This paper proposed three different kinds of vehicle stability control systems all based on IMC strategy. As to control models, 4WS IMC used the simplest internal model which was linear and time invariant, Brake-FAS IMC applied two-input-two-output nonlinear internal model, and Brake IMC introduced two-input-one-output nonlinear internal model. Due to the different internal models, the controller parameters which were mainly the filter's time constants were of different conditions accordingly: for 4WS IMC the filter time constants could cover each kind of driving situation, while the nonlinear internal involved IMC had to adjust the filter time constants according to different driving situations, and the online tuning of time constants should be further developed. Based on different simulations combined different manoeuvres and road surfaces, several conclusions could be made: 4WS IMC is based on relatively control yaw moment which derives from the difference between the front- and rear-wheel lateral forces, and brake IMC is based on absolutely control yaw moment which is mainly generated from the braking torque applied on different wheels, and Brake-FAS IMC is a partly combination of the above two kinds IMC; 4WS IMC could use a linear internal model and fixed filter time constants to achieve comparatively good yaw rate tracking and maintain small sideslip angle with small frontand rear-wheel steering angles and the vehicle speed were nearly constant during the whole control process; Brake IMC could come to fast yaw rate tracking owing to the even bigger brake torques and large front-wheel steering inputs equal to the driver's intended steering inputs while vehicle sideslip angles were large and oscillations due to brake torques existed in yaw rate, and the vehicle speed obviously decreased but still greater than that of Brake-FAS IMC for shorter effective time; Brake-FAS IMC could come to as fast yaw rate tracking as brake IMC with smaller front-wheel active steering angle than the driver's intended steering input and smaller brake torques compared with the Brake IMC while the vehicle sideslip angle was a little bigger than 4WS IMC but smaller than brake IMC and oscillations were also mixed into yaw rates, and the vehicle speed decreased to smallest of all the three kinds of controls due to the long control process. Of the proposed control strategies, steering ability represented by yaw rate of brake IMC was the best with the fastest tracking rate, and of the Brake IMC better; stability characterised by sideslip angle of 4WS IMC was the best, and of the Brake-FAS better; controllability embodied by tyre characteristics of 4WS was the best with linear tyre characteristics, and of the Brake-FAS better; vehicle speed indicating vehicle safety to some extent of Brake-FAS IMC was the smallest, and of Brake IMC smaller. Thus, an optimisation of the combination between active-steer-based and active-brake-based IMC control which could come to very good vehicle stability control with all kinds of aspects taking into account should be further studied in the future.
Comparisons of vehicle stability controls based on 4WS, Brake, Brake-FAS and IMC techniques
Vergleich von Fahrzeug-Stabilitätsregelungen auf der Basis der IM-Regelstrategie (4WS-, Brake-, Brake-FAS- sowie IMC-Technik)
Vehicle System Dynamics ; 50 , 7 ; 1053-1084
2012
32 Seiten, 41 Bilder, 2 Tabellen, 24 Quellen
Article (Journal)
English
Comparisons of vehicle stability controls based on 4WS, Brake, Brake-FAS and IMC techniques
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