Study Of Electric Power Steering System Assisted Control Strategy

Steering system has gone through several stages, including Mechanical Steering System, Hydraulic Power Steering System, Electronic Hydraulic Power Steering, and Electric Power Steering System (referred to as EPS). EPS combines the mechanical steering system with a controlled motor. The motor provides direct assist, the assisted force to be controlled by ECU. Compare with traditional power systems, EPS has the following advantages, including energy saving, environmental protection, and better handling characteristics. EPS is cosely linked to the theme of modern automotive development, so it has become a hot spot.This paper has analyzed the basic principle of EPS system, simplified the EPS dynamics mathematical model, constructed a mathematical model of EPS system, established the output to the input of the transfer function and analyzed stability.The work is important for the construction of control Strategy.The design of control strategy affects directly the performance of EPS. This paper has focused on assisted control strategy, discussed how the motor current tracked the steering wheel torque quickly and accurately, proposed fuzzy adaptive PID control strategy. Fuzzy adaptive PID control can change PID parameters in real-time dynamic process. Compared with the PID control, fuzzy adaptive PID control has faster response, better stability and reliability. This paper built Simulation Model of EPS System in Saber and verified the effectiveness of the fuzzy adaptive PID control by Simulation.Finally this paper has completed hardware and software of the EPS system with dsPIC30f4011. It has verified the feasibility of hardware and software, the effectiveness of fuzzy adaptive PID control strategies by bench.