【正文】 electrohydraulic power steering system Electrohydraulic power steering system at work steering characteristics can be changed. It basically has two kinds: electric hydraulic steering system (ECHPS) and electric hydraulic steering system (EHPS). Now automotive applications is the largest electric hydraulic booster turn from system. electronic control hydraulic power steering system Electric hydraulic steering system (ECHPS) in hydraulic steering system is based on the liquid flow rate increased control solenoid valves, torque sensor, the wheel speed sensors and steering control unit etc ponents. Ideally, car in spin to try to deft, request when in cars to different speed operation, which can realtime provide corresponding steering to overe the running speed to make drivers to resistance to manipulate the steering wheel can both lightweight, and have enough way feeling. In steering process, through the torque sensor, speed sensor etc sensing device will shift to rate, speed transfer to parameters such as steering control unit. After decoding, control by electromagnetic valve with liquid flow speed changing, and change the size of the moment, make grants to individual driver according to speed and driving conditions, changes to manipulate portability and stability to harmony. But at the same time, ECHPS also exist because of oil pump continuous work caused by excess energy consumption, the hydraulic system occupies a large space, easy to leak, noise big shortings, and increased its speed detection control device. And the control valve of structure than HPS plex and cost is higher, which are mainly applied in limousines and sports by using the car. electric hydraulic steering system Electric hydraulic steering system (EHPS) is in hydraulic steering system developed on the basis of. Its characteristic is driven by the engine turns ZhuLiBeng shifted the hydraulic motor drive, and increased its speed sensor, steering angular velocity sensor and steering control unit etc electricals. The system of hydraulic oil tank, oil pump, motors and steering control unit has integrated in motor oil pump in the group. Work steering control unit according to car of the speed and steering Angle calculated as the input signal output signal, control ideal appropriate power, motor output ZhuLiBeng driven hydraulic work. Through the hydraulic oil for steering gear provide power [3]. When the automobile lowspeed road, steering control unit control motor output large torque, make drivers can easily turned the steering wheel。 While the car is a high speed, steering control unit control motor output smaller torque, such drivers in manipulating the steering wheel is more stable. Due to the speed adjustable motor, can instantly shut, pared with hydraulic steering system, it saves engine fuel consumption, improve the economy. Electrohydraulic power steering system although in hydraulic steering system basis of technology has greatly improved, but the existence of hydraulic equipment are still made the system, such as the hard to overe shortings existing oil leakage, not easy installation and maintenance, etc. Although realized the change, but the dynamical characteristics in hydraulic booster system based on electronic control device increased again, making the system structure is plex, cost increases. Because electrohydraulic steering system technology, may realize the mature electroniccontrolled system integration, vehicle as traditional hydraulic steering system to electric power steering system of intermediate technology of transition, in certain time will continue to receive applications and development. electric power steering system (EPAS or EPS) Electric power steering system is the traditional mechanical steering system foundation, increased sensor device, electronic control devices and steering mechanism, etc. Its characteristic is to use electric actuators in different driving conditions for pilot provide appropriate support. System mainly consists of the electronic control unit ECU, torque sensor, the wheel speed sensors, motor, clutch and the steering assembly etc. Electric power steering system working principle is: the pilot control steering, the sensor will pilot role in steering wheel torque signal, speed signal, engine speed signal input ECU, ECU of the input signal calculations, inquires the booster form, determine the size and direction target current, so as to control motor current and the direction, by slowing institutions and clutch motor torque transfer to steering mechanism will be, so as to provide the proper power。 driver When steering system malfunction, EPS system does not support. Don39。t turn circumstances, motor doesn39。t work. Electric power steering system can realtime in different speed for car turned to provide different under the instrumentality of guarantee in lowspeed driving car deft and agile, high speed is stable and reliable. Electric power steering system generally consists of mechanical parts and controlling part. Mechanical parts mainly include transmission unit (the clutch, the steering assembly) and execution unit (electrical), etc. Control part mainly according to sensors to speed and torque signal for puting, drive motor control instructions issued to provide power for steering. EPS pared with HPS, except to save energy outside, due to the elimination of the hydraulic system and improve the environmental performance, solves the malpractices of hydraulic drive brings. The system is made of manufacturers to provide to the vehicle manufacturer, can be directly mounted. Under different conditions of different models, and different for different drivers steering properties, through software modification, convenient and quick. Complete EPS system also includes fault diagnosis and safety protection system. When malfunction happened, could stop booster, automatic recovery to manually control mode and warning signal, and show the memory of abnormal cont