【正文】 e corresponding phase winding must be conductive when the rotor goes to certain position and every phase windings should be switched correctly all the time. Otherwise, motor not only can not operate as per requirement, but also the phenomena such as motor reversion, stop or rotating random may occur. In order to obtain instantaneous position of rotor while motor runs, the angle displacement sensor must be installed within motor to output correct rotor position information. This is also an obvious difference between switched reluctance motor and other motors. III. USE DESIGN OF CONTROLLER FOR SRM SPEEDREGULATION SYSTEM The method of bining hardware circuit and singlechip puter is adopted in the design of controller for SRM speedregulation system. Hardware circuit takes charge fast regulation task and singlechip puter pletes the plex functions such as logic and parameter setting. AT89C51 singlechip puter is used as the core ponent of controller, in addition, other control circuits such as position detector, current and voltage detector, overcurrent protection, over voltage protection, analog and digital input, output circuit as well as display circuit and so on. The block diagram of controller for SRM speedregulation system is shown in Figure 2. The hardware structure of the system controller The AT89C51 singlechip puter is the key part of controller and its function is paring the given value of external rotate speed with actual value of motor speed, then calculating controllable variables (mostly including current chopping basis Ig and motor winding firing angle θon ) according to preestablished PID regulating formula, lastly, based on the external operation requirements (rotating clockwise or counterclockwise) and the wave shape of position sensor to decide phase output signal. Moreover, the singlechip puter pletes also some display functions, for instance, over voltage, low voltage, over loading and system status and so on. (1) Position sensor signal input circuit is the role of the motor position sensor signal waveform input is provided to the microcontroller, and also both isolation protection function. Single chip microputer according to the circuit provides the waveform can be identified motor rotor position so as to determine the corresponding output signal, can also be based on the sensor waveform cycle to calculate the practical operation of the motor speed values to PID operations and other functions. (2) Phase interruption circuit function is when the position sensor waveform changes state generates an interrupt signal to the microprocessor to provide a phase signal output to prepare. (3) Phase locked frequency multiplier circuit is used to position sensor signal cycle frequency. But the puter from accurate in conduction angle and critical angle corresponding to the output signal is broken. (4) A/D conversion and speed circuit which is to be set by the user simulation speed value through the A/D conversion module conversion to digital quantity input to the puter. (5) Overvoltage and undervoltage protection circuit when the role of the power circuit voltage exceeds the specified voltage and control the supply voltage is less than the given value to the puter sends out alarm signals from but make the corresponding treatment and pr