運用QFT/Hinfinity方法設計多輸入多輸出之懸吊系統

Abstract

本論文將 之設計方法用於四分之一車子( Quarter Car )的懸吊系統( Suspension System )上，再配合MIMO 控制理論將控制器設計出來。此四分之一車子的懸吊系統的控制器是以混合靈敏度標準 架構( Mixed Sensitivity Standard Regular Structure )計算求得的。此控制器之主要架構亦包含三個權重函數(Weight Function)，此三個權重函數分別為靈敏度權重函數(Sensitivity Weighting Function, )、控制權重函數(Control Effort Weighting Function, )以及互補靈敏度權重函數(Complementary Sensitivity Weighting Function, )。靈敏度權重函數屬低頻加權，是用來調整靈敏度函數 。選取夠小的靈敏度權重函數使得在给定的控制頻寬內，以降低干擾，如性能(Performance)，以及選取夠小的互補靈敏度權重函數，使得在希望的控制頻寬以外，能幫助確保較好的穩定度邊界，如穩健度(Robustness)。控制權重函數目的是用來限制系統在高頻時之增益，抑制感測器雜訊干擾，以及調整系統在高頻時增益衰減的速度。 控制方法係結合 技術解決二維自由度(2-Degree-of-Freedom)之系統。本論文所提出的方法包含兩種型式，第一種是系統有未確定(Uncertainty)變數之穩健控制(Robust Control)方法。在此控制方法中，控制器是處於一維自由度(1-Degree-of-Freedom)的架構經由 方法所設計的。第二種的設計方法是 結合 的方法，在迴路外加上一前置濾波器(Prefilter)，此架構為二維自由度之系統。此一架構可藉由傳統控制理論來完成軌跡追蹤(Tracking)的結果，並將 結合 的設計程序應用到四分之一車的懸吊系統上，使得MIMO懸吊系統之位移在給定的邊界內。

This dissertation uses a combined design method for the quarter-model vehicle suspension system to design a controller for the multi-input multi-out (MIMO) control algorithm. This research calculates the controller parameters of the quarter-model suspension system by the mixed-sensitivity standard regular structure. The controller of the main structure containing three weighting functions, sensitivity weighting function , control effort weighting function , and complementary weighting function . The sensitivity weighting function, weighted for low frequency, shapes sensitivity function . Choosing to be small inside the desired control bandwidth to achieve good disturbance attenuation (i.e., performance), and choosing to be small outside the control bandwidth, help to ensure a good stability margin (i.e., robustness). A control effort weighting function confines the system gain at high frequency, to suppress sensor noise disturbance, and adjusts the gain decay speed at high frequency. The combined techniques copy a 2-degree-of-freedom (2DOF) system. This dissertation proposes two-types of design methodologies. The first design method describes the robust control method, by which the 1-degree-of-freedom (1DOF) structure designs the controller. The second design method adds a pre-filter into the 1DOF, or the 2DOF structure. The current study uses this structure to outcome tracking by the classical control theory, and applies the combined design procedures in the vehicle quarter-model suspension system, such that displacement of the MIMO suspension system lies in the given boundaries. Keywords: QFT/ robustness, Weighting function, MIMO system