New strategy of adaptive position control of electro-hydraulic linear drive

High speed and high accuracy positioning is a key element in modern machines and mechanical systems. Besides the high speed operations, which yields increased productivity and high accuracy positioning, which ensures improved product quality the insensibility of positioning system to external disturbances and parameter uncertainties, provides reliability and flexibility of these systems. Fluid power actuators are characterized by their high power density and excellent dynamic response. The hydraulic actuator in particular is capable of very high output power levels combined with very compact drive unit dimensions. It is ideally suited to many high dynamic applications. However the disadvantages of hydraulic system such as non-linear dynamic behaviour due to friction, fluid compressibility, etc., need to be overcome. This is successfully obtainable only by implementation of modern digital control systems designed on basis of modem control theory. An adaptive digital control concepts for position control of electro-hydraulic linear drive is represented in this paper. It is developed on basis of conventional control theory and consists of forefilter, self tunning controller and switching integrator. It enables a perfect reference signal tracking and precise positioning, as well as a good adaptation on external disturbances and parameter changes. The usefulness of the digital control algorithm is experimentally tested to the level that it is completely applicable in industrial practice.