State and parameter estimation in a hydraulic system - moving horizon approach

In most control systems the best quality of control can be achieved if an exact model of a plant is known and if disturbances-free and continuous (instead of discrete) measurements of all its state space variables are available. Since it is seldom the case in real-life installations, state observers, adapting (parameters identification) algorithms, anti-noise filters and continuous signal estimators must be often employed. The paper describes an application of the moving horizon estimation (MHE) and continuous state estimation from discrete output measurements (CSE-DOM) based method to a laboratory hydraulic three-tank system. The resulting algorithm encompasses all the four above-mentioned mechanisms (state observation, parameters identification, disturbances filtration and continuous state estimation) and can be used for nonlinear systems as well, which is the case in the presented article. The paper provides a detailed explanation of how the MHE and CSEDOM methods were adapted to be applicable to the three-tank system. Results of computer simulations and practical laboratory experiments are also included.