Position Control Apparatus Dynamic Aging Correction
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Solution Overview
Problem
Existing position control apparatuses for machine tools face challenges in detecting a reduction in the rigidity of a working part due to factors like aging or increased sliding friction, leading to low-frequency vibrations and reduced responsiveness, as they struggle to accurately adjust the time constant of first-order delay circuits and gain settings in response to these changes.
Innovation Solution
A position control apparatus that includes a motor position detector, driven member position detector, and an aging corrector to detect vibratory states and adjust the time constant of first-order delay circuits and gain settings dynamically, thereby increasing the time constant when vibrations are detected and reducing gain settings when necessary to prevent low-frequency vibrations and maintain system responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the gain of speed loop and position loop are set to higher values to reduce position error in transient response, then the driven member can be accurately controlled and adverse influence of unpredictable load change or disturbance is reduced, but the mechanical resonance frequency decreases due to aging or temperature increase, causing low frequency vibrations
Solution Approach 1:
The patent implements dynamic adjustment of control parameters (gain values and time constants) based on real-time detection of mechanical resonance frequency changes. The system transitions from static parameter settings to dynamic adaptation, allowing the control gains and filter time constants to vary automatically as the mechanical resonance frequency shifts due to aging, temperature, or load changes, thereby preventing low-frequency vibrations while maintaining positioning accuracy
Solution Approach 2:
The patent changes the parameters of the control system (specifically the time constant of the speed filter and gain values) in response to detected changes in mechanical resonance frequency. When the resonance frequency decreases below a threshold, the system automatically adjusts these parameters to maintain stability, directly addressing the contradiction between high-precision control and system stability
2Stability of the object's composition
If the time constant of first-order delay circuit is increased to suppress low frequency vibrations, then system stability is improved, but the responsiveness of the control system deteriorates
Solution Approach 1:
The patent makes the time constant dynamic rather than fixed. The time constant of the speed filter is automatically adjusted based on the detected mechanical resonance frequency: it is increased when resonance frequency decreases to suppress vibrations, and maintained at lower values when resonance frequency is normal to preserve responsiveness. This dynamic adaptation resolves the contradiction between stability and responsiveness
Solution Approach 2:
The system uses feedback from the vibration detector to automatically adjust the time constant. The detected mechanical resonance frequency serves as feedback that triggers appropriate adjustments to the filter time constant and gain values, creating a closed-loop adaptation mechanism that balances stability and responsiveness based on actual system conditions
3Stability of the object's composition
If gain settings are reduced to prevent low-frequency vibrations, then system stability is improved, but the position control accuracy and responsiveness deteriorate
Solution Approach 1:
The patent implements dynamic adjustment of gain settings based on real-time detection of mechanical resonance frequency. Rather than using fixed reduced gains, the system automatically adjusts gain values according to current operating conditions: gains are reduced only when and where vibrations occur, while maintaining high gains in normal conditions to preserve positioning accuracy and responsiveness
Solution Approach 2:
The patent applies different gain adjustments to different control loops (speed loop and position loop) based on local vibration conditions. The speed loop gain is adjusted in response to detected vibrations, while the position loop gain is maintained separately, allowing selective suppression of vibrations without compromising overall positioning accuracy
Data Source
AI summary
A position control apparatus calculates a position detection value by adding an output of a first-order delay circuit 17 that receives a difference between a driven member position detection value Pl and a motor position detection value Pm to the motor position detection value Pm, and uses the obtained position detection value as a position feedback value. An aging corrector 30 suppresses low frequency vibrations by controlling a time constant Tp of the first-order delay circuit 17 in such a way as to increase the time constant when a vibratory state of the driven member is detected.