CN118305576A

CN118305576A - Automatic docking system and method for ultra-low temperature fluid delivery

Info

Publication number: CN118305576A
Application number: CN202410729701.2A
Authority: CN
Inventors: 杨亮; 肖立; 许佳伟; 扬帆; 宋坤; 郝思佳; 邱灶杨; 范嘉堃; 盖小刚; 李方遒; 陈举; 李欣欣; 袁思琪
Original assignee: CNOOC Gas and Power Group Co Ltd
Current assignee: CNOOC Gas and Power Group Co Ltd
Priority date: 2024-06-06
Filing date: 2024-06-06
Publication date: 2024-07-09
Anticipated expiration: 2044-06-06
Also published as: CN118305576B

Abstract

The invention relates to an automatic docking system and method for ultra-low temperature fluid delivery, comprising the following steps: a loading arm main body and an automatic docking control device; the loading arm main body comprises a stand column, a gas phase loading arm and a liquid phase loading arm which are arranged on the stand column, can freely rotate and are not interfered with each other; the automatic docking control device comprises a target identification and positioning module, a path planning module and a servo control module; the target identification positioning module is used for realizing identification positioning of a target butt joint pipe orifice; the path planning module is used for planning the movement path of the loading and unloading arm according to the identification and positioning result of the target butt joint pipe orifice to generate a movement track; the servo control module is used for controlling the position and the gesture of the loading arm main body according to the motion track, and realizing automatic butt joint and fluid delivery of the loading arm and a target butt joint pipe orifice. The invention can be widely applied to the field of fluid transportation.

Description

Automatic docking system and method for ultra-low temperature fluid delivery

Technical Field

The invention relates to an ultralow temperature fluid conveying automatic docking system and method, in particular to an ultralow temperature fluid conveying automatic docking system and method applicable to a liquefied natural gas or liquid hydrogen conveying system, and belongs to the field of fluid conveying.

Background

The floating liquefied natural gas production storage and offloading device (LNG Floating Production Storage and offloading Unit, FLNG) is a floating production device for offshore natural gas field development, is positioned on the sea through a mooring system, has the functions of exploiting, processing, liquefying, storing and loading and unloading natural gas, and realizes the exploitation and natural gas transportation of the offshore natural gas field by being matched with a liquefied natural gas (Liquefied Natural Gas, LNG) ship. The development of the offshore natural gas field by using the FLNG ends the single mode that the offshore natural gas field can only be transported by pipelines to land, so that the transportation cost is saved, and the land space is not occupied. In addition, FLNG can also be used for the second time after the offshore natural gas field is exploited, and is arranged in other offshore natural gas fields, so that the economic performance is higher.

The LNG unloading arm is a rigid hinged pipeline system which is arranged on a stacking head or FLNG and used for unloading LNG, and the main structure comprises a rotary joint, an outer arm, an inner arm, a basic vertical pipe, a rotary joint connecting the inner arm and the basic vertical pipe, and other process pipelines, supporting structures and accessories. The large LNG unloading arm stands at the forefront end of a wharf zone of an LNG receiving station, is used as key core equipment for connecting an LNG ship with a land pipeline and a storage facility of the receiving station, and is a throat of the whole receiving station. When the LNG carrier arrives at the special wharf of the receiving station, LNG is fed into the storage tank of the receiving station by the cryogenic pump on the ship through the liquid phase unloading arm and the unloading pipeline, and Boil-Off Gas (BOG) Gas in the storage tank is returned to the LNG carrier through the Gas return pipeline and the gaseous Gas return arm. In the LNG unloading arm operation process, the end part of the LNG unloading arm and the receiving end of the LNG carrier are guided to be interconnected through the traction wire, so that accurate butt joint can be ensured under the condition of relative motion, and the hydraulic system of the LNG unloading arm is controlled, so that the LNG unloading arm can bear the influence of speed and acceleration caused by the motion of a ship body.

Aiming at the severe sea conditions of deep open sea in south China, if the existing mooring technology and the traditional rigid unloading arm are difficult to effectively solve the problem of differential motion between the FLNG floating platform and the carrier of the transport ship, a LNG low-temperature external conveying and unloading system with special design is needed to meet the severe requirements of low-temperature and shaking working conditions. The LNG low-temperature hose conveying system has obvious comprehensive advantages in the aspects of weight, flexibility, corrosion resistance, heat insulation and the like, and an effective mode is to adopt serial mooring, namely, the LNG low-temperature hose conveying system is connected with an LNG carrier through a mooring rope, and is used for unloading LNG, so that the cryogenic hose is required to bear ultralow temperature, and meanwhile, the influence of relative motion between the FLNG and the LNG carrier is required to be overcome.

The transportation of LNG on land generally adopts tank trucks, and because the loading and unloading working environment between LNG and tank trucks is complicated, the loading and unloading arm structure characteristics and the control performance of realizing intermediate transmission work have extremely high requirements, the stability and the flexibility of the loading and unloading arm support system, which adapt to external load change, must be ensured during operation, and the safe and stable transmission of LNG is finally realized. The working principle of the mode is also applicable to the land liquid hydrogen loading and unloading prying technology.

In addition, the liquid hydrogen shipping test has been successfully implemented, a more economic and safe way is provided for the liquid hydrogen industry chain, the method has positive significance for the popularization and use of hydrogen energy in the global scope, and the method has stronger development potential in the future. The liquid hydrogen has the characteristics of ultralow temperature, easy volatilization, inflammability and explosiveness, and has the advantages of high loading and unloading and conveying difficulty on the liquid hydrogen ship bank, high safety requirement and multiple technical barriers. The hydraulic hydrogen ship shore loading and unloading system has the advantages of severe operation condition, severe operation precision requirement and complex electromechanical system coordination, has the functions of quick docking, emergency release, automatic closing and the like, bears the ultralow temperature cryogenic test at minus 253 ℃ for a long time, automatically adapts to the influence of tide fall, and only few countries in the world master the key design and manufacturing technology.

In conclusion, the key technology of the ultralow temperature fluid conveying system such as the LNG rigid unloading arm, the LNG low-temperature hose conveying system, the LNG and liquid hydrogen loading and unloading shore loading and unloading system and the like relates to a plurality of links such as low-temperature material selection, molding manufacturing, sealing, test verification and the like. The material selection and structural design difficulty is high, the processing and manufacturing and performance testing work is difficult, the ultra-low temperature sealing, connection and leakage monitoring difficulty is high, the whole ultra-low temperature fluid conveying system is complex in structure, and the safety requirement is high.

At present, the ultra-low temperature fluid conveying system mainly has the following technical defects,

1) The butt joint is completed manually, and the efficiency is low. The existing operation mode mainly relies on manual intervention, a worker operates the loading arm to move to complete the butt joint by closely observing the position relation between the loading arm for the vehicle and the butt joint part of the tank truck, and the operation mode has high labor intensity and low manual operation efficiency;

Take LNG and liquid hydrogen handling skid as examples: the low-temperature loading and unloading arm is used as a core component on the skid and is directly in butt joint with the external tank car, and the operation difficulty of the low-temperature loading and unloading arm determines whether the whole skid-mounted equipment is good or not. At present, each tank car operator can only charge two loading and unloading sleds and two tank cars, and a two-shift work mode is implemented, so that the tank car loading process is complicated, and the operation process needs to manually rotate 5-7 valves for more than 10 times. The sequence is easy to make mistakes, the operation safety is lower, the whole process is time-consuming and labor-consuming, the labor intensity is higher, and the intelligent upgrading is imperative.

2) The potential safety hazard is high. The liquefied natural gas in the transportation pipe has high pressure and low temperature, the whole current process is completed by manual operation, and the operation mode has high repeatability, is easy to generate visual fatigue and has certain potential safety hazard in manual operation.

Therefore, the loading and unloading arm is ensured to be safe and stable in quantitative loading, and meanwhile, the economic performance of easy and simple operation, time saving and labor saving can be realized, so that the loading and unloading arm is a mainstream trend of future development. Thereby advancing the realization of the crossing from the traditional management mode to the modernization, the digitization and the intellectualization.

Disclosure of Invention

Aiming at the problems, the invention aims to provide an ultralow temperature fluid conveying automatic docking system and method, which take machine vision and robot kinematics as cores, and solve the problem of automatic docking of a loading arm by combining the technologies of computer technology, motion control technology and the like, thereby realizing the automatic docking function.

In order to achieve the above purpose, the present invention adopts the following technical scheme:

In a first aspect, the present invention provides an ultra-low temperature fluid delivery auto-docking system comprising:

a loading arm main body and an automatic docking control device;

the loading arm main body comprises a stand column, a gas phase loading arm and a liquid phase loading arm which are arranged on the stand column, can freely rotate and are not interfered with each other;

the automatic docking control device comprises a target identification and positioning module, a path planning module and a servo control module;

the target identification positioning module is used for realizing identification positioning of a target butt joint pipe orifice;

The path planning module is used for planning the movement path of the loading and unloading arm according to the identification and positioning result of the target butt joint pipe orifice to generate a movement track;

The servo control module is used for controlling the position and the gesture of the loading arm main body according to the motion track, and realizing automatic butt joint and fluid delivery of the loading arm and a target butt joint pipe orifice.

Further, the gas phase loading and unloading arm comprises a gas phase inner arm, a gas phase rotary joint, a gas phase spring cylinder balance system, a gas phase air bag switch main valve, a gas phase air bag purging valve, a gas phase outer arm and a gas phase three-dimensional joint;

The gas-phase inner arm, the gas-phase outer arm and the gas-phase three-dimensional joint are sequentially connected through the gas-phase rotary joint, the other end of the gas-phase inner arm is arranged on the upright post through the gas-phase rotary joint, and the other end of the gas-phase three-dimensional joint is connected with a target butt joint pipe orifice on a carrier through a claw mechanism arranged at the front end of the gas-phase three-dimensional joint;

The gas-phase spring cylinder balancing system is arranged between the gas-phase inner arm and the gas-phase outer arm and is used for realizing balance of the counterweight and labor saving in the action process of the loading and unloading arm under the control of the servo control module;

The gas-phase air bag switch main valve is arranged on a main pipeline of the gas-phase outer arm and is used for realizing fluid conveying and switching-off of the gas-phase pipeline;

The gas phase outer arm is further connected with a nitrogen pipeline through a bypass pipeline, and a gas phase air bag purging valve is arranged on the nitrogen pipeline and used for purging a pipeline in the gas phase loading and unloading arm under the control of the automatic butt joint control device.

Further, the liquid phase loading and unloading arm comprises a liquid phase inner arm, a liquid phase rotary joint, a liquid phase spring cylinder balancing system, a liquid phase air bag switch main valve, a liquid phase air bag purging valve, a liquid phase outer arm and a liquid phase three-dimensional joint;

the liquid phase inner arm, the liquid phase outer arm and the liquid phase three-dimensional joint are sequentially connected through the liquid phase rotary joint, the other end of the liquid phase inner arm is arranged on the upright post through the liquid phase rotary joint, and the other end of the liquid phase three-dimensional joint is connected with a target butt joint pipe orifice on a carrier through a claw mechanism arranged at the front end of the liquid phase three-dimensional joint;

The liquid-phase spring cylinder balancing system is arranged between the liquid-phase inner arm and the liquid-phase outer arm and is used for realizing balance of the counterweight and labor saving in the action process of the loading and unloading arm under the control of the servo control module;

The liquid-phase air bag switch main valve is arranged on a main pipeline of the liquid-phase outer arm and is used for realizing fluid conveying and switching-off of the liquid-phase pipeline;

The liquid phase outer arm is further connected with a nitrogen pipeline and a waste liquid pipeline through bypass pipelines respectively, and the nitrogen pipeline and the waste liquid pipeline are respectively provided with a liquid phase purging inlet air bag valve and a liquid phase purging outlet air bag valve which are used for purging pipelines in the liquid phase loading and unloading arm under the control of the automatic butt joint control device.

Further, the target identification and positioning module comprises a visual positioning module, a three-dimensional laser positioning module, a target identification module and a target positioning module;

The visual positioning module comprises industrial cameras respectively arranged at the tail ends of the gas phase loading arm and the liquid phase loading arm and is used for acquiring image data of a target butt joint pipe orifice;

the three-dimensional laser positioning module comprises three-dimensional laser scanners which are respectively arranged at the tail ends of the gas phase loading arm and the liquid phase loading arm and is used for collecting three-dimensional laser point cloud data of a target butt joint pipe orifice;

the target recognition module is used for roughly positioning the target butt joint pipe orifice according to the image data acquired by the visual positioning module to obtain the position coordinates of the target butt joint pipe orifice;

The target positioning module is used for precisely positioning the target butt joint pipe orifice according to the image data and the three-dimensional laser point cloud data to obtain the three-dimensional pose information of the target butt joint pipe orifice.

In a second aspect, the present invention provides a control method of an automatic docking system for ultra-low temperature fluid delivery, comprising the steps of:

determining the movement space ranges of the gas phase loading arm and the liquid phase loading arm;

Coarsely positioning the target butt joint pipe orifice by utilizing a target identification positioning module to obtain the position coordinate of the target butt joint pipe orifice, and moving the gas phase loading and unloading arm to a preset distance away from the target butt joint pipe orifice by utilizing a servo control module;

The target recognition positioning module is utilized to precisely position the target butt joint pipe orifice, so that three-dimensional pose information of the target butt joint pipe orifice is obtained;

Planning a motion path of the tail end of the gas phase loading and unloading arm by using a path planning module based on the obtained three-dimensional pose information of the target butt joint pipe orifice to generate a motion track;

Based on the obtained motion trail, automatically butting the tail end of the gas-phase loading arm with a target butting pipe orifice by utilizing a servo control module;

The same method is adopted to automatically butt-joint the liquid phase loading and unloading arms.

Further, the coarse positioning of the target docking nozzle by using the vision positioning module in the target recognition positioning module, to obtain the position coordinates of the target docking nozzle, and moving the corresponding loading arm to a preset distance from the target docking nozzle by using the servo control module, includes:

after receiving the starting signal, starting an automatic butt joint control device;

acquiring an image of the tail end of the loading arm;

selecting all the butt joint pipe orifices of the tank truck from the acquired image by using a machine learning algorithm, and then selecting a target butt joint pipe orifice;

calculating the coordinate of the target butt joint pipe orifice under the loading arm base coordinate system based on the conversion relation between the camera coordinate system and the loading arm base coordinate system which are acquired in advance;

and moving the loading arm to a preset distance from the target butt joint pipe orifice by using the servo control module based on the obtained coordinates of the target butt joint pipe orifice under the loading arm base coordinate system.

Further, the precisely positioning the target docking nozzle by using the target recognition positioning module to obtain three-dimensional pose information of the target docking nozzle includes:

Based on the recognition result of the target recognition module, performing circle or circle-like fitting by using an ellipse detection algorithm of the arc segment adjacency matrix to obtain the contour information of the target butt joint pipe orifice;

And based on the three-dimensional laser point cloud data of the target butt joint pipe orifice, which is acquired by the three-dimensional laser positioning module, performing space fitting and space circle fitting on the contour information of the target butt joint pipe orifice to acquire the three-dimensional pose information of the target butt joint pipe orifice.

Further, the method for obtaining the contour information of the target butt joint pipe orifice based on the recognition result of the target recognition module performs circle or circle-like fitting by using an ellipse detection algorithm of the arc segment adjacency matrix comprises the following steps:

based on the recognition result of the target recognition module, elliptical arc section extraction is carried out;

establishing candidate combinations based on arc segment adjacency matrixes based on the extracted elliptical arc segments;

carrying out ellipse fitting acceleration on the ellipse candidate combination to obtain a plurality of candidate ellipses;

Carrying out ellipse verification on each candidate ellipse, and taking the verified candidate ellipses as ellipse clusters;

and aggregating the elliptical clusters to obtain the contour information of the target butt joint pipe orifice.

Further, the three-dimensional laser point cloud data of the target butt joint pipe orifice acquired based on the three-dimensional laser positioning module performs space fitting and space circle fitting on the contour information of the target butt joint pipe orifice to obtain three-dimensional pose information of the target butt joint pipe orifice, and the method comprises the following steps:

noise point elimination is carried out on the collected three-dimensional laser point cloud data of the target butt joint pipe orifice;

performing least square method plane fitting by using the residual point cloud data;

iterative value taking is carried out until all the remaining points meet preset convergence conditions;

And performing space circle fitting based on the plane fitting result to obtain a circle center coordinate and a plane normal vector, wherein the circle center coordinate is used as the position description of the target butt joint pipe orifice, and the plane normal vector is used as the gesture description of the target butt joint pipe orifice.

Further, the planning of the motion path of the gas phase loading and unloading arm terminal by using the path planning module based on the obtained three-dimensional pose information of the target butt joint pipe orifice to generate a motion track comprises the following steps:

based on the actual structure of the loading arm, a robot motion model is established by using a D-H modeling method, wherein the method comprises the steps of determining a loading arm connecting rod coordinate system and a connecting rod transformation matrix;

And substituting the obtained planned track points into a connecting rod transformation matrix by adopting a Cartesian space track planning method to obtain inverse solutions corresponding to all the planned track points, and taking the inverse solutions as motion tracks.

Due to the adoption of the technical scheme, the invention has the following advantages:

(1) Simple operation

The pneumatic valve is adopted to replace a manual valve, an operator can control the opening and closing of the valve on the filling arm through the batch controller, the opening and closing of the valve do not need to be manually carried out back and forth, and the labor intensity of the operator is reduced; the claw mechanism is used for replacing the loose flange to be in butt joint with the tank car, so that the time for connecting or dismantling the loading and unloading arm and the tank car is reduced, and the efficiency of the loading and unloading car is improved.

(2) High butt joint efficiency

Unlike manual butt joint, the invention has the advantages that the target positioning, path planning and motion control are completed by the upper computer, the human eyes do not need to observe the target position and then gradually operate the loading and unloading arm to complete, and the butt joint system has the advantages of quick and accurate butt joint and high working efficiency.

(3) High automation degree

The system is high in automation degree, and can greatly improve the butt joint efficiency and save the butt joint cost while realizing the butt joint of pipe orifices.

(4) High technology integration

The invention combines various technologies such as image processing technology, testing technology, robot motion control technology and the like, and the whole automatic butt joint system can realize automatic butt joint of pipe orifices, and has reliable butt joint and high efficiency.

Therefore, the invention can be widely applied to the field of fluid transportation.

Drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Like parts are designated with like reference numerals throughout the drawings. In the drawings:

FIG. 1 is a frame diagram of an automatic docking system for cryogenic fluid transfer provided by an embodiment of the present invention;

FIG. 2 is a perspective view of an automatic charging arm of an ultra-low temperature fluid delivery automatic docking system provided by an embodiment of the present invention;

FIG. 3 is a front view of an automatic charging arm of an ultra-low temperature fluid transfer automatic docking system provided by an embodiment of the present invention;

FIG. 4 is a flow chart of a control method of an automatic docking system for ultra-low temperature fluid delivery according to an embodiment of the present invention

FIG. 5 is a flowchart of an identification algorithm of the HOG feature+SVM classifier provided by the embodiment of the invention;

FIG. 6 is a flowchart of a nozzle detection algorithm provided by an embodiment of the present invention;

FIG. 7a is a diagram of an original docking nozzle provided by an embodiment of the present invention;

FIG. 7b is an arc segment extraction diagram provided by an embodiment of the present invention;

FIG. 8 is a circle center coordinate determined by ellipse fitting provided by an embodiment of the present invention;

FIG. 9 is a flowchart for determining center coordinates according to an embodiment of the present invention;

FIG. 10 is a diagram of a loader arm link coordinate system provided by an embodiment of the present invention;

The reference numerals in the figures are as follows:

1. A column; 2. a gas phase inner arm; 3. a gas phase rotary joint; 4. a gas phase spring cylinder balancing system; 5. a gas-phase air bag switch main valve; 6. a gas-phase airbag purge valve; 7. a gas phase outer arm; 8. a gas phase three-dimensional joint; 9. a liquid phase three-dimensional joint; 10. a liquid phase outer arm; 11. liquid phase purging inlet bladder valve; 12. liquid phase purging outlet air bag valve; 13. a main valve of a liquid-phase air bag switch; 14. a liquid phase spring cylinder balancing system; 15. a liquid phase rotary joint; 16. a liquid phase inner arm.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. It will be apparent that the described embodiments are some, but not all, embodiments of the invention. All other embodiments, which are obtained by a person skilled in the art based on the described embodiments of the invention, fall within the scope of protection of the invention.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the present application. As used herein, the singular is also intended to include the plural unless the context clearly indicates otherwise, and furthermore, it is to be understood that the terms "comprises" and/or "comprising" when used in this specification are taken to specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof.

Aiming at the working mode with low efficiency, high potential safety hazard and high labor intensity of the existing ultra-low temperature fluid conveying technology, which is an urgent need for a reform way, the development of a set of intelligent loading and unloading arm system which can complete automatic butt joint without manual intervention has important significance. However, because the operation environment of the loading arm is a complex outdoor condition, factors such as weather, light, tank truck types and the like cause great challenges to automation of the loading arm docking process, particularly great difficulties exist in the aspects of target pipe orifice identification and positioning, and the development and application of ultra-low temperature fluid conveying automatic loading and unloading docking are still blank at home and abroad.

Based on this, in some embodiments of the present invention, problems exist in the process of automatically docking a focusing handling arm and the process of identifying and positioning a target nozzle, an ultra-low temperature fluid delivery automatic docking system is provided, which includes a handling arm body and an automatic docking control device. The loading arm main body adopts two sets of loading arms which can flexibly rotate, the two sets of loading arms are not mutually interfered when in motion, and a channel formed in a pipeline of the loading arm can convey transport fluid to a carrier such as a tank truck; in the automatic butt joint control device, the characteristics of complex butt joint environment, butt joint interference problem, complex shape of a terminal three-dimensional joint, relatively regular butt joint part and the like of the loading arm are combined, the automatic butt joint control device uses machine vision and robot kinematics as cores, and solves the problem of automatic butt joint of the loading arm by combining the technologies of computer technology, motion control technology and the like, thereby realizing the automatic butt joint function.

In accordance with other embodiments of the present invention, a method for controlling an automatic docking system for cryogenic fluid delivery is provided.

Example 1

As shown in fig. 1, the present embodiment provides an automatic docking system for ultra-low temperature fluid delivery, which includes: and the loading arm main body and the automatic butt joint control device. The loading arm main body comprises an upright post 1 and two sets of loading arms which are arranged on the upright post 1, can freely rotate and are not interfered with each other; the automatic butt joint control device is arranged in the upper computer and comprises a target identification positioning module, a path planning module and a servo control module; the target identification positioning module is used for realizing identification positioning of a target butt joint pipe orifice; the path planning module is used for planning the motion path of the loading arm according to the identification and positioning result of the target butt joint pipe orifice to generate a motion track; the servo control module is used for controlling the position and the gesture of the loading arm according to the motion track, and realizing automatic butt joint of the loading arm and a target butt joint pipe orifice and fluid delivery.

Preferably, as shown in fig. 2 and 3, the two sets of loading arms in the present embodiment are respectively provided as a gas phase loading arm and a liquid phase loading arm. All joints of the gas phase loading arm and the liquid phase loading arm adopt a rotary design, one ends of the gas phase loading arm and the liquid phase loading arm are arranged on the upright column 1 side by side, and the other ends of the gas phase loading arm and the liquid phase loading arm can be connected with corresponding target butt joint pipe orifices in a non-interfering manner under the automatic control of an automatic butt joint control device, so that transport fluid can be transported to vehicles such as tank trucks.

Preferably, the gas phase loading and unloading arm comprises a gas phase inner arm 2, a gas phase rotary joint 3, a gas phase spring cylinder balancing system 4, a gas phase gas bag switch main valve 5, a gas phase gas bag purging valve 6, a gas phase outer arm 7 and a gas phase three-dimensional joint 8. The gas phase inner arm 2, the gas phase outer arm 7 and the gas phase three-dimensional joint 8 are sequentially connected through the gas phase rotary joint 3, the other end of the gas phase inner arm 2 is arranged on the upright post 1 through the gas phase rotary joint 3, and the other end of the gas phase three-dimensional joint 8 is connected with a target butt joint pipe orifice on a carrier such as a tank truck through a claw mechanism arranged at the front end of the gas phase three-dimensional joint 8; the gas-phase spring cylinder balancing system 4 is arranged between the gas-phase inner arm 2 and the gas-phase outer arm 7 and is used for realizing counterweight balance (such as the gravity of a spring cylinder and a bracket thereof, the gravity of an outer arm steel pipe, a pipe fitting, a rotary joint, the gravity of a snap-off valve and a quick joint and the like) and saving labor in the action processes of lifting, twisting and the like of the gas-phase loading and unloading arm under the control of the servo control module; the gas-phase air bag switch main valve 5 is arranged on a main pipeline of the gas-phase outer arm 7 and is used for realizing fluid conveying and switching-off of the gas-phase pipeline; the gas phase outer arm 7 is also connected with a nitrogen pipeline through a bypass pipeline, and a gas phase air bag purging valve 6 is arranged on the nitrogen pipeline and used for purging a pipeline in the gas phase loading and unloading arm under the control of the automatic butt joint control device.

When the three-dimensional gas-phase joint is used, the upright post 1, the gas-phase inner arm 2 and the gas-phase outer arm 7 are mainly responsible for adjusting the position of the terminal pipe orifice, and the gas-phase three-dimensional joint 8 is mainly responsible for adjusting the posture of the terminal pipe orifice. In this embodiment, the jaw mechanism at the front end of the gas phase three-dimensional joint 8 is driven by a hydraulic cylinder, the hydraulic cylinder is controlled by an automatic butt joint control device, and separation or connection between the gas phase three-dimensional joint 8 and a flange at a target butt joint pipe orifice can be realized by opening or tightening the jaws.

Preferably, the liquid phase handling arm includes a liquid phase three-dimensional joint 9, a liquid phase outer arm 10, a liquid phase purge inlet bladder valve 11, a liquid phase purge outlet bladder valve 12, a liquid phase bladder on-off main valve 13, a liquid phase spring cylinder balancing system 14, a liquid phase rotary joint 15, and a liquid phase inner arm 16. Similarly, the liquid phase inner arm 16, the liquid phase outer arm 10 and the liquid phase three-dimensional joint 9 are respectively connected in sequence through a liquid phase rotary joint 15, the other end of the liquid phase inner arm 16 is also arranged on the upright post 1 positioned below the gas phase loading and unloading arm through the liquid phase rotary joint 15, and the other end of the liquid phase three-dimensional joint 9 is connected with a target butt joint pipe orifice on a carrier such as a tank truck through a claw mechanism arranged at the front end of the liquid phase three-dimensional joint 9; the liquid phase spring cylinder balancing system 14 is arranged between the liquid phase inner arm 16 and the liquid phase outer arm 10 and is used for realizing balance weight and labor saving in the action processes of lifting, torsion and the like of the liquid phase loading arm; the liquid-phase air bag switch main valve 13 is arranged on the main pipeline of the liquid-phase outer arm 10 and is used for realizing the fluid delivery and the shutoff of the liquid-phase pipeline; the liquid phase outer arm 10 is also connected with a nitrogen pipeline and a waste liquid pipeline through bypass pipelines respectively, and the nitrogen pipeline and the waste liquid pipeline are respectively provided with a liquid phase purging inlet air bag valve 11 and a liquid phase purging outlet air bag valve 12 which are used for purging pipelines in the liquid phase loading and unloading arm under the control of an automatic butt joint control device.

Preferably, the loader arm body further comprises a bracket wrapped around the gas phase inner arm 2 and the liquid phase inner arm 10.

Preferably, the target recognition positioning module comprises a visual positioning module, a three-dimensional laser positioning module, a target recognition module and a target positioning module. The visual positioning module comprises two sets of industrial cameras and clamps which are respectively arranged at the tail ends of the gas phase loading arm and the liquid phase loading arm and is used for acquiring image data of a target butt joint pipe orifice; the three-dimensional laser positioning module comprises two sets of three-dimensional laser scanners and clamps which are respectively arranged at the tail ends of the gas phase loading arm and the liquid phase loading arm and is used for collecting three-dimensional laser point cloud data of a target butt joint pipe orifice; the target recognition module is used for roughly positioning the target butt joint pipe orifice according to the image data acquired by the industrial camera to obtain the position coordinates of the target butt joint pipe orifice; the target positioning module is used for precisely positioning the target butt joint pipe orifice according to the image data acquired by the industrial camera and the three-dimensional laser point cloud data acquired by the three-dimensional laser scanner, so as to obtain the three-dimensional pose information of the target butt joint pipe orifice, and realize the precise butt joint of the gas phase loading arm and the liquid phase loading arm and the corresponding target butt joint pipe orifice.

In this embodiment, the docking operation of the loading arm mainly includes two stages of coarse positioning and fine positioning. Firstly, in the coarse positioning stage, a working base station operator sends out a starting working signal through a control console, and after receiving the signal, the system starts a target identification positioning module, a path planning module, a servo control module and the like. The upper gas phase loading arm firstly acquires the position of a target butt joint pipe orifice on a tank truck through image data acquired by an industrial camera with a larger field angle arranged at a tail gas phase three-dimensional joint 8, the tank truck is usually provided with three butt joint pipe orifices, the upper gas phase loading arm is usually abutted against the rightmost pipe orifice of the tank truck, in order to ensure that interference phenomenon does not occur in the abutting process of the two loading arms, the upper gas phase loading arm is limited to move only in the upper half part of a preset space, after the coarse positioning coordinates of the corresponding target butt joint pipe orifice are acquired through the industrial camera, the gas phase loading arm moves towards the direction of the target butt joint pipe orifice under the guidance of the coarse positioning coordinates, and is switched into a visual servo control mode combining a three-dimensional laser scanner and the industrial camera when the gas phase loading arm reaches the visual range of the industrial camera, and the precise positioning stage is entered. The accurate positioning of the target butt joint pipe orifice is mainly realized through an industrial camera and a three-dimensional laser scanner at the tail end of the loading arm, and the automatic butt joint control device utilizes an image shot by the industrial camera to perform characteristic extraction and fuses the image with three-dimensional laser point cloud data to reconstruct the position information of the target butt joint pipe orifice in a three-dimensional way. In the precise positioning stage, the nozzle position information under the current pose is continuously acquired through the industrial camera and the three-dimensional laser scanner, the control information is continuously compensated, and the precise butt joint of the loading arm and the target butt joint nozzle is realized.

After the upper gas phase loading arm is in butt joint with the target butt joint pipe orifice, the visual control system and the servo control system of the lower liquid phase loading arm are continuously started, and the butt joint steps are repeated until the butt joint of the two loading arms is completed.

Example 2

As shown in fig. 4, the present embodiment provides a control method of an automatic docking system for ultra-low temperature fluid delivery, which includes the following steps:

1) Determining the movement space ranges of the gas phase loading arm and the liquid phase loading arm;

2) Coarsely positioning the target butt joint pipe orifice by utilizing a visual positioning module in the target recognition positioning module to obtain the position coordinates of the target butt joint pipe orifice, and moving the gas phase loading and unloading arm to a preset distance from the target butt joint pipe orifice by utilizing a servo control module;

3) The visual positioning module and the three-dimensional laser positioning module in the target recognition positioning module are utilized to precisely position the target butt joint pipe orifice, so that three-dimensional pose information of the target butt joint pipe orifice is obtained;

4) Planning a motion path of the tail end of the gas phase loading and unloading arm by using a path planning module based on the obtained three-dimensional pose information of the target butt joint pipe orifice to generate a motion track;

5) Based on the obtained motion trail, the tail end of the gas phase loading arm is accurately butted with a target butt joint pipe orifice by utilizing a servo control module;

6) And (3) adopting the same method as the step (2) to the step (5) to automatically butt-joint the liquid phase loading arm.

Preferably, before the step 2), the method further comprises: the method comprises the steps of calibrating a visual positioning module and a three-dimensional laser positioning module in advance, wherein the visual positioning module and the three-dimensional laser positioning module comprise industrial camera monocular calibration, three-dimensional laser scanner calibration and hand-eye calibration, and the conversion relation between an industrial camera internal reference and a camera coordinate system and a loading arm base coordinate system is obtained.

Preferably, in the step 2), the method includes the steps of:

2.1 After receiving a start working signal sent by a working base station operator through a control console, starting an automatic docking control device, wherein the automatic docking control device comprises a visual positioning module, a three-dimensional laser positioning module, a target identification module, a target positioning module, a path planning module and a servo control module;

2.2 The visual positioning module is used for collecting images of the tail end of the gas-phase loading and unloading arm and sending the images to the target recognition module;

2.3 The target recognition module selects all the butt joint nozzles of the tank truck from the acquired image by utilizing a machine learning algorithm, and then selects a target butt joint nozzle;

2.4 Based on the conversion relation between the camera coordinate system and the loading arm base coordinate system acquired in advance, calculating the coordinate of the target butt joint pipe orifice under the loading arm base coordinate system;

2.5 Based on the obtained coordinates of the target butt joint pipe orifice under the loading arm base coordinate system, the loading arm is moved to a position with a preset distance (for example, 0.5m from the target butt joint pipe orifice) from the target butt joint pipe orifice by utilizing the servo control module, so that the rough positioning of the target butt joint pipe orifice is realized.

Preferably, in the step 2.3), in the coarse positioning stage, the present embodiment determines the target docking nozzle by using a machine learning algorithm with lower accuracy but higher efficiency. The algorithm based on machine learning has the advantages of strong anti-interference performance, high detection speed and the like in the aspect of detecting the pipe orifice. In addition, in the process of docking the loading and unloading arms, different tank trucks are provided with different docking nozzles, which is a great challenge for target detection, and the nozzle is identified by adopting the method of HOG characteristics and SVM classifiers.

The HOG features describe image features by calculating and counting local gradient information and forming a gradient direction histogram in a statistics unit as a feature descriptor. The HOG features can keep good invariance to image geometry and optical deformation, have strong robustness to changes of external environments such as illumination, shielding, contrast and the like, and are widely used in the fields of facial expression recognition, traffic detection vehicle positioning, license plate recognition and the like.

The SVM classifier is widely applied to a small-sample, nonlinear and high-dimensional data set as a statistical machine learning algorithm, and is one of the best fixed-form algorithms in supervised learning.

As shown in fig. 5, the whole machine learning algorithm in the present embodiment can be divided into a training phase and an identification phase. Specifically, the method comprises the following steps:

2.3.1 Extracting HOG features from a pre-acquired sample data set to perform SVM training, and obtaining an xml file meeting multi-condition constraint verification.

Specifically, the training method comprises the following steps:

① After a sample data set is obtained and preprocessed, the sample data set is randomly divided into a training data set and a testing data set according to a preset proportion;

When the sample data set is acquired, the sample data set should be as much as possible so as to improve the accuracy of data processing; the distance between the butt joint pipe orifices is controlled in a certain range according to the operation process requirements; when the sample data set is preprocessed, the preprocessing mainly comprises noise reduction processing and filtering processing, the preprocessing method is a technology known to a person skilled in the art, and the invention is not repeated;

② Extracting HOG features from the training dataset;

③ SVM training is carried out by utilizing the extracted HOG features, and an xml file is generated;

④ Performing multi-condition constraint verification on the generated xml file by using the test data set, ending training if the multi-condition constraint verification is met, otherwise, performing capacity expansion on the training data set, and returning to the step ② to perform training again until the multi-condition constraint verification is met;

⑤ And taking the xml file meeting the multi-condition constraint verification as a final xml file for the identification and use of the identification stage.

The method of extracting HOG features from the training data set and performing SVM training using the extracted HOG features may be known to those skilled in the art, and the present invention is not limited thereto.

2.3.2 Extracting HOG characteristics from target images acquired by an industrial camera in real time, and obtaining an identification result meeting multi-condition constraint verification by utilizing an xml file generated in a training stage, namely a detection frame comprising each butt joint interface of the tank truck.

Specifically, the method comprises the following steps:

① Preprocessing a target image acquired by an industrial camera, including noise reduction processing, filtering processing and the like;

② Extracting HOG features from the preprocessed target image;

③ Reading an xml file generated in a training stage by using an SVM classifier, and taking HOG characteristics of a target image as input to obtain a recognition result of the target image;

④ Processing the preprocessed target image by using a preset verification mechanism to generate a verification result;

⑤ If the identification result is consistent with the verification result, outputting the identification result, otherwise, returning to the step ① to acquire the image again until the identification result is consistent with the verification result.

Preferably, in step ④, the preset verification mechanism includes 2 key steps of pre-verification preprocessing and multi-condition constraint verification.

The pre-verification preprocessing refers to the image preprocessing processes of applying an OTSU (maximum inter-class variance) segmentation algorithm under PSO optimization, morphological closing operation, canny shape feature extraction, circular fitting and the like, and separating a butt joint pipe orifice from a background of a preprocessed target image to obtain a segmentation result.

The multi-condition constraint verification comprises two conditions of roundness detection and area distance constraint verification, wherein the area distance constraint verification refers to the relation expression between the area of a target pixel and the distance from a camera to the target; the roundness detection is mainly used for filtering objects with only partial arc edges in the background, and the area distance constraint detection is used for filtering objects with circular outlines but not in target positions in the background.

Preferably, in the step 3), when the target butt joint pipe orifice is close to the target butt joint pipe orifice, the industrial camera cannot shoot the complete image of the target butt joint pipe orifice, so in the embodiment, the pipe orifice circle is fitted according to the partial pipe orifice arc section shot by the industrial camera, and the three-dimensional reconstruction of the target butt joint pipe orifice is performed by combining the depth information acquired by the three-dimensional laser scanner, so that the pipe orifice pose information with close range and high precision is acquired, and the butt joint reliability is improved.

Specifically, the method comprises the following steps:

3.1 Based on the recognition result of the target recognition module, performing circle or circle-like fitting by using an ellipse detection algorithm of the arc segment adjacency matrix to obtain the contour information of the target butt joint pipe orifice;

3.2 Based on the three-dimensional laser point cloud data of the target butt joint pipe orifice, which is obtained by the three-dimensional laser positioning module, performing space fitting and space circle fitting on the contour information of the target butt joint pipe orifice to obtain the three-dimensional pose information of the target butt joint pipe orifice.

Preferably, in the step 3.1), as shown in fig. 6 to 8, the ellipse detection algorithm (AAMED) based on the arc segment adjacency matrix specifically includes the following steps:

3.1.1 Based on the recognition result of the target recognition module, elliptical arc segment extraction is performed.

The arc segment extraction method comprises the following steps:

① Performing fuzzy denoising on the detection frame image output by the target recognition module;

② Performing edge extraction on the denoised image by using a self-adaptive Canny algorithm to obtain a plurality of edge arc segments without branches;

③ Approximating the edge arc segments by using a polygon approximation algorithm to obtain a plurality of approximation segments;

④ After the excessively short approximation segment is removed according to a preset threshold value, the remaining approximation segment is segmented by using a curvature and convexity-based method, and an elliptical arc segment is obtained.

Specifically, the method comprises the following steps:

First, the too short approximation segment is removed based on a preset threshold.

Threshold of overshort approximation segmentThe calculation formula of (2) is as follows:

（1）

In the method, in the process of the invention, The maximum degree of curvature in the approximated segment is indicated for a threshold value set in advance.

Second, segmentation is performed using curvature and convexity based methods to obtain elliptical arc segments.

Assume that an approximation segment is represented asOrder-makingThe angle between all pairs of approximation segments is expressed asThe arc sequence of the approximated contours must satisfy convexity, i.eAnd the curvature of，。

Namely, satisfies the following formula:

（2）

In the method, in the process of the invention, Is an approximation segment between any two points of the elliptical arc segment; Is that To the point ofIs a radian of (b); Is that To the point ofIs a curvature of (2); And Is an unknown function.

If it isThen,AndBelonging to the same arc section.

And then, continuing to judge the next group of approximation segments until all approximation segments are judged to be complete, thus obtaining a group of elliptical arc segments. The arc segment is extracted and then processed in a clockwise direction.

3.1.2 Based on the extracted elliptical arc segments, candidate combinations based on an arc segment adjacency matrix are established.

Specifically, the method comprises the following steps:

① And traversing all elliptical arc segments by adopting a region constraint and curvature constraint method, and establishing an arc segment adjacency matrix AAM.

It is very difficult to directly determine whether 3 (i.e., formula (2)) or more arc segments are from the same ellipse, and it is relatively easy to determine whether two elliptical arc segments can be combined. The present embodiment adopts a method of region constraint and curvature constraint to determine the adjacency of a pair of elliptical arc segments.

Extracting a group of elliptical arc segments from an image. For any elliptical arc segmentOrder-makingIs thatIs the first of (2)A point of the light-emitting diode is located,Is thatPenultimate (last to last)A point. Order theRepresents the firstTail point of each elliptical arc section to the firstThe distance of the first point of the elliptical arc segments.

Representing elliptical arc segmentsAndCan also be expressed as pointsTo the pointIs a function of the adjacency of the first layer.Representing elliptical arc segmentsAndNot belonging to the same ellipse, but belonging to the same ellipse,Indicating that the two elliptical arc sections are not adjacent and can be directly judgedAndWhether or not they belong to the same ellipse,Representing that two elliptical arc segments are contiguous and belong to the same ellipse.

The invention uses two criteria to judge connectivity, namely, when judging whether the elliptical arc sections are connected, mainly judges whether the corresponding head and tail points meet curvature and convexity, namely, judges whether the head and tail points are mutually in the search interval. The method is characterized in that the first and the last points are particularly close, and are easily influenced by noise and the like, so that the elliptic geometric property is not satisfied, and the first and the last points are directly fused as one point, and whether the curvature is satisfied or not is judged at two adjacent points.

According to the thought, traversing all arc segments to obtain the adjacency matrix AAM.

② Based on the established arc segment adjacency matrix, a plurality of ellipse candidate combinations are selected and obtained.

Obtaining a combination of all elliptical arc segments by using AAM, and giving one elliptical arc segmentThe arc segment searches all the arc segments comprising ellipsesIs a combination of the results of (a).

Make a group include elliptical arc sectionsIs from the same ellipseWherein, the method comprises the steps of, wherein,In order to search for the root node,，，. AggregationIs an elliptical arc combination, and each element is an arc segment corner mark.

（3）

In the method, in the process of the invention,Searching a plurality of points for the reverse direction; Searching a number point for the forward direction; is a set of arc segments in the reverse direction of the ellipse; Is a set of arc segments along the forward direction of the ellipse.

Because it is very difficult to directly search for arc segment combinations, the embodiment splits arc segment selection into 3 steps, namely arc segment forward search, arc segment reverse search, and bidirectional combination verification.

A. Forward search.

Depth-first traversing method is adopted in forward search to obtain all forward combinationsExpressed as: Wherein Satisfy the following requirementsIs defined in the definition of (a),Indicating the number of combinations of forward searches. For the firstThe number of combinations of the two,Is initialized toI.e. search corner markInitializing to. Then find the next elliptical arc segmentThis elliptical arc segment satisfies→That is. If no arc segment is satisfied↛That isThis arc sectionWill be pressed intoIn, and the search corner mark is set asUntil no arc segments can be placed inThis time, a forward arc segment combination is obtained。

（4）

B. And (5) reverse searching.

The reverse search method is similar to the forward search, and is mainly different in that the search strategy is different, and the following formula is a reverse search strategy formula. Reverse search can obtain all combinationsWhereinSatisfy the following requirementsAnd (2) andThe number of reverse combinations is shown:

（5）

c. And (5) two-way combination verification.

After the two steps, two sets can be obtainedAnd. Thus in total can obtainAnd two-way combinations. Then, the process is carried out,Ordered in descending order of the number of pixels combined.

Will be set to 0, which does not satisfy the following equation.

（6）

3.1.3 Ellipse fitting acceleration is carried out on the ellipse candidate combination, so that a plurality of candidate ellipses are obtained.

3.1.4 Oval verification is carried out on each candidate oval, and the candidate oval passing verification is taken as an oval cluster.

3.1.5 Aggregating the elliptical clusters to obtain the contour information of the target butt joint pipe orifice.

Preferably, in the step 3.2), the system enables the three-dimensional laser scanner and the industrial camera to have a known and reliable position relationship through the reliable clamp, when the pipe orifice is in butt joint at a short distance, the industrial camera obtains complete pipe orifice image information, meanwhile, according to the coordinate system conversion relationship between the three-dimensional laser scanner and the industrial camera, the three-dimensional laser point cloud information of the three-dimensional target pipe orifice obtained by the three-dimensional laser scanner is converted into depth information on the industrial camera, further, the three-dimensional information of the edge point of the relatively complete target butt joint pipe orifice is obtained, a plane and a space circle with relatively high precision are fitted, and the positioning information with high precision is obtained.

Specifically, as shown in fig. 9, the method comprises the following steps:

3.2.1 Noise point elimination is carried out on the collected three-dimensional laser point cloud data of the target butt joint pipe orifice.

Because the three-dimensional target nozzle point cloud data is the edge point of the target butt joint nozzle obtained by combining the ranging of the industrial camera and the three-dimensional laser scanner, camera parameter errors, calculation errors, matching errors and the like can cause random noise in the three-dimensional laser point cloud data of the target butt joint nozzle, and in order to improve fitting precision and reduce errors, filtering processing is needed to be carried out on the three-dimensional laser point cloud data of the target butt joint nozzle. In this embodiment, the pixel points with larger jitter are calculated and screened out, and then removed. The method for calculating and screening the pixel point with larger jitter can adopt the known technology of the person skilled in the art, and the invention is not limited to the method.

3.2.2 Using the residual point cloud data to perform least square method plane fitting.

3.2.3 And (3) carrying out iterative value taking until all the remaining points meet the preset convergence condition.

All the residual points meet the condition, namely the distance between each residual point and the fitting plane in the step 3.2.2) is smaller than the standard deviation, and the convergence condition is met.

3.2.3 Based on the plane fitting result, the space circle fitting is carried out to obtain the circle center coordinate and the plane normal vector, wherein the circle center coordinate is the position description of the target butt joint pipe orifice, and the plane normal vector is the gesture description of the target butt joint pipe orifice.

Preferably, in the step 4), the three-dimensional pose information of the target butt joint pipe orifice is obtained by using the target positioning module, the path planning module performs motion path planning of the three-dimensional joint at the tail end of the loading arm, adjusts the pose information of the three-dimensional joint at the tail end of the loading arm, ensures that two loading arms do not interfere with each other and collide with other objects in the butt joint process, controls the movement of the loading arms by using the servo control module after the planning is completed, and finally completes one-time butt joint work, thereby realizing no deviation of the butt joint position and no deviation of the angle.

Specifically, the method comprises the following steps:

4.1 Based on the actual structure of the loader arm, a robot motion model is built using a D-H modeling method, including determining the loader arm link coordinate system and link transformation matrix.

In this embodiment, a D-H modeling method is used to build a robot motion model, and this method builds a coordinate system on each link, and transforms coordinates on two links through homogeneous coordinate transformation. The control of the three-dimensional joint at the tail end of the loading arm can be realized by changing the rotation angle among all the joints.

Through analysis, the loading and unloading arm provided by the invention has 5 degrees of freedom, wherein the base, the inner arm and the outer arm control the position of the terminal three-dimensional joint; the three-dimensional joint at the tail end is provided with adjustment of deflection and pitching, and is mainly used for adjusting the posture of the three-dimensional joint.

As shown in FIG. 10, the D-H parameters are shown in Table 1 for the loader arm link coordinate system established according to the D-H modeling method. In order to ensure that two sets of loading arms do not interfere in the butt joint process, the embodiment adopts the simplest pipe orifice butt joint area division method to realize the interference prevention effect. I.e., the upper vapor phase loadarm has a range of motion of only z > h, while the lower liquid phase loadarm has a range of motion of only h > z > 0. The butt joint process of the two loading arms is similar to other butt joint processes except that the motion range is different from the butt joint pipe orifice logic, so that each loading arm is set with an independent coordinate system, and the two loading arms respectively limit different z-axis motion ranges so as to achieve the purposes of independent mutual motion and no mutual interference.

TABLE 1D-H parameter Table

Each link transformation matrix can be obtained from the D-H parameter table as:

（7）

（8）

（9）

（10）

（11）

wherein s represents sin, c represents cos, Is a connecting rodPose under the coordinate system of the connecting rod i. Multiplying the link transformation matrices to obtain a robot transformation matrix of the loading armExpressed as:

（12）

4.2 And (3) substituting the obtained planned track points into a connecting rod transformation matrix by adopting a Cartesian space track planning method to obtain inverse solutions corresponding to all the planned track points.

In this embodiment, cartesian space trajectory planning is selected, and the obtained planned trajectory points are substituted into the loading and unloading arm inverse kinematics (i.e., a robot transformation matrix) And then selecting one inverse solution from a plurality of inverse solutions according to two principles that the distance between the front joint angle and the rear joint angle is the nearest and the sum of the rotation angles is the smallest, and finally, all the track points are subjected to corresponding inverse solution.

4.3 Based on the obtained inverse solutions corresponding to all the track points, the motion control is performed in the loading arm.

Preferably, the above method further comprises the steps of:

7) After the butt joint is completed, the loading process is carried out, and the ultralow-temperature fluid conveying is realized.

Preferably, the step 7) includes the steps of:

7.1 Leak detection procedure: after the loading arm is accurately butted with a target butting pipe orifice on the tank truck, a signal is sent to the target butting pipe orifice in place (electrostatic grounding) and then enters a leakage detection program, and a nitrogen pipeline isolation valve, a gas-phase air bag purging valve 6 and a liquid-phase purging inlet air bag valve 11 are automatically opened, wherein the nitrogen pipeline isolation valve is arranged on a nitrogen pipeline connected with a gas-phase outer arm 7 and a liquid-phase outer wall 10.

7.2 Purge): and (3) keeping the opening states of the nitrogen pipeline isolation valve, the gas-phase air bag purging valve 6 and the liquid-phase purging inlet air bag valve 11, and automatically closing the nitrogen pipeline isolation valve, the gas-phase air bag purging valve 6 and the liquid-phase purging inlet air bag valve 11 after the purging is confirmed.

7.3 Pressure relief): and automatically opening a gas phase crane pipe valve on the tank truck, automatically opening a main valve 5 of a gas phase air bag switch to release pressure if the pressure of the tank truck is higher than 3.5bar until the pressure is released to 0.2MPa, and entering a precooling process if the pressure of the tank truck is lower than 3.5 bar.

7.4 Pre-cooling: and (3) automatically opening a liquid phase pipeline cut-off valve on the grooved tank truck, namely, a liquid phase air bag switch main valve 13, keeping the gas phase air bag switch main valve 5 in an open state, precooling at a low flow rate by a batch controller, judging whether the condition of entering the loading is met according to the liquid phase temperature and the pressure value, entering the step 5.5) for loading if the condition is met, and otherwise, continuing precooling.

7.5 Loading: after loading, automatically closing the valve, and closing the liquid phase pipeline cut-off valve, the gas phase air bag switch main valve 5 and the liquid phase air bag switch main valve 13; and opening a valve regulating bypass, a clean pipeline valve and a cold circulation pipeline valve, ending loading and entering purging.

7.6 End of loading purge): after purging is confirmed, the nitrogen isolation valve and the gas-phase air bag purging valve 6 are automatically opened, the liquid-phase purging inlet air bag valve 11 is automatically closed after 20 seconds, and the liquid-phase purging outlet air bag valve 12 is opened. And according to the prompt of the batch controller, opening a gas phase emptying valve of the grooved tank truck to release pressure, closing a liquid phase purging outlet air bag valve 12 after 15 seconds, and automatically completing the control of each valve by the batch controller in the whole process of loading and purging, and stopping or stopping loading once alarm information is available.

Finally, it should be noted that: the above embodiments are only for illustrating the technical aspects of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the above embodiments, it should be understood by those of ordinary skill in the art that: modifications and equivalents may be made to the specific embodiments of the invention without departing from the spirit and scope of the invention, which is intended to be covered by the claims.

Claims

1. An automatic docking system for ultra-low temperature fluid delivery, comprising:

a loading arm main body and an automatic docking control device;

2. The system of claim 1, wherein the gas phase handling arm comprises a gas phase inner arm, a gas phase swivel joint, a gas phase spring cylinder balancing system, a gas phase bladder on-off main valve, a gas phase bladder purge valve, a gas phase outer arm, and a gas phase three-dimensional joint;

3. The system of claim 1, wherein the liquid phase handling arm comprises a liquid phase inner arm, a liquid phase rotary joint, a liquid phase spring cylinder balancing system, a liquid phase air bag on-off main valve, a liquid phase air bag purge valve, a liquid phase outer arm, and a liquid phase three-dimensional joint;

4. The system of claim 1, wherein the target recognition positioning module comprises a visual positioning module, a three-dimensional laser positioning module, a target recognition module, and a target positioning module;

5. A control method using the ultra-low temperature fluid transfer automatic docking system according to any one of claims 1 to 4, characterized by comprising the steps of:

6. The method of claim 5, wherein: the rough positioning is carried out on the target butt joint pipe orifice by utilizing the visual positioning module in the target recognition positioning module to obtain the position coordinates of the target butt joint pipe orifice, and the corresponding loading arm is moved to a preset distance from the target butt joint pipe orifice by utilizing the servo control module, and the method comprises the following steps:

acquiring an image of the tail end of the loading arm;

7. The method of claim 5, wherein: the method for precisely positioning the target butt joint pipe orifice by utilizing the target recognition positioning module to obtain the three-dimensional pose information of the target butt joint pipe orifice comprises the following steps:

8. The method of claim 7, wherein: the identification result based on the target identification module is obtained by performing circle or quasi-circle fitting by using an ellipse detection algorithm of an arc segment adjacency matrix, and the contour information of the target butt joint pipe orifice is obtained, and the method comprises the following steps:

9. The method of claim 7, wherein: the three-dimensional laser point cloud data of the target butt joint pipe orifice, which is acquired based on the three-dimensional laser positioning module, performs space fitting and space circle fitting on the contour information of the target butt joint pipe orifice to obtain the three-dimensional pose information of the target butt joint pipe orifice, and comprises the following steps:

10. The method of claim 5, wherein: the method for planning the motion path of the tail end of the gas phase loading and unloading arm by utilizing the path planning module based on the obtained three-dimensional pose information of the target butt joint pipe orifice, and generating the motion track comprises the following steps: