Robust LMI-Based Controller Design using H∞ and Mixed H2/H∞ for Semi Active Suspension System

Control of vehicle suspension systems has been the focus of extensive work in the past two decades. Many control strategies have been developed to improve the overall vehicle performance, including both ride quality and stability conditions. In this paper, we use the H∞ and mixed H2/H∞ techniques with a semi active suspension system to increase the passenger’s ride comfort performance A two degree of freedom dynamic model of a vehicle semi-active suspension system was presented. The role of H∞ is used to minimize the disturbance effect on the system output whereas H2 is used to improve the transients against random disturbances. The capability of the system of improving comfort of operators has been evaluated through simulations carried out with a validated model of the entire vehicle. The results of this study revealed that the use of mixed H2/H∞ with pole placement for a semi-active suspension system showed a great improvement compared with H∞ systems. In addition, the results of the simulation showed that ride comfortable of the vehicle can be improved effectively by using the semi-active suspension with mixed H2/H∞ control method, and also the mixed H2/H∞ control method more effective than the H∞ control method. Finally, this paper showed a robust use of both H∞ and mixed H2/H∞ problem which can be solved using linear matrix inequality (LMI) techniques.