Actuation of a thumb prosthesis using remaining natural fingers

A simple but useful concept for the actuation of finger prosthesis, using the ability of remaining natural fingers of a partially deformed human hand, is presented in this work. The design is based on very simple principles drawn from the concept of opposition space. A prosthetic mechanism for a hand, which has lost a thumb but retains the abilities of the other fingers, is developed as an example to demonstrate the concept. This presentation is a system integration of the concept, design, modeling, simulation and development of the prosthetic mechanism. The system is modeled using the powerful technique of bond graphs. Effects such as extensibility of actuation strings and their internal damping, bearing friction at joints, etc., which are encountered in the prosthetic system, have been modeled and simulated. A simple prototype has been developed based on the proposed concept and demonstrated the effectiveness of the design. The prosthesis is very affordable and simple, and holds great promise for persons with such prehensile disabilities.