Integrated optimization design of electric power steering and suspension systems based on hierarchical coordination optimization method

Both the steering and suspension systems have significant impacts on the dynamic performance of vehicles. Considering the coupling effect and aiming to improve the holistic performance of the full vehicle matching with mechanical elastic wheels (MEW), this paper carries out an integrated parameters optimization design of the electric power steering system and suspension systems. Comprehensive performance evaluation indices of the vehicle are formulated, including steering performance, ride comfort, and full vehicle stability. In order to deal with the multi-objective optimization design of the vehicle chassis, this paper puts forward an improved two-level multidisciplinary optimization method named hierarchical coordination optimization (HCO). The HCO method decomposes the optimization problem hierarchically with shared variables and local variables. Furthermore, consistency constraints and penalty functions are introduced into the objective functions of each optimizer to realize the decoupling between the system level and subsystem level. Therefore, system-level and discipline-level optimization can be carried out alternately, which not only simplifies the original optimization problem but also solves the coupling problem. Moreover, the particle swarm optimization algorithm is adopted to realize the entire optimization work. Finally, the optimization results of both vehicle chassis optimization design and numerical example are obtained, which show that HCO performs better than the linear weighted sum method. The simulation results reveal that the proposed optimization strategy can improve the performance of the vehicle equipped with MEW in multiple aspects.