The Research On Dynamic Performance And Energy Consumption Of Electro-Hydraulic Steering Systems

The reduction of fuel consumption in vehicles remains an important target in vehicle development. To reduce the energy consumption, an electric motor can be used to drive the pump in Electro-hydraulic power steering system. Besides EHPS enables the amount of assistance with steering to be varied depending on the running condition of vehicle, so as to get a good road feel. Because of its simple and compact structure, convenient installment, this steering system is widely accepted in many vehicles abroad the world. The domestic research of this steering system is still in the starting phase, and the technology of core components is still in foreign monopoly. Therefore it is very necessary to do research in this steering system. The paper mainly describes the following aspects.The working principle of Electro-hydraulic power steering system is firstly analyzed and the steering valve characteristics at various driving conditions are described. Secondly EHPS system is split into the mechanical, hydraulic, and electric module and the controller; each is established mathematical model and simulation model. Then vehicle steering dynamics model is established. Finally the values of various parameters are ascertained in the model, laying the foundation for the simulation analysis research.According to detailed analysis of the steering wheel torque characteristics, the characteristic of alignment torque is simulated. The design method about characteristic curves of steering assistance is put forward. By the analysis of working characteristic curve about the steering valve in EHPS system, the relationship between the motor speed, steering angular velocity and vehicle speed is explored. At last, the control method of EHPS system is analyzed, and the characteristics of steering assistance are simulated.According to"steering wheel angle step input vehicle handling and stability"and"on-center handling test", the steering wheel torque, yaw velocity and the hydraulic fluid pressure difference in the cylinder are analyzed through simulation. And these response characteristic effects of various parameters in EHPS system are explored. Then the power consumption and energy flow in electro-hydraulic power steering system are investigated. Energy losses mainly occur in the electric motor and in the orifices of the steering valve. The energy consumption of an EHPS system is mainly determined by the performance in standby mode. With the help of the simulation model a parameter sensitivity investigation has identified the energy consumption effects of certain parameters.By way of studying the steering assistance feature and energy flow in EHPS system for small sized cars, investigate the matching methods for EHPS system and small sized cars. By means of mathematical model, a simulation model with EHPS system and vehicle is developed and validated to investigate the influence of various parameters on the energy consumption and the handling stability, providing the theoretical and engineering foundation for the optimization and development of EHPS system.