Geometric recursive local obstacle avoidance operation method for redundant robot arm

Abstract

This invention belongs to the field of robotic arm manipulation and control technology, and discloses a geometric recursive local obstacle avoidance operation method for redundant robotic arms. The method involves identifying the obstacle-contacting links and contact force directions of the robotic arm during operation, and selecting the two end joints as local adjustment reference joints. The reference joints are translated according to the contact force direction to obtain the initial adjustment position. An arc is drawn with the adjusted reference point as the center and the length of the adjacent link as the radius. The target position of each adjacent joint is recursively solved through geometric relationships. If the included angle between adjacent links exceeds the limit, the joint position is calibrated using the parallelogram law and the sine theorem; otherwise, the parameters are updated and the recursion continues. This process is repeated until all joints are adjusted. Finally, the rotation angle of each joint is calculated through homogeneous coordinate transformation, and the drive motor completes local obstacle avoidance. This method can quantitatively guarantee the obstacle avoidance safety clearance, effectively avoid the problem of joint jamming due to exceeding limits, and improve the accuracy and real-time performance of obstacle avoidance for robotic arms in narrow and enclosed working environments.

Description

Technical Field

[0001] This invention relates to the field of robotic arm manipulation and control technology, specifically to a geometric recursive local obstacle avoidance operation method for redundant robotic arms. Background Technology

[0002] In aerospace, nuclear power, and other fields, there exists a category of robotic arm tasks that require operation in confined spaces. Redundant robotic arms exhibit dexterity and have broad application potential. However, due to factors such as motion errors, uncertain environmental constraints, and inappropriate path selection, robotic arms are prone to localized collisions or jamming when operating in narrow, enclosed spaces, leading to damage to both the robotic arm and the workpiece. Therefore, it is essential to develop obstacle avoidance methods for redundant robotic arms suitable for confined space operation constraints.

[0003] In the prior art, CN108908331A discloses a method of locally adjusting two adjacent joints, which can only temporarily bypass obstacles, but it is difficult to guarantee a safe distance from the obstacle after adjustment, and there is a risk of secondary collision. At the same time, this type of operation method lacks consideration of the physical constraints of joint angles. After local adjustment, the joint angle is prone to exceed the maximum limit range, which can lead to the mechanism getting stuck and make it difficult to return to the original working path efficiently, which has an adverse impact on the execution efficiency of the robot's work and the safety of the equipment.

[0004] The obstacle avoidance method for industrial robotic arms based on EIT tactile sensors disclosed in publication number CN119115933A relies on the physical contact between obstacles and the robotic arm to achieve perception. This not only easily causes damage to the workpiece and the robotic arm itself, but also requires multiple touches to gradually improve the obstacle model, resulting in a long obstacle avoidance process and low work efficiency. In addition, this method uses a single artificial potential field method for path planning, which is prone to getting trapped in local optima and has insufficient adaptability in environments with dense or dynamically changing obstacles, resulting in poor reliability of robotic arm operation in complex work scenarios.

[0005] To address the issue of the effectiveness of redundant robotic arms in obstacle avoidance within narrow, enclosed spaces, it is necessary to provide a geometric recursive local obstacle avoidance operation method for redundant robotic arms. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, this invention proposes a geometric recursive local obstacle avoidance method for redundant robotic arms. Its main principle is that when the redundant robotic arm collides with or faces potential collision risks with the constrained environment, the redundant degrees of freedom of the robotic arm are used to adjust the configuration of the robotic arm at the local collision point. Based on the proposed geometric recursive method, the overall operational motion posture of the robotic arm is adjusted, thereby ensuring that the redundant robotic arm can achieve local obstacle avoidance during the operation while maintaining the original trend of the overall operational path.

[0007] The technical solution of the present invention is as follows: A geometric recursive local obstacle avoidance operation method for a redundant robotic arm includes the following steps:

[0008] Step 1: Obtain the collision positioning point and contact force direction of the redundant robotic arm during the operation, and select the obstacle-contacting link. Select the two joints at both ends of the obstacle-contact linkage. and Two reference joints for local adjustments;

[0009] Step 2: Determine the translation vector based on the direction of the contact force. Translation vector Parallel to the direction of the contact force; relative to the reference joint. and Perform a global translation transformation to obtain the translated joints. and And set the recursive initial parameters: the ordinal number of the adjacent joint on the left side of the obstacle-touching link. Number of adjacent joints on the right side of the obstacle-touching link ;

[0010] Step 3: Perform position update operations on adjacent joints using geometric relationships; using the translated joints respectively and Draw an arc with the center as the radius and the length of the adjacent link as the radius, and solve for the current ordinal number using geometric relationships. , Corresponding joint target position , ;

[0011] Step 4: Calculate the joint angles between adjacent links when using the target position based on geometric relationships. ,Will Maximum limiting angle between adjacent links Compare; If the joint angle between the links is determined to be out of limit, then the joint angle is set to a value of [value to be filled in]. Extend the corresponding link axis, and perform a correction operation on the target position of the joint point using the parallelogram law and the sine theorem to obtain the corrected target position of the joint point. ;like If the condition is met, the recursive parameters will be updated to... , Return to step 3 to continue solving for the next set of joint target positions;

[0012] Step 5: Repeat steps 3 and 4 until the recursion termination condition is met. and ,in The number of redundant robotic arm links, the total number of joints is Complete the operation pose adjustment calculations for all joints of the redundant robotic arm to obtain the target positions of all relevant nodes;

[0013] Step 6: Based on the target position of all relevant nodes, solve the rotation angle of each joint through homogeneous coordinate transformation. Finally, the motor drives the redundant robotic arm to complete the work posture adjustment based on the solved joint rotation angles, thereby realizing local obstacle avoidance during the operation of the redundant robotic arm.

[0014] The translation vector mentioned in step 2 The method for determining it is as follows:

[0015] Normalized vector of the contact force direction Set a safety distance for the translation direction. Translation vector The overall translation of the reference joints satisfies the following geometric relationships:

[0016]

[0017] The safety distance These are positive values ​​pre-set based on the link dimensions of the redundant robotic arm and the actual obstacle avoidance requirements.

[0018] The specific method for performing the position update operation of adjacent joints through geometric relations in step 3 is as follows:

[0019] Solve for the left joint. When the target position is reached, the adjusted joint points are used. Centered on the left, the adjacent link length Draw an arc with radius Adjusting the joint points on the left side and adjusted joints The lines connecting them intersect at point . ;

[0020] Then adjust the anterior joint. With the center of the circle, Draw an arc with length as the radius, and adjust the joint points before intersection. and The line lies at point After connection and adjustment of joints With point B, and with the arc The intersection point is the desired joint point. Target location;

[0021] The coordinates are represented as:

[0022]

[0023] in, This indicates the calculation of Euclidean distance.

[0024] Similarly, the right-side joint points are obtained. The target location.

[0025] Step 4 specifically involves:

[0026] The maximum limiting angle between adjacent links The inherent structural parameters of the redundant robotic arm are pre-calibrated by the mechanical motion range of the links and are fixed values; the joint points are adjusted afterward. Target location Then, perform over-limit joint angle correction and solve for the corrected joint points. , causing the connecting rod and The joint angle is the maximum limiting angle between the links. extension link Axis and Arc Intersection point To adjust the back joints and the points to be solved Construct parallelograms for the diagonal vertices, and use the sine theorem to obtain the joint points after joint angle over-limit correction. coordinate;

[0027] The coordinates are represented as:

[0028]

[0029] Link Length; Indicates the link before over-limit joint angle correction. The right joint point;

[0030] Right side adjustment joint points When the target position causes the joint angle to exceed the limit, the same logic applies to the joint point after the right joint angle exceeds the limit correction. The target location.

[0031] In step 5, the translation constraints of the reference joint points and the fixed inherent length of the link are the core constraints. The target positions of the joint points obtained through recursion are generated by the joint point constraints after the previous round of correction, and the distance between adjacent joint points is consistent with the inherent length of the corresponding link. The joint points after joint angle over-limit judgment and correction are used as the new recursive references. The recursive index is updated and the operation process of steps 3 and 4 is repeated until the conditions are met. and The termination condition is to complete all joint adjustments.

[0032] The redundant robotic arm is equipped with One link, among which For the base joint, the base and the connecting rod Connecting joints; For actuator joints; in the recursive termination condition This indicates that the left-side recursion has been completed up to the base joint. This indicates that the recursion on the right side has been completed up to the actuator joint, achieving position adjustment of all joints.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention makes an initial adjustment by translating the entire obstacle-touching link and constrains the position of adjacent joint points by using the geometric arc method, which can quantitatively ensure the safe clearance between the redundant robotic arm and obstacles during operation; it introduces a link joint angle over-limit calibration mechanism and corrects it with the help of the parallelogram law. At the same time, the algorithm of this operation method has low computational complexity and fast response speed, which effectively solves the problems of insufficient temporary obstacle avoidance safety distance, easy over-limit jamming in local adjustment, and long calculation time for real-time obstacle avoidance operation in the prior art. It realizes the precise local obstacle avoidance and coordinated control of the overall operation posture of the redundant robotic arm in a narrow and closed working environment. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of a redundant robotic arm performing local obstacle avoidance.

[0035] Figure 2 This is a schematic diagram of the translation and transformation operation of the obstacle-touching linkage;

[0036] Figure 3 This is a schematic diagram of the local obstacle avoidance operation method in this invention;

[0037] Figure 4 This is a flowchart of the local obstacle avoidance operation method described in this invention. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0039] Example:

[0040] Please see Figures 1-4 A redundant robotic arm operates in a confined space. This robotic arm has a total of 10 links (at this time...). The connecting rods are respectively denoted as connecting rods. ~ The connecting rod adjacent to the base is a connecting rod. ), 11 joints (denoted as joints) ~ The base and connecting rod Connected joints are joints ).

[0041] During operation, the connecting rod (at this time In the event of a collision with the workpiece, the specific steps of the obstacle avoidance operation based on this method include:

[0042] Step 1: Based on methods such as force sensor detection or collision perception neural networks, identify the obstacle-touching link of the robotic arm as a link. Determine the direction of the contact force and select the joints at both ends of the obstacle-contacting link. , As a reference joint point for local adjustments;

[0043] Step 2: Determine the translation vector parallel to the direction of the contact force, perpendicular to the connecting rod. Direction of the connecting rod The joints are obtained by translating the entire object by 50mm. and Set the initial parameters for the recursion. , ;

[0044] Step 3: Using joints Centered on the left, the adjacent link length Draw an arc with radius The adjacent joints are solved through a series of geometric relationships. and Target location;

[0045] Step 4: At this point, use geometric relationships to calculate the adjacent links when using the target position. and The joint angle between them is greater than the maximum limiting angle The joint angle was determined to be out of limit, and the joint position needs to be corrected. The connecting rod... and The interarticular angle is taken as the maximum limiting angle. The joint points after joint angle over-limit calibration can be obtained by using the parallelogram law and the sine theorem. Target position, and linkage and If the joint angles between them meet the requirements, no correction is needed, and the joint points can be used directly. Target location;

[0046] Step 5: Repeat the recursive logic of Steps 3 and 4 to determine the target positions of all 11 joints of the robotic arm in sequence;

[0047] Step 6: Solve the rotation angle of each joint through homogeneous coordinate transformation, drive the motor to move the redundant robotic arm, and achieve local obstacle avoidance.

[0048] It should be noted that in step 3, the joint points The key points are derived through geometric relationships. The target location can be represented as:

[0049]

[0050] However, due to the physical rotation angle limitations of the redundant robotic arm joints, this value does not meet the actual requirements. Therefore, joint angle over-limit correction is performed in step 4 to obtain the calibrated joint points. The target location can be represented as:

[0051]

[0052] Using the same solution method and calibration logic as described above, the right-side joint points can be obtained. The target position can be obtained by recursively applying the above method to adjust all joints of the redundant robotic arm.

[0053] In this embodiment, the recursion termination condition is set to ensure that the target positions of all 11 joints of the robotic arm have been calculated. Specifically, the termination condition is... and ;in, This indicates that the left-side recursion has been completed up to the base joint. This indicates that the right-side recursion has been completed up to the actuator joint, ensuring that the target position calculation is completed for all joints, and achieving coordinated correction of the overall posture of the robotic arm.

[0054] After all joints have been adjusted, the rotation angle requirements of each joint can be accurately calculated through homogeneous coordinate transformation, ensuring the accuracy of motor drive commands and ultimately achieving effective execution of obstacle avoidance actions.

[0055] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. The scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A geometric recursive local obstacle avoidance operation method for a redundant robotic arm, characterized in that, Includes the following steps: Step 1: Obtain the collision positioning point and contact force direction of the redundant robotic arm during the operation, and select the obstacle-contacting link. ; Select the two joints of the obstacle-touching link and Two reference joints for local adjustments; Step 2: Determine the translation vector based on the direction of the contact force. Translation vector Parallel to the direction of the contact force; relative to the reference joint. and Perform a global translation transformation to obtain the translated joints. and And set the recursive initial parameters: the ordinal number of the adjacent joint on the left side of the obstacle-touching link. Number of adjacent joints on the right side of the obstacle-touching link ; Step 3: Perform position update operations on adjacent joints using geometric relationships; using the translated joints respectively and Draw an arc with the center as the radius and the length of the adjacent link as the radius, and solve for the current ordinal number using geometric relationships. , Corresponding joint target position , ; Step 4: Calculate the joint angles between adjacent links when using the target position based on geometric relationships. ,Will Maximum limiting angle between adjacent links Compare; If the joint angle between the links is determined to be out of limit, then the joint angle is set to a value of [value to be filled in]. Extend the corresponding link axis, and perform a correction operation on the target position of the joint point using the parallelogram law and the sine theorem to obtain the corrected target position of the joint point. ;like If the condition is met, the recursive parameters will be updated to... , Return to step 3 to continue solving for the next set of joint target positions; Step 5: Repeat steps 3 and 4 until the recursion termination condition is met. and ,in The number of redundant robotic arm links, the total number of joints is Complete the work pose adjustment calculations for all joints of the redundant robotic arm to obtain the target positions of all relevant nodes; Step 6: Based on the target position of all relevant nodes, solve the rotation angle of each joint through homogeneous coordinate transformation. Finally, the motor drives the redundant robotic arm to complete the work posture adjustment according to the solved joint rotation angle, so as to realize local obstacle avoidance in the operation of the redundant robotic arm.

2. The geometric recursive local obstacle avoidance operation method for redundant robotic arms according to claim 1, characterized in that, The translation vector mentioned in step 2 The method for determining it is as follows: Normalized vector of the contact force direction Set a safety distance for the translation direction. Translation vector The overall translation of the reference joints satisfies the following geometric relationships: The safety distance These are positive values ​​pre-set based on the link dimensions of the redundant robotic arm and the actual obstacle avoidance requirements.

3. The geometric recursive local obstacle avoidance operation method for redundant robotic arms according to claim 1, characterized in that, The specific method for performing the position update operation of adjacent joints through geometric relations in step 3 is as follows: Solve for the left joint. When the target position is reached, the adjusted joint points are used. Centered on the left, the adjacent link length Draw an arc with radius Adjusting the joint points on the left side and adjusted joints The lines connecting them intersect at point . ; Then adjust the anterior joint. With the center of the circle, Draw an arc with length as the radius, and adjust the joint points before intersection. and The line lies at point After connection and adjustment of joints With point B, and with the arc The intersection point is the desired key point. The target location; The coordinates are represented as: in, This indicates the calculation of Euclidean distance. Similarly, the right-side joint points are obtained. The target location.

4. The geometric recursive local obstacle avoidance operation method for redundant robotic arms according to claim 3, characterized in that, Step 4 specifically involves: The maximum limiting angle between adjacent links The inherent structural parameters of the redundant robotic arm are pre-calibrated by the mechanical motion range of the links and are fixed values; the joint points are adjusted afterward. Target location Then, perform over-limit joint angle correction and solve for the corrected joint points. , causing the connecting rod and The joint angle is the maximum limiting angle between the links. extension link Axis and Arc Intersection point To adjust the back joints and the points to be solved Construct parallelograms for the diagonal vertices, and use the sine theorem to obtain the joint points after joint angle over-limit correction. coordinate; The coordinates are represented as: Link Length; Indicates the link before over-limit joint angle correction. The right joint point; Right side adjustment joint points When the target position causes the joint angle to exceed the limit, the same logic applies to the joint point after the right joint angle exceeds the limit correction. The target location.

5. The geometric recursive local obstacle avoidance operation method for redundant robotic arms according to claim 1, characterized in that, In step 5, the translation constraints of the reference joint points and the fixed inherent length of the link are the core constraints. The target positions of the joint points obtained through recursion are generated by the joint point constraints after the previous round of correction, and the distance between adjacent joint points is consistent with the inherent length of the corresponding link. The joint points after joint angle over-limit judgment and correction are used as the new recursive references. The recursive index is updated and the operation process of steps 3 and 4 is repeated until the conditions are met. and The termination condition is to complete all joint adjustments.

6. The geometric recursive local obstacle avoidance operation method for redundant robotic arms according to claim 1, characterized in that, The redundant robotic arm is equipped with One link, of which For the base joint, the base and the connecting rod Connecting joints; For actuator joints; In the recursion termination condition This indicates that the left-side recursion has been completed up to the base joint. This indicates that the right-side recursion has been completed up to the actuator joint, achieving position adjustment of all joints.

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