Design and testing of a robust linear controller for secondary controlled hydraulic drive

Abstract

Variable-displacement hydraulic motors supplied from a constant pressure source, also called ‘secondary controlled hydraulic drives’ (SCHDs), are modern hydrostatic rotary drives that combine the advantages of excellent dynamic behaviour and low energy consumption. Mainly because of problems with the control system they can only be found in a few industrial applications. This paper presents a novel approach to the position and speed control of SCHDs. To improve the state of the art in terms of static and dynamic performance and to facilitate the implementation procedure, a robust high-bandwidth control system with a new structure is developed. Although highly nonlinear phenomena such as saturation and static friction occur, linear frequency domain methods are used successfully in order to meet demanding specifications.