COMPARISON OF TWO METHODS TO SOLVE PRESSURES IN SMALL VOLUMES IN REAL-TIME SIMULATION OF A MOBILE DIRECTIONAL CONTROL VALVE

In fluid power systems, especially in many types of valves, there exists very small volumes which are particularly problematic in the case of dynamic analysis. Small volume with respect to the so-called normal sized orifice, formulate the system of equations which become mathematically stiff. This is a common source of numerical problems. To solve the stiffness problem, the present paper employs two alternative methods for conventional integration. Both implementations have in common that direct integration of pressures in small volumes is avoided and they are freely applicable regardless of used integration routine. Conventional numerical simulation with sufficiently small time increment is used as reference response. The valve studied is commonly available, proportional, load-sensing directional valve designed for mobile hydraulic systems, containing main spool and load-holding poppet with pilot spool. The present paper describes the methods in general level using a real-time simulation application of a relatively complex valve as a case study. Results are compared to those computed using conventional method.