Hydraulic actuators are well described by nonlinear system modeling. Nonlinear control for differential cylinders may be realized in order to obtain disturbance decoupling. However, such a system cannot be decoupled from the disturbance and therefore it is necessary to compute a nonlinear disturbance attenuation controller that reduces the influence of the disturbance with respect to the system output. The controller synthesis of nonlinear disturbance attenuation is based on linear error dynamics. Measurements on a testbed represent the basis of this contribution and show the mode of operation for the disturbance attenuation controller under real conditions. The measurements yield very good tracking performance for the cylinder piston position up to a particular disturbance force margin.