A singular perturbation-based observer design for nonlinear multivariable systems with non-vanishing disturbances and application to synchronous motors

A singular-perturbation-based approach to a nonlinear observer design for systems with multiple outputs is investigated, expanding existing results for systems with a single output. A novel result shows that the observer error converges despite non-vanishing disturbances in the fast subsystem of the observer error dynamics. These results allow the observer to apply to a larger class of nonlinear systems under weaker assumptions compared to previous studies. The application of the nonlinear observer is demonstrated for the observation of the rotor position of permanent magnet synchronous machines, where a simple reduced-order observer is proposed. Moreover, the observer is validated based on real-world measurement data of a test bench with an internal permanent magnet synchronous motor. The results show high performance and accuracy of the observer even for low speed.