Abstract: Aiming at the existing researches that rarely consider the deterioration of vehicle vibration caused by the increase of unsprung mass and the torque fluctuation of the wheel motor at the wheel in-wheel active suspension system, the influences of the sprung mass, suspension rigidity, suspension damping and high-order nonlinear unmodeled dynamics of the in-wheel active suspension system are considered. The LFT method is used to establish the oriented hybrid uncertain active suspension dynamic model, in which in-wheel motor is suspended as dynamic vibration absorber(DVA). Under the unified framework of the generalized μ synthesis system, the μ synthesis robust controller about the active suspension augmentation system is designed according to the robust μ synthesis singular value theory, and solved by the D-G-K iterative method. The μ synthesis analysis reveals that the designed μ synthesis controller can ensure the robust stability and robust performance of the closed-loop active suspension system under a good stability margin, and reduce the conservativeness of the traditional H_∞ controller. In the Matlab/Simulink environment, the feasibility and effectiveness of the controller are verified through frequency domain and time domain responses. The simulation results show that the comprehensive performance of designed DVA-μ control system is better than the DVA-H_∞, it can effectively suppress the vertical vibration of the active suspension system and still improve the ride comfort and road-holding ability even if external interference and multi-parameter perturbations exist, which is helpful for the theoretical reference of the vibration reduction design of the active suspension system of electric vehicles.

Key words: in-wheel-motor-driven, electric vehicle, vibration suppression, activesuspension, μ synthesis robust control