Self-tuning torque control of brushless motors

A ripple-free feedforward torque control (electronic commutation) of a brushless motor is applicable if the torque-angle relationship associated with the motor phases is accurately known. We propose a linear estimator technique, based on an electric model of the motor, which requires the measurements of phase current, voltage and motor angle to extract the Fourier coefficients of the phase torque-angle profile. The torque tracking error asymptotically converges to zero, if the estimated parameters are used in the computation of phase currents dictated by any ripple-free commutation law. Experimental results have demonstrated convergence of the estimated parameters to their true values