Multi-Joint Robot Arm Impedance Control for Stable Operation
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Solution Overview
Problem
Conventional robots with multi-joint arms face instability and complexity in control systems when attempting to regulate operation ranges due to changes in joint movements, leading to potential breakdowns during cooperative tasks with humans.
Innovation Solution
A control system incorporating external force detection, joint movable-state calculation, and external force conversion to enable impedance control, allowing the robot arm to adjust operations based on the movable state of each joint, preventing exceeding of the operational range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed limiter is installed to regulate the work range of the robot arm, then the operation range can be controlled, but the method becomes difficult to apply when the movable range changes in a complicated manner due to relationships among multiple joints
Solution Approach 1:
The patent changes the control parameter from a fixed limiter to a variable impedance parameter (spring constant k and damping coefficient c) that can be dynamically adjusted based on the robot arm's operational state and joint relationships, enabling adaptation to complex movable range variations
Solution Approach 2:
The patent transforms the static fixed limiter into a dynamic impedance control system where the spring constant and damping coefficient can be varied in real-time according to the robot arm's position and velocity, allowing the system to adapt to changing operational conditions and complex joint interactions
2Reliability
If the control parameter such as spring constant is changed to generate repulsive force for regulating operation, then the operation can be regulated, but the structure of the control system becomes complicated
Solution Approach 1:
The patent integrates the impedance control mechanism into the existing robot control system, making the control system multi-functional by combining operation regulation, force control, and joint protection functions within a unified impedance control framework, thereby avoiding the need for separate complex regulation systems
3Reliability
If the control parameter is changed to regulate operation exceeding the limiter, then the operation can be controlled, but the control system becomes unstable and the robot action becomes unstable
Solution Approach 1:
The patent implements a feedback mechanism where the impedance parameters (spring constant k and damping coefficient c) are continuously adjusted based on real-time detection of the robot arm's position, velocity, and operational state, ensuring stable control by preventing parameter changes that would destabilize the system
Solution Approach 2:
The patent uses dynamic impedance control where the spring constant and damping coefficient are varied smoothly based on the robot arm's state, preventing abrupt parameter changes that would cause instability, while still achieving effective operation regulation
Data Source
AI summary
A robot is provided with a multi-joint robot arm, an external force detection unit that is installed in the arm, and detects an external force, a joint movable-state calculation unit that calculates a movable state of a joint of the arm, an external force conversion unit which, based on the movable state calculated by the joint movable-state calculation unit, converts the external force detected by the external force detection unit to a converted external force, and a control unit that controls the arm based on the converted external force so as to regulate the operation of the arm.