Servo Control Apparatus with Dual-Position Feedback for Quadrant Protrusion
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Solution Overview
Problem
Existing servo control systems face challenges in reducing position errors on both the servo motor and driven load sides, particularly in machining operations with large cutting reaction forces, where high gain is needed for accuracy but may lead to instability due to distortion or backlash, and quadrant protrusion issues are not adequately addressed in dual-position feedback control.
Innovation Solution
A servo control apparatus that performs dual-position feedback control using a combination of position detectors, error calculators, a time constant circuit, and a learning controller to select and compensate for position errors, allowing for stable and accurate control by switching between motor and load position errors based on stability and accuracy requirements, and compensating for detection delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the position loop gain or speed loop gain is set to a high value to improve machining accuracy under large cutting reaction forces, then machining accuracy is improved, but the learning control may not converge due to distortion or backlash between the servo motor and the machine
Solution Approach 1:
The patent segments the feedback control into two independent channels: one using servo motor position feedback and another using machine side position feedback. This allows the system to separately handle the stability requirements (using motor side feedback with high gain) and the accuracy requirements (using machine side feedback for learning control), resolving the contradiction between high gain for accuracy and convergence stability.
Solution Approach 2:
The patent introduces an intermediary mechanism that combines both motor side feedback and machine side feedback to create a composite feedback signal. This intermediary approach allows the system to benefit from both high gain stability (from motor side) and accurate position information (from machine side) without the learning control failing to converge.
2Reliability
If the position loop gain or speed loop gain is reduced to ensure learning control convergence, then learning control stability is improved, but machining accuracy degrades due to cutting reaction forces
Solution Approach 1:
The patent divides the control system into two parallel feedback paths: one dedicated to stability (motor side feedback with appropriate gain) and another dedicated to accuracy (machine side feedback for learning). This segmentation allows each path to be optimized independently, so learning control can converge while maintaining high machining accuracy under cutting forces.
Solution Approach 2:
The patent merges both motor side position feedback and machine side position feedback into a unified dual-position feedback control system. This combination allows the system to simultaneously achieve the stability needed for learning control convergence and the accuracy needed to counteract cutting reaction forces.
3Manufacturing precision
If dual-position feedback control is implemented to reduce position errors on both servo motor and driven load sides, then comprehensive position accuracy is improved, but the system complexity increases
Solution Approach 1:
The patent designs the dual-position feedback control system to serve multiple functions simultaneously: it provides both motor side error compensation and machine side error compensation, enables learning control convergence, and maintains stability under cutting forces. This multi-functionality justifies the added complexity by delivering comprehensive performance improvements that a single feedback path cannot achieve.
Data Source
AI summary
A servo control apparatus that performs dual-position feedback control and thereby achieves a reduction in position error according to the purpose of machining. The servo control apparatus includes: a first position detector for detecting the position of a motor; a second position detector for detecting the position of a driven load; a first position error calculator for calculating a first position error based on a position command and motor position feedback; a second position error calculator for calculating a second position error based on the position command and driven load position feedback; a third position error calculator for calculating a third position error to be used for position control, by adding to the first position error a difference taken between the first position error and the second position error and passed through a time constant circuit; a selector for selecting either the second position error or the third position error for output; and a learning controller for learning an output of the selector, and for outputting an amount of compensation to be applied to the third position error.