Position and Speed Sensorless Control of Brush-Less DC Motor Based on an Adaptive Observer.

A permanent magnet synchronous motor can be controlled as a DC brushless motor, for which the position sensor is needed for detecting the rotor position.In this paper, the research on speed control system without position and speed sensors is reported, where the rotor position and speed of the motor are estimated by means of an adaptive observer.To make the state equations linear, two new state variables are introduced.Consequently, based on the linear control theory, an adaptive observer is designed by which the estimated speed and position are converged to real ones.The system is verified to be asymptotically stable.The operation of the system at zero speed and the effects of the mismatched parameters used in the observer are also discussed.Finally, the speed control of the system is implemented.The computer simulation and the experiments show that the system is valid.