High-gain observers in the state and parameter estimation of robots having elastic joints

The paper deals with the state and parameter estimation of robots having elastic joints. The estimation of the unknown parameters of the robot is reduced to the estimation of its state variables by a state space immersion. The Luenberger observer is used in the state estimation of the extended robot model. The use of high gains is studied in the cancellation of nonlinearities in order to simplify the observer design. The high gain induces a time scale separation between the robot model and the observer and therefore the singular perturbation theory can be used in the stability analysis of the estimate error dynamics. In particular, it is shown that the error dynamics reaches the stable equilibrium in a very fast transient ensuring that the slow dynamics of the observer is just that of the given robot. © 1989.