Artificial neural network EMG classifier for functional hand grasp movements prediction

Objective: To design and implement an electromyography (EMG)-based controller for a hand robotic assistive device, which is able to classify the user's motion intention before the effective kinematic movement execution. Methods: Multiple degrees-of-freedom hand grasp movements (i.e. pinching, grasp an object, grasping) were predicted by means of surface EMG signals, recorded from 10 bipolar EMG electrodes arranged in a circular configuration around the forearm 2-3 cm from the elbow. Two cascaded artificial neural networks were then exploited to detect the patient's motion intention from the EMG signal window starting from the electrical activity onset to movement onset (i.e. electromechanical delay). Results: The proposed approach was tested on eight healthy control subjects (4 females; age range 25-26 years) and it demonstrated a mean +/- SD testing performance of 76% +/- 14% for correctly predicting healthy users' motion intention. Two post-stroke patients tested the controller and obtained 79% and 100% of correctly classified movements under testing conditions. Conclusion: A task-selection controller was developed to estimate the intended movement from the EMG measured during the electromechanical delay.