Design of Electrohydraulic Force Loading System

This paper discusses the design of an electrohydraulic force loading system. This system is able to produce any desired arbitrary forces. As an example, the loading system is designed to load force to a hydraulic position servo. It is shown that if the loading system is designed by using a combination of a servo valve with critical center and a hydraulic cylinder to realize a force feedback close-loop system, the position system may generate a large additional force to frustrate this loading system to work properly. By using a bypass adjustable throttle valve across the two flow lines of the loading cylinder, it is verified by theoretic analysis and simulation that the additional force generated by position system can be greatly reduced. Because an asymmetric cylinder is used as the loading actuator, modelling of its characteristics is also carried out.