Nicholas Thayer and Shashank Priya, study leaders and researchers from Virginia Tech, have developed a robotic hand that is capable of performing human tasks such as opening doors and typing. 

The robotic hand is called a dexterous anthropomorphic robotic typing hand, or DART hand. It is designed to both look and act just like a real human hand, and closely mimics the actions of the human hand more than any other robotic version to date.  

Other robotic hands created before the DART hand have had varied numbers of fingers that did not look or act like an actual human hand. In addition, these other robotic hands could not accurately type at the speed that the DART hand can. 

To make the DART hand, the Virginia Tech researchers studied the physiology of the human hand. The human hand has 40 muscles with 23 degrees of freedom in both the wrist and hand. By observing the hand's range of motion, grasp force and musculoskeletal structure, Thayer and Priya were able to make servomotors and wires imitate the human hand's actions. 

Using a total of 19 motors, researchers were able to reach 19 degrees of freedom. Rapid prototyping was used to fabricate components, which cut weight, costs and fabrication time.

The DART hand is controlled through input text by a keyboard or a voice recognition program, where individual fingers receive commands on where to position themselves. For example, when typing, a finger receives a command to place itself above the correct letter. The finger presses the key, and the letter is checked for accuracy. If the letter pressed was incorrect, the DART hand is able to twist and turn the wrist to navigate the keyboard and press the backspace key. 

"The greatest significance of our work is the optimization of the hand design to reduce the number of motors in order to achieve a similar degree of freedom and range of motion as the human hand," said Priya. "This allowed us to achieve dimensions that are on par with the human hand. We were also able to program the hand in such a manner that a high typing efficiency can be obtained."

The DART hand is capable of typing 20 words per minute with just one hand on a regular computer keyboard. Using both hands, researchers expect that the DART hands will be able to type at least 30 words per minute. The average human types approximately 33 words per minute. 

The main difference between the DART hand and a human hand is that the DART hand's fingers are controlled independently while tendons, moving joints in more than one finger, connect human hand muscles. 

"We have already experimented with grasping tasks," said Priya. "In the current form it is not optimized for grasping, but in our next version there will be enough sensors to provide feedback for controlling the grasping action." 

Other improvements that the researchers plan to apply to the DART hand are silicon skin, tactile sensors, temperature sensors, and tension sensors. 

This study was published in Smart Materials and Structures.