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Path planning and tracking are two important means for autonomous vehicle in obstacle avoidance in the last decade. In this study, the reference path is planned on the basis of the sigmoid function which represents the driver’s intent in accordance with obstacle information. Meanwhile, a nonlinear model predictive controller for path tracking of autonomous vehicles is proposed. The proposed controller drives vehicle to track the reference path by controlling the front steering angle and braking torques of four wheels. Computer simulation based on CarSim and MATLAB/Simulink was performed to verify the feasibility and effectiveness of the controller.

With motor and reduction mechanism applied to Electric Power Steering (short for EPS) system of automobile, the frictional loss torque of steering system is increased. The common friction compensation control through the sign function of angular velocity or the saturation function of angular velocity is conducted to reduce the frictional loss torque of steering system. However, when the motor used in steering system generates assist torque based on the common friction compensation control, the longitudinal intercepts of steering torque change obviously at different steering wheel angles. The driver will get different frictional loss torque of steering system at different steering wheel angle. The information of steering torque contains the change of steering reaction torque and the frictional loss torque of steering system, so the change of frictional loss torque can cause the fuzzy of road feeling.

Impact torque will be generated on the steering wheel when one tire suddenly blows out on high way, which may cause driver's psychological stress and result in driver's certain misoperations on the car. In this paper, the model of tire blowout vehicle was established; the tire blowout was detected based on the change rate of tire pressure, meanwhile, the rack force caused by tire blowout was estimated through a reduce observer; finally the compensation current was figured out to reduce the impact torque on the steering wheel. Results of simulation tests showed that the control strategy proposed in this paper can effectively reduce the impact torque on the steering wheel and reduce the driver's discomfort caused by tire blowout.

The EPS motor will be over-heated if large current lasts for a long time, which will decline the performance of EPS motor and even lead to irreparable damage. So the over-temperature protection control should be conducted in order to protect the components of EPS system, especially the durability of EPS motor. In this paper, the motor temperature was estimated according to the environmental temperature and the current of motor armature, and then the EPS assist current was limited based on the estimated temperature of motor to ensure that the EPS motor had a good working condition. So the over-temperature protection control for motor can be realized without increasing the EPS system components. Finally the control strategy for over-temperature protection was conducted in a vehicle with EPS system and its performance was verified.