Improvements to the measurement of electrically controlled hydraulic pumps’ flow/pressure characteristics

Abstract

To increase the measurement accuracy, and also to automate the measurement operation, we modify the electrically controlled hydraulic pumps’ (ECHPs’) flow/pressure performance characteristic description and improve the test method in existent standards. According to ECHPs’ working principle, we divide ECHPs’ operation into two models: constant flow operating mode (CFOM) and constant pressure operating mode (CPOM). A direct drive servo-proportional control valve (DDV) is used to load the test pump. In the CFOM, we change the pressure load at a constant rate by driving the DDV's displacement with nonlinear feedback and a proportional–integral (PI) controller. In the CPOM, we take advantage of the DDV's inherent linearity between its input signal and output flow, and change the flow load at a constant rate by using open-loop spool displacement control. A mathematic model is built for the derivation of a stable condition and the analysis of steady-state pressure tracking error. The theoretical analysis shows that the feedback linearization and PI controller with negative proportional and integral gains are able to track a slope pressure load command with a desired rate. The test results also show that the mathematical model is valid and the proposed method can improve the measurement accuracy remarkably.

Modeling and Performance Improvement of the Constant Power Regulator Systems in Variable Displacement Axial Piston Pump

“…Recently, electronic regulators have been studied and commercialized [ 1 – 4 ]. However, the mechanical regulators are mainly applied in the industrial field because a proportional reducing pressure valve which is used as main part of the electronic regulator has relatively poor durability than mechanical regulator.…”