Speed and rotor position estimation of the PMSM by SM observers with compound manifolds and linear feedback

The paper presents a method to estimate the speed and rotor position of the permanent magnet synchronous motor (PMSM). Estimation is done using cascaded sliding mode (SM) observers. A front observer estimates the EMFs of the motor in the stationary reference frame; these are obtained by filtering the manifolds of the SM observer. The EMFs are passed to a back SM observer that estimates the speed and re-estimates the EMFs. The method uses only the measured voltages and currents - it is useful for sensorless speed controlled PMSM drives where the EMFs are used to compute the rotor position angle and the speed is needed for feedback. The paper presents the design of the EMF observer; then, it shows three versions of the speed observer - this is a two-dimensional SM design that uses compound manifolds and linear feedback as well. The mathematics of the observers is validated with simulations and experimental results.