MODE SWITCHING AND ENERGY RECUPERATION IN OPEN-CIRCUIT PUMP CONTROL

Today’s mobile machines most often contain hydraulic valve controlled drives in an open loop circuit. For the purpose of saving energy, the constant pressure pumps have in the past frequently been replaced by load-sensing pumps and load-sensing valves. However, considering applications where the load is helped by the gravitational force, even these hy-draulic systems often suffer from poor efficiency. In this article, a novel pump-controlled hydraulic system is studied where energy recuperation from lowering motions is possible. The pumps are fully displaceable in both directions, working as motors when lowering loads. The amount of recuperated energy is highly dependent on the chosen control strat-egy, the hydromechanical properties as well as the target application. Furthermore, the article describes how valve design becomes an important feature in an attempt to reach high efficiency and machine operability