Motor Controller Vibration Damping via Frequency-Adaptive Filter
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Solution Overview
Problem
Existing motor controllers for machine tools and industrial machines face challenges in reducing low-frequency vibrations during speed control, as methods disclosed for position control do not effectively address vibrations in speed control scenarios.
Innovation Solution
A motor controller design that includes a speed control unit with feedforward and feedback control units, utilizing filters with a transmission characteristic that approximates the inverse of the system's transmission characteristic, adjusting parameters like frequency ω, vibration damping coefficient ζ, and cutoff frequency ωadj to reduce vibrations by setting ω between the antiresonant and resonant frequencies of the machine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a filter is used for servo position control loop, then low-frequency resonance is reduced in position control, but vibration reduction is not achieved in speed control
Solution Approach 1:
The patent applies dynamics by making the control system adaptable to different control modes. The same motor controller dynamically switches between position control and speed control modes, and the filter parameters are dynamically adjusted based on the control mode and detected resonance frequencies, allowing the system to effectively reduce vibrations in both position and speed control scenarios
Solution Approach 2:
The patent implements parameter changes by modifying filter characteristics based on detected resonance frequencies. The controller detects resonance frequencies in the speed control band and adjusts the filter parameters (cutoff frequency, damping ratio) accordingly to suppress vibrations. This allows the system to adapt filter parameters to different operating conditions and control modes
2Adaptability or versatility
If the servo motor and machine are coupled with low rigidity (spring coupling), then the system is more flexible, but low-frequency resonance occurs in the servo control band
Solution Approach 1:
The patent applies feedback by using the detected resonance frequency information to adjust the filter parameters. The controller continuously monitors the system for resonance frequencies in the speed control band and uses this feedback to dynamically adjust the filter characteristics, thereby suppressing vibrations caused by spring coupling while maintaining system flexibility
Solution Approach 2:
The patent introduces a filter as an intermediary element in the control loop. This filter acts as a mediator between the motor controller and the machine, selectively attenuating frequency components that cause vibrations while allowing other frequency components to pass through, thus reducing the harmful effects of spring coupling without compromising system flexibility
Data Source
AI summary
A motor controller which controls a servo motor for driving a machine, includes: a speed command unit which commands the speed of the machine; a speed detection unit which detects the speed of the servo motor; and a speed control unit which produces a torque command based on a speed command and a motor speed detected so as to control the speed of the servo motor, where the speed control unit includes a filter which approximates the inverse characteristic of a transmission characteristic from the servo motor to the machine, the filter has a transmission characteristic F(s) based on a frequency ω, a vibration damping coefficient ζ and a cutoff frequency ωadj which are adjustment parameters and the frequency ω is adjusted so as to be equal to or more than an antiresonant frequency ω0 of the machine but less than a resonant frequency ωp.