Design Of Integrated Torque/Angle Sensor And Research Of Control Strategy For EPS

As one of the most important parts of the car, steering system has great influence on vehicle’s control stability, driving safety and comfort. Electric Power steering has become the research focus of the power steering technology due to the advantages of energy saving, environmental protecting, driving safety which matches the three themes of the development of automobile. As a result, the study of EPS has very practical and long-term significance. This paper mainly introduces the design of integrated torque/angle sensor and the research of control strategy for EPS.Firstly, through introducing the main torque/angle integrated sensors which are applied on the market at present, the advantages and disadvantages of them are compared and analyzed. Under the premise of grasping the current development trend of integration and intelligent, this paper proposing a non-contact torque/angle integrated sensors based on magnetoresistive effect. The main mechanical components and circuit design of the torque measurement part and the angle measurement part is presented in the paper, also introduces their related calibration tests. Also do the motor drive test of torque measurement part. On the basis of these, it presents the structure design scheme of the integrated sensor. The integrated circuit board is made according to overall mechanical structure.Secondly, According to the mechanical and electrical structure of steering system, in this paper establish the dynamic equations of mechanical steering system and electric power steering system; Finally EPS system input-output model. Then get the state equation of EPS. The paper slso analysis influence of load transfer on vehicle running state, and establishes a reduced seven-degree-of-freedom vehicle model. Tire force and vehicle resistance are separately studied, then establish dugoff tire model and vehicle drag model. All modles are realized in MATLAB/Simulink. Finally, make all sub-models together by intermediate variables.Thirdly, analize effect the EPS system on the vehicle handling and stability. Put forward an Electric power steering control strategy, including the following aspects:basic power assistant control algorithm; returnable control algorithm; torque compensation control algorithm; motor current control algorithm. Design every part’s response control algorithm and build a comprehensive model in MATLAB/Simulink. Finally, the performance assessment of vehicle’s power assisted characteristic, return-to-center performance, and stability are described. And the corresponding simulation is carried out on the basic of the models and control algorithms according to these indicators. The simulation results indicate that the power characteristic curve studied could ensures steering lightly when in low speed driving cycle or pivot steering driving cycle and returnable control algorithm enables vehicle to achieve a good return effect. Besides, it also shows that EPS steering wheel torque compensation control algorithm could improve the stability of vehicle.