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AthenaZero: A low-inertia, bimanual robot for dynamic manipulation

AthenaZero: A low-inertia, bimanual robot for dynamic manipulation

Andrew S. Morgan, Gregory Xie, Capprin Bass, Rachel Thomasson, Chunpeng Wang, Erfan Shahriari, Harrison Busa, Oluwaseun Araromi, Joseph Aronov, Michael Burgess, Velin D. Dimitrov, Matthew A. Estrada, Faris Hamdi, Samuel Kendig, Taeyoon Lee, Jose Oscar Mur-Miranda, Emma Sommers, Paul Titchener, Margaret Wang, Achu Wilson, Mark Yeatman, Osman Dogan Yirmibesoglu, Alfred A. Rizzi, Annan Mozeika, Nicolas Rojas, Lael Odhner · N/A · 2026

manipulation control
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Summary

AthenaZero is a bimanual manipulator designed to minimize inertia without compromising control authority.

Abstract Summary

AthenaZero is a bimanual manipulator designed to minimize inertia without compromising control authority. By utilizing quasi-direct drive actuation and transmission remotization techniques, the system achieves an effective endpoint mass comparable to that of a human---about an order of magnitude less than conventional robot manipulators. This characteristic, combined with its inherent torque transparency, makes AthenaZero exceptionally well-suited for dynamic manipulation. We describe the methodology} that led to this design and demonstrate the robot's capabilities on three baseball-inspired tasks: throwing, catching, and batting, which showcase complex interactions on human-comparable timescales where milliseconds matter. AthenaZero was capable of throwing at speeds in excess of 30 m/s, with catching and batting at speeds in excess of 14 m/s over a short 7.3 m distance. Batting practice and a game of catch were subsequently performed in robot-to-robot and human-to-robot variations, showcasing the efficacy and adaptability of our system in tasks that require high acceleration.

Key Points

  • AthenaZero is a bimanual manipulator designed to minimize inertia without compromising control authority.
  • By utilizing quasi-direct drive actuation and transmission remotization techniques, the system achieves an effective endpoint mass comparable to that of a human---about an order of magnitude less than conventional robot manipulators.
  • This characteristic, combined with its inherent torque transparency, makes AthenaZero exceptionally well-suited for dynamic manipulation.
  • We describe the methodology} that led to this design and demonstrate the robot's capabilities on three baseball-inspired tasks: throwing, catching, and batting, which showcase complex interactions on human-comparable timescales where milliseconds matter.
  • AthenaZero was capable of throwing at speeds in excess of 30 m/s, with catching and batting at speeds in excess of 14 m/s over a short 7.3 m distance.

Results

AthenaZero is a bimanual robot consisting of a 1 DoF torso, two 7 DoF arms, and two 6 DoF hands (Fig. 2 ). The entire robot is powered by a family of four custom quasi-direct drive, and highly force-transparent actuators in 95 mm, 76 mm, 38 mm, and 25 mm diameter variations. The robot stands at about 1.6 m tall with an approximate wingspan of 1.8 m.

The shoulders have a 0.44 m lateral separation, modeled after a human male.

Results — AthenaZero: A low-inertia, bimanual robot for dynamic manipulation
Figure 2: Motor-level and joint-level architecture of AthenaZero . Nomenclature: Torso (T), Right (R), Left (L), Joint (J), and Motor (M) . Two torso motors (TM1 and TM2) connect directly to the TJ1 torso joint in parallel via a belt. Shoulder motors RM1-RM3 (LM1-LM3) are axially coincident, combining towards RJ1-RJ3 (LJ1-LJ3) and acting as a spherical shoulder joint. Elbow junction actuators RM4-RM5 (LM4-LM5) through a belt transmission are axially perpendicular, mimicking a universal joint RJ4-RJ5 (LJ4-LJ5) at the elbow. Wrist motors RM6-RM7 (LM6-LM7) are differentially coupled, symbolically representing a near-universal joint RJ6-RJ7 (LJ6-LJ7) at the wrist junction. Translational offset between the two axes is 6 mm. A total of 3 motors for each hand are located within the torso, with Bowden transmissions that remote actuation out to three fingers via tendons.

Materials and Methods

Actuator design reigns as a central ingredient to execute our design methodology. To minimize reflected inertia and maximize transparency, we utilize quasi-direct drive motors. Since we aim for human-like mass properties, we concurrently require human-like torques, deriving our targets from the isometric torque production of equivalent human joints [ 46 , 40 , 77 ] .

Materials and Methods — AthenaZero: A low-inertia, bimanual robot for dynamic manipulation
Figure 3: Remoting actuation via transmissions reduces effective mass. Shoulder and Elbow: The majority of the arm’s mass is contained via the combination of motors RM1-RM5 (equivalently LM1-LM5). Shoulder motors are located at the joint, but elbow flexion leverages a belt transmission. Wrist: The wrist is a 2 DoF parallel mechanism which remotes the motors to the elbow junction. Hand: The hand is a 6 DoF, 3-tendon underactuated mechanism that interdigitates. Tactile sensors are placed inside of the fingertips and palm for contact sensing (denoted in blue).

Sources and Demonstrations

Figures are reproduced from Morgan et al. See the full paper for experimental details and the project page, when the paper links one, for demonstrations and videos.

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