Eps System On The Vehicle To Manipulate The Stability Of The Simulation Study

Electric Power Steering System (EPS) is a new type power steering system which directly depending on electromotor to supply assistant tortile. It can easily realize to supply different power when the velocity of automobile changed and guarantee the automobile steering handily and agilely in low velocity, running steadily and reliably in high velocity. EPS has the advantages of saving fuel, reducing overall weight, improving driving security and being in favor of environmental protection, etc. The research emphases of EPS is always on the system itself ,but the vehicle's maneuver stability is one of the most important thing of vehicle design, so it's very necessary to carry on a system research combined the two aspects.At first, considering the proportional, proportional plus derivative (PD) and PID control mode, a second-order dynamic model of EPS was established. Then, the transfer function between the yaw rate and steering wheel angle was deduced. the vehicle's maneuver stability of PID control mode was investigated for the first time and rectified the inaccurate define of the transfer function between the yaw rate and steering wheel angle for the automobile which not equipped with EPS.Used the GUI flat of Matlab, the integrated software of the automobile which equipped with EPS was designed and programmed, which has powerful function, convenient manipulation and predigested the simulation and analysis to automobile equipped with EPS. The software has exoteric framework that could be extended and upgraded easily.Based on the model, the formula of the steady-state and transient response conduced by phase step input was deduced. Based on the software,the influences on the vehicle's response in time and frequency domain, which contributed to the control mode, control coefficient and structural parameter of EPS, have been discussed detailedly. A diver-vehicle (equipped with EPS) closed-cloop model was established.The results show that the EPS can strongly impact on vehicle's maneuver stability. If the the control mode, control coefficient and structural parameter of EPS are selected reasonably, the influence will reduce effectively. Inducting yaw rate feedback to the EPS could enhance vehicle's stability.