Novel differential mechanism enabling two DOF from a single actuator: Application to a prosthetic hand

There will always be a drive to reduce the complexity, weight, and cost of mobile platforms while increasing their inherent capabilities. This paper presents a novel method of increasing the range of achievable grasp configurations of a mechatronic hand controlled by a single actuator. By utilizing the entire actuator space, the hand is able to perform four grasp types (lateral, precision, precision/power, and power) with a single input resulting in a potentially lighter and simpler hand design. We demonstrate this strategy in a prototype hand that is evaluated to determine the benefit of this method over the addition of a second actuator. Results show a decrease in weight but a 0.8 sec transition time between grasp types with the proposed method. The prototype hand can be controlled by a single EMG signal that can command a change in grasp type or an opening/closing of the hand. We discuss the potential of this mechanism to improve prosthetic hand design as compared to current myoelectric systems.