應用適應性參考模型於四論轉向車輛側向控制

Abstract

本論文為研究四輪轉向車輛控制系統，四輪轉向系統能夠使車輛前輪與後輪獨立轉向，使車輛擁有更好的操控性與穩定性。本研究將採用H_∞穩健控制理論設計控制器，使系統在受到外在干擾以及受控車輛參數改變時仍能控制車輛動態跟隨側滑角與橫擺角速度的參考訊號。 參考模型將使用腳踏車模型為基礎，考量車輛行駛的安全性，設計其參數使輸出的側滑角參考訊號穩態時為零，並設計適應性法則使車輛在面臨緊急狀況時自行調整參考模型的參數，避免參考訊號超過車輛運動的物理極限，造成車輪轉角飽和或者輪胎側向力不足導致打滑等情況發生，並產生夠大的側向加速度，降低車輛的轉彎半徑，使參考訊號擁有最適合的避障軌跡。 最後在1/10實車縮小比例的模型車上安裝陀螺儀、加速規、電位計等感測器與DSP控制器，以實現四輪轉向系統。實驗結果證實穩態側滑角為零的參考模型確實能有效的降低車輛側滑角，而適應性參考模型也能在緊急時提供較好的避障軌跡。

In this paper, a four-wheel-steering (4WS) control system consisting of a robust H∞ output tracking controller and an adaptive reference model is proposed to enhance driving safety. The controller commands front and rear steering angles with the objective of tracking reference sideslip angle and yaw rate signals corresponding to the desired vehicle handling performance. The desired vehicle handling performance is expressed as a reference model designed based on the single track vehicle model. For better driving safety, the reference model has zero sideslip angle in steady state. In order to ensure that the reference signals comply with the physical limits of the vehicle, we designed an adaptive law to adjust the parameters of the reference model such that a feasible trajectory is generated in emergency cases. Experiments are conducted based on a remote controlled model car. This experimental vehicle is equipped with sensors and a DSP controller to implement the proposed 4WS control system. The experimental results confirm that the sideslip angle is decreased and that the adaptive reference model can provide a better trajectory in emergency cases.