Design Of E-ECHPS Assistance Characteristic Based On Global Power Matching And Energy Consumption Analysis

At present, Hydraulic power steering system(HPS) has been widely used in heavy vehicles. Because of its design features, the assist characteristic is unable to both guarantee low-speed maneuverability and high-speed stability. At the same time, since the steering pump of HPS system is driven directly by the vehicle engine, pump speed followed by engine speed would lead it easily exceed the threshold of valve, causing greater loss of overflow and higher energy consumption of the whole steering system and higher vehicle’s energy consumption and lower fuel economy. Due to the shortcomings above, based on the structure advantages of Electromagnetic Clutch-Electrical Controlled Hydraulic Power Steering(E-ECHPS) that is added an Electromagnetic Clutch-Electrical(ESC) between engine and steering pump makes output power adjustable and the unity of steering portability, road feel and energy saving by assistance characteristic based on global power matching. Through the entire system modeling, simulation and experiment of ESC test bench is carried out, it accumulated a theoretical basis for the subsequent development work.Dynamical combined simulation model of AMESim and Matlab/Simulink is established based on analysis of E-ECHPS and ESC composition and working principle. According to the forming principle and mathematical models of steering resisting torque, the steering resisting torque distribution at specific speed is derived. Meanwhile, the accuracy of ESC empirical formula is verified by experiment.Assist characteristic is designed based on the principle of global power matching. ESC input current is adjusted by accepting momentary steering resisting torque signal. Deterioration of ESC is adjusted to achieve power steering torque and steering resisting torque matched. Double closed-loop control of E-ECHPS is designed. From simulation results of global power matching assistance characteristic and vehicle models, the assist characteristic could adapt the steering resisting torque changes made the output power of the system followed the corresponding changes in the torque of resistance when steering resisting torque changed and drives’ input torque constant, which overcomes design insufficient of the traditional assistance characteristic. Through the handling and stability of E-ECHPS and HPS simulation, E-ECHPS could significantly improve abilities of steering portability and road feel of heavy vehicle.On the basis of comparison between E-ECHPS and HPS, the energy flow characteristics of E-ECHPS is studied and energy consumption of every part of the whole system is established. Simulation results of multiple conditions suggest energy consumption of E-ECHPS is lower than HPS and E-ECHPS could reduce almost 44% energy consumption to HPS.Through the bench test of, experimental results of agility of response, stability, slip recovery and loss of ESC is obtained, which shows the ESC has rapid response, good stability and it is able to achieve the slip energy recovering that has less energy consumption better.