Establishing Operating Points for a Linearized Model of a Load Sensing System

Abstract

A load sensing system is one in which the pump flow is adjusted to keep pressure across an orifice constant and independent of any variation in the load pressure. This ensures that the pressure losses across the orifice are kept to a minimum which increases efficiency substantially. Because the system is closed loop, stability can become a problem. To establish stability bounds, linearized analysis is often employed. However, to do this, operating points of all linearized parameters and coefficients must be established as a function of certain parameters such as load pressure. This can only be done by solving a series of nonlinear algebraic equations. This paper presents a set of equations for three special conditions. The experimental verification of operating points that are predicted for such a load sensing system is presented. The three regions are established theoretically and are verified experimentally. It is found that the operating points undergo a noticeable change when in transition from one region to another (as dictated by variations in load pressure or orifice area). It was also found that the agreement between the predicted and measured operating points was quite satisfactory and could be used with confidence in future studies.