Atlas's New Hand Has No Pinky and 13 Joints, Up From Seven

Boston Dynamics unveiled a redesigned hand for its Atlas humanoid on Oct. 1, with four fingers and 13 degrees of freedom, up from seven in the previous generation. The company left out the pinky on purpose, and the choice says more about how it expects to build the robot than the missing finger does.

A degree of freedom is one independent way a joint can move. Counting them is the quickest way to compare hands, because each one needs an actuator, a sensor path and a way to fail.

An Atlas on display at Hyundai Motorstudio Goyang in July. The photograph does not show the new hand.

What the 13 degrees of freedom are

The thumb has four degrees of freedom and each of the other three fingers has three, according to The Robot Report, which covered the announcement on Oct. 1. The hand is about the size of a large human hand, and Boston Dynamics says its strength matches the old seven-degree hand.

Every joint is driven directly by a single actuator type, and the actuators are fully encapsulated, with no cables crossing the joints. IEEE Spectrum, in a piece by robotics editor Evan Ackerman, adds that each actuator pack is one replaceable unit and that the hand uses fewer, larger actuators than a fully human-shaped design would need. Dense pressure sensors cover the fingertips and palm.

Neither outlet gives a payload, a unit cost, a weight or a cycle life. Those are the numbers that decide whether a hand survives a shift, and Boston Dynamics has not published them.

Why the pinky went

Dylan Thrush, a mechanical engineer on the Atlas team, said the extra dexterity of a fifth finger did not justify three more degrees of freedom plus the added size, power draw and actuators, per The Robot Report. Zachary Jackowski, Boston Dynamics' chief product and technology officer, had the team tape their pinky and ring fingers together for a day. They concluded the hand did not need the pinky.

That gives the arithmetic. Thirteen plus the three the company says a pinky would add is 16 degrees of freedom for a five-finger layout. The table below sets the three side by side; the 16 is my calculation from the company's description, not a figure Boston Dynamics published.

Hand	Fingers	Degrees of freedom
Previous Atlas hand	3	7
New Atlas hand	4	13
Five-finger layout (derived)	5	16

Alberto Rodriguez, Boston Dynamics' director of robot behavior for Atlas, said in IEEE Spectrum that "hands are a ruthless design trade-off." He also said the team is working out what must change to "make 100,000 of these hands a year."

What 100,000 hands a year implies

At 13 degrees of freedom, 100,000 hands is 1.3 million degrees of freedom a year. A 16-degree design at the same volume is 1.6 million, or 300,000 more joints to build, test and replace. If a pinky costs three joints per hand, it costs 300,000 joints per 100,000 hands, and that is the denominator the design decision hides in.

The number that matters here is not the finger count but the replaceable-unit count. An actuator pack that swaps out as a unit turns a hand failure from a repair into a part change, and that is a cost per robot-hour argument, not a dexterity one.

Atlas is also not the first company to argue for a simpler hand. The Terminal reported on why a robot with 99 percent per-action success finishes only 37 percent of 100-step jobs, the case for "minimum sufficient dexterity" over maximal hands. Jabil, a contract manufacturer, separately told The Robot Report that humanoid makers are heading for "tens of thousands" of units, with cost and compute as the limits. The Atlas hand is a design built for that second number.

What is claimed and what is shown

The company says the hand is built for mass manufacture and for simulation-to-real reinforcement learning, in which a policy trained in a physics simulator is moved onto hardware. Boston Dynamics argues that human demonstrations capture what a task looks like but not the force control, so simulation is needed. Early hardware results show transfer on dynamic tasks using only actuator proprioception, per The Robot Report. That is a vendor description, and neither source reports an independent test.

The listed capabilities are sliding the thumb tip along the other fingers, pinch and tripod grasps, in-hand reorientation, recovery from a slipping grasp, and triggered tool grasps on drills, torque drivers, grinders, nail guns and welding torches. Neither article says whether the demonstrations were autonomous or teleoperated. The Robot Report found no hand-specific deployment date.

The deployment context is a week old. Boston Dynamics opened its Robotics Metaplant Application Center at Hyundai Motor Group's Metaplant America in Georgia about a week before the hand announcement, a training site for putting Atlas into automotive plants.

What would change this read is a published failure rate. If Boston Dynamics reports mean cycles between actuator-pack swaps in a Georgia plant, the pinky trade can be priced. Until then, Rodriguez's 100,000-a-year figure remains a target, and Boston Dynamics has given no date for it.