Improving Characteristics of Electrohydraulic Servo System by using DSP.

A DSP (digital signal processor) is applied to an electrohydraulic servo system, and feed-forward compensation called ZPETC (zero phase error tracking control) which is impossible by analog techniques, greatly improves the frequency responses of the system. However, the relation-ship between load pressure and flow rate for the servo valve is highly nonlinear. Because ZPETC, which is feed forward compensation, assumes the controlled system to be linear, we must make this nonlinearity linear. Therefore, the dependence of servo valve on load pressure is removed by detecting load pressure, and the system is linearized. DSP performs the calculation for ZPETC and for linearizing the system. This effect of improving frequency responses of the system by the digital signal processing technique is investigated.