Enhanced Discrete-Time Differentiators for State Observers of Sensorless Permanent Magnetic Synchronous Motor Drives

In sensorless motor drive applications, the rotor and the speed of the rotor are usually estimated through state observer algorithms. A key part of such algorithm is the computation of the derivative of the rotor position, resulting in the estimated rotor speed. Computing derivatives brings challenges due to their inherent noise amplification characteristic. This paper presents enhanced discrete-time differentiators for state observers of sensorless permanent magnetic synchronous motor drives. A class of discrete-time differentiators based on finite impulse response filters and one based on Kalman filter are proposed. Details about how to obtain the coefficients of the differentiators are presented. To verify the performance of the proposed differentiators, all of them were executed in F28379D LaunchPad microcontroller. Results show that the proposed discrete-time differentiators compute the derivative of the rotor position signal in a satisfactory manner, even in the presence of noise.