New Hydraulic System Modelling

One of the drawbacks of classical hydraulic system models consists in the fact, that the simulation programs couple the hydraulic components by compressible joints. Since the compressibility of oil is very small, we get stiff differential equations. To avoid these difficulties stiff elastic couplings can be replaced by unilateral constraints. Examples for hydraulic components with unilateral behavior are check valves, cylinders with stop limits and fluid volumes, in which cavitation can occur. The resulting complementarity equations can be solved with a standard Lemke algorithm. Compared to conventional methods, this leads to a significant reduction of computing times.