Design method of active suspension LQG controller for rolling motion safety of vehicle

To improve the steering-rolling motion safety of vehicle, a LQG controller for active suspension was developed. A dynamics model with 3 degrees of freedom depicting vehicle steering-rolling motion was established. Lateral-load transfer ratio(LTR), rolling angle and its acceleration were chosen to construct the evaluating indexes of comprehensive performance for vehicle rolling motion safety. In order to solve the problem that the general design approachs couldn't track the system disturbance term, namely the steered angle of front axle, and the control vector couldn't be solved because the determinant of weighted control coefficient matrix equaled to zero, the new method was scheduled as follows: the steered angle of front axle was introduced into a differential equation in accord with the minimum phase system, the differential equation was combined with the original system equation into an augmented system equation, and the infinitely small terms including control terms were added to the evaluating indexes of comprehensive performance to meet the design condition of LQG controller. Based on the analytic hierarchy process(AHP) and normalization method, the statistical data of automotive steering-rolling motion were obtained by simulation under fish-hook working condition, and then the weighted coefficients of LQG controller were determined. The working effects of LQG controller of active suspension for steering-rolling motion safety of vehicle were verified by numerical simulation under multiple working conditions. Simulation result shows that the developed LQG controller does not interfere with the steering operation of driver. Compared with the passive suspension, when the active suspension is regulated by the developed LQG controller under fish-hook working condition, slalom working condition and double-lane change working condition, the variances of LTR, namely the most important evaluating index of rolling motion safety, decrease by 32.08%, 32.82%, and 29.24%, respectively, the variances of rolling angle reduce by 47.74%, 44.19%, and 63.41%, respectively, and the variances of rolling angle acceleration reduce by 87.30%, 60.00%, and 86.39%, respectively. So, adopting the active suspension with the new developed LQG controller can significantly improve the rolling motion safety of vehicle and achieve good steering condition adaptability. © 2017, Editorial Department of Journal of Traffic and Transportation Engineering. All right reserved.