以Brush輪胎縱向力模型為基礎之個別輪胎的路面摩擦係數估測之研究

Abstract

本研究利用Brush 輪胎模型設計以下四種方法以即時估測四個輪胎個別的路面摩擦係數：1) 假設輪胎縱向剛度為已知，並使用輪胎縱向力的資訊，藉由Lyapunov 原理設計摩擦係數估測器。2) 考慮在縱向剛度未知的條件下，設計縱向剛度估測器，並將摩擦係數估測器與縱向剛度估測器結合成新的估測系統。3) 將路面摩擦係數與輪胎縱向剛度的動態結合，使用一個估測器同時估測兩未知參數。4) 利用最佳化的方法估測路面摩擦係數，設計成本函數為輪胎縱向剛度和輪胎正向力的關係式，藉由此估測方法，在沒有輪胎縱向剛度資訊的狀況下估測路面摩擦係數。最後，使用14 個自由度的複雜車輛模型與貼近真實輪胎的Magic Formula 輪胎模型進行模擬，探討各種估測方法的效果。由模擬結果可知，本研究提出之方法可在車輛直線加減速的情況下正確估測得驅動輪的路面摩擦係數。然而在同時轉向與加減速的情況下，估測效果仍有待加強。

This thesis presents four algorithms for real-time estimation of the tire-road friction coefficient of each individual wheel based on the brush longitudinal tire model. These algorithms include 1) a tire-road friction coefficient estimator based on the longitudinal tire force and Lyapunov theorem under the assumption of known tire longitudinal stiffness, 2) a feedback connection of a tire-road friction coefficient estimator and a tire longitudinal stiffness estimator for the case of unknown tire longitudinal stiffness. The longitudinal stiffness will be estimated by an estimator. The tire-road friction coefficient estimator and the longitudinal stiffness estimator are connected and form an estimated system. 3) an estimator for simultaneous tire-road friction coefficient and longitudinal stiffness estimation, and 4) an optimization algorithm exploring the relation between tire normal forces and longitudinal stiffness. The performance is verified by simulations based on a 14-DOF complex nonlinear vehicle model and magic formula. Simulation results show that the proposed algorithms are able to correctly estimate the tire-road friction coefficient of each driving wheel when the vehicle is accelerating/decelerating along a straight line. However, the performance deteriorates whenever the vehicle is under a combined motion of turning and accelerating/decelerating.