A novel robust speed sensor-less control of DC motor

Until now, Physical sensors have been used for estimating the speed of the DC motor for precise speed control. These Physical sensors not only increase the cost but also contribute to the failure of the overall control system. This paper proposes a novel observer for estimating the rotor speed of the DC motor based on the assumption that the speed will not vary during a short sampling period. Speed estimation is carried out by using the armature current and the supply voltage. Initially, a half order observer has been proposed where the speed is the only estimation variable. It has been found out that the half order observer has maintained an accurate speed estimation until a load disturbance has been introduced. In order to overcome this problem, a robust full order observer is proposed where both the speed and current are estimated. The proposed full order observer shows an accurate estimation during both speed step change and load variation. The closed loop operation of the speed sensor-less DC motor is verified through extensive simulation.