Additive manufacturing for agile legged robots with hydraulic actuation

Agile and versatile legged robots are expected to become useful machines for applications in unstructured environments where traditional vehicles with wheels and tracks cannot go. Hydraulic actuation has proven to be a suitable actuation technology due to its high power density, robustness against impacts and high stiffness for high bandwidth control. In this paper we demonstrate how additive manufacturing (AM) can produce highly integrated hydraulic components with reduced weight and higher complexity when compared to traditionally manufactured manifolds. To the best knowledge of the authors, this is the first time a successful implementation of direct metal laser sintering (DMLS) of hydraulic manifolds made in aluminium alloy AlSiMg is presented. AlSiMg has several advantages for the construction of hydraulic components when compared to the commonly used Titanium alloys (e.g. Ti64): lower cost, higher thermal conductivity, lower density and easier to post-process. This paper first explains the build process with DMLS of AlSiMg and a pre-study of a pressure-tested hydraulic tube that demonstrated the suitability of AlSiMg for AM hydraulic components. Then, we discuss part orientation and support material during the build process of a highly-integrated hydraulic manifold for the legs of IIT's new hydraulic quadruped robot HyQ2Max. A comparison of this manifold with a traditionally manufactured alternative concludes the paper.