Non-linear adaptive robust control of electro-hydraulic systems driven by double-rod actuators

This paper studies the high performance robust motion control of electro-hy draulic servo-systems driven by double-rod hydraulic actuators. The dynamic s of hydraulic systems are highly non-linear and the system may be subjecte d to non-smooth and discontinuous non-linearities due to directional change of valve opening, friction and valve overlap. Aside from the non-linear na ture of hydraulic dynamics, hydraulic servosystems also have large extent o f model uncertainties. To address these challenging issues, the recently pr oposed adaptive robust control (ARC) is applied and a discontinuous project ion based ARC controller is constructed. The resulting controller is able t o take into account the effect of the parameter variations of the inertia l oad and the cylinder hydraulic parameters as well as the uncertain non-line arities such as the uncompensated friction forces and external disturbances . Non-differentiability of the inherent non-linearities associated with hyd raulic dynamics is carefully examined and addressing strategies are provide d. Compared with previously proposed ARC controller, the controller in the paper has a more robust parameter adaptation process and may be more suitab le for implementation. Finally, the controller guarantees a prescribed tran sient performance and final tracking accuracy in the presence of both param etric uncertainties and uncertain non-linearities while achieving asymptoti c tracking in the presence of parametric uncertainties.