An extended state observer-based control design for electro-hydraulic position servomechanism

The electro-hydraulic servomechanism is widely used in marine vehicles due to its higher power density. However, the servomechanisms suffer from serious throttling loss which leads to its low efficiency, and the parameter uncertainty and disturbances from the changing marine environment damage its control performance. In order to enhance the efficiency of the electro-hydraulic servo system, a robust position control scheme combined with extended state observer (ESO) and finite-time backstepping filtered control (FTBF) technology is developed to compensate for the aggravating performance, while the method of reducing the throttling loss by lower the pressure is adopted. Firstly, with the advantages of the ESO, the robust control without velocity and pressure measurement is realized, and the estimate of the uncertain nonlinear term is obtained. Then, the finite-time design method is introduced to realize the convergence of tracking error in finite time, which possesses a fast error convergence speed and small tracking error. Additionally, the design of a dynamic surface and the adaptive error compensation signals can effectively solve the problem of differential explosion in backstepping design. Finally, the comparative experiment is performed to verify the effectiveness of the controller.