Michael A. Hopkins

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Series elastic actuators are frequently modeled using a conventional lumped mass model which has remained mostly unchanged since their introduction almost two decades ago. The lumped model has served well for early development but more descriptive models are now needed for new actuator designs and control approaches. In this paper we propose a new unlumped(More)
This paper presents a framework for dynamic humanoid locomotion on uneven terrain using a novel time-varying extension to the Divergent Component of Motion (DCM). By varying the natural frequency of the DCM, we are able to achieve generic CoM height trajectories during stepping. The proposed planning algorithm computes admissible DCM reference trajectories(More)
This paper presents a compliant locomotion framework for torque-controlled humanoids using model-based whole-body control. In order to stabilize the centroidal dynamics during locomotion, we compute linear momentum rate of change objectives using a novel time-varying controller for the Divergent Component of Motion (DCM). Task-space objectives, including(More)
This paper provides an overview of the embedded joint-space control approach developed for THOR, a new series elastic humanoid. The 60 kg robot features electromechanical linear series elastic actuators (SEAs), enabling low-impedance control of each joint in the lower body via linear to rotary and parallel mechanisms. We present a distributed joint(More)
This paper provides an overview of the bipedal walking controller implemented on ESCHER, a new torque-controlled humanoid designed by Virginia Tech to compete in the DARPA Robotics Challenge (DRC). The robot's compliant control approach relies on an optimization-based inverse dynamics solver proposed in a previous publication. This work presents two unique(More)
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(More)
This paper presents a framework for dynamic walking on uneven terrain using a novel timevarying extension of the divergent component of motion (DCM). By varying the natural frequency of the DCM, we are able to achieve generic CoM height trajectories during stepping. The proposed approach computes admissible DCM reference trajectories given desired zero(More)