Gradl, C: Hydraulic Stepper Drive - Conceptual Study, Design

Costs, energy consumption and reliability are the major criteria in the development of many mechatronic systems. In this context, the avoidance of sensors plus accessories in position control is an important topic and a relevant cost saving measure. This book presents the development and test of a linear, compact hydraulic stepper drive made up of only few, cheap components to avoid expensive position sensors. The basic idea is to transmit very precise fluid quanta to a hydraulic cylinder to create in this way well defined motion steps. The first part deals with the practicability of the sensorless concept based on a 220 kN cylinder drive which performs 5 µm steps with an accuracy and repeatability of ±5 µm. Based on this concept a hydraulic stepper converter for an energy efficient control and the capability to recuperate energy is developed. The second part deals with the advancement of its most critical components, a fast check valve and a combined hydrostatic hydrodynamic bearing which uses elastic deformation of one of its constituents to obtain full fluid film lubrication in all phases of operation.