Design of a series elastic humanoid for the DARPA Robotics Challenge

This paper describes the mechanical design of ESCHER, a series elastic humanoid developed to compete in the DARPA Robotics Challenge (DRC). The design methodology was informed by preliminary experimental results obtained using the THOR humanoid, a prototype platform developed for the DRC Trials, relying heavily on an accurate model of the torque-controlled robot in the Gazebo simulation environment. The redesigned lower body features a unique double actuated knee; by driving the single degree of freedom joint with two identical linear series elastic actuators (SEAs), the lower body is able to meet the necessary speed and torque requirements for locomotion on rough terrain. Experimental results demonstrating ESCHER's ability to step onto a 23 cm block, representative of the stairs task at the DRC Finals, validating the proposed approach. Joint torques measured on the hardware platform approximate those in simulation, validating the proposed design methodology.