CN115859645A - Modelica language-based hydraulic system model base construction method - Google Patents
Modelica language-based hydraulic system model base construction method Download PDFInfo
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Abstract
The invention discloses a hydraulic system model base construction method based on a Modelica language, which comprises the following steps: the method comprises the following steps that firstly, according to the physical characteristics and functions of the structure of a hydraulic system, the hydraulic system is decomposed into a basic layer model, a realization layer model and an application layer model; step two, constructing a universal base layer model by using a Modelica language; step three, constructing a hydraulic component realization layer model by using a Modelica language, wherein the hydraulic component realization layer model is constructed according to the design principle and the characteristics of the hydraulic component and a real test curve; and fourthly, establishing and testing an application layer model of the typical hydraulic system, wherein the application layer model realizes combination and information transmission between the layer models and external equipment through the hydraulic component parts through the connector. The model base construction method disclosed by the invention gets rid of the limitation of a simulation tool to the maximum extent, and is stronger in applicability.
Description
Technical Field
The invention belongs to the field of modeling and simulation of a hydraulic system in an electromechanical system, and particularly relates to a hydraulic system model base construction method based on a Modelica language.
Background
The hydraulic transmission is derived from the hydrostatic principle found in pascals, a typical application of which is, for example, a hydraulic jack, implementing a jack with four or two dials. The hydraulic transmission has the advantages of high power-weight ratio, flexible control mode, easy realization of stepless speed regulation, safety, reliability, easy realization of overload protection and the like, thereby being widely applied to various industries which are closely related to our lives, such as aerospace, heavy industry machinery, industrial machine tools, steel smelting, injection molding and die casting, automobile manufacturing, agricultural machinery and the like. Meanwhile, along with the development of intelligent manufacturing in recent years, the hydraulic technology is further developed towards the direction of miniaturization, intellectualization and flexibility, and the hydraulic technology is also mature and applied to some humanoid robots and wearable equipment. The application of the hydraulic transmission technology in engineering needs coupling mechanical structure stress, electrical control, fluid control, heat transfer analysis and software control strategies, and the decoupling analysis of a complex hydraulic system cannot completely describe the transient and steady-state response characteristics of the system through a mathematical equation in a single field. The complex system is disassembled according to the functional discipline characteristics by using a model library mode, the characteristic equation definition of the element part is respectively completed in a single field, and the modular construction and solution of the hydraulic system are completed by applying a unified platform modeling tool and a solution platform, so that the modeling simulation analysis method which is universal in the industry at present is also formed.
At present, hydraulic system modeling simulation software in the market is basically monopolized by products of foreign software companies, the foreign software companies generally do not open bottom codes of software models to the outside in order to ensure the core competitiveness of the foreign software companies, so that the software models cannot be modified and customized and developed, model resources of different software cannot be called mutually due to different storage data formats of the models and model libraries, joint simulation interfaces are not opened or opened in a limited way, and the realization of the joint simulation operation is complex. Most modeling software has poor readability of English interfaces, limited modification permission is only opened for parameter setting and simulation, the modification which is more in line with the actual engineering cannot be carried out by contrasting equations, modeling personnel cannot complete modeling simulation on the basis of deeply understanding the physical background, and modeling simulation needs to be simplified and approximately completed on the basis of adapting to the modeling software.
The model library is used as the basis of system simulation and has very important significance for the development of industrial software. The development and application of the independent intellectual property model base in China are blank, the development of the independent controllable model base is carried out based on the method, the accumulation and the reuse of knowledge can be realized, the independent intellectual property is possessed, and the digital process is not limited by people.
Disclosure of Invention
In order to solve the technical problem, the invention provides a hydraulic system model base construction method based on a Modelica language. The method is a modeling method based on the same platform, can realize seamless integration of the hydraulic system, effectively reduces the difficulty and complexity of a hydraulic system model library, increases the reusability and expansibility of the model, and shortens the research and development period and the cost of the hydraulic system.
In order to achieve the purpose, the invention adopts the technical scheme that:
the invention provides a hydraulic system model base construction method based on a Modelica language, which comprises the following steps:
the method comprises the following steps that firstly, according to the physical characteristics and functions of the structure of the hydraulic system, the hydraulic system is decomposed into a basic layer model, a realization layer model and an application layer model;
step two, a Modelica language is used for constructing a general basic layer model which comprises a medium, a connector and a single-function sub-function model;
step three, constructing a hydraulic component realization layer model by using a Modelica language, wherein the hydraulic component realization layer model is constructed according to the design principle and the characteristics of the hydraulic component and a real test curve;
and fourthly, establishing and testing an application layer model of the typical hydraulic system, wherein the application layer model realizes combination and information transmission between the layer models and external equipment through the hydraulic component parts through the connector.
Optionally, the method for constructing the hydraulic system model library includes: converting a physical model corresponding to the hydraulic component model into a mathematical model expressed by an equation by utilizing a mass continuity principle, a momentum conservation principle and an energy conservation principle; and converting the mathematical model into a Modelica model of the corresponding component by using a modeling software platform and a Modelica language.
Optionally, the base layer model is characterized in that most functions of the model can be embodied only by being inherited, and a single base layer model generally has no independent function, and some base layer models are not even closed. The medium model comprises two media of water and hydraulic oil commonly used by a hydraulic system; the connector comprises a mechanical connector, a hydraulic connector and a signal connector; the single function subfunction comprises various physical property interpolation functions established according to different media.
Alternatively, the implementation layer model is characterized in that all elements can be directly used and have specific functions. The hydraulic component realization layer model comprises basic components in the hydraulic field and is divided into a power element, a control element, an execution element and an auxiliary element according to the composition of a hydraulic system; after the hydraulic component realization layer model is constructed, the method further comprises the following steps: carrying out simulation verification on the hydraulic component realization layer model, and judging whether a simulation result is in accordance with an expected theoretical result or not through comparison; and if the simulation result is not accordant with the expected theoretical result, modifying the model topology, the parameter configuration and the like of the hydraulic component realization layer model until the simulation result is accordant with the expected theoretical result.
Alternatively, the application layer model is characterized in that the components in the model library can generally directly find the corresponding product in the hydraulic system. After the hydraulic system test model is constructed, the method further comprises the following steps: carrying out simulation verification on the hydraulic system test model, and judging whether a simulation result is in accordance with an expected theoretical result or not through comparison; and if the simulation result is not accordant with the expected theoretical result, modifying and adjusting the hydraulic system test model until the simulation result is accordant with the expected theoretical result.
Has the advantages that:
the hydraulic system is constructed based on Modelica language to realize statement type modeling, modelica is used as a multi-field unified modeling language based on an equation, object-oriented and strong componentization modeling capacity, the requirement of the modeling simulation development direction is met, and the modeling method is suitable for modeling and simulation of various subsystem models such as hydraulic transmission and large-scale complex physical systems. Meanwhile, the Modelica model adopts mathematical description of differential, algebraic and discrete equations, has the characteristics of universality, openness and standardization, adheres to statement modeling and object-oriented modeling, and has good reusability, reconfigurability and expandability, so that in the modeling of the hydraulic system, the development difficulty is reduced, the reusability is increased, the working efficiency is improved, and the system can reflect an actual physical system.
According to the model library model building method, the model library specifications and the process based on Modelica are used for building the model library typical element and component models of the autonomous hydraulic system to form the model library with autonomous intellectual property rights, and the models are reusable and expandable. The modularized, standard and reusable simulation component is provided for the design and research and development of a hydraulic system, and a more efficient auxiliary design means is provided for the research and development of new products. The model is developed from the source code level, the limitation of a simulation tool is eliminated to the maximum extent, a closed foreign software 'black box' model is converted into a 'white box model' for mastering the source code, and the model can be optimized by correcting a formula and an algorithm behind the model when the accuracy of the model is insufficient. The model can be used under any tool supporting Modelica language, and the model is more applicable. And the aim of valve simulation calculation according to a real test curve in system simulation is realized for the first time.
Drawings
FIG. 1 is a general flow diagram of the method of the present invention.
FIG. 2 is an exploded view of a hydraulic system model library according to an embodiment of the present invention.
Fig. 3 is a tree diagram of a hydraulic system model library according to an embodiment of the present invention.
4a, 4b, 4c and 4d are comparison graphs of expected models built by mature commercial software and models built by a hydraulic system model library in the invention, and comparison graphs of simulation results; fig. 4a is an expected model constructed by using mature commercial software, fig. 4b is a model constructed by using a hydraulic system model library according to the present invention, fig. 4c is a simulation result of the expected model constructed by using the mature commercial software, and fig. 4d is a simulation result of the model constructed by using the hydraulic system model library according to the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments, and all other embodiments obtained by a person skilled in the art based on the embodiments of the present invention belong to the protection scope of the present invention without creative efforts.
In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
An embodiment of the present invention provides a method for constructing a hydraulic system model library based on a Modelica language, and referring to fig. 1, fig. 1 is a flowchart of a method for constructing a hydraulic system model library based on a Modelica language provided in an embodiment of the present invention, it should be understood that the method may further include additional blocks not shown and/or may omit the blocks shown, and the scope of the present invention is not limited in this respect. The invention comprises the following steps:
the method comprises the following steps that firstly, according to the physical characteristics and functions of the structure of a hydraulic system, the hydraulic system is decomposed into a basic layer model, a realization layer model and an application layer model;
step two, a Modelica language is used for constructing a general basic layer model which comprises a medium, a connector and a single-function sub-function model;
step three, constructing a hydraulic component realization layer model by using a Modelica language, wherein the hydraulic component realization layer model is constructed according to the design principle and the characteristics of the hydraulic component and a real test curve;
and fourthly, establishing and testing an application layer model of the typical hydraulic system, wherein the application layer model realizes combination and information transmission between the layer models and external equipment through the hydraulic component parts through the connector.
Specifically, in the first step, the hydraulic system model base is divided into three layers according to the physical characteristics and functions of the hydraulic system structure:
base layer: most basic parts are inherited and used, and comprise working media, abstract classes, icons, interfaces and subfunctions with single functions; the basic layer model library is characterized in that most functions of the models can be embodied only by being inherited, and an independent basic layer model generally has no independent function, and some models are even not closed (cannot be solved);
and realizing a layer: the method comprises the following steps of providing basic component libraries in various fields, wherein the basic component libraries comprise a pneumatic library, a thermal fluid library, a hydraulic library and an electromagnetic library; in the implementation layer, all elements can be directly used and have specific functions;
an application layer: and constructing a model library according to the parts and components of the hydraulic system, wherein the components in the model library can generally directly find corresponding products in the hydraulic system.
The basic layer among the three layers is the bottommost layer, and the implementation layer is supported. The application layer is the uppermost layer, which is the layer that ultimately faces the user. If a completely new model library is constructed from scratch, the model library must be constructed from the base layer; if the construction of the model base is carried out on the basis of the existing model base, the model base can be constructed from the implementation layer or the application layer in an inheritance mode.
The method constructs and hierarchically divides the model base according to the basic principle of the table 1.
TABLE 1 model library construction and hierarchy partitioning principles
the medium model in the invention comprises two media of water and hydraulic oil commonly used in a hydraulic system.
Each medium contains physical parameters such as density, kinematic viscosity, bulk modulus, etc., and is calculated by temperature. Then, the temperature is taken as an abscissa, the physical property parameter is taken as an ordinate, a physical property parameter graph is drawn, and finally, a physical property parameter function with the temperature T as an independent variable is obtained by an interpolation method, such as a density formula:
ρ＝ρ 0 (1-α*Δt)
the equation is an ideal hydraulic oil density transformation equation and can be used for establishing a component-level model control equation. When the temperature is known, all the required physical property parameters can be calculated by the method. The physical properties of each medium can be inherited by the component model, and are called and calculated by a mathematical formula in the component model.
And establishing a medium subfunction in the model library base layer, and establishing various physical property interpolation functions according to different working media.
The names and functions of the subfunctions contained in each medium of the method of the invention are shown in the following table 2:
TABLE 2 Medium Functions Table
| Name of formula | Function(s) |
| Rho_T | Knowing the temperature, calculating the density |
| Viscosity_T | Knowing the temperature, calculating the kinematic viscosity |
| K_T | Temperature, calculation of bulk modulus of elasticity |
The connector comprises a mechanical connector, a hydraulic connector and a signal connector; in the Modelica language, the connection between models is implemented by a connector (connector), which is a special type and is a method for exchanging information between models and models. Meanwhile, the modeica language specifies two variable forms, namely: "cross" variables (also called potential or utility variables) and "cross" variables (also called flow variables). The principle of "potential equality, flow sum zero" is followed.
The variable P in the hydraulic connector represents the pressure and the variable v _ flow represents the volume flow. The volume flow v _ flow statement has a flow qualifier. The flow qualifier tells the Modelica compiler that v _ flow is a pass through variable.
The mechanical connector is divided into translation and rotation: the translation connector comprises a traversing variable f (force) and a traversing variable x (displacement); the traversing variable in the rotating coupling is torque and the traversing variable is phi (angular displacement).
Specifically, in the third step, a hydraulic component implementation layer model is constructed by using Modelica, and the method specifically includes:
the hydraulic component realization layer model comprises basic components in the hydraulic field, and is divided into a power element, a control element, an execution element, an auxiliary element and the like according to the composition of a hydraulic system; the power element comprises a constant-voltage source, a constant-current source and various hydraulic pumps, and the control element mainly comprises various control valves: the hydraulic control system comprises a pressure control valve, a flow control valve, a directional control valve and the like, wherein an executing element comprises various hydraulic cylinders, hydraulic motors and the like, and an auxiliary element comprises an oil tank, a pipeline, a containing cavity, a sensor and the like.
All element icons of the hydraulic element part realization layer model library are drawn according to a Modelica standard and by referring to element shapes or international universal element icons.
The hydraulic component realization layer model library has high debugging and sample test error reporting rate and error reporting points are difficult to determine due to the fact that the number of components is large. For example, the simplest throttle valve has only one theoretical formula on a manual, and the flow is calculated according to the pressure flow area, but the calculation cannot be completed if only the one formula is used in model development.
The problems encountered in the actual development of the model are much more complex than those briefly described in the engineering manual. For example, the energy forward and backward transfer problem, the curve 0-point crossing problem.
In engineering application, the flow-pressure characteristics of each hydraulic valve are different, and the different characteristic curves of each manufacturer due to the existence of the machining process are not the same. The flow-pressure characteristic curve calculated by the flow coefficient is different from the actual test data. The curve of the change rate of the added flow is not possessed by all the existing hydraulic simulation software.
In engineering application, because the reversing valve is provided with a plurality of valve ports, the flow-pressure characteristics corresponding to each valve port are different, and the existing simulation software only gives the flow change rate of each port, which is a straight line, and has larger difference with practical application.
In all completed hydraulic component realization layer model libraries, an IR-C-IR pipeline is a model which consumes the longest time, the difficulty of model development is increased due to the fact that resistance, capacitance and inertia exist in the same pipeline at the same time, experimental pressure-flow calculation and sectional calculation cannot meet the requirement of example calculation, and the example target is realized through multiple times of experiments and mass flow sectional calculation.
Specifically, the step four of establishing and testing an application layer model of a typical hydraulic component system specifically includes two methods:
the method comprises the following steps: comparative test of test curves
In reality, all hydraulic component data are designed through theoretical calculation, then various parameter curves of components are drawn through test of a test bed, and the products are optimized through comparison of the test curves and the theoretical design curves. The model developed by the Modelica language is also obtained from real hydraulic components, and the theoretical development model is checked and optimized by a test curve to achieve the expected accuracy of the model. The method has high cost, the test curve is not easy to obtain, and the optimization period is long.
The second method comprises the following steps: mainstream business software contrast testing
In the modern simulation field, a great number of system simulation software such as AMESim, simulink, simlationX and the like are mainstream simulation tools, and development elements of the autonomic model library are basically consistent with elements of the mainstream simulation tools, so that the development elements can be tested and verified through the mainstream simulation tools.
A typical model in a hydraulic system model base test model is a servo hydraulic system controlled by a position, under the action of constant pressure, a signal input end of a proportional valve inputs a certain step position signal, and under the control of PID, a hydraulic cylinder outputs a displacement consistent with the signal input end. 4a, 4b, 4c and 4d are the comparison of a prospective model built by mature commercial software and a model built by a hydraulic system model library in the invention, and the comparison of simulation results.
Although the illustrative embodiments of the present invention have been described in order to facilitate those skilled in the art to understand the invention, it is to be understood that the invention is not limited in scope to the specific embodiments, but rather, it will be apparent to those skilled in the art that various changes may be made without departing from the spirit and scope of the invention as defined and defined in the appended claims, and it is intended that all matter contained in the invention and created by the inventive concept be protected.
Claims (5)
1. A hydraulic system model base construction method based on a Modelica language is characterized by comprising the following steps:
the method comprises the following steps that firstly, according to the physical characteristics and functions of the structure of the hydraulic system, the hydraulic system is decomposed into a basic layer model, a realization layer model and an application layer model;
step two, constructing a basic layer model by using a Modelica language, wherein the basic layer model comprises a medium, a connector and a single-function sub-function model;
step three, constructing a hydraulic component realization layer model by using a Modelica language, wherein the hydraulic component realization layer model is constructed according to the design principle and the characteristics of the hydraulic component and a real test curve;
and fourthly, establishing and testing an application layer model of the hydraulic system, wherein the application layer model realizes combination and information transmission between the layer models and external equipment through the hydraulic component parts through the connector.
2. The Modelica language-based hydraulic system model base construction method according to claim 1, wherein the first step specifically comprises the following steps:
the basic layer is used by inheritance and comprises media, abstract classes, icons, interfaces and subfunctions with single functions;
the realization layer is a basic component library in each field, and comprises a pneumatic library, a thermal fluid library, a hydraulic library and an electromagnetic library; in the implementation layer, all elements can be directly used and have specific functions;
the application layer is a model library constructed according to parts and components of the hydraulic system, and elements in the model library can directly find corresponding products in the hydraulic system.
3. The Modelica language-based hydraulic system model base construction method according to claim 1, wherein the second step specifically comprises the following steps:
the medium model comprises two media of water and hydraulic oil commonly used by a hydraulic system; the connector model comprises a mechanical connector, a hydraulic connector and a signal connector; the subfunction with single function includes various physical property interpolation functions established according to different media.
4. The Modelica language-based hydraulic system model base construction method according to claim 1, wherein the third step specifically comprises the following steps:
the hydraulic component realization layer model comprises basic components in the hydraulic field and is divided into a power element, a control element, an execution element and an auxiliary element according to the composition of a hydraulic system; after the hydraulic component realization layer model is constructed, the method further comprises the following steps: carrying out simulation verification on the hydraulic component realization layer model, and judging whether a simulation result is in accordance with an expected theoretical result or not through comparison; and if the simulation result is not accordant with the expected theoretical result, modifying the model topology and the parameter configuration of the hydraulic component realization layer model until the simulation result is accordant with the expected theoretical result.
5. The Modelica language-based hydraulic system model base construction method according to claim 1, wherein the fourth step specifically comprises the following steps:
constructing the hydraulic system test model, performing simulation verification on the hydraulic system test model, and judging whether a simulation result is in accordance with an expected theoretical result or not through comparison; and if the simulation result is not accordant with the expected theoretical result, modifying and adjusting the hydraulic system test model until the simulation result is accordant with the expected theoretical result.
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| CN116257942A (en) * | 2023-05-16 | 2023-06-13 | 东方空间技术(山东)有限公司 | Rocket simulation model determining method and device |
| CN116257942B (en) * | 2023-05-16 | 2023-08-15 | 东方空间技术(山东)有限公司 | Rocket simulation model determining method and device |
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