Mixed H2/H∞ control & μ analysis of vehicle active suspension system

A state-space model was built for 4 degree-of-freedom vehicle active suspension systems. Under the road disturbance excitations, mixed H₂/H_∞ optimal controller was designed to improve the ride comfort of the vehicle. H₂ index was used to make the system have good time-domain LQR performance, while H_∞ index was used to overcome the unmodeled dynamic uncertainties. The mixed H₂/H_∞ optimal controller was obtained based on linear matrix inequalities (LMI). Structured singular value theory was used to analyze robust stability of the system. The results of the simulation in MATLAB show that, compared with the passive suspension system, the active suspension systems effectively suppress the vehicle´s vibration in the range of sensitive frequencies of human body, and improve the ride comfort. At the same time the active suspension systems have strong robustness.