Abstract
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.
Highlights
Dynamic tracking has become one of the most significant performances of servo controlling systems
The following three controllers are compared: 1. PD + disturbance observer (DOB) + zero-phase error tracking controller (ZPETC): This compound control strategy is commonly used in servo system
The three controllers are first tested for two specified sinusoidal trajectories in 5 and 11 Hz, that is, the tracking command signals are employed as r = 0:5 sin (2p Á 5t) and r = 0:5 sin (2p Á 11t)
Summary
Dynamic tracking has become one of the most significant performances of servo controlling systems. This indispensable servo technique is used in a wide variety of high-performance mechatronic systems, including a typical hard disk drive,[1] a nanopositioning stage,[2] an XY-table positioning mechanism,[3] and a hydraulic servo system.[4] Over the past decades, the existing researches are focused on the design of feedforward controller to improve the dynamic performance of servo systems.[5] Instead of altering the stability, a feedforward controller provides the overall system with specific frequency tracking characteristics. A closed-loop controller is essential to guarantee the stability of the system. As an effective feedforward design approach, zero-phase error tracking controller (ZPETC) counteracts the closed-loop poles and the cancellable zeros of the control plant to turn the gain
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