Riccati equation based nonlinear filter: A case study for hydraulic actuators in the presence of dead-zone

Abstract

One of the most common hard nonlinearities in hydraulic actuator is the dead-zone. More specifically, dead-zone characterizes 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).