Research And Realization Of Control Algorithm For Electro-Hydraulic Power Steering System

Electro-hydraulic power steering (EHPS) system is a new technique, which is based on traditional hydraulic power steering (HPS) system. Compared with HPS system, EHPS system can supply more comfortable handle and save much more energy. The math model of the system is established in this paper and the control algorithm is analyzed in depth. Then simulate and realize the system.First, the structure of EHPS system is analyzed and the static and dynamic math models are obtained. Based on the models, the assistant power and turning following character are studied. The method to control motor speed changed with the vehicle speed and the steering speed is mainly analyzed. Considering the control error of this method in practice, back propagation neural network is applied to study the control algorithm at any vehicle speed. This new control algorithm can overcome effectively blind zone generated by discrete vehicle speed.EHPS system is established by AMESim to test the effect of the control algorithm. The basic character of HPS system is analyzed and the assist character influenced by the control algorithm is studied. Besides economy, system performance is improved distinctly by the control algorithm according to the simulation.Motor control is significant in the system. The math model and control method of brushless DC motor (BLDCM) are analyzed and studied. The application of BLDCM used in the system is introduced specially in this paper, too.The core of EHPS system is the controller which is a part to realize the control algorithm, collect and process the signals, control the BLDCM and communicate with other systems. Based on the structure of DSP, a new method to generate the complementary is developed. The hardware circuit is designed and the control software is compiled. The pivotal signal processing is described in detail.Finally, the EHPS system integrated experimentation platform is established to test the assist character and the performance of controller and BLDCM. The safety and handiness are improved by the control algorithm according to the experiments.