The Design Of BLDC Motor And Its Control System In EPS Application

Compared with the Hydraulic Power Steering (HPS), the Electrical Power Steering (EPS) systems have several distinct advantages. They have simpler structure, higher efficiency, better performance, while do less harm to the environment. With the development of the vehicle electronics, the EPS systems are taking the place of HPS systems gradually.With a good knowledge on the characteristic and operation principles of EPS systems, we compared several different types of EPS motors in use, and got the conclusion that the Brushless DC (BLDC) motor is a good choice for the EPS application.The BLDC motor is a system composed of motor and controller. Their performance on starting and speed adjusting is as good as DC motors, and due to brushless, their commutation performance is much better. However, BLDC motor is not faultless as EPS motor. The cogging torque resulted from the interaction between permanent magnet and stator slots will greatly affect the performance of EPS systems, while the commutation style will make the torque ripple more serious.This thesis laid its emphasis on BLDC motors in the application of EPS systems. According to the requirement of EPS, we designed a PM BLDC motor, and then analyzed the performance of the motor with FEA method. The analytical method is also used to indicate the influence of different parameters on the motor performance. Then we studied the cogging torque with energy method, and proposed a cogging torque reduction method, which is very useful for BLDC motors equipped with concentrated windings and few slots. A 3-d model is established and analyzed with MAGNET to prove its availability. At the end of this paper, a control system for the BLDC motor is designed. Some related experiments are carried out, and the results convey that the control system works well.