The Mathematical Modelling of Hydrostatic Pumps and Motors

Abstract

Accurate mathematical models of hydrostatic pumps and motors are required in the synthesis and analysis of hydraulic systems. Increasingly the models are used in computer simulation work where the performance of the machines must be represented over a wide range of operating conditions. Examination of test data has shown significant differences in the real performance characteristics of hydrostatic machines compared to the characteristics predicted by classical models based on simple linear theory. This paper describes these differences and shows the way that the characteristics can change with different designs of machine. A mathematical model is developed which may be adapted to describe the wide range of characteristics associated with the different designs. This model has shown good agreement with test data. Recommendations are made for more comprehensive performance tests to provide the data required for more accurate models.