A rotor position and speed observer for permanent magnet motors with nonsinusoidal EMF waveform

A nonlinear reduced order observer for estimating the rotor speed and position for permanent magnet motors is presented. The EMF is estimated first assuming only that it can be approximated by a Fourier series. Then rotor position and speed are reconstructed using the relationship between the EMF and the rotor variables. The EMF generated by the motor, which is neither sinusoidal nor trapezoidal, is obtained experimentally off-line. Then, it is approximated by a Fourier series in order to construct the model to be estimated on-line. The proposed observer is ideal for the realization of torque control with minimum torque ripple, since it allows an easy synthesis of nonsinusoidal currents. The proposal is validated with experimental results.