Robust sensorless speed tracking controller for surface-mount permanent magnet synchronous motors subjected to uncertain load variations

We address a solution of the sensorless high-speed tracking control problem for surface-mount permanent magnet synchronous motors under load torque variations. Since the only available measurements are the stator currents, the proposed scheme consists of a second-order sliding-mode observer interconnected with an H_∞ controller. Thus, disregarding the use of additional sensors to measure the mechanical variables. The observer-controller interconnection is robust against uncertainties and unknown load torque variations. First, the observer estimates rotor angular position and speed variables, theoretically, in finite-time. Then, an H_∞ controller attenuates the effects of uniformly bounded disturbances. Sufficient conditions are provided to ensure that the closed-loop system is stable. Moreover, it is internally asymptotically stable in the absence of uncertainties and external disturbances. The analysis shows that the observer-controller system possesses an L₂-gain less than a priori given disturbance attenuation level. Emulation trials showed the feasibility of the method.