Servo Control Mixing Velocity Feedback for Stability
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Solution Overview
Problem
Conventional servo control systems for feed drive mechanisms with multiple motors face instability due to varying transfer functions with object position, leading to phase lag and limited control gain, making it difficult to enhance response speed.
Innovation Solution
A servo control method that mixes velocity feedback signals from multiple motors to generate a stable torque instruction, preventing phase lag and allowing for increased control gain by averaging or ratio-adjusting the feedback signals based on object position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If velocity feedback control is performed using a single encoder signal from one motor, then the control system is simple, but the transfer function varies with object position causing phase lag and limiting control gain
Solution Approach 1:
The patent combines velocity feedback signals from multiple encoders (one from each motor) into a single mixed velocity feedback signal. This merging approach eliminates the problem of transfer function variation with object position, as the combined signal represents the average velocity of the driven object regardless of its position along the travel path. The mixed feedback signal is then used in the velocity control loop to generate torque instructions for all motors, ensuring stable control characteristics throughout the entire range of motion.
Solution Approach 2:
The mixed velocity feedback signal serves as a universal feedback source for controlling multiple motors simultaneously. Instead of requiring separate control loops for each motor, the single mixed feedback signal is used to generate torque instructions for all motors in the system, simplifying the control architecture while maintaining stable performance across different object positions.
2Speed
If control gain is increased to improve response speed, then response speed improves, but phase lag increases causing instability
Solution Approach 1:
By merging velocity feedback signals from multiple encoders, the patent creates a position-independent feedback signal that maintains consistent phase characteristics across the entire object travel range. This allows the control gain to be increased uniformly without encountering position-specific phase lag problems, thereby improving response speed while maintaining stability throughout the system's operating range.
3Force
If multiple motors are used to drive one object, then driving force and reliability are improved, but control complexity increases due to varying transfer functions
Solution Approach 1:
The patent simplifies the control of multiple motors by merging their velocity feedback signals into a single mixed feedback signal. This approach maintains the advantages of multiple motors (increased driving force and reliability) while eliminating the control complexity that would otherwise result from position-dependent transfer function variations. The mixed feedback signal provides a unified basis for generating torque instructions for all motors.
Data Source
AI summary
A method according to an example of the present invention is a servo control method to be applied to a feed drive mechanism configured to drive an object to be driven by using a plurality of motors, in which velocity control of the object to be driven is carried out by using a signal obtained by mixing velocity feedback signals of the motors with each other, and a torque instruction obtained by the velocity control is used for drive of all the motors. By this example, there is provided a servo control system capable of preventing a phenomenon in which a transfer function changes depending on the position of the object to be driven, and the phase abruptly lags to make the operation unstable, thereby making it difficult to increase the gain, from occurring.