Redundant Robotic Arm Null-Space Control for Collision Avoidance
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Solution Overview
Problem
Current robotic arm control methods fail to effectively manage external forces acting on the end and links, leading to collisions and impact forces when obstacles are encountered, causing deviations from the intended trajectory.
Innovation Solution
A redundant robotic arm control method that uses a combination of force and torque sensors, Jacobian matrices, and impedance control theory to calculate joint speeds, allowing the robotic arm to move in a zero-space to avoid obstacles while maintaining the end's position, thereby minimizing impact forces and trajectory deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the robotic arm adjusts joints based on end speed deviation when external force acts on the end, then the end position can be corrected, but the link will collide with obstacles and produce large impact forces
Solution Approach 1:
The patent segments the control task into two independent parts: end-task control (maintaining trajectory) and link-task control (avoiding obstacles). By calculating zero-space velocity that is orthogonal to the end-task velocity, the system can adjust link positions without affecting end position, thus avoiding collisions while maintaining trajectory accuracy.
Solution Approach 2:
The patent introduces a new control dimension by using the null space of the Jacobian matrix. The zero-space velocity operates in a dimension orthogonal to the end effector's motion space, allowing independent adjustment of link configurations without disrupting the primary task of maintaining end position accuracy.
2Object-affected harmful factors
If the robotic arm drives the end to move when external force acts on the link, then obstacle collision can be avoided, but the actual position of the end will deviate from the intended trajectory
Solution Approach 1:
The control is segmented into end-task velocity (maintaining trajectory) and zero-space velocity (avoiding obstacles). The end-task velocity ensures the end effector stays on the intended trajectory, while the zero-space velocity independently adjusts link positions to avoid obstacles without affecting end position.
Solution Approach 2:
The system uses feedback from external force sensors on both the end and links to dynamically calculate the appropriate zero-space velocity. This feedback mechanism allows the controller to respond to obstacle forces while maintaining trajectory accuracy through continuous adjustment of joint velocities.
3Device complexity
If traditional control methods are used without zero-space velocity calculation, then the control system is simpler, but the robotic arm cannot effectively respond to external forces on links
Solution Approach 1:
The system implements feedback control by continuously measuring external forces on the end and links, then calculating zero-space velocity adjustments. This feedback loop enables the robotic arm to adaptively respond to external forces while maintaining task accuracy, transforming a complex control problem into a systematic solution.
Data Source
AI summary
The present disclosure provides a redundant robotic arm control method, a redundant robotic arm, and a computer readable storage medium. The method includes: obtaining an external force acting on an end of the robotic arm and an external torque acting on each joint; calculating a first joint speed of each joint based on a degree of influence of the joint on the end in each motion dimension and the external force acting on the end; determining a zero space speed of each joint corresponding to a current position of the end based on a link torque of an external force acting on a link with respect to the joint; calculating a total joint speed based on the first joint speed and the zero space speed; and controlling the robotic arm to the move according to the total joint speed.