Generalized charts of the effects of nonlinearities in 2-stage electrohydraulic control valves

THIS paper, which is an extension of previous work,1,2 presents a collection of charts derived from full instrumentation on an analog computer of the equations of a closed-loop control system controlled by a 2-stage electrohydraulic control valve of the type shown in Fig. 1. The curves included in this paper show variations in the performance of the control system under the effect of variations of the individual linear and nonlinear parameters of the valve itself and of the other parts of the control system. Usually just one parameter was varied at a time while the other linear and nonlinear components had a constant, nominal value. In some cases, however, as many as three parameters were varied simultaneously. The resulting curves are presented in a general normalized way which permits the use of these results in drawing conclusions on valves of different physical dimensions. As a whole these results are believed to promote a better understanding of the performance of valves of this type. The results listed have also been used to test the accuracy of theoretical investigations.3