Method, device and equipment for controlling multi-link liquid hydrogen conveying arm and medium

Abstract

The invention provides a method, device and equipment for controlling a multi-link liquid hydrogen conveying arm and a medium. The method comprises the steps of determining a target position when an execution tail end of a liquid hydrogen conveying arm is in butt joint with a liquid hydrogen conveying ship; the expected displacement, the expected speed and the expected acceleration of a piston in a target hydraulic cylinder during movement are determined according to the target position, and the target hydraulic cylinder is arranged in a hydraulic system corresponding to the liquid hydrogen conveying arm; the actual displacement and the actual speed during piston movement are obtained, and the displacement error and the speed error during piston movement are further obtained; according to the displacement error, the speed error and the expected acceleration, a control instruction for the target hydraulic cylinder is obtained, and the control instruction is used for achieving butt joint between the execution tail end and the liquid hydrogen transport ship; and the control instruction is sent to a hydraulic system, and the hydraulic system controls movement of the target hydraulic cylinder according to the control instruction so as to control butt joint of the liquid hydrogen conveying arm and the liquid hydrogen conveying ship. Accurate butt joint of the multi-connecting-rod liquid hydrogen conveying arm and the liquid hydrogen conveying ship can be achieved.

Description

Technical Field

[0001] The present application relates to the field of control technology, and particularly to a method, device, equipment and medium for controlling a multi-link liquid hydrogen transfer arm. Background Art

[0002] According to the prediction of the International Renewable Energy Agency, by 2050, more than 30% of hydrogen production will be used for international trade. The safe and efficient transportation technology of hydrogen energy is the key link determining the long-term development of the hydrogen energy industry. The existing transportation forms mainly include gaseous hydrogen, liquid hydrogen, and organic hydrogen storage and transportation. Among them, liquid hydrogen has become the preferred form for solving large-scale and long-distance hydrogen energy transportation and utilization in the future due to its advantages such as high energy density and high transportation efficiency. The liquid hydrogen ship transportation test has been successfully implemented, providing a more economical and safe way for the liquid hydrogen industrial chain, and having a positive significance for the popularization and use of hydrogen energy globally, with strong development potential in the future. Liquid hydrogen has characteristics such as ultra-low temperature, easy volatilization, and flammability and explosiveness. The liquid hydrogen ship-shore loading and unloading and transportation are difficult, with high safety requirements and many technical barriers. The operating conditions of the liquid hydrogen ship-shore loading and unloading system are harsh, the action accuracy requirements are demanding, and the electromechanical system cooperation is complex. It is necessary to have functions such as rapid docking, emergency disconnection, and automatic shutdown, and also withstand the ultra-low temperature cryogenic test of -253°C for a long time and automatically adapt to the influence of tidal drop.

[0003] At present, the liquid hydrogen ship-shore transportation system is still in the research and development and testing stage, and has not yet formed a systematic commercial application. Different from the traditional LNG unloading and transportation system, the key technologies of the ultra-deep cryogenic liquid hydrogen transportation system involve many aspects such as low-temperature material selection, forming manufacturing and sealing, and test verification. The material selection and structural design are difficult, the processing manufacturing and performance testing work are difficult, the ultra-low temperature sealing, connection and leakage monitoring are difficult, and the whole low-temperature transportation system has a complex structure and high safety requirements. The existing liquid hydrogen ship-shore transfer arm system structures mainly include two forms, one is a multi-link structure, and the other is a structure combining rigid hinges and flexible pipes. Among them, the research on the multi-link structure started earlier, and relatively reliable effects have also been shown in the research and development and testing stage. However, there are few docking optimization schemes for the multi-link liquid hydrogen transfer arm and the liquid hydrogen transport ship in the related technologies, and there is a problem of poor docking accuracy. Summary of the Invention

[0004] The present application provides a method, device, equipment and medium for controlling a multi-link liquid hydrogen transfer arm, which can achieve the precise docking of the multi-link liquid hydrogen transfer arm and the liquid hydrogen transport ship.

[0005] The present application provides a method for controlling a liquid hydrogen transfer arm in a multi-link form, which is applied to a host computer, and the method includes: Determine the target position when the execution end of the liquid hydrogen transfer arm docks with the liquid hydrogen transport ship; Determine the desired displacement, desired velocity, and desired acceleration during the movement of the piston in the target hydraulic cylinder according to the target position. The target hydraulic cylinder is arranged in the hydraulic system corresponding to the liquid hydrogen transfer arm, and the hydraulic system is used to provide power for the operation of the liquid hydrogen transfer arm; Obtain the actual displacement and actual velocity during the movement of the piston; Determine the displacement error during the movement of the piston according to the desired displacement and the actual displacement, and determine the velocity error during the movement of the piston according to the desired velocity and the actual velocity; Obtain a control command for the target hydraulic cylinder according to the displacement error, the velocity error, and the desired acceleration. The control command is generated with the goal that both the displacement error and the velocity error are within the corresponding preset error ranges, and the control command is used to achieve the docking between the execution end and the liquid hydrogen transport ship; Send the control command to the hydraulic system, so that the hydraulic system controls the movement of the target hydraulic cylinder according to the control command to control the action of the liquid hydrogen transfer arm.

[0006] This application also provides a device for controlling a liquid hydrogen transfer arm in the form of a multi-link, including: A first determination module, configured to determine the target position when the execution end of the liquid hydrogen transfer arm docks with the liquid hydrogen transport ship; A second determination module, configured to determine the desired displacement, desired velocity, and desired acceleration during the movement of the piston in the target hydraulic cylinder according to the target position. The target hydraulic cylinder is arranged in the hydraulic system corresponding to the liquid hydrogen transfer arm, and the hydraulic system is used to provide power for the operation of the liquid hydrogen transfer arm; A first acquisition module, configured to acquire the actual displacement and actual velocity during the movement of the piston; A third determination module, configured to determine the displacement error during the movement of the piston according to the desired displacement and the actual displacement, and determine the velocity error during the movement of the piston according to the desired velocity and the actual velocity; A second acquisition module, configured to obtain a control command for the target hydraulic cylinder according to the displacement error, the velocity error, and the desired acceleration. The control command is generated with the goal that both the displacement error and the velocity error are within the corresponding preset error ranges, and the control command is used to achieve the docking between the execution end and the liquid hydrogen transport ship; A sending module, configured to send the control command to the hydraulic system, so that the hydraulic system controls the movement of the target hydraulic cylinder according to the control command to control the action of the liquid hydrogen transfer arm.

[0007] The present application also provides an electronic device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, it implements a method for controlling a liquid hydrogen delivery arm in a multi-link form as described in any one of the above.

[0008] The present application also provides a non-transitory computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, it implements a method for controlling a liquid hydrogen delivery arm in a multi-link form as described in any one of the above.

[0009] The present application also provides a computer program product, including a computer program. When the computer program is executed by a processor, it implements a method for controlling a liquid hydrogen delivery arm in a multi-link form as described in any one of the above.

[0010] To implement the method of the present application, first determine the target position when the execution end of the liquid hydrogen delivery arm is docked with the liquid hydrogen carrier; then, according to the target position, determine the desired displacement, desired speed, and desired acceleration when the piston in the target hydraulic cylinder moves. The target hydraulic cylinder is arranged in the hydraulic system corresponding to the liquid hydrogen delivery arm, and the hydraulic system is used to provide power for the operation of the liquid hydrogen delivery arm; obtain the actual displacement and actual speed when the piston moves; then, determine the displacement error when the piston moves according to the desired displacement and the actual displacement, and determine the speed error when the piston moves according to the desired speed and the actual speed; according to the displacement error, speed error, and desired acceleration, obtain a control command for the target hydraulic cylinder. The control command is generated with the goal that both the displacement error and the speed error are within the corresponding preset error ranges. The control command is used to achieve the docking between the execution end and the liquid hydrogen carrier; send the control command to the hydraulic system, so that the hydraulic system controls the movement of the target hydraulic cylinder according to the control command to control the movement of the liquid hydrogen delivery arm. Through the method of the present application, precise docking between the multi-link liquid hydrogen delivery arm and the liquid hydrogen carrier can be achieved. Description of the Drawings

[0011] To more clearly illustrate the technical solutions in the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0012] Figure 1 is a flowchart of a method for controlling a liquid hydrogen delivery arm in a multi-link form shown in an embodiment of the present application; Figure 2 is a structural schematic diagram of a multi-link liquid hydrogen delivery arm shown in an embodiment of the present application; Figure 3It is a schematic diagram of the control process of a liquid hydrogen transfer arm shown in an embodiment of the present application; Figure 4 It is a simplified spatial mechanism diagram of a liquid hydrogen transfer arm shown in an embodiment of the present application; Figure 5 It is a schematic diagram of a generalized motion atlas chain shown in an embodiment of the present application; Figure 6 It is a schematic diagram of a general universal kinematic chain shown in an embodiment of the present application; Figure 7 It is a schematic diagram of the parameters of a specific chain shown in an embodiment of the present application; Figure 8 It is a schematic diagram of the relationship between a hydraulic cylinder and a boom shown in an embodiment of the present application; Figure 9 It is another schematic diagram of the relationship between a hydraulic cylinder and a boom shown in an embodiment of the present application; Figure 10 It is a simplified spatial mechanism diagram of a liquid hydrogen transfer arm after rotating the coordinate system shown in an embodiment of the present application; Figure 11 It is a schematic diagram of the control principle of a PD control model shown in an embodiment of the present application; Figure 12 It is a schematic diagram of a three-position four-way directional control valve shown in an embodiment of the present application; Figure 13 It is a schematic diagram of the structure of the hydraulic system of a multi-link liquid hydrogen transfer arm shown in an embodiment of the present application; Figure 14 It is a simplified schematic diagram of a hydraulic system shown in an embodiment of the present application; Figure 15 It is a block diagram of the structure of a device for controlling a multi-link type liquid hydrogen transfer arm shown in an embodiment of the present application; Figure 16 It is a schematic diagram of the physical structure of an electronic device shown in an embodiment of the present application.

[0013] Reference numerals: 1: Quick street flange; 2: Rotary interface; 3: Boom system; 4: Balance weight system; 5: Rotary mechanism; 6: Leg; A, B, C, D, F, G: Rotation nodes at different positions. Detailed implementation manners

[0014] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in this application will be clearly and completely described below in conjunction with the accompanying drawings in this application. Obviously, the described embodiments are part of the embodiments of this application, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts belong to the scope of protection of this application.

[0015] This application provides a method for controlling a multi-link liquid hydrogen transfer arm, which is applied to a host computer. Figure 1 It is a flowchart of a method for controlling a multi-link liquid hydrogen transfer arm shown in an embodiment of this application. Refer to Figure 1 The method of this application includes: Step 101: Determine the target position when the execution end of the liquid hydrogen transfer arm docks with the liquid hydrogen carrier.

[0016] The liquid hydrogen transfer arm in this application refers to the transfer arm of the liquid hydrogen ship-shore loading and unloading system, and the liquid hydrogen transfer arm is a multi-link structure liquid hydrogen transfer arm.

[0017] In this application, the docking of the execution end of the liquid hydrogen transfer arm with the liquid hydrogen carrier includes two types. One is that the execution end of the liquid hydrogen transfer arm actively docks with the liquid hydrogen carrier, and the other is that after docking, the execution end follows the movement of the liquid hydrogen carrier to maintain a stable docking state. In other words, steps 101-step 106 in the method of this application can be continuously executed until the liquid hydrogen transfer arm no longer needs to dock with the liquid hydrogen carrier. Therefore, the target position can be the position expected to dock before docking, or the position expected to dock at the next moment when the liquid hydrogen carrier moves with the wind speed and waves after docking.

[0018] Figure 2 It is a schematic structural diagram of a multi-link liquid hydrogen transfer arm shown in an embodiment of this application. Refer to Figure 2 The liquid hydrogen transfer arm mainly includes a quick coupling flange 1, a swivel joint 2, a boom system 3, a balance weight system 4, a windproof locking device, a slewing mechanism 5, legs 6, a hydraulic system, and a driving force system.

[0019] The quick-connect flange 1 adopts the three-point positioning principle. The expansion, contraction, and rotation of the pressing block are controlled by a hydraulic cylinder. When docking, the quick connector moves from top to bottom and is positioned by three points on the pressing plate, enabling the rapid connection or disconnection between the execution end of the liquid hydrogen transfer arm and the ship. The swivel joint 2 is a crucial component in the liquid hydrogen transfer arm. It is installed at the connection between the boom and the boom or at the flange of the execution end of the liquid hydrogen transfer arm. The outer ring and the inner ring are connected by rolling bearings and seals made of special materials, allowing relative rotation. The boom system 3 is mainly composed of the liquid hydrogen transfer arm pipes and rods. The rods are generally supported by welding, with a hollow structure, light weight, and good stiffness, and are used for the main movement of the entire liquid hydrogen transfer arm. The balance counterweight system 4 is the balancer of the liquid hydrogen transfer arm, responsible for keeping the liquid hydrogen transfer arm balanced at any position. Due to the weight of the boom itself, the flange joint at the execution end of the liquid hydrogen transfer arm is relatively heavy. When the boom is in the floating state of no-load or working, a balance counterweight system needs to be configured for the boom to keep it balanced. The windproof locking device is similar to the safety belt of the liquid hydrogen transfer arm. When the loading and unloading arm is not working, it will firmly lock the boom with two driving linkages. The windproof locking device is usually controlled by an independent hydraulic manual valve to ensure that the boom will not swing or move randomly in the non-working state. The slewing mechanism 5 enables the entire liquid hydrogen transfer arm to rotate horizontally, allowing the liquid hydrogen transfer arm to flexibly rotate to different angles and orientations, so as to accurately align with the target position where liquid hydrogen needs to be transported, such as the corresponding interface on the ship, etc. The outriggers 6 are used to stably support the entire liquid hydrogen transfer arm. The hydraulic system is used to provide the power required for the movement of the liquid hydrogen transfer arm. The hydraulic system consists of a hydraulic station and a hydraulic cylinder assembly. When a fault occurs in the equipment, a manual pump can be used to replace the hydraulic station to disconnect the liquid hydrogen transfer arm from the transport ship and retract the boom. The driving force system is the power source of the liquid hydrogen transfer arm and the core part of the mechanical equipment, responsible for ensuring the normal operation of the equipment. The hydraulic system is an important part of the driving force system.

[0020] Step 102: According to the target position, determine the expected displacement, expected speed, and expected acceleration when the piston in the target hydraulic cylinder moves. The target hydraulic cylinder is set in the hydraulic system corresponding to the liquid hydrogen transfer arm, and the hydraulic system is used to provide power for the operation of the liquid hydrogen transfer arm.

[0021] In this application, the number of target hydraulic cylinders can be multiple, and the control principle for each target hydraulic cylinder is exactly the same, that is, they can all be controlled according to Step 102 - Step 106.

[0022] Execute Step 102. The upper computer can determine the expected displacement, expected speed, and expected acceleration when the piston in the target hydraulic cylinder moves according to the target position. This process will be described in detail later.

[0023] Step 103: Obtain the actual displacement and actual speed of the piston during movement.

[0024] After obtaining the desired displacement, desired speed, and desired acceleration, the piston will act according to the desired displacement, desired speed, and desired acceleration. After the action is completed, the present application will also collect the actual displacement and actual speed of the piston during movement.

[0025] In the present application, the actual displacement of the piston during movement can be obtained according to a displacement sensor, and the actual speed can be determined according to the change rate of the actual displacement over time.

[0026] Step 104: Determine the displacement error of the piston during movement according to the desired displacement and the actual displacement, and determine the speed error of the piston during movement according to the desired speed and the actual speed.

[0027] In step 104, the difference between the desired displacement and the actual displacement can be determined as the displacement error of the piston during movement, and the difference between the desired speed and the actual speed can be determined as the speed error of the piston during movement.

[0028] Step 105: Obtain a control command for the target hydraulic cylinder according to the displacement error, speed error, and desired acceleration. The control command is generated with the goal that both the displacement error and the speed error are within the corresponding preset error ranges, and the control command is used to achieve the docking between the execution end and the liquid hydrogen carrier.

[0029] In one implementation, step 105 may include: Analyze the displacement error, speed error, and desired acceleration through a proportional-derivative control model pre-constructed for the liquid hydrogen delivery arm to obtain the control command for the target hydraulic cylinder.

[0030] In the present application, a proportional-derivative control model is pre-established. The proportional-derivative control model can obtain the displacement error according to the desired displacement and the actual displacement, can obtain the speed error according to the desired speed and the actual speed, and then, according to the set control principle, obtain the control command for the target hydraulic cylinder according to the displacement error, speed error, and desired acceleration. This control principle will be described in detail later.

[0031] Step 106: Send the control command to the hydraulic system, so that the hydraulic system controls the movement of the target hydraulic cylinder according to the control command to control the movement of the liquid hydrogen delivery arm.

[0032] Execute step 106. The hydraulic system controls the movement of the target hydraulic cylinder according to the control command, specifically controls the movement of the piston in the target hydraulic cylinder, thereby controlling the movement of the entire liquid hydrogen delivery arm and achieving the docking between the execution end and the liquid hydrogen carrier.

[0033] Implementing the method for controlling the multi-link liquid hydrogen transfer arm in this application, the host computer comprehensively analyzes the displacement error, velocity error, and desired acceleration during the movement of the piston in the target hydraulic cylinder, and can obtain a control command for the target hydraulic cylinder. By controlling the movement of the piston with this control command, the accurate docking of the multi-link liquid hydrogen transfer arm and the liquid hydrogen carrier can be achieved, overcoming the problems in the related art.

[0034] Combined with the above embodiments, in one implementation, the hydraulic system in this application includes a first hydraulic system and a second hydraulic system. The target hydraulic cylinder includes a first hydraulic cylinder located in the first hydraulic system and a second hydraulic cylinder located in the second hydraulic system. The host computer is electrically connected to the hydraulic drive circuit module through a microcontroller unit. The hydraulic drive circuit module is electrically connected to the first hydraulic system and the second hydraulic system respectively. The control command includes a first control command corresponding to the first hydraulic cylinder and a second control command corresponding to the second hydraulic cylinder, as Figure 3 shown.

[0035] Figure 3 is a schematic diagram of the control process of a liquid hydrogen transfer arm shown in an embodiment of this application. In Figure 3 , the MCU control system is the microcontroller unit, the loop one hydraulic system is the first hydraulic system, and the loop two hydraulic system is the second hydraulic system. Correspondingly, sending the control command to the hydraulic system can include: sending the first control command to the first hydraulic system through the microcontroller unit and the hydraulic drive circuit module; sending the second control command to the second hydraulic system through the microcontroller unit and the hydraulic drive circuit module.

[0036] Exemplarily, the target position is P(x, y). According to the control command, the desired displacement of the piston in the first hydraulic cylinder is determined as a, and the desired displacement of the piston in the second hydraulic cylinder is determined as b. Then, the first hydraulic system controls the movement of the piston in the first hydraulic cylinder to make its displacement reach a. At the same time, the second hydraulic system controls the movement of the piston in the second hydraulic cylinder to make its displacement reach b. When controlling the displacement of the piston to reach the desired displacement, it is also necessary to control the speed of the piston to reach the desired speed and control the acceleration of the piston to reach the desired acceleration to achieve accurate control of the attitude of the liquid hydrogen transfer arm, and further achieve accurate docking with the liquid hydrogen carrier.

[0037] It should be specifically noted here that in subsequent embodiments of this application, it is taken as an example that the hydraulic system includes a first hydraulic system and a second hydraulic system, and the target hydraulic cylinder includes a first hydraulic cylinder located in the first hydraulic system and a second hydraulic cylinder located in the second hydraulic system. In actual implementation, the number of hydraulic systems can also be set according to actual business requirements, and the control principles for other numbers of hydraulic systems are similar to those of the above two hydraulic systems.

[0038] Combined with the above embodiments, in one implementation manner, in step 102, according to the target position, determining the expected displacement, expected speed, and expected acceleration when the piston in the target hydraulic cylinder moves may include: Step 1021: Obtain the spatial mechanism schematic diagram corresponding to the liquid hydrogen transfer arm.

[0039] Specifically, the spatial mechanism schematic diagram is obtained through the following steps in advance: Analyze the kinematic chain of the liquid hydrogen transfer arm to obtain a candidate contracted link adjacency matrix representing the topological structure of the kinematic chain and a kinematic graph chain corresponding to the candidate contracted link adjacency matrix; Determine the specific kinematic graph chain that meets the preset conditions in the kinematic graph chain; According to the specific kinematic graph chain and the parameter information of the liquid hydrogen transfer arm, obtain the spatial mechanism schematic diagram.

[0040] In this application, configuration analysis can be performed on the liquid hydrogen transfer arm in the form of a multi-link mechanism to obtain the spatial mechanism schematic diagram, as Figure 4 shown. Figure 4 It is the spatial mechanism schematic diagram of a liquid hydrogen transfer arm shown in an embodiment of this application.

[0041] Figure 2 The corresponding positions of A, B, C, D, F, and G are marked in. A, B, C, D, F, and G are all rotation nodes. Through the cooperation of these rotation points, the angle and position of the liquid hydrogen transfer arm can be adjusted.

[0042] A linkage mechanism is a mechanism connected by different types of lower pairs (such as prismatic pairs, revolute pairs, cylindrical pairs, etc.). These lower pair components are combined together through specific connection methods to form a mechanism with good transmission performance, which can achieve various different motion trajectory curve laws. In this application, the linkage mechanism theory is used for configuration analysis of the liquid hydrogen transfer arm. First, the complex physical object of the liquid hydrogen transfer arm is simplified into a linkage mechanism model for subsequent analysis and design. In the simplified spatial mechanism schematic diagram, OA and FG are determined as the driving components, responsible for driving the movement of the entire mechanism. OA and FG are respectively driven by two hydraulic cylinders. Then, an innovative design method of the mechanism is used to perform configuration analysis on the liquid hydrogen transfer arm. By generalizing, number synthesis, and kinematic chain synthesis on it, all multi-link mechanism kinematic chains are obtained, and their rationality is analyzed. Generalization means regarding each link and joint in the liquid hydrogen transfer arm as general components without considering their specific shapes and sizes to facilitate finding all possible kinematic chain combinations. Number synthesis means determining the number and types of each link and joint and their connection methods according to the actual requirements and constraint conditions of the liquid hydrogen transfer arm. Kinematic chain synthesis means comprehensively obtaining all possible multi-link mechanism kinematic chains based on considering the motion laws and interactions of the links and joints.

[0043] The process of obtaining the spatial mechanism sketch by performing configuration analysis on the multi-link liquid hydrogen transfer arm in this application may include the following multiple steps: (1) Analyze the kinematic chain of the liquid hydrogen transfer arm mechanism.

[0044] Generalized chain rule: 1) Connection of kinematic pairs. All kinematic pairs in the mechanism can be replaced by general kinematic pairs. The revolute pair is replaced by J R the general kinematic pair symbol, and the prismatic pair is replaced by J P etc. 2) Links. Links with N L adjacent connecting rod mechanisms are replaced by a link with N L general universality. A generalized chain is a closed, connected chain without any separation and consists only of simple kinematic pairs. Usually, a chain with N L links and N J joints is denoted as ( N L , N J ) and can be represented by a general topological matrix. Then, the topological structure of the kinematic chain is represented by the reduced-link adjacency matrix, and the reduced-link adjacency matrix is represented by M CLA as follows: (1-1) In (1-1), M 1 represents the configuration matrix of the multi-joint link, and its diagonal elements represent the type of the multi-joint link i . M 4 represents the two-joint series link, which is called the reduced link, M 2 and M 3 are transpose matrices of each other. If i represents a multi-joint link with m kinematic pairs, then M the 1 diagonal element e ii = +m; if i represents a reduced link with n links, then M the 4 diagonal element e ii = -n. The non-diagonal element e ij represents the kinematic pair element between link i and j , and its value is defined as: if link i and link j are connected by ωIf connected by e ij = ω , ω The value of can only be 0, 1, or 2. Only when one of the two adjacent rods has three or more telescopic rods, and the other is a multi-joint rod, and both ends of this telescopic rod are connected to the multi-joint rod, ω = 2.

[0045] (2) Kinematic chain synthesis of the liquid hydrogen transfer arm.

[0046] 1) Link class matching: Link class matching in the generalized chain A L is composed of a set of data of two-joint rods ( N L2 ), three-joint rods ( N L3 ), four-joint rods ( N L4 ), etc., expressed as: A L= N L2 / N L3 / N L4... (1 - 2) This step obtains the element values of the M 1 diagonal in the telescopic rod adjacency matrix.

[0047] For the multi-link liquid hydrogen transfer arm involved in this application, since only the planar link kinematic chain containing revolute joints is considered, the number of kinematic pairs N J can be expressed as: (1 - 3) Among them, N L is the number of components, F P is the degree of freedom of the mechanism. For a two-degree-of-freedom ( F P = 2) multi-link ( N L = 7) kinematic chain, according to Equation (1 - 3), the number of kinematic pairs N J is 8, that is, a (7, 8) kinematic chain. For a mechanism with N L links and N J kinematic pairs, the link class matching A L= N L2 ​​ / N L3 / N L4... , it can be obtained according to the following equation: (1 - 4) And the number of kinematic pairs of the mechanism N J must satisfy the following constraint conditions: The maximum value m Using can be expressed as: (1 - 5) For the liquid hydrogen transfer arm in this application, the number of connecting rods is set to 7. Therefore N L = 7, the degree of freedom F P = 2 kinematic chain, the number of joint chains N J = 8 generalized chain. According to equations (1 - 3) to (1 - 5), it can be obtained that m max is: (1 - 6) Therefore, equation (1 - 4) becomes: (1 - 7) Solving this equation can obtain N L2 = 5 and N L3 = 2, that is, the corresponding connecting rod type is: A L = [5 / 2].

[0048] Therefore, it can be obtained that the liquid hydrogen transfer arm A L = [5 / 2] (7, 8) kinematic chain is composed of 5 two - joint rods and 2 three - joint rods. The generalized atlas chain of the liquid hydrogen transfer arm obtains different closed kinematic chain forms through different combinations of connecting rod type matching.

[0049] 2) Shrink - rod type matching: The two - joint rods connected in series in the kinematic chain are defined as a shrink - rod, and the shrink - rod type matching is to N L2 divide the N C number of two - joint rods into N C parts, A LC = N c1 / N c2 / ... / N cr ], which is equivalent to the adjacency moment of the shrink rod M The diagonal elements of 4 are not connected because of the shrinkage type matching, so M The off-diagonal elements of 4 are zero, so we can get M 4 matrices, the rod type matching must satisfy the following equation: (1-8) one F P A kinematic chain with degrees of freedom cannot contain F P +2 or more drawbars, so r = F P +2, N c The value range of is: (1-9) Where, 2 J m =3 N L3 +4 N L4 +...+q N q ； in, N m is the number of multiple rods. The number of multiple rods involved in this application is N m =2, according to formula (1-8) to (1-9), we can get N c =2 or 3. N c =2, the type of retraction is [0 / 1 / 1]. N c =3, the type of retraction is [1 / 2 / 0] or [2 / 0 / 1].

[0050] 3) Reduction Matrix M CLA ： Through the shrinking rod matrix, all diagonal elements of the shrinking rod adjacency matrix have been obtained. Then the non-diagonal elements are solved, that is, the number of kinematic pairs shared by multiple pairs of rods. The total number is expressed as a i express: (1-10) Equation (1-10) is called M the compatibility constraint of 1. In this application, the set of multi-link secondary rods is S ML =( L 1, L 2), the number of kinematic pairs e ii value is (3, 3), and in the number of secondary movements of the multi-link secondary rod a i the value is (1, 1). Combining these, we get M the matrix of 1 as: or .

[0051] From the calculation and derivation of 1, 2, 3, and 4 in the reduced-link adjacency matrix of the multi-link rod described above, the possible reduced-link adjacency matrices M 1, M 2, M 3, M 4 can be obtained as follows: M CLA as follows: (1-11) (1-12) (1-13) The above M CLAa、 M CLAb、 M CLAc all are candidate reduced-link adjacency matrices. The corresponding kinematic generalized kinematic atlas chain (the kinematic atlas chain corresponding to the candidate reduced-link adjacency matrix) is as Figure 5 shown. Figure 5 is a schematic diagram of the generalized kinematic atlas chain shown in an embodiment of this application.

[0052] 4) Specialization of the multi-link liquid hydrogen transfer arm: According to the design requirements and constraints of the equipment, specific components and kinematic pairs are set in the generalized kinematic atlas chain. This process is called specialization, and the specific kinematic chain that meets the design requirements is called a feasible specialization chain. In this application, a seven-link mechanism with two degrees of freedom of hybrid drive needs to be obtained. First, determine the frame in the mechanism, allocate the fixed rod K , and two driving linkages D , and use P to represent the output link at the end. All kinematic pairs in the mechanism are lower pairs (revolute pairs), and the output link is not connected to the driving component, and the drive needs to be connected to the frame. Therefore, the general kinematic chains that meet the kinematic requirements are the six forms shown in Figure 6 . Figure 6It is a schematic diagram of a general and common kinematic chain shown in an embodiment of the present application. In Figure 6 Among the compliant kinematic chain atlases shown, in comparison with the multi-link liquid hydrogen transfer arm mechanism involved in the present application, two driving links are connected to the frame, and another three-link rod is not connected to the driving rod. Two of the three-link rods are connected. Therefore, the kinematic chain F can be obtained as a specific chain structure of the liquid hydrogen transfer arm (i.e., a specific kinematic atlas chain that meets the preset conditions). By comparing the five kinematic chains A, B, C, D, and E with the kinematic chain F, all kinematic chains are composed of a four-bar mechanism and a five-bar mechanism combined. The difference is that the kinematic chain F shares two connecting rods during the combination process, while the other mechanisms share three connecting rods. The extra connecting rod connects two three-link rods. According to the spatial mechanism schematic diagram of the specific chain F (such as Figure 4 shown), the positions of the corresponding rods of the liquid hydrogen transfer arm can be assigned respectively, and the parameters of the specific chain F as shown in Figure 7 can be obtained, where R represents a revolute pair. Figure 7 It is a schematic diagram of the parameters of a specific chain shown in an embodiment of the present application. If the specific constraint conditions are changed, many different kinematic chains can be obtained. Step 1022: Obtain the parameter information of each component in the spatial mechanism schematic diagram and the kinematic analysis results satisfied by different components; Step 1023: Determine the desired displacement, desired velocity, and desired acceleration according to the target position, the parameter information of each component, and the kinematic analysis results.

[0053] Specifically, step 1023 may include: determining the parameter information of the target component corresponding to the target hydraulic cylinder in the spatial mechanism schematic diagram according to the position of the target position in the coordinate system of the spatial mechanism schematic diagram and the parameter information of each component. The target component is the active component, that is, OA or FG; determining the desired displacement according to the kinematic analysis results satisfied between the parameter information of the target component and the displacement of the piston in the target hydraulic cylinder; taking the derivative of the time parameter in the desired displacement to obtain the desired velocity; taking the derivative of the time parameter in the desired velocity to obtain the desired acceleration.

[0054] In one implementation manner, the parameter information of the target component includes the angle between the target component and the coordinate axes of the coordinate system in the spatial mechanism schematic diagram.

[0055] In the present application, kinematic analysis can be performed on each component in the spatial mechanism schematic diagram corresponding to the liquid hydrogen transfer arm in advance to obtain kinematic analysis results, deduce the kinematic equation of the liquid hydrogen transfer arm of the multi-link mechanism, obtain the velocity transformation Jacobian matrix, and analyze the kinematic singularity of the liquid hydrogen transfer arm mechanism to initially determine the basic parameters of each connecting rod. Finally, the working space of the position P of the execution end is analyzed. The kinematic analysis process may include the following multiple links: (1) Kinematic equations of the support structure of the liquid hydrogen transfer arm.

[0056] The kinematic analysis of a mechanism includes the analytical method. The analytical method is more suitable for programmed processing to obtain the desired data through calculation. Kinematic analysis is to analyze the change of the position, velocity, and acceleration of a certain point in the mechanism over time through mathematical derivation when the type of the mechanism is known, and to obtain the variation law of the driven member of the mechanism with the driving member. No matter which method is chosen, it is based on vectors. First, the vector equation of the mechanism must be obtained, and then the displacement can be derived. Differentiating the displacement with respect to time gives the velocity, and differentiating again gives the acceleration. When analyzing a planar linkage mechanism, the displacement equation can be obtained according to the projection of the closed-loop vector equation on the coordinate axes. Its general formula can be expressed as: (2-1) The general displacement formula equation after projection is: (2-2) Next, differentiating Equation (2-2) with respect to time gives the velocity equation: (2-3) Generally, for the convenience of expression, the above Equation (2-3) can be written in a simplified expression. The known input variables are represented as q = ( q 1, q 2,... q i )), i = 1, 2... n , and the position variables to be solved are represented as φ = ( φ 1, φ 2,... φ i ). i = 1, 2... n . The position equation can be expressed as f ( φ , q ) = 0, and the velocity equation can be expressed as A φ' = B q ']. Among them, A is the position parameter matrix of the driven member, such as the Jacobian matrix, B is the known parameter position matrix, and the numerical iteration method is generally used to solve such equations.

[0057] 1) Relationship between the position of the support frame of the liquid hydrogen transfer arm and the displacement of the piston in the hydraulic cylinder.

[0058] The liquid hydrogen transfer arm of this application is driven by a hydraulic system. The measured values are fed back to the driving force system through angle sensors, enabling precise control of the position of the boom. Secondly, it can provide sufficient motive power. Figure 8 It is a schematic diagram showing the relationship between a hydraulic cylinder and a boom in an embodiment of this application. The relationship between the displacement of the piston in the hydraulic cylinder and the rotation angle of the boom will be analyzed below for Loop 1 OABC For the drive (driven by the first hydraulic system) for research and analysis, the boom OA (target component) and the first hydraulic cylinder are as follows Figure 8 shown. The first hydraulic cylinder is connected to the slewing platform and the boom OA at M, N two points, and the boom OA and the slewing platform are connected at O point, where ON the length of L is OM 1, L the length of L’ is OM 2, the telescopic length of the piston during the operation of the oil cylinder is θ γ s, OA the angle between θ b and the horizontal direction is θ b b , (2 - 4) From Equation 2 - 4, we can obtain: (2 - 5) Through analysis, it can be seen that the angle OA between the boom θ b and the horizontal direction has a one-to-one correspondence with the telescopic displacement of the piston of the hydraulic cylinder. When a given angle θ b between the boom and the horizontal direction is given, the telescopic displacement of the piston of the first hydraulic cylinder can be determined. Alternatively, the displacement L’ of the first hydraulic cylinder can be given to obtain the angle θ b between the boom and the horizontal direction.

[0059] Figure 9 It is another schematic diagram showing the relationship between a hydraulic cylinder and a boom in an embodiment of this application. The relationship between the second hydraulic cylinder (the second hydraulic cylinder in the second hydraulic system) in Loop 2 and the boom FG is similar to that in Loop 1. The telescopic length of the piston during the operation of the oil cylinder is L s', L 3 and L4 is the distance from the rotation center of the boom g to the intersection point of the second hydraulic cylinder and the boom g and the turntable. Assuming FG and x the angle between the θ g axis and the KG axis is x δ θ δ , as Figure 9 , similarly, we can get: (2-6) 2) Position analysis of the liquid hydrogen transfer arm.

[0060] When analyzing the position of the execution end of the liquid hydrogen transfer arm P , it is necessary to clarify the position of the mechanism in the entire coordinate system. Before calculation, for the convenience of calculation, the simplified diagram of the multi-link liquid hydrogen transfer arm is rotated around O to obtain Figure 10 . Figure 10 is the spatial mechanism simplified diagram of the liquid hydrogen transfer arm after rotating the coordinate system shown in an embodiment of the present application.

[0061] Project the spatial mechanism of the liquid hydrogen transfer arm onto the xoy plane and first establish OG ' and OG ' axes along the x direction and perpendicular to the y direction respectively. After the plane x ' oy ' rotates around z by θ angle, the plane xoy can be obtained. According to the connection diagram of the boom OA and the hydraulic cylinder, in the x' oy' plane, the coordinates of the position P of the execution end can be expressed as: (2-7) Among them, L a , L m , L e are the lengths of the rods a, m, e respectively, x p ', y p ' are the abscissa and ordinate of the P point in the x'oy' coordinate system respectively, and θ a in the formula is the roda The included angle with x ' direction. In the formula, θ d is the connecting rod m and e included angle. Since the final requirement is to obtain P the position of the point in xoy coordinates, let OG and x the included angle with the θ axis be (2 - 8) (2 - 9) In formula (2 - 6), θ is a known quantity, θ a , θ d are all unknown quantities and need to be derived through calculation θ a , θ d values. Next, the values of θ a , θ d will be obtained. θ g is the included angle between the connecting rod g and the x ' axis. The coordinates of the midpoint of the connecting rod D and the point F are respectively expressed as P D and P F , and their expressions are as shown in formula (2 - 10): (2 - 10) DF The distance of

[0062] is constant, so formula (2 - 11) holds. Among them, L f is the length of the rod f . Substituting formula (2 - 10) into formula (2 - 11), we can get θ a As shown in formula (2 - 12): (2 - 12) Among them: If OAPosition determination, loop OABC can be transformed into a typical four-bar mechanism. Similarly, we can obtain θ d As shown in Equation (2-13): (2-13) Where:[[]]END]] L b and L c and L d are the lengths of rods b, c, d respectively; θ b is the angle between rod b and the x 'axis, θ d is the angle between rod d and the x 'axis.

[0063] First, substitute Equations (2-5) and (2-6) into Equations (2-12) and (2-13) to obtain the displacement of the piston in the hydraulic cylinder and the relationship between θ a and θ d . Then, substitute Equations (2-12) and (2-13) into Equation (2-7) to obtain the position coordinates of the endpoint P in x'oy' . Finally, substitute Equation (2-7) into Equation (2-8). After the transformation of the rotation coordinates, the position of the execution end of the liquid hydrogen transfer arm P with the movement of the hydraulic cylinder in the xoy projection plane can be obtained.

[0064] 3) Velocity analysis of the liquid hydrogen transfer arm.

[0065] When calculating the velocity, we only need to take the time derivative of Equation (2-9) to obtain the P velocity equations of point x and y . As shown in Equation (2-14), in Equation (2-14), θ b and θ g are the angular velocities of the connecting rod b, g in sequence; x P and y P are the horizontal and vertical velocities of the execution end P in sequence.

[0066] (2 - 14) In the mechanism schematic diagram, the loop ODFG The closed - loop position equation is shown in Equation (2 - 15): (2 - 15) For the θ b and θ g in Equation (2 - 15), taking the derivatives respectively, we get: (2 - 16) By solving the simultaneous equations of (2 - 16), we get: (2 - 17) Where: Among them, θ c is the angle between link c and the x ' axis, θ f is the angle between link f and the x ' axis.

[0067] Substituting Equation (2 - 17) into Equation (2 - 14), we get Equation (2 - 18): (2 - 18) Where: ; ; ; .

[0068] J is the velocity transformation Jacobian matrix of the liquid hydrogen transfer arm of the multi - link mechanism, and it can also represent the transformation of the execution velocity of the execution end of the transfer arm and the joint velocity. Equation (2 - 18) represents the relationship between the velocities of the execution end of the liquid hydrogen transfer arm along the x axis and the y axis and the angular velocities of the two driving components. The Jacobian matrix is only related to the kinematic dimensions and the relative positions between the mechanisms, and has nothing to do with the motion states of the prime movers.

[0069] After completing the kinematic analysis of the liquid hydrogen transfer arm, this application can analyze the control strategy (control principle of the control model) of the liquid hydrogen transfer arm based on the kinematic analysis results. The control objectives of this application include active tracking control and follow-up control that follows the ship affected by waves and wind speed after docking. In this application, the liquid hydrogen transfer arm has two hydraulic systems, and each hydraulic system has an independent servo drive system for position closed-loop control. The two position closed-loop control loops constitute the motion control system of the liquid hydrogen transfer arm. The schematic diagram of the control system is as shown in Figure 3 shown.

[0070] The following will detail the process of deriving from the dynamic analysis of the liquid hydrogen transfer arm to obtaining the control model: (1) Dynamic model of the liquid hydrogen transfer arm.

[0071] In the dynamic analysis of the liquid hydrogen transfer arm, only the relationship between the mechanical motion and the external forces is considered, and it is not necessary to calculate the constraints and constraint reaction forces of each kinematic pair. The Lagrange equation can solve this problem. The corresponding Lagrange equation is as follows: (3-1) In the formula: is the kinetic energy of the system; is the potential energy of the system; is the generalized coordinate; is the generalized force; when the generalized coordinate is the angular displacement, F i is the torque, and when it is the linear displacement, F i is the force; n is the number of generalized coordinates in the system.

[0072] It can be obtained from formula (3-1) that Lagrange establishes the relationship between the kinetic energy, potential energy and work of the system from the perspective of energy. The formula does not contain unknown constraint reaction forces, which greatly reduces the number of equations. Therefore, the Lagrange equation has been widely used in the solution of mechanism dynamics, thus making up for the deficiency of calculating the dynamic equation by Newton's law. According to the actual situation, assume that the liquid hydrogen transfer arm is an ideal mechanical system, ignore the elastic deformation of each component, and regard it completely as a rigid body; ignore the friction between each kinematic pair and there is no gap between each kinematic pair. Then the dynamic analysis steps of the mechanical system of the liquid hydrogen transfer arm are as follows: 1) Kinetic energy of the system: Assume that the i th link component in the mechanical system of the liquid hydrogen transfer arm makes general planar motion, and the center of mass i of the S i th link has a speed of v si and its angular velocity is φj , with a mass of m i , and the moment of inertia about the centroid s i is J si , and its kinetic energy E k can be expressed as: (3 - 2) When the component is in translational motion, the kinetic energy only contains the first term of Equation (3 - 2). When the component rotates about the centroid as a fixed-axis rotation, it only contains the second term. Therefore, the total kinetic energy of the mechanical system is: (3 - 3) Among them, n is the total number of system components. For the multi-link liquid hydrogen transfer arm mechanism, analyze the geometric position relationships of each component. The angular displacements φ i of each moving component and the relevant points s on the component, such as the centroid s i on the component and the coordinates of the external force application point are represented by the generalized coordinates q 1, q 2, that is: q 1 is φ 5, q 2 is φ 6, that is: (3 - 4) Among them, φ i is the rotation angle of the i -th component in the mechanical system, x si , y si are respectively the abscissa and ordinate of the centroid of the i -th component. Taking the time derivative of Equation (3 - 4) can obtain the generalized velocity: (3 - 5) When s the point represents the centroid s i , from Equation (3 - 5), x si and y si can be obtained, and thus the centroid velocities of each component can be calculated: (3 - 6) After transformation, it can be expressed as: (3 - 7) It can be obtained that the total kinetic energy of this two-degree-of-freedom liquid hydrogen transfer arm system is: (3-8) The final kinetic energy E can be expressed as: (3-9) In the formula Among them, the coefficients J 11 , J 22 , J 12 are the system parameters with moments of inertia, and can also be called the equivalent moments of inertia of the two-degree-of-freedom system. J 11 , J 22 , J 12 are related to the two active link mechanisms. In the actual scenario, through position analysis, it can be directly obtained that x si , y si and φ i As q 1, q 2 function expressions, and the corresponding partial derivatives with respect to q 1, q 2 can be obtained respectively. Substituting them into the above formula, J 11 , J 22 , J 12 can be obtained, and finally the kinetic energy E can be obtained.

[0073] 2) Potential energy of the system: The potential energy of the system only depends on the position of the center of mass of the system. For the liquid hydrogen transfer arm, select x axis as the zero potential energy surface, y the negative direction of the axis is the direction of potential energy. Therefore, the potential energy of the system is: (3-10) Among them, m i is the mass of the i th component in this mechanism system, y ic is the i th ordinate of the center of mass of the component.

[0074] 3) Generalized force of the system: The generalized force is determined according to the principle of virtual work. The virtual work of the generalized force (3 - 11) where σ 1 and σ 2 are two virtual displacements corresponding to the generalized coordinates, F 1 and F 2 are the corresponding generalized forces; assume F k and M j are the external force and external torque acting on the liquid hydrogen transfer arm respectively, then the virtual work can be expressed by these forces and torques as: ((3 - 12) In the formula σ i is the virtual displacement of the rotation angle of the mechanical component acted on by the external torque M i ; σ sk is the displacement of the acting point of the external force σ k is the acting force F k and the virtual displacement σ sk the included angle between them.

[0075] From the basic principle of virtual work σW 1= σW 2, the generalized force can be deduced as: (3 - 13) (3 - 14) where F 1 is the driving torque of the first driving cylinder to the connecting rod g ; F 2 is the driving torque of the second driving cylinder to the connecting rod b . Therefore, for the liquid hydrogen transfer arm of this application, the two generalized forces are the driving torques of the two hydraulic cylinders to the corresponding driving rods.

[0076] (2) Driving model of the liquid hydrogen transfer arm: In this application, the two drives of the liquid hydrogen transfer arm are independent of each other, and the mutual coupling between the connecting rods is not considered. Studying one of the hydraulic cylinders in the liquid hydrogen transfer arm, the driving hydraulic cylinder generates a driving force, which is converted into an output force through the connection between the boom arms. Generally, the liquid hydrogen transfer arm is simplified to a rigid body, and a second-order linear system of single-link hydraulic drive can be simplified to: (3 - 15) where F is the output force of the hydraulic cylinder;S is the displacement of the piston process; C is the damping coefficient; K is the stiffness of the spring; f 0 is the initial value of the spring force. Assume the open-loop motion equation of the second-order system is: (3-16) where, f is the input variable; x is the output variable; m, b, n is the system parameter. Therefore, the expression of the control part based on the model can be expressed as: (3-17) where, α，β is a function or constant; f ' is the new input variable. Comparing the above formula (3-17), we can get: (3-18) , In summary, from (3-18), we can get: (3-19) Design control rate calculation f ': (3-20) where, k v is the velocity gain; k p is the displacement gain; The servo control expression of the single-link is obtained: (3-21) Thus, the error control expression of the system can be obtained as: (3-22) where, k i is the integral gain; e is the error value of the piston displacement output by the hydraulic cylinder.

[0077] The parameters selected for motion control by controlling a single rotating link joint are: (3-23) where, S d is the expected input value of the load displacement. The load displacement is the displacement generated by the driving device such as a motor during each rotation when bearing the load. Specifically, the load displacement is the distance that the mechanical device moves when rotating one week under the action of the load, Sd refers to the expected input value of the load displacement parameter; S is the actual output value of the displacement of the piston of the hydraulic cylinder. Therefore, the closed-loop system dynamics is: (3-24) On this basis, a PD control model for the loading and unloading arm is established. The control model contains a feedforward control scheme with feedback to control the deviation between the actual position and the desired position until the deviation is zero or within a preset range. The PD model is as Figure 11 shown. Figure 11 is a schematic diagram of the control principle of a PD control model shown in an embodiment of the present application. In Figure 11 , represents the displacement of the piston of the expected output, represents the error between the displacement of the piston of the expected output and the displacement of the piston of the actual output.

[0078] In the present application, the hydraulic system of the liquid hydrogen transfer arm mainly includes three parts: a pump station, a hydraulic cylinder, and a control valve. A key component in the hydraulic system is the three-position four-way directional control valve, which can not only change the movement direction of the hydraulic cylinder, but also when the liquid hydrogen transfer arm is in the follow-up control mode, the hydraulic cylinder can move under the action of an external force, the pump does not unload, and the hydraulic cylinder is in a floating state. The present application selects a three-position four-way Y-type directional control valve, and its structural schematic diagram is as Figure 12 shown. Figure 12 is a schematic diagram of a three-position four-way directional control valve shown in an embodiment of the present application. When the directional control valve is in the left position or the right position, the valve ports P, T, A, and B are directly connected or cross-connected to control the movement direction of the hydraulic cylinder, thereby adjusting the pose of the liquid hydrogen transfer arm; after the execution end is docked with the liquid hydrogen transport ship, the execution end detection system sends a signal to make the three-position four-way directional control valve in the middle position function, the P port is closed, the A, B, and T ports are connected, the oil inlet and outlet of the hydraulic cylinder are connected, the hydraulic system is in a floating state, and it can move under the action of an external force, so as to ensure that the liquid hydrogen transfer arm can move with the movement of the liquid hydrogen transport ship to realize the safe transportation of liquid hydrogen. Another key component of the hydraulic system is the electro-hydraulic proportional speed control valve, which controls the output flow by inputting an electric signal to control the size of the valve port, thereby controlling the speed adjustment of the actuator. When the input electric signal is different, the electromagnetic force is different, and the force on the push rod is different, so there are different opening degrees. The electro-hydraulic proportional speed control valve occupies a small volume and has a fast response ability. The electro-hydraulic proportional speed control valve is used in combination with the oil cylinder between the rodless cavity of the hydraulic device and the directional control valve. In addition, two-way hydraulic locks are installed in the two hydraulic circuits, and the actuator can be locked for a long time even under the action of an external force in the non-working state. In summary, the hydraulic system of the multi-link liquid hydrogen transfer arm is as Figure 13 shown. Figure 13It is a schematic structural diagram of the hydraulic system of the multi-link liquid hydrogen transfer arm shown in an embodiment of the present application. The core of the control system of the liquid hydrogen transfer arm is the control of the movement of the boom. Model the dynamics of the transfer arm, and then establish its control model, as Figure 11 shown.

[0079] In the present application, the movement of the liquid hydrogen transfer arm is driven by a hydraulic cylinder with bidirectional movement. The drive control of this method is relatively simple and can meet the requirements of the driving force of the liquid hydrogen transfer arm. The liquid hydrogen transfer arm reaches the specified position smoothly and quickly without vibration, and can ensure following the target position during operation to realize the normal transmission of liquid hydrogen. Therefore, it is necessary to design and analyze the control system of the hydraulic cylinder. In order to enable the execution end of the liquid hydrogen transfer arm to reach the target position stably through the drive of two hydraulic cylinders, it is necessary to achieve stable and rapid control of each hydraulic cylinder. The hydraulic system is simplified as Figure 14 shown. Figure 14 It is a simplified schematic diagram of a hydraulic system shown in an embodiment of the present application.

[0080] Assume that the oil pressure on both sides of the oil cylinder is evenly distributed. From this, the motion equation of the hydraulic cylinder can be obtained as follows: Where, M is the mass of the piston rod; S is the displacement during the movement of the piston; P1 and P2 are the pressures of the rodless chamber and the rod chamber of the hydraulic cylinder respectively, A1 and A2 are the acting areas of the rodless chamber and the rod chamber of the hydraulic cylinder respectively; C is the damping coefficient; K is the stiffness of the spring; f0 is the initial value of the spring force. Then the driving force F of the hydraulic cylinder is: Combining the above two formulas, the final driving force of the hydraulic cylinder can be obtained: In summary, the technical solution of the present application at least includes the following technical effects: (1) It can realize the configuration analysis of the liquid hydrogen transfer arm, calculate the degrees of freedom of the liquid hydrogen transfer arm mechanism, analyze and obtain a general general chain structure, and then be able to perform specific processing on the general chain for the frame and drive to obtain a specific chain map that meets the requirements, and obtain a general motion chain map that meets the motion requirements. (2) In the present application, a position mathematical equation of the liquid hydrogen ship-shore transfer arm is established by a vector method, and the velocity equation of the transfer arm mechanism can be obtained by differentiating the position equation. The Jacobian matrix of the liquid hydrogen transfer arm is obtained from the velocity equation. To ensure the normal operation of the liquid hydrogen transfer arm mechanism without jamming, a singularity analysis of the mechanism is performed. Under the conditions of mobility, non-singularity, and actual working conditions, the parameters of each link of the liquid hydrogen transfer arm can be determined and its working space can be analyzed, thereby providing a basis for the overall device modeling, manufacturing, and processing of the liquid hydrogen transfer arm. (3) It can analyze the dynamics of the liquid hydrogen transfer arm, establish a dynamic model of the hydraulic actuator, and complete the position control model of the liquid hydrogen transfer arm on this basis, which can lay a foundation for the prototype manufacturing, testing, and motion control optimization of the liquid hydrogen transfer arm.

[0081] The device 1500 for controlling a multi-link type liquid hydrogen transfer arm provided by the present application will be described below. The device for controlling a multi-link type liquid hydrogen transfer arm described below can be correspondingly referred to with the method for controlling a multi-link type liquid hydrogen transfer arm described above.

[0082] Figure 15 is a structural block diagram of a device for controlling a multi-link type liquid hydrogen transfer arm shown in an embodiment of the present application. Referring to Figure 15 , the device 1500 includes: A first determination module 1501, configured to determine a target position when the execution end of the liquid hydrogen transfer arm is docked with a liquid hydrogen transport ship; A second determination module 1502, configured to determine an expected displacement, an expected speed, and an expected acceleration when a piston in a target hydraulic cylinder moves according to the target position. The target hydraulic cylinder is disposed in a hydraulic system corresponding to the liquid hydrogen transfer arm, and the hydraulic system is used to provide power for the operation of the liquid hydrogen transfer arm; A first acquisition module 1503, configured to acquire an actual displacement and an actual speed when the piston moves; A third determination module 1504, configured to determine a displacement error when the piston moves according to the expected displacement and the actual displacement, and determine a speed error when the piston moves according to the expected speed and the actual speed; A second acquisition module 1505, configured to obtain a control command for the target hydraulic cylinder according to the displacement error, the velocity error, and the desired acceleration. The control command is generated with the goal that both the displacement error and the velocity error are within corresponding preset error ranges, and the control command is used to achieve the docking between the execution end and the liquid hydrogen carrier ship; A sending module 1506, configured to send the control command to the hydraulic system, so that the hydraulic system controls the movement of the target hydraulic cylinder according to the control command to control the movement of the liquid hydrogen transfer arm.

[0083] According to a device for controlling a multi-link type liquid hydrogen transfer arm provided by the present application, the second determination module 1502 includes: A first acquisition sub-module, configured to acquire a spatial mechanism schematic diagram corresponding to the liquid hydrogen transfer arm; A second acquisition sub-module, configured to acquire parameter information of each component in the spatial mechanism schematic diagram and kinematic analysis results satisfied by different components; A first determination sub-module, configured to determine the desired displacement, the desired velocity, and the desired acceleration according to the target position, the parameter information of each component, and the kinematic analysis results.

[0084] According to a device for controlling a multi-link type liquid hydrogen transfer arm provided by the present application, the first determination sub-module includes: A second determination sub-module, configured to determine parameter information of a target component corresponding to the target hydraulic cylinder in the spatial mechanism schematic diagram according to the position of the target position in the coordinate system of the spatial mechanism schematic diagram and the parameter information of each component; A third determination sub-module, configured to determine the desired displacement according to the kinematic analysis result satisfied between the parameter information of the target component and the displacement of the piston in the target hydraulic cylinder; A third acquisition sub-module, configured to take the derivative of the time parameter in the desired displacement to obtain the desired velocity; A fourth acquisition sub-module, configured to take the derivative of the time parameter in the desired velocity to obtain the desired acceleration.

[0085] According to a device for controlling a multi-link type liquid hydrogen transfer arm provided by the present application, the parameter information of the target component includes the angle between the target component and the coordinate axes of the coordinate system in the spatial mechanism schematic diagram.

[0086] According to a device for controlling a multi-link type liquid hydrogen transfer arm provided by the present application, the spatial mechanism schematic diagram is obtained in advance through the following steps: Analyze the kinematic chain of the liquid hydrogen transfer arm to obtain a candidate reduced-link adjacency matrix representing the topological structure of the kinematic chain and a kinematic graph chain corresponding to the candidate reduced-link adjacency matrix; Determine a specific kinematic graph chain that meets the preset conditions in the kinematic graph chain; Obtain the spatial mechanism schematic diagram according to the specific kinematic graph chain and the parameter information of the liquid hydrogen transfer arm.

[0087] According to a device for controlling a multi-link type liquid hydrogen transfer arm provided by the present application, the second acquisition module 1505 includes: A fifth acquisition sub-module, configured to analyze the displacement error, the velocity error, and the desired acceleration through a proportional-derivative control model pre-constructed for the liquid hydrogen transfer arm to obtain a control command for the target hydraulic cylinder.

[0088] According to a device for controlling a multi-link type liquid hydrogen transfer arm provided by the present application, the hydraulic system includes a first hydraulic system and a second hydraulic system. The target hydraulic cylinder includes a first hydraulic cylinder located in the first hydraulic system and a second hydraulic cylinder located in the second hydraulic system. The host computer is electrically connected to the hydraulic drive circuit module through a microcontroller unit. The hydraulic drive circuit module is electrically connected to the first hydraulic system and the second hydraulic system respectively. The control command includes a first control command corresponding to the first hydraulic cylinder and a second control command corresponding to the second hydraulic cylinder; the sending module 1506 includes: A first sending sub-module, configured to send the first control command to the first hydraulic system through the microcontroller unit and the hydraulic drive circuit module; A second sending sub-module, configured to send the second control command to the second hydraulic system through the microcontroller unit and the hydraulic drive circuit module.

[0089] Figure 16 It is a schematic diagram of the physical structure of an electronic device shown in an embodiment of the present application. As Figure 16 shown, the electronic device may include: a processor 1610, a communication interface 1620, a memory 1630, and a communication bus 1640. Among them, the processor 1610, the communication interface 1620, and the memory 1630 complete mutual communication through the communication bus 1640. The processor 1610 can call logical instructions in the memory 1630 to execute a method for controlling a multi-link type liquid hydrogen transfer arm.

[0090] In addition, when the logical instructions in the above-mentioned memory 1630 are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on such an understanding, the technical solution of the present application, in essence, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in various embodiments of the present application. The foregoing storage medium includes: various media such as USB flash drives, mobile hard disks, read-only memories (ROMs), random access memories (RAMs), magnetic disks, or optical discs that can store program codes.

[0091] On the other hand, the present application also provides a computer program product. The computer program product includes a computer program that can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer can execute a method for controlling a multi-link type liquid hydrogen transfer arm provided by the above-mentioned various methods.

[0092] In yet another aspect, the present application also provides a non-transitory computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, it is configured to execute a method for controlling a multi-link type liquid hydrogen transfer arm provided by the above-mentioned various methods.

[0093] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. A person of ordinary skill in the art can understand and implement it without creative labor.

[0094] Through the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on such an understanding, the technical solution, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disks, optical discs, etc., and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute the methods described in various embodiments or some parts of the embodiments.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit them. Although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. These modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present application.

Claims

1. A method for controlling a multi-link type liquid hydrogen transfer arm, characterized in that, Applied to the host computer, the method includes: Determine the target position when the execution end of the liquid hydrogen transfer arm is docked with the liquid hydrogen carrier; According to the target position, determine the expected displacement, expected speed, and expected acceleration when the piston in the target hydraulic cylinder moves. The target hydraulic cylinder is arranged in the hydraulic system corresponding to the liquid hydrogen transfer arm, and the hydraulic system is used to provide power for the operation of the liquid hydrogen transfer arm; Obtain the actual displacement and actual speed when the piston moves; Determine the displacement error when the piston moves according to the expected displacement and the actual displacement, and determine the speed error when the piston moves according to the expected speed and the actual speed; According to the displacement error, the speed error, and the expected acceleration, obtain a control command for the target hydraulic cylinder. The control command is generated with the goal that both the displacement error and the speed error are within the corresponding preset error ranges, and the control command is used to achieve the docking between the execution end and the liquid hydrogen carrier; Send the control command to the hydraulic system, so that the hydraulic system controls the movement of the target hydraulic cylinder according to the control command to control the action of the liquid hydrogen transfer arm.

2. The method according to claim 1, wherein The step of determining the expected displacement, expected speed, and expected acceleration when the piston in the target hydraulic cylinder moves according to the target position includes: Obtain the spatial mechanism diagram corresponding to the liquid hydrogen transfer arm; Obtain the parameter information of each component in the spatial mechanism diagram and the kinematic analysis results satisfied by different components; According to the target position, the parameter information of each component, and the kinematic analysis results, determine the expected displacement, the expected speed, and the expected acceleration.

3. The method according to claim 2, wherein The step of determining the expected displacement, expected speed, and expected acceleration according to the target position, the parameter information of each component, and the kinematic analysis results includes: According to the position of the target position in the coordinate system of the spatial mechanism diagram and the parameter information of each component, determine the parameter information of the target component corresponding to the target hydraulic cylinder in the spatial mechanism diagram; According to the kinematic analysis result satisfied between the parameter information of the target component and the displacement of the piston in the target hydraulic cylinder, determine the expected displacement; Take the derivative of the time parameter in the expected displacement to obtain the expected speed; Take the derivative of the time parameter in the expected speed to obtain the expected acceleration.

4. The method according to claim 3, characterized in that, The parameter information of the target component includes the angle between the target component and the coordinate axes of the coordinate system in the spatial mechanism diagram.

5. The method according to claim 2, wherein The spatial mechanism diagram is obtained in advance through the following steps: Analyze the motion chain of the liquid hydrogen transfer arm to obtain a candidate contracted link adjacency matrix representing the topological structure of the motion chain and a motion map chain corresponding to the candidate contracted link adjacency matrix; Determine a specific motion map chain that meets the preset conditions in the motion map chain; According to the specific motion map chain and the parameter information of the liquid hydrogen transfer arm, obtain the spatial mechanism diagram.

6. The method according to claim 1, wherein Obtaining a control command for the target hydraulic cylinder according to the displacement error, the velocity error, and the desired acceleration includes: Analyzing the displacement error, the velocity error, and the desired acceleration through a proportional-derivative control model pre-constructed for the liquid hydrogen transfer arm to obtain the control command for the target hydraulic cylinder.

7. The method according to claim 1, wherein The hydraulic system includes a first hydraulic system and a second hydraulic system. The target hydraulic cylinder includes a first hydraulic cylinder located in the first hydraulic system and a second hydraulic cylinder located in the second hydraulic system. The host computer is electrically connected to a hydraulic drive circuit module through a microcontroller unit. The hydraulic drive circuit module is electrically connected to the first hydraulic system and the second hydraulic system respectively. The control command includes a first control command corresponding to the first hydraulic cylinder and a second control command corresponding to the second hydraulic cylinder. Sending the control command to the hydraulic system includes: Sending the first control command to the first hydraulic system through the microcontroller unit and the hydraulic drive circuit module; Sending the second control command to the second hydraulic system through the microcontroller unit and the hydraulic drive circuit module.

8. A device for controlling a multi-link type liquid hydrogen transfer arm, characterized in that, Including: A first determination module for determining the target position when the execution end of the liquid hydrogen transfer arm docks with the liquid hydrogen carrier; A second determination module for determining the desired displacement, desired velocity, and desired acceleration during the movement of the piston in the target hydraulic cylinder according to the target position. The target hydraulic cylinder is arranged in the hydraulic system corresponding to the liquid hydrogen transfer arm, and the hydraulic system is used to provide power for the operation of the liquid hydrogen transfer arm; A first acquisition module for acquiring the actual displacement and actual velocity during the movement of the piston; A third determination module for determining the displacement error during the movement of the piston according to the desired displacement and the actual displacement, and determining the velocity error during the movement of the piston according to the desired velocity and the actual velocity; A second acquisition module for obtaining a control command for the target hydraulic cylinder according to the displacement error, the velocity error, and the desired acceleration. The control command is generated with the goal that both the displacement error and the velocity error are within the corresponding preset error ranges, and the control command is used to achieve the docking between the execution end and the liquid hydrogen carrier; A sending module for sending the control command to the hydraulic system, so that the hydraulic system controls the movement of the target hydraulic cylinder according to the control command to control the action of the liquid hydrogen transfer arm.

9. An electronic device, comprising a memory, a processor, and a computer program stored on the memory and running on the processor, characterized in that, When the processor executes the computer program, it implements a method for controlling a liquid hydrogen transfer arm in the form of a multi-link as described in any one of claims 1 to 7.

10. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements a method for controlling a liquid hydrogen transfer arm in the form of a multi-link as described in any one of claims 1 to 7.

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