| Abstract |
Applying the principle of field orientation and providing a closed-loop speed control the stepper motor becomes a high-dynamic, robust, four-quadrant ac-servo drive considerably differing from its normal use in the open-loop control mode. However, improving the motor in this way, a rotor position encoder is necessary. This can be avoided if an extended Kalman filter is used which reconstructs the state variables by only measuring the phase vollages and currents. This filter requires a detailed mathematical description of the stepper motor. An additional disturbance model. considering the load torque influence, is introduced into the filter. The discrete Kalman filter algorithm is implemented in a completely digital field oriented state control of the speed. Experimental results confirm that this four-quadrant sensorless drive covers high range of speeds, reaching nearly standstill. It can replace the mechanically commutated d.c. machines mostly used in lowpower
range which is bigger in size and has a limited life span. |
