In this paper the nonlinear dynamics of a hydraulic system consisting of centrifugal pump, pressure accumulator and connected load are modeled and a Feedback Linearization controller is designed. Furthermore an Extended Kalman Filter is implemented to include the hydraulic dynamics into the estimation and simultaneously overcome the necessity of flow and pressure measurements. Therefore, the combined control scheme only interacts with the variable-speed drive. The functionality of the proposed control algorithm is demonstrated by test bench experiments.