Direct Position Control for Ultrahigh-Speed Switched-Reluctance Machines Based on Low-Cost Nonintrusive Reflective Sensors

High-speed switched-reluctance machines (SRMs) are gaining popularity in both academia and industrial communities. One of the reasons that limit the maximum speed of SRMs is the speed limit of commercial rotary encoders due to mechanical considerations. In this paper, a novel direct position control for ultrahigh-speed SRMs is proposed based on nonintrusive reflective sensors. It uses reflective optical sensors to detect the relative position between the rotor and the stator so as to control the on and off states of the switches directly through the analog output trigger signals generated by the optical sensors. In order to generate the maximum output torque, the switching- on and switching- off angles are optimized based on the equivalent Simulink model with the torque- and flux-linkage characteristics obtained from a corresponding finite-element analysis of a high-speed SRM. Finally, the proposed method is validated by experiments with a 500-W 4/2 SRM running up to 100 000 r/min. The proposed control system has many advantages such as low cost and virtually no speed limit, which makes it suitable for ultrahigh-speed applications.