Reducer-Coupled Robot Arm Control for Vibration and Transmission Error
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Solution Overview
Problem
Current motor control methods 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 mechanical resonance, making it difficult to satisfy the required precision and speed simultaneously.
Innovation Solution
A control device and method for motor drive systems that incorporate a thrust control unit for precise feedback control and a motor control unit for suppressing vibration phenomena, allowing for increased operation speed while effectively managing transmission errors and vibrations, thereby enabling precise and rapid 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 device complexity increases and productivity decreases due to slow action speed
Solution Approach 1:
The patent implements a dual feedback control structure: semi-closed feedback from the motor output shaft for rapid response, and full-closed feedback from the moving member position sensor for high precision. The control device processes both feedback signals to generate corrected position commands, achieving both speed and precision simultaneously.
Solution Approach 2:
The patent introduces an intermediary calculation process that computes the difference between semi-closed and full-closed feedback positions. This intermediary value is used to generate correction commands that compensate for transmission mechanism errors without directly using the slow full-closed feedback signal, thereby maintaining high speed while achieving precision.
2Productivity
If operating speed is increased to improve productivity, then action speed is improved, but positional precision deteriorates due to amplified single harmonic motion and mechanical resonance
Solution Approach 1:
The patent applies preliminary anti-action by using the full-closed feedback position information to predict and compensate for transmission errors before they cause significant positional deviation. The control device calculates correction values based on the difference between expected and actual positions, applying counteracting commands proactively to prevent resonance amplification.
Solution Approach 2:
The system performs preliminary action by continuously monitoring the difference between semi-closed and full-closed feedback positions and pre-calculating correction commands. This allows the system to prepare compensatory actions in advance, enabling high-speed operation without sacrificing precision due to resonance effects.
3Productivity
If semi-closed control is used to achieve rapid action speed, then productivity is improved, but manufacturing precision deteriorates due to transmission mechanism errors
Solution Approach 1:
The patent replaces direct mechanical coupling for precision transmission with an electronic substitution system. Instead of relying solely on mechanical precision, the system uses electronic sensors and control algorithms to detect and correct transmission errors, substituting mechanical precision requirements with electronic measurement and computational correction.
Data Source
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AI summary
Motion control of a robot arm (106) is performed via a reducer (105) connected to a motor (103). A controller (101) thereof includes thrust control means (302) that generate a motor position command value based on an input thrust command value, and motor control means (303) that generate a current value based on the motor position command value. The motor control means (303) feed back a motor position detected by a motor encoder (104), and the thrust control means (302) feed back thrust detected by a thrust meter (107). The feedback from the motor control means (303) suppresses vibration phenomena at the reducer (105), and the feedback from the thrust control means (302) suppresses transmission error, thereby enabling motion control of the arm (106) with rapidity and precision.