PERFORMANCE ASSESSMENT OF DIGITAL HYDRAULICS IN A QUADRUPED ROBOT LEG

ABSTRACT cylinders and/or This paper presents an investigation of the performance of digital hydraulic actuation in robot applications. The research compares two different hydraulic actuation systems, utilizing servo and digital hydraulic valves, developed to drive leg one of a hydraulic quadruped robot (HyQ). Comparisons between the two systems for position tracking, required flow rate and system efficiency are discussed. Results show that digital hydraulic systems can be a valid alternative to servo valves in terms of position tracking, and show that digital valves can greatly improve system performance in the form of reduced required flow rate and improved overall system efficiency. INTRODUCTION Electric motors are the typicalactuation method employed in robotics because of their low cost and the large availability of sizes and specifications. although electric motors However, are simple and accurate to control their performance is limited by several factors. Including that their available torque is small relative to their size and weight, and they often require a gearbox and gears introduce backlash and reduce that driveefficiency. Alternatively, hydraulic actuators have relatively faster a response, and a higher force/torque-to-weight ratio thanelectric actuators. Hydraulic actuation has been employed in a wide range of robotic systems, namely the exoskeleton system BLEEX [1-2], Raytheon SARCOS [3], SARCOS hydraulically actuated humanoid robot CB [4], legged robots Kenken [5], BigDog [6-8], Petman [9], KITECH and POSTECH Korean Quadruped Robot [10] andthe hydraulic quadruped HyQ [11 -13].

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