supernumerary robotic fingers MIT
July 20, 2014

Wrist-Mounted Robotic Device Could Add Two Fingers To A Person’s Hand

redOrbit Staff & Wire Reports - Your Universe Online

Researchers from the Massachusetts Institute of Technology (MIT) have developed a wrist-mounted robotic device that could allow people to complete tasks like removing a bottle cap or twisting a screwdriver using a single hand.

The unit has been called the “supernumerary robotic fingers” device and according to the developers, it enhances the human hand’s natural grasping motion. It is worn around the wrist and essentially provides a pair of extra, artificial digits – one next to the pinky and one next to the thumb – that automatically move in synch as the wearer moves his or her actual fingers.

It mimics the hand’s movement thanks to a novel control algorithm and sensors that measure the position of the wearer’s finger, BBC News explained in a report Thursday. The algorithm controls the output from the sensors to the robotic fingers, causing them to move once the device detects that the wearer is attempting to grab and manipulate an object such as a tool or a container in need of opening.

“This is a completely intuitive and natural way to move your robotic fingers,” Harry Asada, the Ford Professor of Engineering in MIT's Department of Mechanical Engineering, said in a statement. “You do not need to command the robot, but simply move your fingers naturally. Then the robotic fingers react and assist your fingers.”

With some training, Asada believes that people could come to view the robotic fingers like an extension of their own hand. He added that he was hopeful that the supernumerary robotic fingers could be used to help those with limited dexterity complete routine household tasks, such as opening jars and lifting heavy objects.

Asada and graduate student Faye Wu presented a paper on the robot at last week’s Robotics: Science and Systems conference in Berkeley, California, and according to Devin Coldewey of NBC News, “the extra grip may be… something which sufferers of arthritis or muscular dystrophy may find helpful.”

While they were developing the glove, the MIT researchers started by analyzing the grasping motion of the hand using a special glove that had motion sensors attached to it, explained Wired UK’s Kadhim Shubber. They focused on two basic motions – first bringing all five fingers together, and then twisting them inwards – in the development of the algorithm.

While a person’s hand may not grab a piece of fruit in exactly the same way that it will a coffee mug, Asada and Wu assert that all grasping actions are basically explained through some combination of these two patterns. They went on to hypothesize that this so-called biomechanical synergy could be expanded to seven fingers, not just five.

In order to test this notion, Wu used a glove with several multiple position-recording sensors attached to her wrist with a light brace. She then went on to grasp several different types of objects throughout the lab, including a soda bottle and a box of cookies, and then manually positioned the robotic fingers to support each specific item.

Wu recorded both hand and robotic joint angles multiple times with each object, and discovered that every grasping movement could be explained using a combination of two or three general patterns among all seven of the fingers. This data was used to develop the control algorithm to correlate the position of the two robotic fingers to the five human ones, basically instructing the robot to assume a position that would be expected by the wearer.

The MIT researchers are currently focusing on the mechanics of grasping, and having the robotic fingers move closer or further away in response to the actions of the human fingers, but they ultimately want to consider force as well as position. They also want to reduce the size of the current unit in order to make it more manageable.

“This is a prototype, but we can shrink it down to one-third its size, and make it foldable,” said Asada. “We could make this into a watch or a bracelet where the fingers pop up, and when the job is done, they come back into the watch. Wearable robots are a way to bring the robot closer to our daily life.”