Robust observer design for a class of nonlinear systems using filtering and dynamic scaling

In this paper we design a robust nonlinear observer for a class of nonlinear systems to account for model/plant mismatches. The observer satisfies a L₂ gain. In the design procedure a partial differential equation needs to be solved. To avoid solving the partial differential equation dynamic scaling and output filtering are used. The results are illustrated with two application examples: engine torque estimation for a combustion engine test bench and for an induction motor.