Investigation of spool-type solenoid operated hydraulic directional control valves

The integrated approach of engineering systems analysis enables one to outline a systematic method of solution of a number of engineering problems.
The investigation of the problem usually starts with the definition of a physical model of the system on the basis of a set of requirements; the system can be some equipment like a valve or a pump. The physical model is normally much too complex to be investigated directly, therefore, through assumptions it is simplified to an abstract model.
From the abstract model, again via assumptions, a mathematical model is derived which combines the separate subsystems (mechanical, hydraulic, etc.,) into an integrated network of ideal network elements. Network topology enables the investigator to obtain a set of independent equations which can then be solved. In parallel with the analytical work tests on the physical model are carried out to compare the accuracy of the analysis and, hence, to make suitable adjustments in the theory.
The knowledge gained from the exercise just described is used with other considerations for the design of a new or improved product.
This is the approach which has been adopted in this thesis to
the analysis of a hydraulic, solenoid-actuated, four-port, directional-control valve.
The experimental work was restricted to the operation of the valve with fluid flow through two ports only, further to Fig. 1.1 the hydraulic supply was connected to port P and port A to tank. This meant that the fluid was passing through a single orifice without flowing into an external load such as a hydraulic motor. This is in accordance with the definition of the system under investigation discussed later.
The complete system was simulated by means of digital and
analogue computers, and in addition, programmes have been suggested to make suitable design changes in the valve.

A Thesis submitted to the Council for National Academic Awards for the degree of Master of Philosophy.