Research On Sliding Mode Control Of Vehicle Active Suspension Based On Multi-objective Optimization

Suspension system,as an important part of vehicle damping,plays an important role in vehicle ride comfort and handling stability.Active suspension system is widely concerned because it can produce real-time forces corresponding to road excitation and body attitude,making the vehicle in the best damping and driving state.Active suspension system is a complex system with high uncertainty,which is superior to the existence of parameter time-varying,external disturbance and non-linear energy factors.The quality of control strategy plays an important role in the performance of active suspension.In the process of control optimization,there are conflicts among multiple performance objectives of vehicle,and conventional control methods are difficult to meet the optimal performance of active suspension.Therefore,the research of active suspension control strategy and the optimization of controller parameters is an important research issue.For the existing problems of active suspension system,this paper took the suspension parameters of a car model of Shandong Lichi as a reference and applied the sliding mode control method which has strong adaptability to the nonlinearity of the system,the uncertainty of the model and the external disturbance and a sliding mode control strategy based on multi-objective optimization method was proposed for active suspension.The specific research work is as follows:(1)This paper summarized the active suspension system and its control strategies at home and abroad.Based on the full analysis of the advantages and disadvantages of each control strategy,the idea of sliding mode control strategy of vehicle active suspension system based on multi-objective optimization was proposed.According to the needs of the vehicle suspension system,a two-degree-of-freedom 1/4 vehicle suspension model and a seven-degree-of-freedom vehicle active suspension model were established after dynamic analysis of the vehicle suspension system.(2)Based on the two-degree-of-freedom 1/4 active suspension model,the sliding mode controller for active suspension was designed in combination with sliding mode control theory.The Lyapunov stability theory and Hurwitz stability criterion were used to verify the stability of the designed sliding mode controller,and the stability range of the sliding mode surface parameters was derived.(3)With the constraints of suspension deflection and the control force output limit of the controller as constraints,a multi-objective optimization problem with vehicle body vertical acceleration,suspension dynamic travel,and tire dynamic load as the control targets was established.The parameters of the sliding mode controller of 2-DOF 1/4 active suspension were multi-objective optimized by using genetic algorithm and particle swarm optimization algorithm,and the simulation program was established in MATLAB environment for numerical simulation.(4)The sliding mode controller of the active suspension system of the whole vehicle was established.With the dynamic travel of the suspension and the dynamic displacement of the tire as constraints,a multi-objective optimization problem with body vertical acceleration,body pitch acceleration and body roll acceleration as the control targets was established.The improved multi-objective genetic-particle swarm algorithm was used to optimize and simulate the sliding mode controller of the 7-DOF vehicle active suspension system.The simulation results show that the multi-objective genetic algorithm optimization of the sliding mode controller parameters of the 2-DOF active suspension resulted in a reduction of vehicle body vertical acceleration,suspension dynamic travel,and tire dynamic load by 8.9%,13.1% and 14.2% compared with the before optimization,and the three objective function values of the vehicle are reduced by 13.5%,10.3% and 16.8%.The parameters of sliding mode controller of 7-DOF vehicle active suspension are optimized by multi-objective genetic particle swarm optimization,which made the body vertical acceleration,body pitch acceleration and body roll acceleration decrease by 7.7%,9.6% and 11.4% compared with the before optimization.The full-text research and simulation analysis prove that the sliding mode control strategy for vehicle active suspension based on multi-objective optimization proposed in this paper was feasible to improve vehicle driving performance and improve active suspension vibration damping performance,which can significantly improve the ride comfort and handling stability of the vehicle,and has important theoretical and practical significance for the research of active suspension.