Experimental Validation of a State Decoupling Method Applied to a Dual Cylinder Electro-Hydraulic Variable-Speed Drive Network

Electro-hydraulic variable-speed drive networks may provide for efficient operation of hydraulic actuators, and allow for reduced power installations in many applications compared to single cylinder electro-hydraulic drive systems. The main reason is attributed the electro-hydraulic power sharing capability enabled by potential hydraulic connections between various chambers, the shared electric power supply and flow control by four quadrant variable-speed pump/motor units. These features cause the cylinder chamber flows, and consequently the chamber pressures, of electro-hydraulic variable-speed drive networks to be highly coupled, preventing the direct application of conventional single axis control methods. Hence, a main challenge in enabling electro-hydraulic variable-speed drive network technology is the control at drive level, and previously published results have implied that state decoupling may be realized and applied successfully, at least from a theoretical point of view. This paper presents an experimental validation of a state decoupling method combined with simple proportional controllers, applied to a dual cylinder electro-hydraulic variable-speed drive network. In this validation, the two cylinders are controlled to follow sinusoidal position trajectories with varying phase shift, while concurrently controlling the lower system pressure in the vicinity of desired level. Results demonstrate appropriate control performance for all load cases investigated, emphasizing the performance potential and feasibility of electro-hydraulic variable-speed drive network technology.