摘要：This article provides systematic analysis and controller design methods for dynamic tracking performance of servo mechanisms associated with practical systems. Discrete general composite nonlinear feedback, as a fundamental controller, will be proposed to yield a good transient performance. Particularly, in the servo systems, there also exist unmodeled disturbances which may lead to tracking errors. A novel repetitive control scheme based on disturbance observer configuration is incorporated into the controller to counteract this unexpected effect. Furthermore, to deal with any periodic signal of variable frequency, a fractional-order repetitive control scheme based on disturbance observer strategy is proposed. The stability of the overall closed-loop system is guaranteed via frequency domain analysis. Three controllers, that is, the proportional–derivative controller with zero-phase error tracking controller scheme and the conventional disturbance observer, the integral backstepping controller, and the compound discrete general composite nonlinear feedback controller with fractional-order repetitive control scheme based on disturbance observer are compared. To demonstrate the dynamic tracking performance of the proposed control strategy, comparative experiments are conducted.
