適用於最佳化輪胎力量分配控制之路面摩擦係數估測法

Abstract

隨著汽車的發明與普及，人們對於車輛的要求日益提高，許多國內外汽車大廠越來越重視車輛安全控制系統的研發，致力於提高車輛的安全性與操控性。而基於成本考量與安全控制系統的需要，許多車輛與輪胎的動態需以估測的方式獲得，藉由這些資訊來幫助安全控制系統穩定的控制車輛行駛。 本研究考慮到車輛行駛中常會遇到各種不同的路面狀況，路況變化會直接影響到輪胎受力，因此可藉由輪胎與路面間受力情形不同來判斷路況變化。透過設計估測系統，即時估測車輛質心之縱向速度、四個輪胎正向力、側向力與摩擦係數，考慮輪胎模型不準確因素，提出以額外參數修正輪胎模型的方法，並透過參數正規化與投影來確保估測結果正確。將估測到的參數回授至最佳化輪胎力量分配控制器，協助此控制器即時得知輪胎與路面間摩擦資訊以提高控制效能。 最後則透過模擬測試所設計之估測系統在路況變化下的估測效果，並驗證了整合於最佳化輪胎力量分配控制器後，估測系統在路面摩擦係數急遽下降的情況，依然能準確估測到摩擦係數，大幅改善此控制器的控制效能，穩定的跟隨給定之參考值。

This paper considers driving vehicles on roads with changed surface conditions which make the tire forces, and in turn the vehicle dynamics vary significantly. Therefore, this study presents a real-time estimation algorithm for the longitudinal velocity of the vehicle, and the normal force, lateral force, and road friction coefficient of each wheel. The proposed estimator scheme takes into account uncertain characteristics of the tire model and presents a method to modify the tire model by an additional parameter; then the result of the estimation is enhanced by techniques of normalization and projection. The estimated road friction coefficient and lateral tire force are fed back to the vehicle control system using optimum tire force distribution method for better performance. Finally, simulations are carried out to test the performance of the proposed estimator under suddenly changed road conditions. In addition, it is verified by simulations that the optimum tire force distribution control system incorporated with the proposed estimation algorithm is able to follow the reference trajectory in the event of suddenly dropped road friction coefficient.