Towards Intuitive Control of Active Arm Supports for Men with Duchenne Muscular Dystrophy: A Hybrid sEMG-Torque Control Interface

Duchenne muscular dystrophy (DMD) is caused by a recessive X-linked mutation, resulting in progressive muscle degeneration and eventual death. While the lifespan of men with DMD increased due to improvements on health care, they still live with severe physical impairments and strong dependency on care. Active arm supports can improve their quality of life, by augmenting their arm’s residual motor capabilities. This research aims to develop a control interface, which detects the user’s movement intention, required to operate these active arm supports. We propose a hybrid sEMG-torque interface controlling three translations and two rotations of the forearm. The translations are proportionally controlled using the envelopes of sEMG signals from six arm muscles. The two horizontal translations can be controlled simultaneously while the vertical translation is sequentially controlled triggering a sEMG-based switch. The passive interaction torques measured between the forearm and the active arm support, are used to release two rotations of the forearm, mimicking a gimbal mechanism. A preliminary evaluation of the control method has been carried out with one healthy subject, within a series of two-dimensional and three-dimensional tasks.
The performance was evaluated, in terms of path efficiency, task completion rate and time, smoothness, and overshoot. The results indicate that the control method is able to successfully detect the intention of the user and translate it to the intended movement. Furthermore, the combination of sEMG and torque control of the forearm translations and rotations, results in a simple, yet functional controller able to support natural movements of the arm.