Modelling and energy efficiency analysis of a hybrid pump-controlled asymmetric (single-rod) cylinder drive system

A conventional valve-controlled cylinder drive system is not energy efficient, and a pump-controlled cylinder system can be unstable in some particular conditions. For drive systems not requiring fast response, a hybrid pump-controlled system, that combines the advantages of both valve and pump-controlled systems, is proposed. As nonlinear behaviours are inevitable in most asymmetric cylinder drive systems, the hybrid pump-controlled system also suffers from such problems, and extra nonlinear behaviours are identified, for example, stall when the cylinder change its direction of motion. A simulation model of the hybrid pump-controlled asymmetric cylinder drive system is developed and used to investigate the system's simulation behaviours which are analysed and compared with the experimental test results. The energy efficiency of the hybrid pump-controlled system is compared with a comparable valve-controlled hydraulic system with the same hydraulic cylinder sizing. The outcome is to demonstrate the advantage of the hybrid pump-controlled system in energy-saving aspect, and the efficiency of the hybrid system is up to five times more than a conventional hydraulic system. Suggestions are given to improve the performance and stability of the hybrid pump-controlled system.