The humanoid robot Atlas has a new hand with four fingers instead of five. Boston Dynamics described the design in a blog post last week. The company left out the little finger on purpose.
The hand is built for work: holding a drill by the handle and pressing its trigger at the same time. Boston Dynamics argues that fewer parts mean fewer things that break, and that this matters more than copying the human hand exactly.
Why no pinky
The new hand has 13 degrees of freedom, the number of separate ways its parts can move, up from seven in the previous version. The thumb has four, and each of the other three fingers has three. A pinky would have added three more.
The team decided that the extra tasks a fifth finger would allow were not worth the added complexity. In an internal test, staff taped their ring and little fingers together for a day.
All joints use one type of motor, sealed inside the hand, with no cables crossing the joints. The fingertips and palm have pressure sensors. The company says the hand is slightly bigger and stronger than an average human hand and can carry a minifridge of over 100 pounds.
Trained in simulation
Boston Dynamics trains the hand's movements with reinforcement learning, a method where software learns by trial and error. The training runs in simulation, then moves to the real hand.
The company lists drills, nail guns and welding torches among the tools it can hold. It has published no independent test of how often the hand succeeds.
