Global Adaptive Sensorless Speed Control of Permanent Magnet Synchronous Motors

This paper deals with the problem of global sensorless speed control of permanent magnet synchronous motors in which the speed and load torque are not available. The key problem in sensorless speed control is the design of the observer that is used to estimate the speed and load torque. The major difficulty in the design of the observer results from the presence of the quadratic term of the speed and direct axis current in the quadrature axis current equation. We first view the quadratic term as a disturbance term. Then we design an adaptive feedback law in the direct axis current equation to reject the influence of the disturbance term on the observer. On the basis of the observation, we propose an observer-based adaptive global control method for the speed control of the motor. The method can ensure that all signals in the closed loop system are bounded and that the speed tracking error converges to zero. Simulations of a motor are performed to show the utility of the control method.