Robot hands are becoming more human

If you want to guess the purpose of any given futuristic humanoid robot, look at its hands. Last week, a pair of videos released by Boston Dynamics and Figure AI  provided clear examples that certain tasks simply require much more “human touch.”

In the first case, Hyundai-owned Boston Dynamics showed off a new pair of “grippers” for its trimmed-down Atlas factory robot. (Readers familiar with the company may be more familiar with Atlas’ older, beefier predecessor). The claw-like, three-digit pincer features three fingers, one functioning as an extra-long thumb, a combination particularly well suited for pinching and holding objects. Though Atlas was designed to resemble a person in other ways, its hands aren’t exactly one-to-one. Instead, company engineers said, the design was optimized for sorting, packing, and handling objects—all tasks Atlas would need to perform repeatedly in a factory or warehouse setting.

“The goal is to apply as little force as possible while maintaining a stable grasp,” Atlas mechanical engineer Karl Price said.

That’s in sharp contrast to the much more seemingly human-like robot hands unveiled by Figure last week. In a flashy video announcing the launch of its knitwear-wearing “Figure 03” model, the company showcases its robots performing delicate tasks like watering a plant, washing dishes, and gently handing a glass of water to their human overlords. Similar to Tesla with its egg-fondling Optimus robot, Figure has made it clear it envisions a future for humanoid robots in the home. The company describes its latest model as a “general-purpose humanoid robot for everyday use.”

But the everyday tasks listed above, as well as many others required of a functional robot butler, pose different engineering challenges than those faced by a machine designed to sort boxes all day. The hands, in other words, offer a clearer glimpse into a robot’s larger place in the world.

Why human hands are so hard to copy

Hands might be one of the hardest human body parts to accurately replicate in robotic form. Each one contains more than 30 muscles and 27 joints, enabling 27 degrees of freedom. They also have over 17,000 touch receptors and nerve endings, allowing us to perform a wide variety of actions—from tapping on a keyboard and delicately writing with a pen to hoisting a heavy barbell.

And while robot hands and advanced prosthetic limbs have made significant progress in recent years, none come close to the sophistication, reliability, and innate simplicity of a human hand. That presents a major challenge for humanoid robots, which are increasingly being pitched as tools to augment, or replace, human labor.

“The majority of the hand-led motor actions in these sectors require not only precise movements but also adaptive responses to unpredictable variables such as irregular object shapes, varying textures, and dynamic environmental conditions,” University of Florida Professor of Civil Engineering Eric Du told the BBC in an interview earlier this year.

Sometimes, three fingers is more than enough

In Atlas’s case, the new three-pronged gripper hand is an evolution of the older robot’s design. The original model worked much of the time but was prone to failure with extended use. That led to the development of a second-generation gripper, designed to be “rugged and reliable.” In the video, Price notes that the current version has seven degrees of freedom and seven actuators, two for each finger and one dedicated solely to an articulated thumb joint. Each fingertip contains tactile sensors that mimic the human sense of touch. Cameras are also embedded in the robot’s palms.

But the most significant innovation came from adding a feature that separates human hands from those of most other animals: an opposable thumb. That might not sound like much at first, but engineers at Boston Dynamics say the change significantly expands the types of grasps Atlas can perform and increases the robot’s flexibility in deciding how to pick something up.

“Really, over the last year or so, we’ve realized we can grasp almost anything that we throw at it,” Atlas Director of Robot Behavior Alberto Rodriguez said.

So, if a thumb is better than no thumb, one may wonder why Boston Dynamics wouldn’t just follow a human hand to the tee. Price says they settled on three fingers because they determined that was the “fewest amount of fingers that can achieve very complex manipulations and tasks.”

The added distance between the fingers granted by the opposable thumb, for example, helps Atlas maintain a more stable grass, especially for heavier objects. Thumbs also allow for more delicate two finger “pinch grasp” which can be used to move smaller objects like bolts. And while the Atlas team says they certainly considered adding even more fingers, they ultimately decided the juice really wasn’t worth the squeeze.

“We decided not to add more fingers because adding more fingers adds more complexity,” Rodriguez said. “If it’s unnecessary, that means lower reliability, higher costs and just in general; lower speed of development.”

Why robot butlers will need human-like hands

Three fingers might be plenty for a factory setting, but Figure—and other companies hoping to bring humanoid robots into the home—believe more are necessary. The slender, 5’6″ Figure 03 features embedded palm cameras in each hand that assist with “close-range visual feedback during grasps.” This newer model also has softer, more adaptive fingertips than previous versions, which Figure says allow for more stable grasping of objects in a wide range of sizes, shapes, and textures. Each finger includes a new type of tactile sensor capable of detecting forces as small as three grams. That means the robot can register objects as lightweight as a paperclip or a playing card.

“The Figure 03 hands represent a major leap in compliant and tactile design,” the company notes.

But as the Boston Dynamics engineers noted, all that added complexity increases the risk of failure. The potential costs are high. While a robot butler breaking a glass or two might seem like a reasonable tradeoff, the stakes become much higher when those robots are tasked with accurately laying out prescription drugs for a senior or safely handling a toddler. Figure and its competitors speak ambitiously about bringing robots into homes sooner rather than later, but the actual time horizon for such a future remains hazy at best.

Future robots may look even more human

Even engineers at Boston Dynamics, who have invested heavily in the gripper path, see a future where robots more closely resemble humans.

There’s some reason to think the future, both for manufacturing-style robots and those designed for the home, could start to look much more human. In cases where robots are expected to work alongside people in factories, having five-fingered hands allows them to use tools already made for human workers. That could reduce the need to develop entirely new tools and systems tailored specifically for robots. It also gives industry leaders more incentive to reduce their human workforce.

“All of these things are pushing us, not necessarily by design but naturally and organically, into more anthropomorphic designs for the gripper,” Rodriguez said.