Robust sensorless estimation of the position and magnet flux of PMSMs

We show how the gradient observer proposed in Bernard & Praly, IFAC 2017, can be practically implemented to estimate online the rotor position and the magnet flux of salient PMSMs, using only electrical measurements and (approximate) knowledge of the resistance and inductance. This sensorless observer ensures global convergence provided the rotation speed remains away from zero and the current and voltages are bounded. Its robustness with respect to errors on parameters and the presence of magnetic saturation is shown, with explicit expression of the resulting steady state error. It is shown how to discretize and practically implement the observer at the PWM’s rate. This observer operates dynamically, in normal conditions, without any constraint on the load, and without any mechanical information. Its performance in open-loop are illustrated on experimental data on a SPM.