The variable drive systems recently have been required in many industrial parts. To control the speed for a motor, the system usually requires the motor speed sensor. However, there are many problems in case of using speed sensors. A sensor requires a mounting space on the motor, reduces the reliability, and increase cost of the drive system.
Therefore various sensorless control algorithms have been proposed for the elimination of sensors.
This paper proposes a new sensorless speed control scheme of permanent magnet DC motor using a numerical model and hysteresis controller, which requires neither shaft encoder, speed estimator nor PI controllers.
By supplying the identical instantaneous voltage to both model and motor in the direction of reducing torque difference, the rotor speed approaches to the model speed, namely setting value and the system can control motor speed precisely.
As the numerical model whose electric parameters are the same as those of the actual motor is adopted, the armature rotating speed can be converged to the setting value by controlling torque on both sides to be equalized.
And the hysteresis controller controls torque by restricting the torque errors within respective hysteresis bands, and motor torque are controlled by the armature voltage.
The simulation and experiment results indicate good speed and load responses from the low speed range to the high, show accurate speed changing performance.