Higher-Order Disturbance Compensation for Variable Structure Servo Control
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Solution Overview
Problem
Conventional variable structure-based external disturbance compensators fail to adequately reduce the impact of model errors in high-frequency bands, leading to reduced stability and performance in industrial servo systems with complex plant models.
Innovation Solution
A controller using a variable structure-based higher-order external disturbance compensator that includes a switching function calculation unit, a high-order external disturbance estimation unit, and a current command generation unit, which utilizes a second-order or higher external disturbance estimator structure to estimate and compensate for external disturbances, reducing the impact of model errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional variable structure-based external disturbance compensator is used, then the external disturbance compensation performance is improved, but the stability of the system deteriorates due to model errors in high-frequency bands
Solution Approach 1:
The patent changes the order parameter of the disturbance compensator from first-order to higher-order (second-order or higher). This parameter change enables the compensator to reduce the impact of model errors in high-frequency bands while maintaining effective external disturbance compensation, thereby resolving the contradiction between compensation performance and system stability
Solution Approach 2:
The patent uses the switching function feedback to estimate external disturbances and feeds this estimation back to the control input. The higher-order disturbance compensator processes this feedback more effectively, improving both disturbance rejection and stability by better utilizing the feedback information to compensate for model uncertainties
2Stability of the object's composition
If the external disturbance estimation gain is reduced to improve stability, then the system stability is improved, but the external disturbance compensation performance deteriorates
Solution Approach 1:
Instead of reducing the estimation gain, the patent changes the order parameter of the disturbance compensator to higher-order. This allows the system to maintain high estimation gain for good compensation performance while the higher-order structure inherently reduces the impact of model errors, thus achieving both stability and compensation performance without the traditional trade-off
Data Source
AI summary
A controller based on a variable structure comprises: a switching function calculation unit for receiving a position reference received from the outside of a motor and a plant to be controlled and a position feedback from the motor and plant, so as to calculate a switching function used for variable structure control; a variable structure high-order external disturbance estimation unit for estimating external disturbance applied to the motor and plant on the basis of the switching function, and outputting an estimated external disturbance signal; and a variable structure current command generation unit for generating a current command applied to the motor and plant, on the basis of the position reference, the position feedback from the motor and plant, the switching function, and the estimated external disturbance signal. Accordingly, the influence on a difference between a system model and an actual load model of an external disturbance compensator can be reduced.