Observer-based leakage detection in hydraulic systems with position and velocity feedback

Nonlinear observers with static feedback are considered for leakage detection in hydraulic servo systems. Two issues, namely fast dynamics reduction and elimination of multiple stationary points in the estimation error dynamics, are treated. It is shown that leakage detection performance is not degraded by the use of a reduced plant model, and that static feedback offers enough degrees of freedom to render one and only one stable stationary point of the error dynamics and that is at the origin. An algebraic condition guaranteeing the above property for the considered class of observers is provided.