A virtual wall construction method for a collaborative robot end effector

Abstract

The present application belongs to the field of robot technology and automation control, and specifically relates to a virtual wall construction method for a collaborative robot end effector, which comprises the following steps: setting a safety boundary for a mechanical arm of the collaborative robot and defining a preset safety boundary plane boundary function; obtaining joint angles of the mechanical arm movement according to six-dimensional force information and executing compliant drag teaching of the mechanical arm; in the teaching process, coordinates of a tool coordinate system at the end of the mechanical arm are obtained in real time and are converted into a coordinate system under the safety plane; in combination with the safety plane boundary function, a mechanical arm controller detects a boundary distance in real time; when the mechanical arm approaches the boundary of the safety plane, the mechanical arm controller monitors the boundary distance in real time and controls the mechanical arm to execute different movement modes according to a set distance measurement threshold for approaching the boundary; according to actual movement conditions of the mechanical arm end corresponding to the different movement modes of the mechanical arm, the above steps are repeated to realize the application of the virtual wall.

Description

Technical Field

[0001] This invention belongs to the field of robotics and automation control, specifically a method for constructing virtual walls for the end effector of a collaborative robot. Background Technology

[0002] In the field of modern robotics, with the increasingly close interaction between robots and humans and the external environment, safety and operational flexibility have gradually become core concerns. Traditional robot control methods mainly focus on precise position control, which performs well in most application scenarios, but may face potential safety risks when interacting with dynamic environments or humans.

[0003] To address these challenges, virtual wall technology has emerged. This technology restricts robot movement by setting virtual boundaries, effectively preventing collisions with people or objects. Virtual walls not only improve the safety of robot operation but also help users more intuitively understand and control the robot's range of motion, thereby reducing potential injury risks. However, current virtual wall technologies rely on a single virtual wall control strategy, which may be insufficient to meet the dual requirements of precision and compliance in complex applications. Summary of the Invention

[0004] The purpose of this invention is to provide a virtual wall construction method for the end effector of a collaborative robot. When a certain degree of freedom of the robotic arm's end effector comes into contact with a boundary, the system switches that degree of freedom to a pure position control mode to ensure that the robotic arm can stop stably and accurately, avoiding collisions. The remaining degrees of freedom continue to move in admittance control mode, achieving smooth movement along the boundary, thus overcoming the shortcomings of the aforementioned virtual wall technology that relies on only a single virtual wall control strategy.

[0005] The technical solution adopted by the present invention to achieve the above objectives is: a method for constructing a virtual wall for an end effector of a collaborative robot, comprising the following steps:

[0006] 1) Set safety boundaries for the robotic arm of the collaborative robot, define a preset safety boundary plane boundary function, and set a distance measurement threshold for approaching the boundary to construct a safe area;

[0007] 2) Read the six-dimensional force information at the end of the collaborative robot by installing a six-dimensional force sensor at the end of the robot; obtain the joint angles of the robotic arm movement based on the six-dimensional force information, and perform compliant drag teaching of the robotic arm;

[0008] 3) During the teaching process, the coordinates pk(xk,yk,zk,rxk,ryk,rzk) of the robotic arm's end-effector coordinate system are acquired in real time, and pk is transformed into the coordinate system of the robotic arm's end-effector. k Transition to safe plane S PCoordinates in the coordinate system (x,y,z)=0 (x k ,y k ); using the safety plane boundary function defined in step 1), combined with the transformed coordinates (x) k ,y k The robotic arm controller detects the boundary distance in real time.

[0009] 4) When the robotic arm approaches the boundary of the safe plane, the robotic arm controller monitors the boundary distance in real time and measures the threshold ∈ based on the set distance to the boundary, and controls the robotic arm to execute different motion modes.

[0010] 5) Repeat step 4) based on the actual movement of the robotic arm end effector corresponding to the different motion modes performed by the robotic arm to realize the application of the virtual wall.

[0011] Step 1) specifically includes:

[0012] With the origin of the current tool system of the robotic arm as the origin of the safety plane (x0, y0, z0, rx0, ry0, rz0), the given boundary function is:

[0013] f(x,y,z),f1(x,y,z)

[0014] Here, f(x,y,z) and f1(x,y,z) are set as single-valued functions to determine the safety plane S. P For: S P (x,y,z)=0, where x,y,z represent spatial coordinates;

[0015] Complete the construction of a safe zone by setting a distance measurement threshold ∈ (epsilon) close to the boundary.

[0016] Step 2) specifically includes:

[0017] 1-1) The collected six-dimensional force information is constrained, and the constrained force information is substituted into the admittance control formula to calculate and generate the target pose;

[0018] 1-2) Transform the calculated target pose from the tool coordinate system to the base coordinate system to ensure that the robotic arm performs the task according to the correct path and posture;

[0019] 1-3) Using the inverse kinematics algorithm of the robotic arm, the corresponding joint angles are calculated, and the calculated joint angles are executed to realize the compliant drag teaching of the robotic arm.

[0020] Step 1-1) specifically includes:

[0021] Let k be the sampling time, Ts be the sampling interval, and i = (0, ∞);

[0022] Gravity compensation is: F(k) = g(F(k))

[0023] Then the degrees of freedom are restricted on the safe plane: F(k) = {f x ,f y Given the variable {0,0,0,0}, restricting the remaining degrees of freedom from forces, and substituting the restricted force information into the admittance control formula to generate the target pose, we have:

[0024]

[0025]

[0026]

[0027]

[0028] Among them, M d ∈R 6 It is the desired inertia matrix, D d ∈R 6 M is the desired damping matrix. d D d All are positive definite matrices. F(k) represents the six-degree-of-freedom forces mounted on the robot's wrist flange, measured by a six-dimensional sensor, and represents the forces in each direction of the tool system. Let F represent the position, velocity, and acceleration of each degree of freedom in the relative safe plane coordinate system generated by the external force F.

[0029] The acceleration and velocity are subject to maximum and minimum constraints, respectively:

[0030]

[0031]

[0032] in, These represent the maximum acceleration and velocity constraints for each degree of freedom in Cartesian space.

[0033] Steps 1-2) are specifically as follows:

[0034] The target pose relative to the safe plane coordinate system is: T p(k)={x k ,y k ,0,0,0,0}

[0035] Will T p(k) is converted into the target pose relative to the base coordinate system, that is:

[0036]

[0037] in, It is the rotation matrix of the end-effector coordinate system origin attitude relative to the base coordinate system, (x k ,y k The coordinate transformation of the robotic arm's end-effector coordinate system to the safety plane S is performed. P The coordinates in the coordinate system (x,y,z)=0.

[0038] Steps 1-3) are specifically as follows:

[0039] Using the inverse kinematics algorithm of the robotic arm, the joint angles are obtained, i.e.:

[0040] q k =ψ( B p k )

[0041] Where, q k ∈R n ψ is the joint angle of the robotic arm, and ψ() is the inverse kinematics function of the robotic arm;

[0042] The obtained joint angle q k Update the robotic arm controller to control the servo motor and achieve servo motion.

[0043] Step 4) specifically includes:

[0044] 2-1) Within the range where the distance to the boundary is greater than the distance measurement threshold ∈, the robotic arm controller adopts an admittance control strategy to achieve zero-force operation and ensure smooth, collision-free movement of the robotic arm within this range;

[0045] 2-2) When a certain degree of freedom of the robotic arm approaches a region where the distance to the boundary is less than the distance measurement threshold ∈, the robotic arm controller switches that degree of freedom to a hybrid position-admittance control strategy;

[0046] 2-3) When the degree of freedom reaches the boundary, the robotic arm controller completely switches that degree of freedom to a pure position control strategy to ensure accurate positioning and avoid collision risks.

[0047] In step 2-1), the adoption of the admittance control strategy specifically refers to:

[0048] When y min +∈≤y ek ≤y max -∈, and x min +∈≤x ek ≤x max When -∈, the x and y degrees of freedom are treated as zero forces, without any processing. The robotic arm controller still uses the admittance control strategy, that is:

[0049]

[0050]

[0051]

[0052]

[0053] Among them, M d ∈R 6 It is the desired inertia matrix, D d ∈R 6 M is the desired damping matrix. d D d All are positive definite matrices. F(k) represents the six-degree-of-freedom forces mounted on the robot's wrist flange, measured by a six-dimensional sensor, and represents the forces in each direction of the tool system. Let F represent the position, velocity, and acceleration of each degree of freedom in the relatively safe plane coordinate system generated by the external force F.

[0054] In step 2-2), the degree of freedom to hybrid position-admittance control strategy includes the following cases:

[0055] a. When y max -∈≤y ek ≤y max And x min +∈≤x ek ≤x max When -∈, the y-degree of freedom representing the safety plane enters the region of mixed control, while the x-degree of freedom is treated as zero force as before. No longer applicable, replaced by a hybrid position and admittance control strategy with y-degree of freedom, i.e.:

[0056]

[0057]

[0058] b. When y min ≤y ek ≤y min +∈andx min +∈≤x ek ≤x max When -∈, the y-degree of freedom representing the safety plane enters the region of mixed control, while the x-degree of freedom is treated as zero force as before. No longer applicable, replaced by a hybrid position and admittance control strategy with y-degree of freedom, i.e.:

[0059]

[0060]

[0061] c. When x max -∈≤x ek ≤xmax And y min +∈≤y ek ≤y max When -∈, the x-degree of freedom representing the safety plane enters the region of mixed control, while the y-degree of freedom remains treated as zero force. No longer applicable, replaced by a mixed position and admittance control formula for the x-degree of freedom, i.e.:

[0062]

[0063]

[0064] d. When x min ≤x ek ≤x min +∈andy min +∈≤y ek ≤y max When -∈, the x-degree of freedom representing the safety plane enters the region of mixed control, while the y-degree of freedom remains treated as zero force. No longer applicable, replaced by a mixed position and admittance control formula for the x-degree of freedom, i.e.:

[0065]

[0066]

[0067] e.When y min ≤y ek ≤y min +∈andx min ≤x ek ≤x min When +∈, the x and y degrees of freedom representing the safety plane enter the region of mixed control. No longer applicable, replaced by a hybrid position and admittance control formula, namely:

[0068]

[0069]

[0070]

[0071]

[0072] f. When y max -∈≤y ek ≤y max &&x max -∈≤x ek ≤x max At this time, the x and y degrees of freedom representing the safety plane enter the region of mixed control. No longer applicable; a hybrid position and admittance control formula has been adopted instead.

[0073]

[0074]

[0075]

[0076]

[0077] In cases a through f, n ∈ {1, 2, 3… 10} is adjusted according to the user's feel, x ek To transition to safe plane S P x-coordinate, y-coordinate ek To transition to safe plane S P y-coordinate, T p k (x) and T p k (y) represents the position of the x and y degrees of freedom in the relative safe plane coordinate system generated by the external force F at time k, ee_p real () represents the safety plane S P The coordinates;

[0078] Depending on conditions a to f, the end-effector coordinates p of the robotic arm are acquired in real time. real =(x k ,y k ,z k (rx, ry, rz), then the coordinates are transformed to the safe plane S. P coordinates ee_p real (x ek ,y ek ,z ek ,rx ek ,ry ek ,rz ek Safety plane S P The boundary function f is then transformed to the base coordinate system according to the admittance control formula, and then the joint angle is obtained by inverse solution for servo motion.

[0079] In steps 2-3), the pure position control mode specifically refers to:

[0080] When y max <y ek ||y ek <y min ||x max <x ek ||x ek <x minWhen this occurs, it indicates that the robotic arm has exceeded the safety boundary and suffered a serious accident. At this point, the positions of each degree of freedom relative to the safety plane coordinate system are... T p(k)=p real The admittance control strategy is no longer effective, and the robotic arm servo remains in its current position.

[0081] The present invention has the following beneficial effects and advantages:

[0082] 1. This invention not only ensures the safety of the robot when approaching the boundary, but also provides it with sufficient compliance and adaptability, enabling it to flexibly cope with changing operating environments.

[0083] 2. This invention also introduces a normalization function to further optimize the performance of the robotic arm under different control modes, allowing the system to interact naturally and safely with the user or external environment while maintaining boundary constraints. When only the degree of freedom entering the safe zone is switched to a hybrid position-admittance control mode, the remaining degrees of freedom will continue to operate according to the pure admittance control strategy, achieving smooth movement along the boundary. The robotic arm can flexibly adapt to different working environments while maintaining overall stability and safety.

[0084] 3. The core of this invention lies in the application of a virtual wall, which intelligently limits the range of motion of the robotic arm, thereby improving the safety and stability of the operation. Attached Figure Description

[0085] Figure 1 This is a schematic diagram of the overall safety plan of the present invention;

[0086] Figure 2 This is a flowchart of the overall algorithm of the present invention;

[0087] Where W is the world coordinate system, B is the robot base coordinate system, E is the robot flange coordinate system, T is the robot tool coordinate system, S is the robot force sensor coordinate system, and ∈ is the hybrid control zone, which is the set distance measurement threshold for approaching the boundary. Detailed Implementation

[0088] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0089] like Figure 2 As shown,

[0090] This invention discloses a method for constructing a virtual wall for an end effector of a collaborative robot, comprising the following steps:

[0091] Step 1: Define the predefined safety boundary plane boundary function:

[0092] When operating and controlling a robotic arm, a safety plane is typically defined to limit its range of motion, ensuring it moves within a safe area. In this case, we can set the origin of the robotic arm's current tool system as the origin of the safety plane for better motion planning and control. Using the origin of the robotic arm's current tool system as the origin of the safety plane, and given boundary functions f(x,y,z) and f1(x,y,z), where f(x,y,z) and f1(x,y,z) are required to be single-valued functions, determine the safety plane S. P (x,y,z)=0, where x,y,z represent spatial coordinates. A safe region is constructed by setting a distance metric threshold ∈(epsilon) close to the boundary.

[0093] Building a secure zone involves the following steps:

[0094] With the origin of the current tool system of the robotic arm as the origin of the safety plane (x0, y0, z0, rx0, ry0, rz0), the given boundary function is:

[0095] f(x,y,z),f1(x,y,z)

[0096] Here, f(x,y,z) and f1(x,y,z) are set as single-valued functions to determine the safety plane S. P For: S P (x,y,z)=0, where x,y,z represent spatial coordinates;

[0097] Complete the construction of a safe zone by setting a distance measurement threshold ∈ (epsilon) close to the boundary.

[0098] Step 2: Implement admittance control:

[0099] When controlling and operating a robotic arm, two coordinate systems are typically involved: the tool coordinate system (end-effector coordinate system) and the base coordinate system (fixed part of the robotic arm). To ensure the safe and precise movement of the robotic arm, we need to read six-dimensional force information within the tool coordinate system and restrict its degrees of freedom to ensure that the robotic arm moves only within a safe plane.

[0100] 1-1) First, read the six-dimensional force information of the end effector in the tool coordinate system. Based on application requirements, restrict or filter this force information to ensure the stability and safety of the robotic arm.

[0101] Next, the constrained force information is substituted into the admittance control formula to calculate and generate the target pose.

[0102] Specifically, the above steps include the following steps:

[0103] Let k be the sampling time, Ts be the sampling interval, and i = (0, ∞);

[0104] Gravity compensation is: F(k) = g(F(k))

[0105] Then the degrees of freedom are restricted on the safe plane: F(k) = {f x ,f y Given the variable {0,0,0,0}, restricting the remaining degrees of freedom from forces, and substituting the restricted force information into the admittance control formula to generate the target pose, we have:

[0106]

[0107]

[0108]

[0109]

[0110] Among them, M d ∈R 6 It is the desired inertia matrix, D d ∈R 6 M is the desired damping matrix. d D d All are positive definite matrices. F(k) represents the six-degree-of-freedom forces mounted on the robot's wrist flange, measured by a six-dimensional sensor, and represents the forces in each direction of the tool system. Let F represent the position, velocity, and acceleration of each degree of freedom in the relative safe plane coordinate system generated by the external force F.

[0111] The acceleration and velocity are subject to maximum and minimum constraints, respectively:

[0112]

[0113]

[0114] in, These represent the maximum acceleration and velocity constraints for each degree of freedom in Cartesian space.

[0115] 1-2) Transform the calculated target pose from the tool coordinate system to the base coordinate system to ensure that the robotic arm performs the task according to the correct path and posture.

[0116] The target pose relative to the safe plane coordinate system is: T p(k)={x k ,y k ,0,0,0,0}

[0117] Will Tp(k) is converted into the target pose relative to the base coordinate system, that is:

[0118]

[0119] in, It is the rotation matrix of the end-effector coordinate system origin attitude relative to the base coordinate system, (x k ,y k The coordinate transformation of the robotic arm's end-effector coordinate system to the safety plane S is performed. P The coordinates in the coordinate system (x,y,z)=0.

[0120] 1-3) Using the inverse kinematics algorithm of the robotic arm, the corresponding joint angles are calculated, and the calculated joint angles are executed to realize the compliant drag teaching of the robotic arm.

[0121] Using the inverse kinematics algorithm of the robotic arm, the joint angles are obtained, i.e.:

[0122] q k =ψ( B p k )

[0123] Where, q k ∈R n ψ is the joint angle of the robotic arm, and ψ() is the inverse kinematics function of the robotic arm;

[0124] The obtained joint angle q k Update the robotic arm controller to control the servo motor and achieve servo motion.

[0125] Step 3: Safety Plane Coordinate Transformation and Boundary Detection:

[0126] During the compliant drag teaching process, the coordinates pk(xk,yk,zk,rxk,ryk,rzk) of the robotic arm's end-effector coordinate system are acquired in real time, and pk(xk,yk,zk,rxk,ryk,rzk) are transformed into coordinates. k Transition to safe plane S P Coordinates in the coordinate system (x,y,z)=0 (x k ,y k (Because of planar motion, attitude transformation is not considered); using the safety plane boundary function defined in step 1), combined with the transformed coordinates (x... k ,y k The robotic arm controller detects the boundary distance in real time.

[0127] Step 4: Safe Interaction and Dynamic Response:

[0128] As the robotic arm approaches the boundary of the safe plane, the system monitors the boundary distance in real time to predict whether it will touch the safety boundary. To ensure precise control of the robotic arm's movement and maintain safety, within a distance greater than ∈, the system employs a pure admittance control strategy to achieve zero-force operation, ensuring smooth, collision-free movement of the robotic arm within this region. When a degree of freedom of the robotic arm approaches a region less than ∈, the system intelligently switches that degree of freedom to a hybrid position-admittance control mode to fully integrate the advantages of both control strategies, balancing safety and operational flexibility. When the degree of freedom reaches the boundary, the system completely switches that degree of freedom to a pure position control mode to ensure accurate positioning and avoid collision risks.

[0129] Specifically, based on a threshold value ∈ determined by the distance to the boundary, the robotic arm is controlled to execute different motion modes, namely:

[0130] 2-1) Within the range where the distance to the boundary is greater than the distance measurement threshold ∈, the robotic arm controller adopts an admittance control strategy to achieve zero-force operation and ensure smooth, collision-free movement of the robotic arm within this range;

[0131] 2-2) When a certain degree of freedom of the robotic arm approaches a region where the distance to the boundary is less than the distance measurement threshold ∈, the robotic arm controller switches that degree of freedom to a hybrid position-admittance control strategy;

[0132] 2-3) When the degree of freedom reaches the boundary, the robotic arm controller completely switches that degree of freedom to a pure position control strategy to ensure accurate positioning and avoid collision risks.

[0133] In step 2-1), the adoption of the admittance control strategy specifically refers to:

[0134] When y min +∈≤y ek ≤y max -∈, and x min +∈≤x ek ≤x max When -∈, the x and y degrees of freedom are treated as zero forces, without any processing. The robotic arm controller still uses the admittance control strategy, that is:

[0135]

[0136]

[0137]

[0138]

[0139] Among them, M d ∈R 6 It is the desired inertia matrix, Dd ∈R 6 M is the desired damping matrix. d D d All are positive definite matrices. F(k) represents the six-degree-of-freedom forces mounted on the robot's wrist flange, measured by a six-dimensional sensor, and represents the forces in each direction of the tool system. Let F represent the position, velocity, and acceleration of each degree of freedom in the relatively safe plane coordinate system generated by the external force F.

[0140] In step 2-2), the degrees of freedom are converted to a hybrid position-admittance control strategy, including the following cases:

[0141] a. When y max -∈≤y ek ≤y max And x min +∈≤x ek ≤x max When -∈, the y-degree of freedom representing the safety plane enters the region of mixed control, while the x-degree of freedom is treated as zero force as before. No longer applicable, replaced by a hybrid position and admittance control strategy with y-degree of freedom, i.e.:

[0142]

[0143]

[0144] b. When y min ≤y ek ≤y min +∈andx min +∈≤x ek ≤x max When -∈, the y-degree of freedom representing the safety plane enters the region of mixed control, while the x-degree of freedom is treated as zero force as before. No longer applicable, replaced by a hybrid position and admittance control strategy with y-degree of freedom, i.e.:

[0145]

[0146]

[0147] c. When x max -∈≤x ek ≤x max And y min +∈≤y ek ≤y max When -∈, the x-degree of freedom representing the safety plane enters the region of mixed control, while the y-degree of freedom remains treated as zero force. No longer applicable, replaced by a mixed position and admittance control formula for the x-degree of freedom, i.e.:

[0148]

[0149]

[0150] d. When x min ≤x ek ≤x min +∈andy min +∈≤y ek ≤y max When -∈, the x-degree of freedom representing the safety plane enters the region of mixed control, while the y-degree of freedom remains treated as zero force. No longer applicable, replaced by a mixed position and admittance control formula for the x-degree of freedom, i.e.:

[0151]

[0152]

[0153] e.When y min ≤y ek ≤y min +∈andx min ≤x ek ≤x min When +∈, the x and y degrees of freedom representing the safety plane enter the region of mixed control. No longer applicable, replaced by a hybrid position and admittance control formula, namely:

[0154]

[0155]

[0156]

[0157]

[0158] f. When y max -∈≤y ek ≤y max &&x max -∈≤x ek ≤x max At this time, the x and y degrees of freedom representing the safety plane enter the region of mixed control. No longer applicable; a hybrid position and admittance control formula has been adopted instead.

[0159]

[0160]

[0161]

[0162]

[0163] In cases a through f, n ∈ {1, 2, 3… 10} is adjusted according to the user's feel, x ek To transition to safe plane S P x-coordinate, y-coordinate ek To transition to safe plane S P y-coordinate, T p k (x) and T p k (y) represents the position of the x and y degrees of freedom in the relative safe plane coordinate system generated by the external force F at time k, ee_p real () represents the safety plane S P The coordinates;

[0164] Depending on conditions a to f, the end-effector coordinates p of the robotic arm are acquired in real time. real =(x k ,y k ,z k (rx, ry, rz), then the coordinates are transformed to the safe plane S. P coordinates ee_p real (x ek ,y ek ,z ek ,rx ek ,ry ek ,rz ek Safety plane S P The boundary function f is then transformed to the base coordinate system according to the admittance control formula, and then the joint angle is obtained by inverse solution for servo motion.

[0165] In steps 2-3), the pure position control mode is specifically as follows:

[0166] When y max <y ek ||y ek <y min ||x max <x ek ||x ek <x min When this occurs, it indicates that the robotic arm has exceeded the safety boundary and suffered a serious accident. At this point, the positions of each degree of freedom relative to the safety plane coordinate system are... T p(k)=p real The admittance control strategy is no longer effective, and the robotic arm servo remains in its current position.

[0167] During this process, only the degree of freedom entering the safe zone will be switched to the hybrid position-admittance control mode, while the remaining degrees of freedom will continue to operate according to the pure admittance control strategy to achieve smooth movement along the boundary. The robotic arm can flexibly adapt to different working environments while maintaining overall stability and safety.

[0168] Step 5: Feedback Control and Optimization

[0169] Based on the actual movement of the robotic arm's end effector, step 4) is repeated to adjust control parameters in real time and optimize control performance. By continuously collecting and analyzing the robotic arm's motion data, the accuracy and stability of the virtual wall technology are continuously improved.

[0170] The embodiments described above will help those skilled in the art to further understand the present invention, but do not limit the present invention in any way. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

Claims

1. A method for constructing a virtual wall for an end effector of a collaborative robot, characterized in that, Includes the following steps: 1) Set safety boundaries for the robotic arm of the collaborative robot, define a preset safety boundary plane boundary function, and set a distance measurement threshold for approaching the boundary to construct a safe area; 2) Read the six-dimensional force information at the end of the collaborative robot by installing a six-dimensional force sensor at the end of the robot; obtain the joint angles of the robotic arm movement based on the six-dimensional force information, and perform compliant drag teaching of the robotic arm; 3) During the teaching process, the coordinates p of the robotic arm's end-effector coordinate system are acquired in real time. k (x k ,y k ,z k ,rx k ,ry k ,rz k ), through coordinate transformation p k Transition to safe plane S P Coordinates in the coordinate system (x,y,z)=0 (x k ,y k ); using the safety plane boundary function defined in step 1), combined with the transformed coordinates (x) k ,y k The robotic arm controller detects the boundary distance in real time. 4) When the robotic arm approaches the boundary of the safe plane, the robotic arm controller monitors the boundary distance in real time and measures the threshold ∈ based on the set distance to the boundary, and controls the robotic arm to execute different motion modes. 5) Repeat step 4) based on the actual movement of the robotic arm end effector corresponding to the different motion modes performed by the robotic arm to realize the application of the virtual wall.

2. The method for constructing a virtual wall for a collaborative robot end effector according to claim 1, characterized in that, Step 1) specifically includes: With the origin of the current tool system of the robotic arm as the origin of the safety plane (x0, y0, z0, rx0, ry0, rz0), the given boundary function is: f(x,y,z),f1(x,y,z) Here, f(x,y,z) and f1(x,y,z) are set as single-valued functions to determine the safety plane S. P For: S P (x,y,z)=0, where x,y,z represent spatial coordinates; Complete the construction of a safe zone by setting a distance measurement threshold ∈ (epsilon) close to the boundary.

3. The method for constructing a virtual wall for a collaborative robot end effector according to claim 1, characterized in that, Step 2) specifically includes: 1-1) The collected six-dimensional force information is constrained, and the constrained force information is substituted into the admittance control formula to calculate and generate the target pose; 1-2) Transform the calculated target pose from the tool coordinate system to the base coordinate system to ensure that the robotic arm performs the task according to the correct path and posture; 1-3) Using the inverse kinematics algorithm of the robotic arm, the corresponding joint angles are calculated, and the calculated joint angles are executed to realize the compliant drag teaching of the robotic arm.

4. The method for constructing a virtual wall for a collaborative robot end effector according to claim 3, characterized in that, Step 1-1) specifically includes: Let k be the sampling time, Ts be the sampling interval, and i = (0, ∞); Gravity compensation is: F(k) = g(F(k)) Then the degrees of freedom are restricted on the safe plane: F(k) = {f x ,f y Given the variable {0,0,0,0}, restricting the remaining degrees of freedom from forces, and substituting the restricted force information into the admittance control formula to generate the target pose, we have: Among them, M d ∈R 6 It is the desired inertia matrix, D d ∈R 6 M is the desired damping matrix. d D d All are positive definite matrices. F(k) represents the six-degree-of-freedom forces mounted on the robot's wrist flange, measured by a six-dimensional sensor, and represents the forces in each direction of the tool system. T p(k), Let F represent the position, velocity, and acceleration of each degree of freedom in the relative safe plane coordinate system generated by the external force F. The maximum and minimum constraints on acceleration and velocity are as follows: in, These represent the maximum acceleration and velocity constraints for each degree of freedom in Cartesian space.

5. A method for constructing a virtual wall for a collaborative robot end effector according to claim 3, characterized in that, Steps 1-2) are specifically as follows: The target pose relative to the safe plane coordinate system is: T p(k)={x k ,y k ,0,0,0,0} Will T p(k) is converted into the target pose relative to the base coordinate system, that is: in, It is the rotation matrix of the end-effector coordinate system origin attitude relative to the base coordinate system, (x k ,y k The coordinate transformation of the robotic arm's end-effector coordinate system to the safety plane S is performed. P The coordinates in the coordinate system (x,y,z)=0.

6. A method for constructing a virtual wall for a collaborative robot end effector according to claim 3, characterized in that, Steps 1-3) are specifically as follows: Using the inverse kinematics algorithm of the robotic arm, the joint angles are obtained, i.e.: what k =ψ( B p k ) Where, q k ∈R n ψ is the joint angle of the robotic arm, and ψ() is the inverse kinematics function of the robotic arm; The obtained joint angle q k Update the robotic arm controller to control the servo motor and achieve servo motion.

7. A method for constructing a virtual wall for a collaborative robot end effector according to claim 1, characterized in that, Step 4) specifically includes: 2-1) Within the range where the distance to the boundary is greater than the distance measurement threshold ∈, the robotic arm controller adopts an admittance control strategy to achieve zero-force operation and ensure smooth, collision-free movement of the robotic arm within this range; 2-2) When a certain degree of freedom of the robotic arm approaches a region where the distance to the boundary is less than the distance measurement threshold ∈, the robotic arm controller switches that degree of freedom to a hybrid position-admittance control strategy; 2-3) When the degree of freedom reaches the boundary, the robotic arm controller completely switches that degree of freedom to a pure position control strategy to ensure accurate positioning and avoid collision risks.

8. A method for constructing a virtual wall for a collaborative robot end effector according to claim 7, characterized in that, In step 2-1), the adoption of the admittance control strategy specifically refers to: When y min +∈≤y ek ≤y max -∈, and x min +∈≤x ek ≤x max When -∈, the x and y degrees of freedom are treated as zero forces, without any processing. The robotic arm controller still uses the admittance control strategy, that is: Among them, M d ∈R 6 It is the desired inertia matrix, D d ∈R 6 M is the desired damping matrix. d D d All are positive definite matrices. F(k) represents the six-degree-of-freedom forces mounted on the robot's wrist flange, measured by a six-dimensional sensor, and represents the forces in each direction of the tool system. T p(k), Let F represent the position, velocity, and acceleration of each degree of freedom in the relatively safe plane coordinate system generated by the external force F.

9. A method for constructing a virtual wall for a collaborative robot end effector according to claim 7, characterized in that, In step 2-2), the degree of freedom to hybrid position-admittance control strategy includes the following cases: a. When y max -∈≤y ek ≤y max And x min +∈≤x ek ≤x max When -∈, the y-degree of freedom representing the safety plane enters the region of mixed control, while the x-degree of freedom is treated as zero force as before. No longer applicable, replaced by a hybrid position and admittance control strategy with y-degree of freedom, i.e.: b. When y min ≤y ek ≤y min +∈andx min +∈≤x ek ≤x max When -∈, the y-degree of freedom representing the safety plane enters the region of mixed control, while the x-degree of freedom is treated as zero force as before. No longer applicable, replaced by a hybrid position and admittance control strategy with y-degree of freedom, i.e.: c. When x max -∈≤x ek ≤x max And y min +∈≤y ek ≤y max When -∈, the x-degree of freedom representing the safety plane enters the region of mixed control, while the y-degree of freedom remains treated as zero force. No longer applicable, replaced by a mixed position and admittance control formula for the x-degree of freedom, i.e.: d. When x min ≤x ek ≤x min +∈andy min +∈≤y ek ≤y max When -∈, the x-degree of freedom representing the safety plane enters the region of mixed control, while the y-degree of freedom remains treated as zero force. No longer applicable, replaced by a mixed position and admittance control formula for the x-degree of freedom, i.e.: e.When y min ≤y ek ≤y min +∈andx min ≤x ek ≤x min When +∈, the x and y degrees of freedom representing the safety plane enter the region of mixed control. No longer applicable, replaced by a hybrid position and admittance control formula, namely: f. When y max -∈≤y ek ≤y max &&x max -∈≤x ek ≤x max At this time, the x and y degrees of freedom representing the safety plane enter the region of mixed control. No longer applicable; a hybrid position and admittance control formula has been adopted instead. In cases a through f, n ∈ {1, 2, 3… 10} is adjusted according to the user's feel, x ek To transition to safe plane S P x-coordinate, y-coordinate ek To transition to safe plane S P y-coordinate, T p k (x) and T p k (y) represents the position of the x and y degrees of freedom in the relative safe plane coordinate system generated by the external force F at time k, ee_p real () represents the safety plane S P The coordinates; Depending on conditions a to f, the end-effector coordinates p of the robotic arm are acquired in real time. real =(x k ,y k ,z k (rx, ry, rz), then the coordinates are transformed to the safe plane S. P coordinates ee_p real (x ek ,y ek ,z ek ,rx ek ,ry ek ,rz ek Safety plane S P The boundary function f is then transformed to the base coordinate system according to the admittance control formula, and then the joint angle is obtained by inverse solution for servo motion.

10. A method for constructing a virtual wall for a collaborative robot end effector according to claim 7, characterized in that, In steps 2-3), the pure position control mode specifically refers to: When y max <y ek ||y ek <y min ||x max <x ek ||x ek <x min When this occurs, it indicates that the robotic arm has exceeded the safety boundary and suffered a serious accident. At this point, the positions of each degree of freedom relative to the safety plane coordinate system are... T p(k)=p real The admittance control strategy is no longer effective, and the robotic arm servo remains in its current position.

Images