Basics for the Energy-Efficient Control of Hydraulic Drives by Switching Techniques

Abstract

Hydraulic drives currently are under strong pressure by the upcoming electric servo-drives. A main reason for this is the poor energy efficiency of many hydraulic drive systems. Switching techniques which are state of the art for electric drives are now also considered for application in hydraulics. This paper reports about a new principle of switching control of hydrostatic drives which is based on periodic wave propagation in a so called resonator. The need for such a resonator is demonstrated by some simple mechanical arguments first. Then a mathematical model in form of a damped wave equation is used to assess its basic performance characteristics and to derive criteria for optimum design. This system turns out to be a pressure converter which controls the output pressure by the pulse-width of the periodic switching between high and low pressure line. Further features to improve the system are described and discussed.