White Papers

Designing for Compliance: ESCHER, Team VALOR’s Compliant Biped

Submitted to Journal of Field Robotics
Contributing Author: Brian Lattimer, JENSEN HUGHES Director

Abstract

This paper presents the hardware platform, software, and control systems developed to field the Electric Series Compliant Humanoid for Emergency Response (ESCHER), Team VALOR’s Track A entry to the DARPA Robotics Challenge (DRC) Finals. The design and assembly of ESCHER commenced 10 months prior to the Finals, leveraging and improving upon bipedal humanoid tech-nologies implemented in previous research efforts. ESCHER’s unique features include custom lin-ear series elastic actuators (SEAs), a dual-axis motor controller enabling high-bandwidth impedance control of parallelly actuated joints, and a whole-body control framework supporting compliant lo-comotion across variable and shifting terrain. Additionally, a high-level software system designed using Robot Operating System (ROS) interfaced with the existing whole-body motion controller and integrated various open-source packages. Empirical data collected before, during, and after the DRC Finals validate ESCHER’s performance in fielded environments. The paper discusses a de-tailed analysis of challenges encountered during the competition, along with lessons learned critical for transitioning research contributions to a fielded robot. The compliant lower body proved crucial for reliable traversal across the 61 m loose dirt course at the Finals, as well as extending compliance to the rigid upper body for safe interaction with the environment.

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