Dynamic Stiffness Control for Redundant Robot Joint Pose
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Redundant manipulators, such as articulated-arm robots, can move into undesirable poses during hand-guided operation in force-compensated mode, leading to collisions with the environment or operator, and require manual reorientation, limiting operator flexibility.
Innovation Solution
A method that uses torque sensors and compliance control to define a range for joint movement, adjusting the stiffness or applying forces to prevent joints from exceeding defined limits, maintaining the tool center point's position and orientation without disrupting the work process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the redundant degree of freedom is allowed to move freely during hand-guided operation, then the flexibility and adaptability of the manipulator is improved, but the manipulator may move into undesirable poses and collide with the environment or operator
Solution Approach 1:
The patent applies parameter changes by dynamically modifying the stiffness parameter of the redundant joint based on its position relative to predefined safe ranges. When the joint is within the safe range, stiffness is reduced to allow flexible movement. When approaching unsafe zones, stiffness is increased to prevent collisions, thus resolving the contradiction between flexibility and collision avoidance.
Solution Approach 2:
The patent implements dynamics by making the stiffness of the redundant joint time-varying and position-dependent rather than fixed. The stiffness parameter is continuously adjusted during operation based on the joint's current state, enabling the system to be flexible when safe and restrictive when necessary, thereby resolving the contradiction between adaptability and safety.
2Object-affected harmful factors
If restricting forces are applied to limit the redundant degree of freedom, then collision avoidance is improved, but the mobility and flexibility of the robot is limited
Solution Approach 1:
The patent uses parameter changes by adjusting the stiffness parameter dynamically rather than applying constant restricting forces. The stiffness is modified based on the joint's position relative to safe ranges, allowing full mobility within safe zones and restrictive forces only when necessary, thus resolving the contradiction between collision avoidance and mobility.
Solution Approach 2:
The patent applies dynamics by making the restricting force dynamic rather than static. The stiffness parameter varies continuously during operation, enabling the robot to move freely when safe and apply restricting forces only when approaching unsafe configurations, thereby maintaining both collision avoidance and mobility.
3Stability of the object's composition
If the elbow joint is fixed or blocked to downgrade the robot to a 6-axis system, then pose control is improved, but the redundant flexibility and adaptability are lost
Solution Approach 1:
The patent applies dynamics by making the elbow joint controllable rather than fixed or blocked. The joint remains active but with dynamically adjusted stiffness, allowing it to be flexible when needed and stable when necessary, thus resolving the contradiction between pose control and redundant flexibility.
Solution Approach 2:
The patent uses parameter changes by adjusting the stiffness parameter of the elbow joint to achieve desired control characteristics without physically fixing or blocking the joint. This maintains the redundant degree of freedom while achieving stable pose control when necessary.
4Stability of the object's composition
If manual reorientation of the elbow angle is performed to correct unfavorable poses, then pose correction is achieved, but the operator must use both hands and productivity is reduced
Solution Approach 1:
The patent applies self-service by enabling the robot to automatically correct its own pose through automated stiffness control of the redundant joint. The system monitors the joint position and autonomously adjusts stiffness to prevent or correct unfavorable poses, eliminating the need for manual intervention and thus resolving the contradiction between pose correction and productivity.
Solution Approach 2:
The patent implements feedback by continuously monitoring the elbow joint position and using this information to dynamically adjust the stiffness parameter. This closed-loop control enables automatic pose correction without operator intervention, resolving the contradiction between maintaining correct poses and maintaining high productivity.
Data Source
AI summary
The invention relates to a method and a system for controlling a robot, which has at least one redundant degree of freedom. The method according to the invention prevents the robot from colliding with its surrounding environment and/or from getting into an inconvenient position as a result of its redundancy, and does so without causing any disadvantageous displacement of the tool center point.