COMPARISON OF UNDER LAPPED AND CRITICALLY LAPPED HYDRAULIC SPOOL VALVES PERFORMANCE

Abstract

The purpose of this study is to compare the spool valve performance on the hydraulics system behaviour for the principal types of hydraulic control valves such as under lapped and critically lapped without applying any control law to the hydraulics system. Mathematical model of the spool valve-cylinder-load system is obtained for each type of valve. In application, hydraulic actuators are typically a single-acting hydraulic cylinder and valves are five port-spool valve. Actuator is selected based on desired velocity and acceleration. Differential equations are obtained from mathematical model. Mathematical models are arranged in the state-space form. Pressure, velocity and position are considered as state-variables. The state-space equations of system are solved by MATLAB program and pressure variations, velocity and position are shown as graphically. It is concluded in numerical study that under lapped valves can be used in fast applications which require a continuous flow and bigger velocity. Critically lapped valve is more desirable than under lapped valve in slow application, if fast velocity is not required for hydraulic systems.