Switched reluctance and permanent magnet brushless motors in highly dynamic situations: A comparison in the context of electric brakes

Vehicular brake systems with electro-mechanical brakes (EMBs) are emerging as a way to enhance system features and performance. Of particular interest in this context is the EMB actuator motor, which needs to be designed to meet the dynamic brake system performance requirements. Two motors with fundamentally different operating principles, a switched reluctance (SR) motor and a permanent magnet (PM) brushless motor, were designed, built, and evaluated in an identical EMB actuator environment. This paper compares their design and performance. Experimental as well as simulation results demonstrate that the upper motor speed limit has a significant effect on the overall dynamic performance of the EMB system. The high-speed capability of the switched reluctance motor, which may be considered an advantage, can actually be a detriment when highly dynamic response patterns are required. In order to improve the dynamic performance of the SR system, a solution with a software-based speed limit for the motor is suggested. The resulting design trade-offs to choose the motor speed limit can be addressed with a graphical approach developed in the paper