Sensorless Control of a Brushless DC motor using an Extended Kalman estimator.

Abstract

Within the appliance motor control industry there is an increasing trend to move towards using brushless dc motors. This trend is in response to recent legislation mandating improved efficiency standards in appliance applications. Brushless dc motors do however require rotor position information in order to select the appropriate commutation angle. In cost sensitive applications such as appliances a sensorless commutation scheme is often desirable. This paper describes the development of such an algorithm based on an Extended Kalman estimator. In its simplest form this algorithm provides estimates for position and velocity based on the back-EMF segments from a trapezoidal driven motor. Unlike previous sensorless algorithms, based on the Extended Kalman techniques, this algorithm doesn’t require stator current measurements. The algorithm simply requires four resistor divider networks to scale the three back-EMF and dc link voltages and a low cost embedded DSP motor controller.