Methods for Combining a Theoretical and an Empirical Approach in ModellingPressure and Flow Control Valves for Cae-Programs for Fluid Power Circuits

摘要

An analytical mathematical model for a fluid power valve uses equations based onphysical laws. The parameters consist of physical coefficients, dimensions of the internal elements, spring constants, etc. which are not provided by the component manufacturers. The valve has to be dismantled in order to determine their values. The model is only in accordance with a particular type of valve construction and there are a large number of parameters. This is a major common problem in computer aided engineering (CAE) programs for fluid power circuits. Methods for solving this problem by combining a theoretical and an empirical approach are presented. Analytical models for single stage pressure and flow control valves are brought into forms which contain fewer parameters whose values can be determined from measured characteristic curves. The least squares criterion is employed to identify the parameter values describing the steady state of a valve. The steady state characteristic curves that are required data for this identification are quite often provided by the manufacturers. The parameters describing the dynamics of a valve are determined using a simple noncomputational method using dynamic characteristic curves that can be easily measured. The importance of the identification accuracy of the different parameters of the single stage pressure relief valve model is compared using a parameter sensitivity analysis method. A new comparison method called relative mean value criterion is used to compare the influences of variations of the different parameters to a nominal dynamic response.