Nonlinear sensorless speed control of PM synchronous motor via an SDRE observer-controller combination

In this paper, a nonlinear control approach for permanent magnet synchronous motor (PMSM) drives, without mechanical sensors, is presented. The proposed method is based on a combination of the well-known nonlinear regulation technique, state-dependent Riccati equation (SDRE), and its filtering counterpart (SDREF) which is derived by constructing the dual of this control method. The SDREF is designed for online estimation of the rotor speed, position and also the load torque by only measuring the motor voltages and currents. The estimated values are applied in the controller structure as state variables. We demonstrate the performance and applicability of this new nonlinear control for PMSM derives by an illustrative simulation in presence of variable load torque. The sensitivity and robustness of the proposed method are also investigated for the motor parameters variations.