Servo Motor Control Device Switching PID and Sliding Mode
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Solution Overview
Problem
Existing servo motor control methods, such as PID and sliding mode control, face challenges where users struggle to understand the transmission characteristic, leading to issues like overshoot and hunting, particularly when the torque output is limited in PID control, and the non-linear nature of sliding mode control makes it difficult for users to comprehend.
Innovation Solution
A control device that selectively implements both sliding mode and PID control based on position and velocity deviations, allowing users to operate the servo motor without being aware of the maximum torque output, while ensuring the transmission characteristic is easily understood, by switching between the two control methods using predetermined values and a switching curve on a phase plane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If sliding mode control is used to prevent overshoot and hunting, then the servo motor can be controlled without the user being conscious of maximum torque, but the transmission characteristic becomes nonlinear and difficult for users to understand
Solution Approach 1:
The control system is segmented into two distinct control modes: sliding mode control for high-speed positioning and PID control for low-speed precision positioning. This segmentation allows each control mode to operate independently in its optimal performance range, resolving the contradiction between ease of operation and understanding transmission characteristics.
Solution Approach 2:
The control system dynamically switches between sliding mode control and PID control based on the current operating state (position deviation and velocity deviation). This dynamic adaptation allows the system to maintain optimal performance across different operating conditions while keeping the control logic understandable through clear switching criteria.
2Device complexity
If PID control is used to maintain linear transmission characteristic, then users can easily understand the control behavior, but overshoot and hunting occur when torque output is limited
Solution Approach 1:
The control system segments the operating range into two zones: a first range where sliding mode control prevents overshoot and hunting, and a second range where PID control maintains linear transmission characteristics. This segmentation resolves the contradiction by applying the appropriate control mode to each operating zone.
Solution Approach 2:
The control mode is changed based on parameter thresholds (position deviation and velocity deviation). When parameters indicate high-speed operation, sliding mode control is applied; when parameters indicate low-speed operation, PID control is applied. This parameter-based switching resolves the contradiction between reliability and simplicity.
3Productivity
If sliding mode control is used for high-speed positioning, then positioning speed can be increased, but the control becomes difficult to understand and requires complex nonlinear control logic
Solution Approach 1:
The control system segments operations into high-speed positioning (sliding mode control) and low-speed positioning (PID control). This segmentation allows high-speed positioning to achieve high productivity while maintaining overall system understandability through the use of simple PID control for the final positioning phase.
Solution Approach 2:
The control system dynamically transitions from sliding mode control to PID control as the servo motor approaches the target position. This dynamic transition maintains high productivity during high-speed positioning while ensuring easy understanding and precise control during the final positioning phase.
Data Source
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AI summary
A control device, by which a user causes a servo motor to perform desired operation without being conscious of a maximum torque of the servo motor while easily understanding the transmission characteristic, selects which one of sliding mode control and PID control is adopted to control a servo motor based on at least one of a position deviation and a velocity deviation.