Gain scheduling control for electro-hydraulic servo system which has time-delay

Electro-hydraulic servo system has been used in many industrial applications for high power in size, high response and fine repeatability. But, load variation causes a degradation of control characteristic. In this papaer, we introduce a scheduling parameter which is a function of hydraulic force against a load. Then, apply it for a controller design in order to maintain a steady control performance under the comparatively large load variation. There are many factors, which cause a time-delay between an input and an output, in the hydraulic system. It often produces unexpected over or undershoot when design an aggressive controller for high bandwidth feature to the plant. In order to have a desirable following behavior in the closed loop system, take a time-delay into consideration as a modeling error and attempt a trade off of rise-time and overshoot characteristic. The usefulness of this design approach is confirmed by the experiment.