Robot Arm Control with Integral Command Limits and Dither
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Solution Overview
Problem
Existing robot control systems face challenges in controlling physical quantities like velocity and acceleration, leading to uncontrollable displacement and excessive movement when feedback loops are separated, resulting in potential collisions and inaccurate force estimation due to static friction.
Innovation Solution
A robot system with a control device that limits control commands based on an integral of the first control quantity, using a command generation unit to generate and adjust acceleration commands to prevent excessive velocity and force, and incorporates a dither signal to reduce static friction effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If feedback loops are separated for controlling velocity and acceleration, then control flexibility is improved, but displacement becomes uncontrollable and excessive movement occurs
Solution Approach 1:
The patent implements feedback by calculating the actual displacement from integrated velocity data and comparing it with the target displacement. The control system adjusts acceleration commands based on the displacement error, ensuring the robot reaches the correct position even when velocity feedback loops are separated. This feedback mechanism resolves the contradiction by maintaining displacement control reliability while preserving control flexibility.
Solution Approach 2:
The patent replaces traditional mechanical position control with a computational approach using integrated velocity feedback. Instead of direct mechanical position sensing, the system calculates position from velocity integration and uses this information to adjust acceleration commands. This substitution allows separated feedback loops to work effectively while maintaining accurate displacement control.
2Productivity
If acceleration commands are increased to improve response speed, then productivity is improved, but static friction causes inaccurate force estimation and collision
Solution Approach 1:
The patent applies dither signals (high-frequency vibrations) to the acceleration commands to overcome static friction. By superimposing small oscillations on the control signals, the system prevents the robot from stalling at dead zones caused by friction, enabling more accurate force estimation and smoother motion at higher acceleration levels. This resolves the contradiction by allowing increased productivity while maintaining measurement precision.
Solution Approach 2:
The patent uses partial action by applying dither signals only when needed to overcome static friction thresholds. The system monitors the acceleration commands and adds dither components selectively rather than continuously, optimizing the balance between response speed and force estimation accuracy. This approach improves productivity without unnecessarily compromising precision.
3Measurement precision
If dither signals are added to reduce static friction effects, then force estimation accuracy is improved, but control complexity increases
Solution Approach 1:
The patent implements dither signals by modifying the acceleration command parameters rather than changing the overall control architecture. The dither component is added as a parameter adjustment to existing control equations, allowing force estimation improvement without significantly increasing control complexity. This approach maintains simplicity while enhancing measurement precision.
Data Source
AI summary
A robot system includes: a robot including one or more motors configured to move an arm; and circuitry configured to: control at least one motor of the one or more motors so that a first control quantity follows a first control command, wherein the first control quantity represents a physical status of the arm; and limit the first control command based on a second control quantity that is an integral of the first control quantity.