Robotic joint soft limit protection methods, devices, and media

Abstract

Embodiments of the present application provide a robot joint soft limit protection method, device and medium, and relate to the technical field of robots, and the method comprises the following steps: when a collaborative robot is in a current loop dragging working condition, a theoretical impedance control law is obtained by analyzing a flexible-ignoring collaborative robot dynamics theoretical model; the theoretical impedance control law is substituted into the dynamics theoretical model to be equivalent to a mass-damping-spring system affected by an external torque, and a target impedance control law is determined. Based on the target impedance control law, the external torque applied to each joint is calculated, and whether the trigger condition of the soft limit protection mechanism is met is determined according to the deviation between the real-time angular position of each joint and the soft limit setting value. In the case of meeting the trigger condition, the required virtual damping torque of each joint is dynamically calculated, the virtual damping torque is taken as a compensation torque, and the compensation torque is superimposed on the current loop instruction, so that the soft limit protection can be reliably realized.

Description

Technical Field

[0001] This invention relates to the field of robotics, and more specifically, to a method, device, and medium for soft limit protection of robot joints. Background Technology

[0002] With technological advancements, collaborative robots are increasingly used in various scenarios, making their operational safety a critical research issue. The range of motion of collaborative robots' joints is typically physically constrained using mechanical hard limits (such as limit posts) to ensure safety. Simultaneously, to adapt to diverse working environments and task requirements, software limiting functions are usually configured, such as setting the joint range of motion through software programs in the motion controller.

[0003] However, when driven by a current loop, the joint is in a torque control state, rendering the soft limit protection mechanism ineffective. For joints without hard limits that can rotate 360° multiple times, soft limit protection is particularly important due to the limitations of the internal wiring harness. In this case, if the joint movement exceeds the soft limit range, the actuator may trigger a fault protection mechanism due to detecting abnormal conditions such as position over-limit, thus affecting operation. Therefore, how to reliably implement soft limit protection for collaborative robots becomes a problem that needs to be studied. Summary of the Invention

[0004] One of the objectives of this invention includes, for example, providing a method, apparatus, and medium for soft limit protection of robot joints to at least partially improve the reliability of soft limit protection implementation for collaborative robots.

[0005] The embodiments of the present invention can be implemented as follows: In a first aspect, embodiments of the present invention provide a method for soft-limit protection of robot joints, comprising: When the collaborative robot is under the condition of being driven by a current loop, the theoretical impedance control law is obtained based on the dynamic theoretical model of the collaborative robot that ignores flexibility. Substituting the theoretical impedance control law into the dynamic theory model, it is equivalent to a mass-damped-spring system affected by external torque, and the target impedance control law is determined. Based on the target impedance control law, the external torque applied to each joint is calculated. The deviation between the real-time angular position of each joint and the soft limit setting value is used to determine whether the triggering condition of the soft limit protection mechanism is met. If the triggering condition is met, the virtual damping torque required for each joint is dynamically calculated. The virtual damping torque is used as a compensating torque and superimposed on the current loop command to achieve soft limit protection.

[0006] In an optional implementation, the collaborative robot dynamics model that ignores flexibility includes:

[0007] in, These are the joint angular position, angular velocity, and angular acceleration, respectively. The inertia matrix; The matrix represents the Coriolis force and the centripetal force. It is the gravitational moment vector; It is the friction torque vector; This is the equivalent output torque of the motor; The external torques acting on each joint due to external factors; The torque equivalent to the end load at each joint; The theoretical impedance control law is used to transform the dynamic theoretical model into a virtual mass-damped-spring system, and the theoretical impedance control law includes:

[0008] in, These are the adjustable mass, damping, and stiffness matrices, respectively; The difference in angular position. , The desired joint angle position; It is an identity matrix.

[0009] In an optional implementation, by substituting the theoretical impedance control law into the dynamic theory model, the following is obtained:

[0010] The target impedance control law includes: .

[0011] In an optional implementation, calculating the external torque applied to each joint based on the target impedance control law includes: Based on current feedback, the external torque is calculated using the following formula:

[0012] in, The reduction ratio of each joint reducer; The torque constants of the motors at each joint; This refers to the motor winding current; Combining the aforementioned external torque calculation formula, and substituting the target impedance control law into the aforementioned dynamic theory model, the joint dynamic characteristics are approximated as a damped-spring system: .

[0013] In an optional implementation, the soft limiting range of each joint is:

[0014] in, These are the lower and upper limits of the soft limit setting value, respectively; The deviations of each joint angle position from the soft limit setting value are calculated using the following formula:

[0015] in, The difference between the lower and upper limits of each joint angle position and the soft limit setting value; The triggering conditions include:

[0016] in, The threshold value for the angular position difference is set.

[0017] In an optional implementation, the dynamic calculation of the virtual damping torque required for each joint includes: The virtual damping matrix is ​​obtained using the following formula. :

[0018] in, The basic damping matrix; This is the gain matrix for nonlinear damping; The curvature constant of the exponential function; This is a constant used to adjust the desired angular position;

[0019] in, The joint angular velocity threshold; The virtual stiffness matrix is ​​obtained using the following formula. :

[0020] in, This is the gain matrix for nonlinear stiffness; The curvature constant of the exponential function; The angular position threshold used for stiffness triggering; Based on the virtual damping matrix, virtual stiffness matrix, and external torque, the virtual damping torque required for each joint is calculated.

[0021] In an optional implementation, the virtual damping torque It is calculated using the following formula:

[0022] The virtual damping moment calculated based on the following formula Limiting the amplitude:

[0023] in, This is a proportionality coefficient, ranging from 0 to 1.0; The rated torque for each joint.

[0024] In an optional implementation, the step of superimposing the virtual damping torque as a compensating torque onto the current loop command includes: Calculate the current loop command using the following formula and issue it: .

[0025] In a second aspect, embodiments of the present invention provide an electronic device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the robot joint soft limit protection method described in any of the foregoing embodiments.

[0026] Thirdly, embodiments of the present invention provide a computer-readable storage medium, the computer-readable storage medium including a computer program, wherein the computer program, when running, controls the electronic device where the computer-readable storage medium is located to execute the robot joint soft limit protection method described in any of the foregoing embodiments.

[0027] The beneficial effects of this invention include, for example, that under current loop drive conditions, a system-level synergistic effect is achieved through a complete closed-loop logic of dynamic modeling, impedance equivalence, conditional triggering, and closed-loop compensation. This enables real-time monitoring of the deviation between the joint angle position and the soft limit setting value, dynamically calculating and applying a virtual damping torque as a compensation torque, thereby achieving active, continuous, and adjustable soft limit protection. This method improves the safety of human-machine collaboration, reduces false triggering, ensures control real-time performance and configurability, and effectively improves the reliability of soft limit protection. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This diagram illustrates a schematic representation of the implementation architecture for soft limit protection of robot joints in a related art, as provided in an embodiment of the present invention.

[0030] Figure 2 The diagram illustrates an application scenario provided by an embodiment of the present invention.

[0031] Figure 3 The diagram shows a flowchart of a robot joint soft limit protection method provided by an embodiment of the present invention.

[0032] Figure 4 This diagram illustrates another flow chart of a robot joint soft limit protection method provided by an embodiment of the present invention.

[0033] Icons: 100 - Electronic device; 110 - Memory; 120 - Processor; 130 - Communication module. Detailed Implementation

[0034] Currently, if the joint movement of a collaborative robot exceeds the soft limit range, the actuator may trigger a fault protection mechanism due to detecting abnormal conditions such as position exceeding the limit, thereby affecting operation.

[0035] like Figure 1 As shown, to improve the reliability of soft limit protection in collaborative robots, a joint space impedance control strategy can be adopted. This strategy virtually constructs a spring-damping model related to the joint angle. When the joint approaches the preset soft limit, a corresponding virtual torque is generated to simulate the physical boundary and prevent further joint movement. In implementation, the joint space impedance control strategy is typically used with the joint soft limit setpoint at the desired position. The specific implementation mainly includes the following two schemes: 1. No virtual damping is set during the movement to the desired position; fixed stiffness-damping parameters are only used at the desired position.

[0036] 2. During the movement towards the desired position, a nonlinear growth strategy is used to adaptively adjust the virtual damping, without setting virtual stiffness.

[0037] In addition, a forced switch to a position loop can be implemented when the soft limit is reached, utilizing its high stiffness to achieve soft limit constraint. For example... Figure 1 As shown, a technical implementation architecture for soft limit protection of joints in collaborative robots is provided in related technologies.

[0038] Given that the effectiveness of soft limit protection mechanisms in collaborative robots significantly impacts the active protection of joint harnesses and user experience during current loop dragging, designing a protection mechanism that can maintain stable, smooth, and reliable execution of soft limit constraints during current loop dragging teaching has significant theoretical and engineering research value.

[0039] Research has found that Figure 1 The scheme for soft limit protection based on joint space impedance control has the following limitations in practical applications: 1. Significant damped oscillations are prone to occur near the soft limit boundary, affecting the stability and accuracy of operation.

[0040] 2. When there is a large angular margin between the joint and the soft limit setting, such as 5° to 10°, continuing to move in the limit direction will generate a sharp increase in virtual damping force, causing the actual effective range of motion of each joint to be significantly smaller than the soft limit setting. Furthermore, the forced switching strategy of the control mode will generate a sudden change in torque at the moment of switching, causing shock and oscillation, which will disrupt the smoothness and naturalness of the dragging process.

[0041] Based on the above research, this invention provides a robot joint soft limit protection scheme, which is a joint space impedance control method based on adaptive spring-damping characteristics. When the current loop is dragged, within a certain angle before the soft limit setting value of each joint, the impedance parameter is dynamically adjusted based on the difference between the real-time angular position feedback of the joint and the soft limit setting value. This achieves stable, smooth and reliable soft limit constraint execution.

[0042] The shortcomings of the above solutions are the result of the inventors' practical experience and careful research. Therefore, the discovery process of the above problems and the solutions proposed by the embodiments of the present invention in the following text should be considered as contributions made by the inventors during the invention process.

[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0044] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0045] It should be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0046] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0047] It should be noted that, where there is no conflict, the features in the embodiments of the present invention can be combined with each other.

[0048] Please refer to Figure 2 This is a block diagram of an electronic device 100 provided in this embodiment. The electronic device 100 in this embodiment can be a server, processing device, processing platform, etc., capable of data interaction and processing. For example, the electronic device 100 can be a controller in a collaborative robot, or a server capable of interacting with a collaborative robot. The electronic device 100 includes a memory 110, a processor 120, and a communication module 130. The memory 110, processor 120, and communication module 130 are electrically connected directly or indirectly to each other to realize data transmission or interaction. For example, these components can be electrically connected to each other through one or more communication buses or signal lines.

[0049] The memory 110 is used to store programs or data. The memory 110 may be, but is not limited to, random access memory (RAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), etc.

[0050] The processor 120 is used to read / write data or programs stored in the memory 110 and to perform corresponding functions.

[0051] The communication module 130 is used to establish a communication connection between the electronic device 100 and other communication terminals through the network, and to send and receive data through the network.

[0052] It should be understood that, Figure 2 The structure shown is only a schematic diagram of the electronic device 100. The electronic device 100 may also include components that are larger than... Figure 2 The more or fewer components shown, or having the same Figure 2 The different configurations shown. Figure 2The components shown can be implemented using hardware, software, or a combination thereof.

[0053] Please refer to the following: Figure 3 This is a flowchart illustrating a robot joint soft limit protection method provided in an embodiment of the present invention. It can be derived from... Figure 2 The electronic device 100 performs the operation, for example, by the processor 120 within the electronic device 100. The robot joint soft limit protection method includes steps S110, S120, and S130.

[0054] S110, under the condition of the collaborative robot being driven by a current loop, the theoretical impedance control law is obtained by analyzing the collaborative robot dynamics model that ignores flexibility.

[0055] S120, Substitute the theoretical impedance control law into the dynamic theory model, which is equivalent to a mass-damped-spring system affected by external torque, and determine the target impedance control law.

[0056] S130, based on the target impedance control law, calculate the external torque applied to each joint, determine whether the triggering condition of the soft limit protection mechanism is met according to the deviation between the real-time angular position of each joint and the soft limit setting value, and dynamically calculate the virtual damping torque required for each joint if the triggering condition is met.

[0057] S140, the virtual damping torque is used as a compensation torque and superimposed on the current loop command to achieve soft limit protection.

[0058] Compared to the soft limit braking mechanism in related technologies, which only brakes at the boundary, this embodiment uses dynamic modeling, impedance equivalence, conditional triggering, and closed-loop compensation to actively generate a predictable and adjustable virtual damping torque as a compensation torque before the triggering conditions, such as approaching the boundary, are met. This achieves a stable, smooth, and reliable protection mechanism for forcibly executing soft limit constraints under the current loop dragging condition of the collaborative robot, and has better application value.

[0059] In this embodiment, the collaborative robot can be flexibly selected. Taking a six-degree-of-freedom collaborative robotic arm (hereinafter referred to as the robotic arm) as an example, the overall implementation process will be illustrated.

[0060] In S110, a collaborative robot dynamics model that ignores flexibility is adopted. Without considering the flexibility factor, the complexity of the dynamic equations is greatly reduced, which effectively simplifies the calculation, improves the response speed, facilitates real-time analysis and optimization design, and meets the requirements of high efficiency and low cost.

[0061] Theoretical models of collaborative robot dynamics that ignore flexibility can include: (1) in, These are the joint angular position, angular velocity, and angular acceleration, respectively. The inertia matrix; The matrix represents the Coriolis force and the centripetal force. It is the gravitational moment vector; It is the friction torque vector; This is the equivalent output torque of the motor; This refers to the external torques exerted on each joint by external factors such as the operator; This is the torque equivalent to the end load applied to each joint.

[0062] Impedance control in the joint space allows the robotic arm to exhibit the desired dynamic response characteristics when subjected to external torque. By designing a suitable impedance control law, the dynamic theoretical model described by equation (1) can be transformed into a virtual mass-damped-spring system, thereby improving the compliance and dynamic response capability of the robotic arm, enhancing safety and robustness, and making the robotic arm more suitable for complex and variable working environments. By simplifying the complex nonlinear dynamic model into a virtual mass-damped-spring system, the design process of the control law can be greatly simplified, and the control system can be understood and optimized more intuitively.

[0063] Theoretical impedance control laws may include: (2) in, These are the adjustable mass, damping, and stiffness matrices, which are generally positive definite diagonal matrices; The difference in angular position, specifically includes , The desired joint angle position; It is an identity matrix.

[0064] Accordingly, in S120, the theoretical impedance control law is substituted into the dynamic theoretical model, which is equivalent to a mass-damped-spring system affected by external torque, and the target impedance control law is determined to be achieved in the following way.

[0065] Substituting equation (2) into equation (1), we get: (3) From equation (3), it can be seen that under the ideal impedance control law, the dynamic theoretical model of the collaborative robot ultimately manifests as a mass-damped-spring system affected by external torque. Considering the joint angular acceleration during current loop dragging... Usually determined by angular position The noise level is too high after obtaining the result through a second difference, and a time delay is likely to occur after filtering. Therefore, by reasonably ignoring the joint angular acceleration, the theoretical impedance control law described in equation (2) can be simplified to the target impedance control law: (4) Given the target impedance control law obtained in S120, the calculation of the external torque applied to each joint in S130, based on the target impedance control law, can be achieved in the following way. Please refer to [reference needed]. Figure 4 This provides another flowchart illustrating the soft limit protection of robot joints.

[0066] Considering that under the influence of the current loop, the external torque directly causes changes in the motion state, its calculation can be indirectly obtained based on current feedback: (5) in, The reduction ratio of each joint reducer; The torque constants of each joint motor are positive definite diagonal matrices; This represents the motor winding current.

[0067] Combining equation (5) and substituting equation (4) into equation (1), the joint dynamic characteristics can be approximated as a damped-spring system: (6) During current loop dragging, the position feedback of each joint angle is calculated in real time. The difference between the soft limit setting value and the set threshold value is compared to determine whether the triggering condition is met. The soft limit range of each joint is shown in equation (7): (7) in, These are the lower and upper limits of the soft limit setting, respectively.

[0068] Based on equation (7), the difference between the joint angle position feedback and the soft limit setting value is calculated in real time using the following formula: (8) in, The difference between the position of each joint angle and the soft limit setting (lower and upper limits).

[0069] Combined with equation (8), the triggering condition for the soft limit protection mechanism is: (9) in, The threshold for the angular position difference can be set to different values ​​for both forward and reverse rotation.

[0070] The stiffness and damping coefficients are dynamically adjusted based on the designed adaptive law. When the soft limit protection mechanism is triggered, the virtual mass matrix... Can be taken as At this point, equation (4) will be further simplified and can also be designed as a fixed parameter.

[0071] To achieve stable, smooth, and reliable enforcement of soft limit constraints during current loop operation, the control strategy after triggering the soft limit protection mechanism (meeting the triggering conditions) can include: 1. The closer to the joint's soft limit, the greater the resistance felt by the operator, achieving smooth deceleration, but without reducing the joint's actual effective range of motion.

[0072] 2. When moving away from the soft limit of the joint, the resistance should decrease smoothly, or it can be withdrawn without resistance.

[0073] 3. When the operator does not apply force, the angular position of the joint vibrates little.

[0074] 4. Soft joint restraints should be considered as hard restraint conditions.

[0075] Therefore, for requirements 1 to 3 in the control strategy, inspired by Max-Min normalization, a virtual damping matrix is ​​used. It can be designed as: (10) / (11) in, It is the basic damping matrix, which is a positive definite diagonal matrix; Let be the gain matrix of the nonlinear damping, and be a positive definite diagonal matrix; The curvature constant of the exponential function; This is a constant used to adjust the desired angular position.

[0076] Combining the adaptive law of virtual damping and requirement 4 in the control strategy, and inspired by the Softplus activation function in deep learning, the virtual stiffness matrix... It can be designed as: (12) / (13) in, Let be the gain matrix for nonlinear stiffness, and be a positive definite diagonal matrix; The curvature constant of the exponential function; This is the angular position threshold used for stiffness triggering.

[0077] When the joint is far from its soft limit, it can be withdrawn without resistance. At this time, equation (14) can be superimposed on equations (10) and (11): (14) in, This is the joint angular velocity threshold, used to avoid the influence of sensor measurement noise.

[0078] Based on the virtual damping matrix, virtual stiffness matrix, and external torque, the required virtual damping torque for each joint is calculated and can be limited.

[0079] The virtual spring-damping torque of each joint is calculated using equations (5), (7) to (14). Virtual damping torque It can be calculated using the following formula: (15) The virtual damping moment calculated based on the following formula Limiting the amplitude: (16) in, This is a proportionality coefficient, ranging from 0 to 1.0; The rated torque for each joint.

[0080] After obtaining the virtual damping torque based on S130, the virtual damping torque is used as a compensation torque in S140 and superimposed on the current loop command to realize soft limit protection. The current loop command can be calculated by equation (4) and equation (16) and sent to the driver.

[0081] The current loop command can be calculated and issued using the following formula: .

[0082] Addressing the issues of significant attenuation oscillations near the soft limit boundary in related technologies' soft limit protection mechanisms, or the actual effective range of motion of each joint being much smaller than the soft limit setting, this invention aims to maintain stable, smooth, and reliable forced execution of soft limit constraints during current loop drag teaching. Based on a dynamic theory model, an impedance control law is derived, and an adaptive stiffness and Max-Min normalized adaptive damping variation law referencing the Softplus function are designed. Through synchronous adaptive changes in stiffness and damping parameters, a virtual spring-damping force is calculated and superimposed on the current loop command. Actual testing shows that this method achieves the task objective; during movement towards the soft limit, the damping force exhibits a smooth increasing trend without reducing the range of motion of each joint, and there are no significant attenuation oscillations at the soft limit. Furthermore, this method demonstrates strong parameter robustness; it can be adapted to different robot models with only minor parameter adjustments, exhibiting excellent reliability.

[0083] Based on the above, embodiments of the present invention also provide a computer-readable storage medium, the computer-readable storage medium including a computer program, wherein the computer program, when running, controls the electronic device where the computer-readable storage medium is located to execute the above-described robot joint soft limit protection method.

[0084] Using the above-described scheme in this embodiment of the invention, a joint space impedance control method based on adaptive spring-damping characteristics is proposed, which can maintain stable, smooth, and reliable enforcement of soft limit constraints during current loop drag teaching. The impedance control law is derived based on the collaborative robot dynamics theory model, and on this basis, an adaptive stiffness referenced to the Softplus function and an adaptive damping variation law normalized to Max-Min are designed. The virtual spring-damping torque calculated thereby can provide a reliable soft limit protection mechanism during current loop drag.

[0085] This embodiment employs a continuous, progressive, and dynamically consistent impedance modeling method, achieving matching of control levels: the current loop is essentially a torque output layer, while impedance control directly acts on the joint external torque calculation layer, resulting in a natural fit without the need to switch control modes, thus avoiding abrupt shocks. It achieves physical interpretability: by abstracting joint motion as a "mass-damping-spring" system, soft-limit behavior is analogous to real mechanical buffering, such as spring pre-compression + damping energy dissipation, resulting in a natural and smooth dragging feel for the user. It achieves theoretical traceability: starting from the dynamic model of the collaborative robot ignoring flexible elements, through transformation and control law derivation, equivalent impedance parameters are rigorously derived, achieving adaptive impedance determination, non-empirical fitting, and possessing verifiability and generalization ability.

[0086] In the several embodiments provided by this invention, it should be understood that the disclosed apparatus and methods can also be implemented in other ways. The apparatus embodiments described above are merely illustrative; for example, the flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of apparatus, methods, and computer program products according to various embodiments of the invention. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order than those marked in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in a block diagram and / or flowchart, and combinations of blocks in block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or action, or using a combination of dedicated hardware and computer instructions.

[0087] In addition, the functional modules in the various embodiments of the present invention can be integrated together to form an independent part, or each module can exist independently, or two or more modules can be integrated to form an independent part.

[0088] If the aforementioned functions are implemented as software functional modules and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a portion 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 to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0089] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for soft limit protection of robot joints, characterized in that, include: When the collaborative robot is under the condition of being driven by a current loop, the theoretical impedance control law is obtained based on the dynamic theoretical model of the collaborative robot that ignores flexibility. Substituting the theoretical impedance control law into the dynamic theory model, it is equivalent to a mass-damped-spring system affected by external torque, and the target impedance control law is determined. Based on the target impedance control law, the external torque applied to each joint is calculated. The deviation between the real-time angular position of each joint and the soft limit setting value is used to determine whether the triggering condition of the soft limit protection mechanism is met. If the triggering condition is met, the virtual damping torque required for each joint is dynamically calculated. The virtual damping torque is used as a compensating torque and superimposed on the current loop command to achieve soft limit protection.

2. The robot joint soft limit protection method according to claim 1, characterized in that, The collaborative robot dynamics model that ignores flexibility includes: in, These are the joint angular position, angular velocity, and angular acceleration, respectively. The inertia matrix; The matrix represents the Coriolis force and the centripetal force. It is the gravitational moment vector; It is the friction torque vector; This is the equivalent output torque of the motor; The external torques acting on each joint due to external factors; The torque equivalent to the end load at each joint; The theoretical impedance control law is used to transform the dynamic theoretical model into a virtual mass-damped-spring system, and the theoretical impedance control law includes: in, These are the adjustable mass, damping, and stiffness matrices, respectively; The difference in angular position. , The desired joint angle position; It is an identity matrix.

3. The robot joint soft limit protection method according to claim 2, characterized in that, By substituting the theoretical impedance control law into the dynamic theory model, we obtain: The target impedance control law includes: 。 4. The robot joint soft limit protection method according to claim 3, characterized in that, The calculation of the external torque applied to each joint based on the target impedance control law includes: Based on current feedback, the external torque is calculated using the following formula: in, The reduction ratio of each joint reducer; The torque constants of the motors at each joint; This refers to the motor winding current; Combining the aforementioned external torque calculation formula, and substituting the target impedance control law into the aforementioned dynamic theoretical model, the joint dynamic characteristics are approximated as a damped-spring system: 。 5. The robot joint soft limit protection method according to claim 4, characterized in that, The soft limit range of each joint is as follows: in, These are the lower and upper limits of the soft limit setting value, respectively; The deviations of each joint angle position from the soft limit setting value are calculated using the following formula: in, The difference between the lower and upper limits of each joint angle position and the soft limit setting value; The triggering conditions include: in, The threshold value for the angular position difference is set.

6. The robot joint soft limit protection method according to claim 5, characterized in that, The dynamic calculation of the virtual damping torque required for each joint includes: The virtual damping matrix is ​​obtained using the following formula. : in, The basic damping matrix; This is the gain matrix for nonlinear damping; The curvature constant of the exponential function; This is a constant used to adjust the desired angular position; in, The joint angular velocity threshold; The virtual stiffness matrix is ​​obtained using the following formula. : in, This is the gain matrix for nonlinear stiffness; The curvature constant of the exponential function; The angular position threshold used for stiffness triggering; Based on the virtual damping matrix, virtual stiffness matrix, and external torque, the virtual damping torque required for each joint is calculated.

7. The robot joint soft limit protection method according to claim 6, characterized in that, The virtual damping torque It is calculated using the following formula: The virtual damping moment calculated based on the following formula Limiting the amplitude: in, This is a proportionality coefficient, ranging from 0 to 1.0; The rated torque for each joint.

8. The robot joint soft limit protection method according to claim 7, characterized in that, The step of adding the virtual damping torque as a compensating torque to the current loop command includes: Calculate the current loop command using the following formula and issue it: 。 9. An electronic device, characterized in that, include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the program, implements the robot joint soft limit protection method according to any one of claims 1 to 8.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes a computer program, which, when executed, controls the electronic device containing the computer-readable storage medium to perform the robot joint soft limit protection method according to any one of claims 1 to 8.

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