- 期刊
Pressure Sensor Free Adaptive Controller Design for Pneumatic Servo Systems with Time-Varying Mismatched Uncertainties
含時變錯配性未知項氣壓伺服系統之無壓力回饋適應性控制器設計
摘要
由於致動器的高度非線性動態特性與媒體的可壓縮特性，氣壓伺服系統的控制頗具挑戰性。大部分以狀態回授做為策略判定基礎的系統，皆需全狀態的回饋以確保閉回路系統之穩定，這也意味著氣壓伺服系統對壓力感測器的需求。有學者利用狀態觀測器進行控制器設計以避免實際的壓力感測回饋。本文則對動態方程式進行重組轉換，如此則壓力回饋感測將不再需要而依舊能維持氣壓伺服系統的閉迴路性能。以函數近似技術為基礎的適應性多層滑動控制器在此展現，以保證閉迴路系統的穩定性。此處多層滑動控制設計用以解決未知項之錯配性結構問題，而未知項的時變特性則由函數近似技術克服。藉由Lyapunov穩定法則，此閉迴路系統已被證明為均極有界。誤差訊號相關的明確界線也被推導，以確保暫態特性之可行性。最後，實驗結果可印證本設計之效益。
關鍵字
無資料並列摘要
Control of pneumatic servo systems is well-known to be challenge due to highly nonlinearities in the actuator dynamics and compressibility of the media. Most state feedback based strategies for the pneumatic servo systems require full state feedback to stabilize the closed loop system which implies the need for pressure measurements of the cylinder. Many researchers used state observers to complete the controller design without using actual pressure sensor feedback. In this paper, a transformation is suggested to reformulate the dynamic equation so that the pressure sensor feedback can be avoided without deteriorating the closed loop performance. A function approximation technique (FAT) based adaptive multiple-surface sliding controller (AMSSC) is proposed for the closed loop stabilization. The multiple-surface sliding control is a backstepping-like design which is used to cope with the mismatched structure of the uncertainties, while the time-varying nature of the uncertainties is handled by the FAT. The closed-loop system is proved to be uniformly ultimately bounded by using the Lyapunov stability method. Explicit bounds for the error signals are also derived to ensure feasible transient performance. Experimental results demonstrate the effectiveness of the proposed design.