimation can be carried out by combining the modes of experience, historical data, investigation, delphi method, modeling and the like;

the progress plan based on BIM realizes the association between WBS code and model member ID number when completing work decomposition structure, and the selected work can check the basic data information of the corresponding model member, so the estimation of the work time can be completed by utilizing the data of the model member such as geometry, function and the like, obtaining the engineering quantity information, combining with a specific calculation method, and completing the estimation of the work period by referring to other project model experience and historical information in a system database;

the progress system based on the BIM can be used for checking and editing detailed progress information of selected operation, wherein the detailed progress information comprises planned starting and finishing dates, actual starting and finishing dates, free floating time, total floating time, limiting conditions, planned construction period, actual construction period and the like, and the labor and non-manual unit cost values and material cost values of the operation can be checked and edited;

after the work period is determined, the next step of creating the project schedule is to establish a logical relationship among the jobs to indicate whether a certain job must be started after another job is started or completed, and after the logical relationship is distributed, the earliest and latest dates of each job are calculated through the project schedule;

the logical relationship from the immediately preceding job to the subsequent job is generally four:

completion-start (FS): only after the operation is completed immediately before, the subsequent operation can be started;

completion-completion (FF): completion of the subsequent job depends on completion of the immediately preceding job;

start-start (SS): the start of the subsequent job depends on the start of the immediately preceding job;

start-finish (SF): only when the immediately preceding operation starts, the subsequent operation can be completed;

where subsequent jobs cannot begin or complete simultaneously with the beginning or completion of an immediately preceding job, a delay may be defined for the relationship, the delay being the number of times from the beginning or completion of a job to the beginning or completion of the subsequent job, the delay may be positive or negative, e.g., a start-start relationship with a three day delay, indicating that the subsequent job may not begin until three days after the beginning of the immediately preceding job;

the BIM-based progress plan has various methods for distributing the logical relationship, can use an operation network diagram to visually display the logical flow of the connection operation, or use a cross-walk diagram to check the logical relationship according to time, or directly select WBS operation to distribute the relationship to other operations of the project, and after the setting of the logical relationship is completed, the formulation of the network diagram and the cross-walk diagram is completed, a plurality of operations can be selected by a system to apply the network plan or the cross-walk diagram for plan analysis, and four-dimensional dynamic simulation of the selected operation can be checked;

with the definition of project jobs and the scheduling of projects, resources must be physically specified in the project plan, the accuracy of the schedule can be improved by adding resources to the project, the progress of the project is tracked in terms of resource man-hours, the use, cost and consumption of raw materials in the project are tracked, it is confirmed that all tasks are assigned responsible and depended resources, resources include both manual and non-manual resources to perform all project jobs, such as engineering coins and equipment, which are usually calculated over time and often assigned to other jobs, material resources, such as supplies and other consumables, which are calculated over unit prices, rather than hours;

the BIM-based progress management system can add resources and create a resource hierarchical structure to reflect the organization of the resource structure and support the allocation of the resources to the operation, can set resource classification codes without hierarchical limitation for grouping and summarizing the resources and generating resource reports and profiles, further analyze the resource allocation and adjust project plans to avoid resource excess allocation and resource use peak and valley periods, and in addition, the system can compile the resource plans to integrate the resources, cost and progress so as to effectively control the project, and can use a 'job profile table', 'resource profile table', 'job histogram' and 'resource histogram' to track the use condition of the project in the process of the project after allocating the resources and specifying the budget amount of the resources expected to be used in the operation by the system;

after the preliminary completion of the schedule plan, the plan needs to be analyzed to confirm the reasonability of the plan itself, and the analysis of the high-level plan mainly comprises the following steps: whether the project plan content is comprehensive, whether the job is the detail division of the WBS minimum level, whether the plan control is convenient: the method comprises the following steps of main resource and cost distribution, operation construction period, construction process logical relation, construction process limiting conditions, construction process time difference, main process cross points, whether working products and documents are distributed to corresponding WBS and operations and other contents, and the BIM-based progress management system provides the functions of network optimization, progress target comparative analysis, earnest value analysis, 4D simulation analysis and the like, and various analysis results have great effects on reasonably determining a project control target;

referring to fig. 14, in the schedule plan period analysis, firstly, the consistency of major milestones should be checked to ensure whether the total target is consistent with the contractually specified date, secondly, a key line is found out, and whether the working duration on the key line is acceptable is analyzed, and in addition, under the condition of comprehensively considering the restriction, whether the starting milestone date and the finishing milestone date meet the project requirements is analyzed, and by establishing a complete hierarchical plan in multiple ways, whether the working period between the aggregated plan and the original plan has a large deviation is analyzed and checked, and project participants should communicate with each other and reach consistency;

referring to fig. 15 and 16, a progress management system based on BIM provides a WBS job list view, a cross-track view, a network view, and a 4D view to analyze the rationality of job duration and logical relationship, through the cross-track view or the network view, key lines and key works can be conveniently found out and displayed in different colors, if the key lines and key works need to be adjusted, the key lines and key works can be directly modified and edited in the view, in addition, through the 4D view, the work can be directly simulated and simulated, the work progress can be more vividly displayed, and whether the logical relationship between jobs is rational or not can be found;

if the project is a time constraint project, the completion time is absolutely prior to other factors, but budget constraint is still balanced and the project range is satisfied, if the project completion time is to be advanced, the schedule plan itself is checked, the accuracy and the necessity of all preset schedule control factors are confirmed, in a job list or Gantt chart, date constraint, construction period, job dependency and job calendar are checked and updated, in order to influence the end time, only key jobs need to be adjusted, the job sequence of a key path can be shortened, another job sequence is changed into the current key path, and the path is ensured to be ended before the target completion time;

the use of resources is the most important limitation in a project, after the resources are distributed to work, the workload and the work resource allocation need to be checked, all the resources can be better utilized and distributed to proper work, the phenomenon of insufficient distribution or over distribution is avoided, when the resources are not distributed enough, the resources do not directly execute the project work, so that the project work cannot be completed on time, the quality is reduced, the cost is increased, when the resources are distributed excessively, the resources need to continuously over work, the working hours exceed the available time, and more expenses are paid for the working hours;

before work begins, a progress plan can be checked and resource allocation can be analyzed, the phenomenon of insufficient allocation or over allocation can be found, necessary adjustment is made to maximize resource contribution and reduce risks brought by resource allocation, the purpose of examination is to maximize workload, waste of resource cost can be reduced, key resources can be utilized most fully, a BIM-based progress management system provides a resource allocation analysis function, the detailed information of selected resources in a resource worksheet is checked to determine whether the real demand condition of a project on the resources can be reflected through modification of availability, project scope can be adjusted, WBS work items can be increased or decreased, resource load can be balanced, the starting budget of a certain resource can be delayed by using a limited amount, or work period can be adjusted, work can be split or delayed until the resources are executed in time, more funds can be invested through adjustment of cost, resources can be increased, under-allocated resources can be added to work to reduce or replace over-allocated resources on the premise of the same skill and availability, and resource allocation analysis can be carried out;

the method comprises the following steps of arranging cameras on all directions of a construction site, acquiring real-time progress information of the construction site, integrating images for generating a real-time model, using the images for progress management, and solving the following problems that firstly, a built building on the construction site is subjected to three-dimensional reconstruction to form a real-time model, then the reconstructed model is compared with a planned model, and finally, progress statistical information is calculated, wherein the three-dimensional reconstruction needs the following processes:

1) Image registration is that a camera takes a large number of pictures from various directions of a construction site, pictures taken from different angles at a time point are selected to form a group, the pictures of the group are subjected to feature point matching, the feature points are points capable of reflecting the initial structure of a scene, SIFT feature detectors can be used for detecting the feature points, the feature detectors are generally called corner detectors, but the feature detectors do not only select corner points, but select any image position with large gradient in all directions at a preset ratio, the SIFT feature detectors are used because the SIFT feature detectors have good invariance, can be used for scaling, vision field and illumination transformation, and have wide application in the field of computer vision, SIFT is translated into scale-invariant feature transformation, and can convert image data into scale-invariant coordinates relative to local features, and the SIFT image feature points are formed by the following steps:

1. scale space extremum detection, searching all scales and image positions, and identifying potential interest points for the scales and the rotation by using a Gaussian differential function;

2. positioning key points, wherein the position and the scale of each candidate position are determined by a fitting fine model, and the key points are selected according to the stability of the key points;

3. determining directions, assigning one or more directions to the position of each key point according to the local gradient direction of the image, and converting all subsequent operations on the image data into direction, scale and position relative to each feature so as to provide invariance for the conversion;

4. keypoint descriptions, measuring, in a neighborhood around each keypoint, at a chosen scale, the local gradients of the image, these gradients being transformed into a representation that allows for relatively large local shape variations and illumination variations;

the acquisition of feature points by SIFT results in a large number of features that densely cover the image over the entire scale and location, and the number of feature point acquisitions is usually determined by the content of the image and the choice of various parameters, but an image with a typical size of 500 x 500 pixels will yield about 2000 stable feature points, whereas to detect small objects in a cluttered background, at least 3 features need to be correctly matched from each object for reliable recognition.

2) After the feature points are detected, image matching and recognition are started, and the method comprises the following steps: firstly, extracting SIFT feature points from a group of reference images and storing the SIFT feature points in a database, respectively comparing each feature point in a new image with the previous database, then finding out candidate matching features according to the Euclidean distance of a feature vector, and further matching a new image;

after detecting feature points on the collected picture data set, matching the feature points, wherein the matching method is a Scale Invariant Feature Transform (SIFT) descriptor, capturing intensity gradients on a pixel window taking the detected key points as the center, then classifying the pixels into 4 x 4 sampling windows, wherein each sampling window and an intensity gradient histogram are stored in 8 basic directions, the descriptor becomes a feature vector with 4 x 8-128 dimensions, the SIFT descriptor matches the feature points by calculating a distance function of two matched intensity gradient histograms, and the feature point matching is realized by using a nearest neighbor matching method, if the number of the features is large enough, a KD tree matching scheme can be used instead of reducing the calculation amount to the maximum extent, and an ANN priority search algorithm can also be adopted;

wrong matching can occur when the features are matched, and in order to eliminate errors, a ratio test method is adopted, and the specific mode is as follows: for the feature descriptor in the image i, two nearest neighbors can be found in the image j, the distances between the two nearest neighbors are d1 and d2 respectively, if d1/d2 is less than 0.6, the two nearest neighbors are matching items to be found, if a plurality of features in the image i are matched with the same feature in the image j, and because one of the features is a wrong matching item, the wrong matching items are deleted;

due to the sensitivity of the reconstruction algorithm to false matches, the debugging method needs to be further refined, i.e. once a matching feature is detected in a pair of images, the basis matrix of the pair of images is robustly estimated using RAXSAC, which imposes that the corresponding features must be consistent under viewpoint translation, i.e.: p,' FP, -0 (P, and P, are point coordinates and F is the fundamental matrix), in our model, at each iteration of RANSAC, the fundamental matrix is computed using an eight-point algorithm, and then the problem is normalized to improve robustness to noise;

setting the rnasa outlier threshold to 0.6% of the maximum image size, i.e., 0.006 times the maximum width or height of the image (about 12 and 9 pixels for a two-dimensional image size of 2144 x 1424), the base matrix returned by RANSAC can be refined by running the levenber marquardt algorithm on eight parameters of the base matrix, the purpose of removing false matches being achieved by using the above suggested thresholds;

if the number of matching items in the image pair is less, even after the base matrix is iteratively fitted through RANSAC, a high false matching rate still exists, therefore, a threshold value of 20 is set as a matching item, if the matching item of the image pair is smaller than the threshold value, the matching item has no reference value and is deleted, after consistent matching between all the image pairs is found, the matching items are organized into a track, the track connects matched key points across a plurality of images for three-dimensional reconstruction of the next stage, and at least two key points are tracked in the three-dimensional reconstruction process of the next stage.

3) SFM is translated into a motion structure, aiming at reconstructing an unknown 3D scene structure and estimating the position and direction of an unknown camera according to a group of characteristic corresponding relations between images, beam adjustment is a key tool for obtaining strong 3D reconstruction from a large number of sparse images, and the beam adjustment is reliable in the aspects of image resolution, time, focal length variability and illumination variation;

first, estimating extrinsic and intrinsic parameters of an image pair, since beam adjustments tend to fall into poor local minima, many researchers have suggested that initial image to camera parameters should be chosen well, and that SPM initial image pairs should not only have a large number of matches, but should also have a large baseline so that the initial as-built scene can be reliably reconstructed, image pairs that are difficult to describe with a homography transform satisfy this condition, 2D image homography is a projection transform that maps points from one plane to another, RANSAC is used to find homographies between all image pairs with an outlier threshold of 0.4% of the maximum of image width and height, and the percentage of feature matches that are outliers from the estimated homographies are stored;

selecting an initial pair of images having the lowest percentage of pixels with respect to the homography image that has been restored, such pair of images matching at least 100, estimating the extrinsic parameters of the pair of cameras by using the five-point algorithm of Niste, then triangulating the trajectories visible in the pair of images, after a two-frame beam adjustment of this initial pair, adding another camera to the optimization, selecting the camera that checks the maximum number of estimated trajectories, and then initializing the new camera extrinsic parameters using the Direct Linear Transformation (DLT) technique, for this sac rand step using an outlier threshold of the maximum value of the image width or height, initialized with the focal length of the new camera and the focal length of the interchangeable image file format tag of the EXIF-JPEG image, for the estimation of the intrinsic camera matrix;

starting from the set of initial parameters, running a beam adjustment algorithm under the condition that the model is kept unchanged, only allowing a new camera and key points observed by the new camera to change, finally adding points observed by the new camera into an optimization algorithm, when at least one existing recovered camera observes the key points, carrying out triangulation on the key points, after triangulation, well estimating the position of the camera, estimating a condition by considering all ray pairs capable of triangulating the key points and finding out the ray pair with the maximum separation angle, if the maximum separation angle is larger than a threshold value, carrying out triangulation on the points, once a new key point is added, running another global beam adjustment to reconstruct a new scene, and finally, minimizing the error of solution through a sparse beam adjustment library, carrying out the process on all cameras until no camera can observe more reliable points for reconstructing 3D, thereby realizing the reconstruction of the construction site model;

4) The progress model generated by the progress management system has three expression modes, one mode is that in a traditional BIM platform, an as-built model is displayed on a planning model in a chromatic aberration mode or an as-built model is displayed in a planning model mode, the other mode is that a virtual model is superposed on a construction site, the progress is distinguished by color distinction, a manager can visually see the construction progress, the third mode is that the real appearance of the built-up building is used for showing the engineering progress, and the specific implementation process is introduced below;

the reconstructed model is aligned with the planned model to determine the absolute geographic coordinates of each camera, the absolute coordinates are estimated by translation, rotation and unified scale conversion of the image, the estimation method uses a closed form solution of the absolute orientation of the unit quaternion, the reconstructed model can be registered in the planned model, the planned model is registered as a built scene, the sparse 3D point set reconstructed in real time is registered in the control point set of the planned 3D model to reduce the residual sum of squares between the reconstructed point set and the model to the maximum extent, after alignment, the model reconstructed by the camera is superposed on the site being built on site, thus, in the view of the model reflecting progress:

the first way is that the manager can see the virtual 3D image of the plan model superimposed on the corresponding position of the construction project on the day of the inspection, if the schedule on the day of the inspection is completely finished, the virtual 3D image is displayed in dark green, if the schedule is built on the day of the inspection and is not finished, the virtual 3D image is displayed in light green, and if the schedule is not started, the virtual 3D image is displayed in red;

the second way is to show the real appearance of the building, and the BIM progress management system can show the planning model in the appearance in the real world, and the data is needed to form the effect: the method comprises the steps of providing a group of key points, wherein each key point comprises a 3D position and a color composition averaged from all live images where the key point is located, providing a group of cameras, wherein external parameters (translation and rotation) and intrinsic parameters (focal length and distortion in the height and width directions) are known, mapping between each key point and cameras where the key points are observed can be stored, a list of cameras where the key points are obtained, the position of the key points in local coordinates of the images and SIFT key point indexes can be stored through mapping, the data can be stored in a system, meanwhile, the cameras can be rendered into view cones, the view cones of the cameras can be mapped into resolution images through texture by accessing the cameras in a reconstructed scene, after the planning model and the reconstructed scene are registered, the planning model covers the reconstructed sparse scene, and the covered reconstructed sparse image is displayed as an image of the planning model, so that the real appearance of the built building is presented to a manager;

the third mode is a three-dimensional display mode of the traditional BIM progress management, namely, the progress is embodied in a mode of displaying color difference on a planning model on a BIM platform.

No matter how detailed planning is, all possibilities can not be anticipated, deviation can still be generated in project plan implementation, project progress is tracked, project change is controlled to be a main task in an implementation phase, after progress planning based on BIM is finished, a project implementation phase is entered, the implementation phase mainly comprises tracking, analyzing and controlling three contents, job progress is tracked, when distributed resources are completed, a task is actually known, deviation between an original plan and the project actual progress is checked, and potential problems are predicted: necessary deviation rectifying actions are taken to ensure that the project is stably developed under the constraint of a completion deadline and a budget;

in the progress planning stage, under the progress management system based on the BIM, a plurality of technologies such as WBS, a cross road map, a network plan, the BIM and the like are comprehensively applied to complete progress arrangement, allocate resources and estimate cost, and in the implementation stage, functions such as a progress curve, a Gantt chart, 4D simulation and the like provided by the progress management system based on the BIM can be used for tracking and controlling project progress;

the project plan after analysis and adjustment realizes the balance among range, progress and cost, and can be used as a target plan, and project operation defines progress information such as earliest starting time, latest starting time and the like, so the system can provide a plurality of target plans to be beneficial to progress analysis, the project target plan cannot be unchanged, and needs to be changed along with project progress;

the BIM-based progress management system provides creation and update of a target plan, the target plan can be distributed to each work, when the target plan is updated, all jobs can be selected to be updated, or jobs meeting a filtering condition are updated by using a filter, the type of data to be updated can be specified, after the target plan is updated, project progress calculation can be automatically carried out by the system, resource distribution is balanced, and resource requirements are guaranteed not to exceed the available quantity of resources, in the balancing process, the system takes the resource requirements of all calculated jobs as the maximum available quantity in the balancing process, in the work period, if the available resources are too few, the jobs are delayed, the resources to be balanced are selected, and after balancing priorities are added, projects or jobs which are balanced in priority under the condition of conflict can be specified, in addition, after the resource information is changed, the cost needs to be recalculated according to the project quantity provided by the BIM model so as to obtain a correct work cost value;

after a project plan is created, project progress needs to be tracked continuously, a BIM-based progress management system provides a plurality of tracking views such as a project table, a Gantt chart, a network chart, a progress curve, a four-dimensional model, a resource curve and a histogram, the project table displays project data in a table form, a project cross-track chart displays the project data in a horizontal cross-track chart format, the project cross-track chart/histogram displays project information in a column and cross-track chart format, time sharing project data in a parsing table or histogram format, the four-dimensional view dynamically displays a building construction process in a three-dimensional model format, a resource analysis view displays resource/project use information in a column and cross-track chart format, and time sharing resource allocation data in a parsing table or histogram format;

all the tracked views can be used for checking items, firstly comprehensive checking is carried out, then more detailed checking is carried out according to work decomposition structure, stage and specific WBS data elements, and functions such as filtering and grouping can be used for customizing the format and the hierarchy of information to be contained in the tracked views;

in the project implementation stage, progress information such as actual starting time of operation, visual progress completion percentage, actual completion time, actual construction period calculation, actual consumed resource quantity and the like needs to be periodically input into a system, sometimes, a work decomposition structure needs to be adjusted, operation is deleted or added, and the logic relationship among the operation is adjusted, the updating progress is important in the project development process, the actual construction period may be different from an original estimated construction period, the operation sequence may be changed as soon as the work starts, in addition, new operation and unnecessary operation also need to be added and deleted, the progress is periodically updated and compared with a target plan progress, resources can be effectively utilized, project cost is monitored by referring to budget, and the actual construction period and cost are timely obtained so as to implement a strain plan when necessary;

in the implementation stage, while maintaining a target plan and updating the progress information, the progress of the project needs to be continuously tracked, the plan is compared with the actual progress, the progress information is analyzed, the deviation and the problem are found, the problem is solved and the potential problem is prevented by adopting corresponding control measures, a progress management system based on BIM provides a plurality of analysis methods from different levels, the comprehensive analysis of the progress of the project is realized, the progress condition, the resource distribution condition and the cost condition need to be checked in the implementation stage, so that the development of the project tends to be consistent with the plan,

(1) progress analysis mainly comprises milestone control point influence analysis, key path analysis and comparison analysis of plan and actual progress, by checking milestone plans and key paths and combining actual completion time of operation, whether project progress is completed according to plan time can be checked and predicted, and key path analysis can be performed by using a cross view or a network view in a system;

referring to fig. 17, regarding the comparison between the planned progress and the time progress, generally, the cross-track graph comparison, the progress curve comparison and the model comparison are comprehensively utilized, and the system can simultaneously display three views to realize the comparison between the planned progress and the actual progress;

referring to fig. 18, the colors of the views can be set to realize the comparison between the planned progress and the actual progress, and in addition, through the comparison between the project plan progress model, the actual progress model and the field conditions, the growth process of the building can be clearly seen, and the progress condition and other problems in the construction process can be found;

(2) in the progress of a resource condition analysis project, the resource condition is mainly analyzed by checking whether the resource is over-distributed or under-distributed on the basis of checking the man-hour difference, based on a BIM progress management system, the resource distribution condition can be analyzed by providing a resource analysis table, a resource histogram or a resource curve in a system, a resource view can be combined with a Gantt chart tracking view to display the distribution condition and the use condition of the resource in a selected time period, and the resource distribution problem and the resource distribution are found in time;

(3) cost situation analysis most projects, particularly budget constrained projects, analysis of budget cost situations during the implementation phase is essential, if the actual progress information indicates that the project may exceed the budget, adjustments to the project plan need to be made, and BIM-based progress management systems may monitor expenses using cost profiling tables, histograms, cost control reports.

After the actual information of the operation is input into the system, the system automatically utilizes the planned value and the actual cost to calculate the earning value to evaluate the current cost and the progress performance, tracks the values for a long time, and can also view the past expenditure and the progress trend of the project, predict the future cost and analyze the earning value;

after the actual progress information is input into the system, through comparative analysis between the actual progress and the project plan, more deviations can be found, potential problems existing in the project are pointed out, in order to avoid the problems caused by the deviations, targets need to be continuously adjusted in the project process, appropriate measures are taken to solve the problems, the project often has the phenomenon that the completion time, the total cost or the resource allocation deviates from the original plan track, corresponding measures need to be taken to enable the project development to be consistent with the project plan, if the project has larger changes or seriously deviates from the project progress, the project progress needs to be rearranged, the target plan needs to be determined, the resource allocation and the budget cost need to be adjusted, and therefore the progress balance is achieved;

the deviation correction of project schedule can be realized by changing the duration of implementation work through rush hour and the like, but resource investment such as man-hour consumption and the like is usually required to be increased, a scheme with shortened construction period, less resource investment and less cost increase is selected by utilizing construction period-one resource or construction period-one cost optimization, the other method is realized by changing the logic relationship or the overlapping relationship of project implementation work, the duration of work is not changed, only the starting time and the ending time of work are changed, if the two methods are difficult to achieve the purpose of shortening the construction period, and the construction period is delayed too seriously, the project schedule needs to be readjusted, and a target plan is updated;

in the project progress, the main deviation rectifying measures for resource allocation are as follows: the main measures of adjusting the availability of resources, adjusting the allocation, such as increasing resources, replacing resources, delaying work or allocation, etc., splitting work to balance workload, adjusting project scope, and correcting cost are as follows: rechecking budget cost setting, such as each use cost of resources, fixed cost of operation and the like, shortening the operation period or adjusting the operation dependence to reduce the cost, properly adding, deleting or replacing resources to reduce the cost, reducing the project scope and reducing the cost;

the adjustment of the progress deviation and the update of the target plan need to take the factors of resources, cost and the like into consideration, and take appropriate measures such as organization, management, technology, economy and the like, so that the multi-aspect balance can be achieved, and the final purpose of progress management is realized.

Example 5

Referring to fig. 19, in the application of the project schedule management system based on BIM according to the present embodiment, the platform function design is as follows:

(1) The management of the transformer substation construction simulation project is realized, and the creation, deletion, import and export of projects are supported;

(2) The data import of a design result GIM format and a construction result IFC format of the transformer substation is supported;

(3) The import supporting the conventional three-dimensional model format comprises the following steps: STL, dgn, dwg, etc.;

(4) Operations such as query, modification and deletion of data are supported, and management and adjustment of terrain data are realized, wherein basic geographic information data comprise image data, digital elevation model data and basic vector data;

(5) The image data comprises satellite images, aerial images, scanned topographic maps and the like;

(6) The digital elevation model data comprises contour lines, discrete points and raster data, wherein the raster data is obtained by converting the contour lines or the discrete points;

(7) The basic vector data comprises administrative divisions, place names, residential areas, traffic, water systems, vegetation distribution, agriculture and forestry land and the like;

the method supports the import of single and integral models of a GIM model, an IFC model and a conventional three-dimensional model (stl, dgn, dwg, rvt, 3ds and dae), realizes the rapid analysis and visual display of the models based on a D3Station platform, and supports the checking of the attributes of the models;

the method is characterized by comprising the following steps of supporting the importing of terrain data such as Dem high-rise data, dom image data and oblique photography, realizing the analysis and visual display of the terrain data based on a D3Station platform, supporting the display of basic terrain data such as image data, digital elevation model data and basic vector data, wherein the image data comprises satellite images, aerial images, scanned terrain maps and the like, the digital elevation model data comprises contour lines, discrete points and grid data, the grid data is obtained by converting the contour lines or the discrete points, the basic vector data comprises administrative divisions, place names, residential areas, traffic, water systems, vegetation distribution, agricultural and forest lands and the like, the special data of a power grid comprises wind areas, ice-covered areas, dirty areas, earthquake divisions, waving areas, lightning areas, bird damage areas and the like, the channel data of a power transmission line comprises important industrial planning areas, environmental water conservation, mineral plant areas and other areas and cross-crossing data in the channel range of the line, and the surveying data comprises professional data such as measurement, hydrology, weather, geological exploration and geological exploration;

model structure, analyzing GIM and IFC model structures, supporting a model structure function panel, checking the hierarchical structure of the model, and performing highlight positioning of the model according to the model structure, wherein not only the imported model is incorporated into the model tree structure, but also the model arranged in the field is incorporated into the tree structure,

the model management comprises the following steps:

character model: a rich variety of character models are built in, the character varieties including: designers, supervisors, general engineers, etc., the attributes including: the height of the character, the animation action of the character, and the material of the character;

the vehicle model is as follows: a rich variety of vehicle models are built in, the vehicle variety comprising: ordinary car, tool car, etc. and the attribute includes: length of the vehicle, width of the vehicle, height of the vehicle, material of the vehicle;

vegetation model: the vegetation model of the abundant kind is built-in, and the vegetation kind includes: ordinary trees, trees such as arbor, shrub trees, etc. the attribute includes: the height of the tree and the material of the tree;

earthwork member model: the section information such as built-in foundation ditch, earthwork, the attribute includes: corresponding to the sectional dimension of the component and the material of the component, the component is placed in a linear drawing mode;

building component model: the built-in section information attributes of the ground, the wall surface, the road, the isolation fence and the like comprise: the method comprises the following steps of corresponding to the sectional dimension of a component, corresponding to the material of the component, placing the component in a linear drawing mode, building models such as a gate and a window in the component, and having the following attributes: size information and material information of the corresponding model;

the safety protection model comprises: the safety protection model of built-in rich kind, the safety protection model kind includes: safety warning lamp, safety warning sign etc. the attribute includes: the material of the safety protection model;

green civilization model: the green civilization model with rich varieties is built in, and the varieties of the green civilization model comprise: LED screen, nine cards one picture, etc., attributes including: the material of the green civilization model;

an adjacent electric device model: the built-in abundant kind faces electric equipment model, faces electric equipment model's kind and includes: lighthouse, switch box, electronic box, electric light, camera etc. the attribute includes: material of the temporary power equipment model;

mechanical equipment model: the construction machinery equipment model of built-in abundant kind, the mechanical equipment model includes: crane, tower crane, electric welding, bull-dozer, road roller etc. the attribute includes: the height, length and width of the mechanical equipment and the material of the mechanical equipment;

FBX editor: the method has the advantages that the editing of model actions is realized, animation production is carried out on the imported model in a displacement and rotation mode through the addition of key frames, all the imported models can be subjected to animation editing processing, the animation production of the models is realized, the models are embodied in the construction simulation process, animation editing work of corresponding actions can be carried out on different types of models, and an FBX editor is an important component for realizing construction simulation at present;

site arrangement: providing a transformer substation site layout area, placing various models in the three-dimensional view port, and supporting calling and placing model management modules, wherein the method comprises the following steps: the method comprises the following steps of selecting a character model, a vehicle model, a vegetation model, a land component model, a building component model, a safety protection model, a green civilization model, an electric equipment model and a mechanical equipment model, filling relevant parameters of the models, rapidly realizing placement of a site layout model in the transformer substation, and rapidly realizing refreshing linkage of the model structure after the models are placed.

The construction management personnel imports an engineering plan list, fills actual progress time along with engineering construction, realizes engineering plan and actual unified management, truly reflects actual difference, is convenient to master construction progress conditions of different characters, constructs a transformer substation construction project tree structure, supports new construction projects of a whole transformer substation project, deletion, import, export, plan progress information filling and actual progress information filling, creation of new support projects and sub-sets, deletion of deletion support projects and sub-sets, import supports import of conventional EXCEL, ACCESS and MPP format files, export supports export of EXCEL, ACCES and MPP format files, plan progress information filling can be manually filled or automatically filled through import files, and actual progress information filling can be manually filled or automatically filled through import files;

acquiring tree structure data in a model structure, establishing an association relationship among a construction milestone plan, a primary network plan and a two-dimensional network plan task by analyzing the corresponding relationship between a construction plan and a three-dimensional model, endowing a model with a time attribute, showing basic conditions by a member 4D, binding the model with each project in a project list, wherein the binding is not repeated, supporting multiple bindings, realizing the binding relationship between the tree structure model and the project plan list, and providing data support for 4D simulation of construction progress;

the time axis information of each project is displayed in a linkage mode through the construction project tree structure list, the project progress of each week, month and quarter can be quickly checked, the time axes of the planned progress and the actual progress can be visually checked, and the parts of the planned progress and the actual progress, which have difference, are displayed in red in the time axes;

generating an overall growth animation of the transformer substation through a binding relation between a planned progress and an actual progress information list and a model and a project time axis, controlling playing, pausing, accelerating and decelerating of the animation, dynamically displaying the overall construction progress of the project at different stages in a model growth mode according to the starting time and the ending time of the overall construction plan of the project, and simultaneously supporting visual display of a single construction progress, realizing dynamic progress display of different dimensions and granularity, and supporting animation display of simulation of the planned progress and the actual progress;

the method comprises the steps that the installation sequence among components of the equipment can be customized, a current equipment model is obtained, the equipment model is disassembled through an FBX editor, key frames are added through FBX, the installation process and sequence of the equipment from beginning to end are subjected to simulation through the combination of displacement and rotation of each component, and equipment installation simulation animation is generated;

the method comprises the steps of realizing the path setting of a model, setting the displacement position, time and speed of the model, simulating the approach of construction vehicles under different scenes and different processes by calling different construction vehicle models (transport vehicles, hoisting vehicles and the like), setting parameters such as vehicle running tracks, channel distances and output safety intervals, checking the safety intervals of vehicle transportation and optimizing the approach time sequence of the construction vehicles;

combining construction machinery construction equipment and hoisting equipment through an FBX editor, splitting the integral model in a manner of adding and adding key frames, and restoring the equipment hoisting simulation process through the combination of displacement and rotation of each part;

hard collision check, which is to detect whether collision between entities occurs in the simulation state of a transformer substation model in the simulation processes of equipment installation simulation, mechanical path simulation, equipment hoisting simulation and installation process simulation, wherein if the collision occurs, the check is unqualified, and the part of the model collision is highlighted;

soft collision checking, namely detecting whether the distance between two objects meets the requirement of the electric clearance or not through setting the parameter distance of the electric clearance in the model form of the transformer substation in the simulation state in the processes of equipment installation simulation, mechanical path simulation, equipment hoisting simulation and installation process simulation, and prompting and marking the safety value and the actual value between equipment or a building if the distance is unqualified;

the Project construction progress plan Project file is directly imported to automatically generate a Project progress plan which comprises the contents of plan names, plan contents, responsible persons, plan starting time, plan finishing time and the like, and the contents of each Project construction progress plan can be refined on the basis, so that the actual work requirements of construction management personnel are met, and the increase of work load caused by repeated progress plan compilation in a system is avoided;

the progress management module can edit personnel input plans of each project, compare the number of actual entrants and planned entrants through personnel input and output data accessed into the intelligent construction site personnel gate, prompt the situation of insufficient manpower arrangement, analyze the influence on the project construction progress possibly, assist managers to adjust constructor input, and ensure completion on schedule;

associating with a project progress planning task according to a GIM hierarchical structure, realizing three-dimensional model simulation of project progress, displaying project construction progress in real time, marking postponed, normal and non-construction item contents on the three-dimensional model through colors, providing assistant decision support for the progress management of field personnel, comprehensively utilizing an unmanned aerial vehicle and oblique photography technology to establish a real-scene model for really restoring a construction field, being used as a process recording file of project progress management, being used as a basis for construction management summarization and progress analysis, and providing a data support means based on the field real scene for the progress management;

the three-dimensional design model is disassembled and recombined through the BIM construction simulation technology, construction simulation is carried out on construction projects with complex construction processes and strict construction sequence requirements, construction simulation animations are generated and provided for construction teams and technicians to carry out technical background alternation, and the problem that the technical process is unclear due to the fact that the scene text schemes are obscure in background alternation is avoided.

It should be noted that, in this document, if there are first and second, etc., relational terms are only used for distinguishing one entity or operation from another entity or operation, and there is no necessarily any requirement or suggestion that any actual relation or order exists between the entities or operations. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising a," "8230," "8230," or "comprising" does not exclude the presence of additional like elements in a process, method, article, or apparatus that comprises the element.

The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims (10)

1. Project progress management system based on BIM, its characterized in that: the system comprises a data model, a progress management model and a comparison model;

the data model is generated by combining a three-dimensional data model expression method and a method for carrying out shielding inquiry on a plurality of viewpoints to identify hidden pieces in an assembly body, the progress management model establishes a real-time model and generates a corresponding calculation model according to the analysis of the data model structure, and the comparison model superposes and compares the real-time model and the plan model to provide a scheme for deviation correction and adjustment of the construction progress.

2. The BIM-based project schedule management system of claim 1, which is characterized in that: the data model comprises a power grid three-dimensional information model, the power grid three-dimensional information model is converted into a surface model through a scanning entity, and the method specifically comprises the following steps:

assuming that points before scanning are A (XA, YA, ZA), B (XB, YB, ZB) \8230 \\8230andK (Xk, yk, zk), scanning vectors V (XV, YV, ZV), and scanning the points along the scanning vectors V to obtain An, bn \8230 \8230andKn, and a line-surface net formed by the points is a boundary model of 3 DGIS:

An＝A+V，Bn＝B+V……Kn＝K+V

for the Curve scanning, the following formula is used to calculate the tangent vector of the Curve Curve = (M1 (X1, Y1, Z1), M2 (X2, Y2, Z2) \8230; mn (Xn, yn, zn)) is Hn = Xn-Xn-1, yn-Yn-1, zn-Zn-1, and if one point is a point A' after A (XA, YA, ZA, 0) scanning, where N is the surface normal:

and the conversion from the solid model to the boundary model is realized in the same way.

3. The BIM-based project schedule management system of claim 2, wherein: the three-dimensional data model comprises a solid model and a mesh model, wherein the solid model is used for describing the geometric and topological information of the part, and the mesh model adopts a polygonal patch to form the geometric shape of the object.

4. The BIM-based project schedule management system of claim 3, characterized in that: the method for conducting occlusion query by the plurality of viewpoints to identify the hidden part in the assembly body comprises the following steps:

(1) Generating a query object ID for an object to be queried;

(2) Starting occlusion query;

(3) Rendering an object needing to be subjected to shielding query;

(4) Ending the occlusion query;

(5) Extracting the number of samples queried by occlusion;

(6) And deleting the ID of the query object and recycling resources.

5. The BIM-based project schedule management system of claim 4, wherein: in the identification algorithm of the hidden part, the visibility value of the part at a certain view point is calculated as follows:

wherein: lambda [ alpha ] ₁ +λ ₂ +λ ₃ ＝1；

Wherein λ is ₁ 、λ ₂ And λ ₃ For weighting, the component visibility, the component area contribution and the component volume contribution occupy the same weight, i.e. lambda, is initially set ₁ 、λ ₂ And lambda ₃ Are all 1/3;

after the part i completes the shielding inquiry at all the set viewpoints, the maximum visibility value of the part i is obtained, namely the maximum visibility value

Defining a critical parameter F _T (0<F _T <1) When the F value of a certain part in the assembly body is larger than the critical parameter, the part is visible when the part is observed outside the assembly body, otherwise, the part is a hidden part.

6. The BIM-based project schedule management system of claim 5, wherein: the hidden part identification algorithm evaluates the vertex priority value C (v) together through the positions of the vertexes in the buffer memory and the degrees of the vertexes, and the priority value C (R) of the triangle ring is the sum of the vertex priority values of all the unoutput triangles in the ring

The vertex priority value C (v) may be calculated by the following formula:

C(v)＝C _p (v)+C _a (v)

wherein,

in the above formula, p represents the position of the vertex v in the buffer, s represents the size of the buffer space, a represents the number of non-output triangles adjacent to the vertex v, k ₁ 、k ₂ 、k ₃ Are coefficients.

7. The BIM-based project schedule management system of claim 6, characterized in that: the model primitive data structure of the three-dimensional information model of the power grid comprises basic data and extended data, wherein the basic data comprises geometric data, physical data and functional data, and the extended data comprises technical data, economic data and management data.

8. The BIM-based project schedule management system of claim 7, which is characterized in that: the real-time model comprises statistical distribution of process duration, the statistical distribution comprises normal distribution, beta distribution, uniform distribution and triangular distribution, in the normal distribution, the mean value, the median and the mode of the process duration coincide, the probability that the process duration is greater than or less than the mean value is equal, the probability that the process is delayed or advanced is equal, in the beta distribution, the distribution range is in [0,1], and the distribution formula of the beta distribution is as follows:

(1) Mean value:

(2) Variance:

the value ranges of alpha and beta are 0:0.1:10000, the value range of the mean value is 0.3:0.05:0.5, the simulation results are stored in the matrix respectively, the first column is alpha value, the second column is beta value, and the third column is variance value.

9. The BIM-based project schedule management system of claim 8, which is characterized in that: in the beta distribution, the safe time is the difference between the duration under 95% completion probability and the duration under 50% completion probability in the working procedure, and the formula is as follows:

T _k ＝[F(x)I _x＝0.95 -F(x)I _x＝0.5 ]×t _k

wherein F (x) is a distribution function of the beta distribution,T _k safe time for Process k, t _k The duration of process k.

10. An application of the BIM based project schedule management system according to any one of claims 1-9, characterized in that: the progress management system is applied to the management of the transformer substation construction simulation project, and is based on a D3Station platform, so that the analysis and the visual display of the model are realized, and the attribute of the model is supported to be checked.

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