Research On Servo Electric Power Steering System With Fuzzy Control Strategy

Electric Power Steering System (EPS) is a dynamic steering control system.EPS Systems offerS improvements over conventional mechanical steering systems or hydraulic assist systems by improving fault-tolerant, disturbance rejection, fuel economy, start-up on low temperature, safety and environmental friendliness, which makes the EPS the main steam of future Power steering systems and an intense target of current technologyFirstly, the search background, significance and developing situation in and abroad of EPS are analyzed in this dissertation. The structures, principle of EPS are explored and the key components (including power steering motor, the master chip, torque sensor, clutch, relay etc) are briefly introduced and selected. On this basis, the dynamic performance of this original model is simulated and discussed in details with the given parameters. A conclusion is formed that the EPS dynamic performance under uncontrolled state is frangible to inherent uncertainty as well as environment disturbance. And then a state feedback control strategy based on pole arrangement method is given. Low-frequency oscillations from the road are greatly inhibited by using the state feedback and pole placement, which greatly enhances the stability of the system.On the basis of analyzing fuzzy control theory and principles of EPS, the EPS's characteristic curves can be obtained by adopting fuzzy control strategy, Following-up the target current by feedback. Stimulation results show that EPS's characteristic curves can be well calculated by the fuzzy controller, proving fuzzy rules based on existing test data effective and reliable.Then a detailed functional analysis of the EPS system are given, designing Electronic Control Unit (ECU) with DSP TMS320F28335 being the core. With reversable bipolar PWM technology and two IR2110 driving H-bridge to control the motor, thus to achieve power steering. Three operational modes of H-bridge circuit, power driver circuit are mainly focused on.Then the overall structure DSP software design are introduced, what's coded is the corresponding software procedure, which adopt interrupt-based modular design method. And data acquisition, motor current PID closed-loop control, and failure alarm functions are implemented.Finally the self-made bench test device are introduced, the designed hardware circuit and software systems are controlled by a bench test. Relevant experimental data is collected at different speeds and analyses are made.The results show that EPS has achieved a good result.