Study On Longitudinal Force Control Distribution Of ESP System Based On Improvement Of Handing Stability

With the rapid development of China's automotive industry and technology,the safety of vehicle itself is also becoming more and more important.ESP system is one of the central guarantee in automotive active safety.The research and development of ESP system has been the focus of the automotive industry.Along with the global energy crisis continues to expand,the development of electric car demand is imminent,four wheel motor drive and distributed electric EV drive is bound to focus on the future development trend,but it is different with traditional car in the vehicle stability control,it put forward the new request to the development of modern ESP system,this paper study on the ESP control system about the longitudinal force control distribution.In this paper,we first study and explore the ESP control system in depth,including the significance,basic structure and working principle of ESP system,the research status at home and abroad,and the key technologies.Then building ESP vehicle nonlinear model,considering the influence of tire characteristics on the stability of the vehicle,and analysis tire characteristics with the commonly tire model: ‘magic formula',HSRI tire model and UA tire model,and compared with the tire test data,choose the appropriate tire model-HSRI model.Under the steady-state conditions,The validity of the vehicle nonlinear model is verified by simulation.Secondly,the control variables are selected and analyzed appropriately,and the nominal values of the control variables are corrected in detail.The conditions considering vehicle speed and road adhesion coefficient are discussed for vehicles to be in a stable area,which lays a foundation for the design of the controller.According to the design of the control system,adopt hierarchical control,the upper controller design the yaw rate and sideslip angle together with weighted coefficient sliding model controller and the linear quadratic regulator LQR controller,and the output of the additional yaw moment way direct input to the whole vehicle model for verify the reliability of the control effects of the upper controller.According to the longitudinal force distribution strategy,the design of three modes : pure braking mode including single wheel braking and two wheel brake,braking driving mode and pure driving mode,depending on the output of real-time yaw moment and the ideal yaw rate value,real-time recognition of vehicle motion state.And the three models fully consider the coupling between the lateral force and the longitudinal force through the reverse model of the tire.At last,the three longitudinal force distribution modes are simulated and analyzed under the condition of low speed and high speed.The research results show that the upper sliding mode variable structure controller and the LQR controller meet the requirements.The three longitudinal force distribution modes can also meet the ESP control effect,and the vehicle handling stability is controlled.The diversified distribution mode also provides reference for the development of ESP system in the future.