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The derating control strategy for motor stator temperature is a very effective protection measures. It not only can make better use of motor ability but also can satisfy the requirement of the vehicle. This paper presents a derating control strategy based on the temperature of stator winding ends since it is the highest temperature point from the simulation results. The motor stator temperature is divided into several regions applied with the various derating control rules. To limit the peak phase current instead of the torque is proposed to inhibit the temperature rise especially in the field weakening region because a large extra demagnetizing current is required in this region.

This paper presents a method for determining the rotor temperature of an electric motor by observing the dq-axis flux linkage. A reference dq-axis flux linkage is obtained at a defined rotor temperature. The difference between calculated and reference flux in the d-axis is supposed to be caused by temperature, therefore the temperature can be back-calculated according to the permanent magnet temperature characteristic. The proposed method was confirmed to be correct and effective by the test results.

The resolver is widely used in the production applications due to the robust mounting and high accuracy at full range. However, the mounting accuracy of such sensors will significantly limit the torque accuracy and performance if the initial positions are not calibrated at the end-of-line (EOL) test. An initial position EOL test system is designed base on the production requirements. A simple initial position measurement method is introduced and applied to the PMSM motor, which measures the back EMF and the North mark (NM) signal of the resolver. The time difference between the back EMF zero crossing point and NM signal is divided by the back EMF period and then the initial position is calculated. The method is validated on the target bench and experiments prove the EOL test system is suit for the mass production.

The dq-axis inductances are important for the voltage decoupling control, torque estimation and steady-state performance analysis of a PMSM machine. In this paper, a measurement method is proposed based on the dq-axis instantaneous flux linkages calculation. The rotor is locked by a positive d-axis current, and then a proper AC current is assigned respectively to the d and q-axis reference current in order to cover the various current ranges. The instantaneous flux linkages are calculated by the integration of dq-axis current and voltage offline. Finally, dq-axis inductances are computed by the integrated flux linkages divided by the dq-axis current.

For electric power steering (EPS) system to the requirement of real-time and stability of the control system, a fuzzy control algorithm applied to the EPS was proposed, and composed a fuzzy controller for appling to the EPS controller. Taking into account both portability and stability of steering, testing the designed fuzzy controller on EPS experiment platform and adjusting fuzzy control parameters online to make the EPS steering feel the best. Experimental results showed that the proposed fuzzy control algorithm had good tracking performance, can meet the requirements of EPS fast and frequent start-stop and the portability and stability of steering.