Robot Arm Motor Control With Dual Feedback for Speed and Precision
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Solution Overview
Problem
Current motor drive control systems for robots face challenges in achieving both high precision and rapid operation due to inherent limitations in transmission mechanisms, such as backlash, friction, and vibrations, which lead to positional deviations and oscillations, making it difficult to balance precision and speed.
Innovation Solution
A control device and method for motor drive systems that incorporate a thrust control unit and a motor control unit, utilizing feedback controls from position and thrust detecting units to generate precise position and current values, effectively suppressing transmission errors and vibrations, allowing for rapid and precise motion control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If full-closed control is used to achieve high positional precision, then manufacturing precision is improved, but speed decreases
Solution Approach 1:
The patent implements dual feedback control: semi-closed feedback from motor position detection and full-closed feedback from moving member position detection. The control device synthesizes both feedback signals to simultaneously achieve rapid response from semi-closed control and high precision from full-closed control, resolving the speed-precision tradeoff
Solution Approach 2:
The control system is segmented into multiple control loops: a fast semi-closed control loop for rapid response and a precision full-closed control loop for accurate positioning. By dividing the control function into segments operating at different speeds and precision levels, the system achieves both speed and precision
2Speed
If semi-closed control is used to achieve rapid action speed, then speed is improved, but manufacturing precision deteriorates
Solution Approach 1:
The patent combines semi-closed feedback (motor position) and full-closed feedback (moving member position) to create a composite control signal that maintains rapid response characteristics while correcting precision errors, thereby achieving both speed and accuracy
3Productivity
If operating speed is increased to improve productivity, then productivity is improved, but positional deviation increases due to reactive force
Solution Approach 1:
The control device uses feedback from both motor position and moving member position detectors to detect and correct reactive force-induced deviations in real-time, enabling high-speed operation without sacrificing position accuracy
Solution Approach 2:
The control system dynamically adjusts motor commands based on real-time position feedback from both semi-closed and full-closed loops, adapting to changing loads and reactive forces during high-speed operation to maintain precision
4Force
If transmission mechanisms are used to increase motor thrust, then force is improved, but manufacturing precision deteriorates due to transmission errors
Solution Approach 1:
The patent implements full-closed feedback by detecting moving member position and feeding it back to the control device, which compensates for transmission mechanism errors (backlash, friction, vibrations) by adjusting motor commands, thereby maintaining precision despite using transmission mechanisms for force amplification
Data Source
AI summary
Motion control of a robot arm is performed via a reducer connected to a motor. A controller thereof includes a thrust control unit that generates motor position command value based on an input thrust command value, and a motor control unit that generates a current value based on the motor position command value. The motor control unit feeds back a motor position detected by a motor encoder, and the thrust control unit feeds back thrust detected by a thrust meter. The feedback from the motor control unit suppresses vibration phenomena at the reducer, and the feedback from the thrust control unit suppresses transmission error, thereby enabling motion control of the arm with rapidity and precision.