Parameter Identification and Real-Time State Estimation in Hydraulic Actuators

This paper deals with the challenging aspect concerning the state estimation in hydraulic actuators characterized by not negligible nonlinearities. Particularly,. One of the most common hard nonlinearities in hydraulic actuator is the deadzone. More specifically, dead-zone occurs in hydraulic control valves when its spool occludes the orifice with an overlap, so that for a range of spool positions there is no fluid flow. This paper focuses on an alternative nonlinear estimation method that is able to fully take into account dead-zone hard nonlinearity and measurement noise. The estimator is based on the State-Dependent-Riccati-Equation (SDRE).