Independent volume-in and volume-out control of an open circuit pump-controlled asymmetric cylinder system

To avoid the flow asymmetry of a closed circuit pump-controlled asymmetric cylinder system, an efficient open circuit pump-controlled asymmetric cylinder system (OPACS) with an independent displacement volume-in and volume-out (VIVO) control method is proposed. The energy transmission path of the OPACS was analyzed, and an energy calculation model was built. A position-pressure combined control method was adopted to validate the proposed OPACS. Based on a 0.6-MN open circuit pump-controlled forging press system, a series of experiments with different return cylinder pressures were conducted. The experimental results confirmed that the proposed OPACS with the position-pressure combined control method was able to recover energy to reduce the installment power without sensitivity to the return cylinder’s pressure variation and that the position accuracy and rapidity could be improved by increasing the pressure in the return cylinder.