The paper deals with the adaptive positioning control of a single-input-single-output electrohydraulic servo system which employs an input filter. This filter spreads a large control input over a period of sampling instants to prevent input saturation. As well, its use enables the proof of stability to be achieved using the standard technique even for unstable plants. A controller structure, which does not require feedback from the output of the input filter, is determined by considering the input filter to be a part of the unknown plant. The design is described in discrete-time form using the Euler operator which has better characteristics than the z operator in many respects. The simulation results are presented to show the performance of the controller.
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