An Adaptive Prosthetic Hand with Compliant Joints and EMG-based Control

In this paper some recent results about the experimental trials we are performing on a functional prosthetic hand characterized by an EMG-control and by a simple and low cost fabrication technology are shown. A compliant under-actuated prosthetic hand has been designed and fabricated. The five-fingered hand (both palm and fingers) is moulded as a soft polymeric single part with compliant joints and embedded tendon driven under-actuated mechanism for providing adaptive grasp. The maximum measured cylindrical grasping force is 30 N. The one DoF prosthetic hand is controlled using two pre-amplified EMG electrodes. The proposed EMG-based control is a Finite State Machine (FSM). A particular attention has been given to the calibration phase. In order to identify the end of the grasp, the intensity of the current is monitored. Moreover, the microcontroller stops the motor when the average current overcomes the value imposed. Compared to other EMG based controllers, the approach proposed is very simple but it presents a good robustness and needs a minimum computational cost. Index Terms – Biomechatronics, Prosthetics, Compliant joints, Under-actuation, Rehabilitation.