Robot Drive Shaft Control With Dual Encoders for Backlash Correction
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Solution Overview
Problem
Existing robot systems face positional deviation issues due to backlash and twisting in deceleration mechanisms, which hinder precise positioning of output shafts when using encoders for rotation angle detection.
Innovation Solution
A robot system with multiple drive shafts, each equipped with a motor, deceleration mechanism, and both input-side and output-side detectors, where the control device prioritizes operation based on detected rotation angles and operation positions to correct deviations, ensuring high responsiveness and precise positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an encoder attached to the motor is used to detect rotation angle for controlling output shaft position, then the positioning control can be implemented, but positional deviation occurs due to backlash and twisting in the deceleration mechanism
Solution Approach 1:
An output-side detector (second encoder) is introduced as an intermediary measurement device between the deceleration mechanism and the output shaft. This second encoder directly detects the actual position of the output shaft, providing accurate position feedback that compensates for the errors introduced by backlash and twisting in the deceleration mechanism.
Solution Approach 2:
The system implements dual feedback loops: the first encoder provides feedback from the motor side for control commands, while the second encoder provides feedback from the output shaft side for position correction. The control device compares the commanded position with the actual detected position and generates correction commands to eliminate positional deviations caused by the deceleration mechanism.
2Measurement precision
If another position detection sensor is disposed on the output shaft side to improve positioning precision, then positioning precision can be improved, but the device complexity increases
Solution Approach 1:
The control device is designed to handle multiple functions: it processes commands from the first encoder, reads feedback from the second encoder, calculates positional deviations, and generates correction commands. This multi-functional design consolidates the control logic into a single device, managing the added complexity through functional integration rather than adding separate control systems.
Data Source
AI summary
A robot system includes: a robot including drive shafts; and a control device configured to control the robot, in which each of the drive shafts includes a drive unit configured to cause a second member to operate with respect to a first member, the drive unit includes a motor, a deceleration mechanism configured to decelerate rotation of the motor and supply the rotation to the first member and the second member, and an input-side detector configured to detect a rotation angle position of the motor, at least one drive unit includes an output-side detector configured to detect an operation position of the second member with respect to the first member, and the control device controls the motor such that each of the drive shafts with high responsiveness is caused to operate with priority, on the basis of the detected rotation angle position of the motor and the detected operation position.