Motor Control Sampling Rate Mismatch Compensation
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Solution Overview
Problem
Conventional motor control systems employing model following control face increased computational burdens when the sampling rate of the model control system is set lower than that of the feedback control system, leading to potential overshoot and extended positioning settling time due to differences in sampling rates.
Innovation Solution
Incorporating a low-pass filter with a specific transfer function corresponding to the delay in the sampling rate of the model control system, combined with an integral control system and proportional control system, to reduce the residual quantity in the speed integrator and mitigate the impact of differing sampling rates, allowing for model following control with reduced computational burden.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the sampling rate of the model control system is set lower than that of the feedback control system to reduce computational burden, then CPU load is reduced, but positioning accuracy deteriorates due to overshoot caused by sampling rate differences
Solution Approach 1:
A sampling rate conversion unit is introduced as an intermediary component between the model control system and feedback control system. This unit converts the sampling rate of the model control system to match the feedback control system's sampling rate, thereby eliminating positioning accuracy deterioration while allowing the model control system to operate at a lower sampling rate and reduce CPU load.
2Loss of time
If the sampling rate of the model control system is set lower than that of the feedback control system, then computational burden is reduced, but positioning settling time is extended due to overshoot
Solution Approach 1:
The sampling rate conversion unit acts as a mediator that synchronizes the timing between model control and feedback control operations. By converting sampling rates, it prevents overshoot that would otherwise extend positioning settling time, thus reducing both computational time required and positioning settling time.
3Device complexity
If model following control is implemented with a lower model control sampling rate, then device complexity is reduced, but command response characteristics are degraded due to sampling rate mismatch
Solution Approach 1:
The sampling rate conversion unit serves as an intermediary that resolves the sampling rate mismatch between the simplified model control system and the feedback control system. This maintains command response characteristics by ensuring synchronized operation timing, while allowing the model control system to operate with lower complexity at a reduced sampling rate.
Data Source
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AI summary
A motor control system is provided that can execute model following control in which an influence of the difference between the sampling rate of a feedback control system and the sampling rate of a model control system is suppressed with a smaller amount of computation than ever. A speed controller includes a low-pass filter having a transfer function corresponding to the delay in the sampling rate of a model control system, an integral control system including a speed integrator, a proportional control system, and a speed proportional gain multiplication section. The integral control system inputs to the speed integrator a command obtained by a subtraction section that subtracts delay speed information output from the low-pass filter from a command obtained by an addition section that adds a speed command and a model speed command.