Developing a haptic hand interface with force feedback from virtual environment and controlling it via electromyography signals

A multi-functional human-machine interface was designed to assist fingers flexion and extension motions. The proposed exoskeleton system may help and improve the rehabilitation progress of hand fingers. This system was designed with 2 degrees of freedom (DOF) for the thumb finger and 3 DOF for the other fingers actuated via direct-driven linear DC actuators, which had PID position and force controllers. An electromyogram (EMG) armband with a built-in gyroscope and accelerometer unit supplies EMG and hand orientation signals to synchronize the exoskeleton hand and fingers with the ones designed in a three-dimensional virtual environment. In addition, this exoskeleton system has also a novel force sensing mechanism designed to sense fingertip forces and also help the motors freely follow human finger movements with a minimal resistance in its virtual reality applications. A contact detection method was developed and applied to sense the 3 dimensional (3D) objects in the virtual environment. The studies showed that the position and force feedback controllers suitably worked for both sensing the 3D virtual objects and for the mechanism's following the user fingers' movements with minimal resistance. In conclusion, such a mechanism with proposed special capabilities could be used to be utilized for finger rehabilitation and also haptic training applications.