Water vs. oil hydraulic actuation for a robot leg

Abstract

The significant competitive advantage of hydraulics (high power density, large output force/torque and wide range of speeds) together with the properties of water (low compressibility, high thermal conductivity, low solubility of air, non-flammability and no environmental hazard) make water hydraulic actuation very suitable for systems such as legged robots. This paper addresses the comparison between a water and an oil hydraulically actuated robot leg. The mechanism and operation principle of a two degree of freedom leg are presented. In details, numerical studies have been carried out to investigate accuracy, responses, required flow, pressure in the actuator chambers and efficiency of the two actuation means.