On fluid power control. With special reference to multiload conditions in load sensing systems

Part 1. For a number of years, load-sensing systems have been increasingly used in mobile fluid power applications, where its high energy saving potential is a special advantage. A load-sensing system is a feedback system with risk of instability. The thesis at hand discusses several origins of instability as well as the problem of load interaction. It especially deals with an instability type where load interaction through the mechanical structure and the fluid power system may cause instability. Pressure-compensated control valves are also discussed. Part 2. During the last ten years, several electrohydraulic proportional seat valves have been designed. This part explores some possible uses of the advantages offered by this new type of valve. The concept studied here is an asymmetrical cylinder controlled by four proportional seat valves in a system which incorporates a variable pump. (au)