Motor Position Control With Switching-Point Overshoot Prevention
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Solution Overview
Problem
Motor position control applications face challenges in minimizing overshooting of target angular positions due to system-specified limits on acceleration, deceleration, and velocity, which affect operational efficiency and accuracy.
Innovation Solution
A motor control method using a combination of proportional and time-optimal controllers, where the proportional controller manages rotational speed near the target position and the time-optimal controller allows maximum velocity before deceleration, with a switching point determined to minimize overshoot and account for communication delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a proportional controller is used to control rotational speed near the target position, then positioning precision is improved, but the time to reach the target position increases
Solution Approach 1:
The control process is segmented into two distinct phases: a time-optimal control phase for most of the travel distance, and a proportional control phase near the target position. This segmentation allows the system to use aggressive acceleration during the majority of the movement while switching to precise control only when necessary, thereby resolving the contradiction between speed and precision.
Solution Approach 2:
The controller dynamically switches between two control modes based on the current position relative to the target. The switching point is calculated to optimize the transition, allowing the system to adapt its control strategy in real-time. This dynamic approach enables the system to achieve both fast response and high precision positioning.
2Productivity
If maximum velocity is used to reach the target position quickly, then productivity is improved, but overshooting the target position occurs
Solution Approach 1:
The switching point is calculated in advance based on system parameters such as maximum velocity, acceleration, and proportional controller gains. This preliminary calculation allows the system to prepare for the transition to proportional control at the optimal moment, ensuring that the reduction in velocity occurs just in time to prevent overshooting while maintaining maximum speed for as long as possible.
3Measurement precision
If system communication delays are accounted for in the control strategy, then positioning precision is improved, but the complexity of the control system increases
Solution Approach 1:
Communication delays are compensated for by calculating the switching point in advance, taking into account the known delay characteristics of the system. This preliminary compensation approach allows the controller to anticipate the effect of delays and adjust the switching point accordingly, without requiring complex real-time delay compensation algorithms.
Data Source
AI summary
A motor controller to control rotational speed of an output shaft of an electric motor. The motor controller includes a proportional controller and a time-optimal controller. The proportional controller controls the rotational speed when a present rotational position of the shaft is between a target rotational position and a switching point, inclusively. The time-optimal controller controls the rotational speed when the present rotational position is not between the target rotational position and the switching point. Also introduced herein are aspects pertaining to determining the switching point in a manner that minimizes overshooting the target rotational position while maximizing expediency at which the target rotational position is reached.