Reduced nonlinear observer for bounded estimation of the static friction model with the Stribeck effect

In this paper, a nonlinear observer to estimate the parameters of the static friction model with the Stribeck effect is presented. This system cannot be expressed as a linear function of the model parameters, however a nonlinear disturbance term can be added to the linear approximation. Then, under the persistency excitation assumption, we prove explicitly that the estimation error is ultimately bounded. Simulation results demonstrate the effectiveness of the proposed method compared with a Coulomb estimator.