Dexterous hand over

In-Depth

A dexterous, bio-inspired artificial hand is being developed by team of European engineers.

A dexterous, bio-inspired artificial hand is being developed by team of European engineers led by Professors Paolo Dario and Maria Chiara Carrozza at the Scuola Superiore Sant’Anna in Italy.

Funded by the Future and Emerging Technologies initiative of the European Information Societies Programme (IST), the developers working on the so-called Cyberhand project aim to produce a hand that can be hard wired into the nervous system, allowing sensory feedback from the hand to reach the brain, and instructions to come from the brain to control the hand - at least in part.

So far, the researchers have developed a fully sensitised five-fingered hand. Their Cyberhand prototype has 16 Degrees of Freedom (DoFs) made possible by the work of six tiny motors. Each of the five fingers is articulated and has one motor dedicated to its joint flexing for autonomous control.

Taking inspiration from a real hand, where a muscle pulls a tendon inside a synovial sheath, Cyberhand ‘s finger cables run through a Teflon sheath pulled by a DC motor. So the proximal, medial and distal phalanges - those bones between the fingers and the knuckles - are all driven by the same tendon. This approach is called underactuation as there are more Degrees of Freedom than Degrees of Movement - it means the prosthesis has a self-adaptive grasp.

“This is a fundamental feature of the Cyberhand prosthesis because only a limited number of control signals are available for user’s voluntary control,” says project manager, Dr. Lucia Beccai. Importantly, it also means less user effort is required to control the hand during its use.

To provide sensory feedback for the user, the new hand includes sensors that can measure tension, force, joint angle, end stroke and contact.

Clinical validation of the Cyberhand system should begin in 2006.

Some companies have already expressed interest in commercialising the system. Nevertheless, it could be five to eight years before the device clears all the tests necessary to prove its safety, usability, and robustness.