Control And Simulation Of Whole Car Model With Semi-active Suspension

As higher vehicle speed is required, traditional passive suspension systems have become a restraint to the further development of vehicle properties. It is required in modern vehicle suspension systems not only to realize basic functions and to ensure driving safety, but more importantly, to provide better vehicle riding comfort as well. Semi-active suspension systems excel passive suspension systems and become the main research field, because of their elegant structures, low costs, little energy exhaustion, and damping effect close to full-active ones.In this paper, as to whole-car model with seven degrees of freedom, new control and simulation strategies were proposed, which include the following three parts:1. The kinetic equations and state-space equations of whole-car model with seven degrees of freedom were founded. According to frequency domain model corresponding to road roughness, the relations between the power spectrums as well as RMS values of vehicle responses and the suspension damping coefficients were analyzed, simulation of passive suspension in time domain was realized and the RMS values as to suspension performance evaluation were calculated.2. The state-space equations of vehicle-road system with stochastic inputs were founded, of which reasonable objective functions were set to deduce instantaneous stochastic optimal control expression of the optimal control strategy. Simulations of passive, semi-active and full-active suspension systems in time domain were taken out.3. The relation between performance evaluation and suspension damping coefficients with traditional skyhook damping strategy was analyzed. According to this strategy, modified skyhook strategy based on multi-targets applications was proposed and simulations of four different groups of parameters with this strategy were accomplished, in which the effects of parameter variations to suspension performance evaluation were analyzed.Innovations in this paper are that two new control strategies in simulation and analysis of whole-car model in time domain were proposed, of which the semi-active suspension control strategies brought up are strategically simple, little calculation consuming, with low costs and easily realized. According to simulation outputs, these two strategies can be effectively practiced in reducing RMS values of vertical body acceleration, advancing vehicle riding comfort as well as exploiting dynamic travel of suspensions and ensure tire load in safe range in the meantime.