Rotor position estimation for permanent magnet synchronous motor

The paper describes rotor position observer for permanent magnet synchronous motor, consisting of calculator of flux vector projections on the axis of the fixed coordinate system α-β and loop tracking this vector by phase (phase-locked loop, referred to as PLL). It is shown that in the electric drive motion modes with constant acceleration the loop tracking error has a DC component. To eliminate it the usage of combined control method is proposed. The reference signal for integrator circuit (in the PLL circuit for VCO) is provided by output coordinate of the equivalent DC motor speed estimator. PI controller compensates small deviations in the tracking loop. Modified observer does not disturb the sliding mode of tracking loop. Outside shaft speed estimator allows to close drive speed loop while preserving the motor dynamics on its maximum.