Motor Controller Vibration Suppression via Regression Torque Control
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Solution Overview
Problem
Existing motor control methods for industrial machines face issues with unstable behavior and vibration when switching between position/velocity control and torque control, especially when the driving object approaches the pressure object, and require complex calculations and special variables, making them costly and impractical for simple applications.
Innovation Solution
A motor controller that includes a velocity controller and a regression torque controller, which calculates a torque command and limits the velocity command to a predetermined velocity limit based on contact velocity, allowing stable approach and contact with minimal impact, and suppresses vibrations by feeding back detected velocity values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the control method is simply switched from position/velocity control to torque control, then the motor can directly generate reference torque, but discontinuous torque change generates impact and vibration or causes excessive motor velocity increase
Solution Approach 1:
The system performs preliminary action by executing position control before torque control to bring the driving object into contact with the pressure object at a controlled velocity. The velocity limit value is predetermined based on contact velocity requirements, ensuring that when torque control begins, the motor velocity is already within acceptable limits, preventing excessive velocity increase and impact upon contact.
Solution Approach 2:
The system applies feedback by continuously monitoring motor velocity and using velocity control with a velocity limit value during the transition phase. When motor velocity approaches the velocity limit value, velocity control is executed to prevent excessive velocity increase. This feedback mechanism ensures smooth transition between control modes and suppresses vibrations generated during switching.
2Speed
If velocity control is frequently switched between ON and OFF to prevent motor velocity exceeding limit, then motor velocity is controlled, but the system exhibits unstable behavior
Solution Approach 1:
The system applies dynamics by making the control mode adaptable based on real-time velocity conditions. Instead of frequent switching between ON and OFF states, the system dynamically selects either velocity control or torque control based on whether motor velocity is approaching the velocity limit value. This dynamic approach maintains velocity control while avoiding unstable frequent switching behavior.
3Device complexity
If torque is simply feed-forward controlled during switching, then the control is simple, but vibration generated when driving object presses pressure object cannot be suppressed
Solution Approach 1:
The system applies feedback by monitoring motor velocity and using this information to suppress vibrations during pressing. When motor velocity approaches the velocity limit value, velocity control is executed rather than simple feed-forward torque control. This feedback-based velocity control prevents excessive velocity and suppresses vibrations generated when the driving object presses the pressure object, while maintaining reasonable control complexity.
4Measurement precision
If position control mode is used to approach pressure object, then positioning is achieved, but complex calculations and special variables are needed making it costly and impractical for simple applications
Solution Approach 1:
The system applies universality by making the command generator multi-functional. The simple command generator can execute both position control (for approaching the pressure object) and torque control (for pressing) without requiring complex calculations or special variables. The motor controller interprets the simple position command and automatically switches between control modes, eliminating the need for complex command generator functionality while maintaining positioning accuracy.
Data Source
AI summary
To stably control a driving object to approach and contact a pressure object at a low impact, to suppress a vibration generated when the driving object presses the pressure object, and to enable a motor controller to operate based on a simple command, a regression torque controller of the motor controller limits a torque-control velocity command to up to a velocity limit value vlim defined based on a contact velocity between a driving object and a pressure object and outputs the torque-control velocity command, and a velocity controller of the motor controller calculates a torque command so that a motor velocity can follow the torque-control velocity command output from the regression torque controller.