Abstract
The paper presents the lumped parameter model of a pressure limiter for axial piston pumps developed in the Simcenter Amesim®environment. The control includes both the absolute and differential (load sensing) pressure limiter in a single body. The continuous position valve was tested experimentally alone on a test rig in order to estimate the discharge coefficients required for tuning the model. The tests were performed at imposed positions of the spool and the corresponding modulated pressure and control flow through the valve were measured. A contactless transducer was used for measuring with a very high accuracy the spool position. The influence of the bleed orifice on the pressure gain was also measured experimentally. It was found that the discharge coefficients have a significant influence on the hydraulic characteristic of the valve with also a consequence on the dynamic behavior of the entire displacement control.
Highlights
The aim of the pressure controls in fluid power pumps is to modify automatically the displacement of the machine in order to maintain constant the delivery pressure or the pressure drop across a direction control valve
The study has brought to evidence the influence of the discharge coefficients on the control dynamics
It was found that for some combinations of the geometric parameters of the system, a variation of the discharge coefficient in the range 0.65÷0.85 can lead to the stability or instability of the control
Summary
The aim of the pressure controls in fluid power pumps is to modify automatically the displacement of the machine in order to maintain constant the delivery pressure (absolute limiter) or the pressure drop across a direction control valve (differential limiter). The simplest architecture is the direct acting control, where the delivery pressure generates a torque on the swash plate, typically by means of a hydraulic actuator, acting against a spring that decides the pressure setting [1]. An almost perfect pressure regulation can be obtained by means of piloted controls, made up of a continuous position pilot valve, sensitive to the delivery pressure, and one or two linear actuators. Aim of the continuous position valve is to modulate a control pressure in an actuator up to the achievement of the condition of equilibrium, for which the displacement is reduced. The system is closed-loop controlled, where the linearized coefficients of the continuous position valve play the role of gains in the block diagram of the state variable model [3]. The developed methodology can be used for tuning a 0D model and it has been proved to be very accurate
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
