Robust force controller design for a hydraulic actuator based on experimental input-output data

A force control design problem is investigated for a hydraulic actuator in the presence of several uncertainties. A method based on nonlinear quantitative feedback theory (QFT) is proposed to design a robust time-invariant controller. The plant model is identified by a family of transfer functions, based on experimental input-output measurements, performed on a hydraulic actuator equipped with a low-cost proportional valve. The designed QFT controller is of low-order which is desirable from practical point of view. Experimental results show that the compensated system is not sensitive to variation of parameters such as environmental stiffness or pump pressure and can equally work well for various set-point forces