Eyes-Free Tongue Gesture and Tongue Joystick Control of a Five DOF Upper-Limb Exoskeleton for Severely Disabled Individuals

• Published in: Frontiers in neuroscience Vol. 15; p. 739279
• Main Authors: Mohammadi, Mostafa, Knoche, Hendrik, Thøgersen, Mikkel, Bengtson, Stefan Hein, Gull, Muhammad Ahsan, Bentsen, Bo, Gaihede, Michael, Severinsen, Kåre Eg, Andreasen Struijk, Lotte N S
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Research Foundation 17.12.2021; Frontiers Media S.A
• Subjects: Activities of daily living; Arm; assistive devices; disabled individuals; Drinking; Electroencephalography; Electromyography; Exoskeleton; Feedback; human-robot interaction; Interfaces; Neuroscience; Paralysis; Quality of life; rehabilitation robotics; Robots; Spinal cord injuries; Tongue; tongue computer interface; upper-limb exoskeleton; Visual perception; assistive devices; human-robot interaction; upper-limb exoskeleton; rehabilitation robotics; tongue computer interface; disabled individuals; tetraplegia
• ISSN: 1662-4548; 1662-453X; 1662-453X
• DOI: 10.3389/fnins.2021.739279

Spinal cord injury can leave the affected individual severely disabled with a low level of independence and quality of life. Assistive upper-limb exoskeletons are one of the solutions that can enable an individual with tetraplegia (paralysis in both arms and legs) to perform simple activities of daily living by mobilizing the arm. Providing an efficient user interface that can provide full continuous control of such a device-safely and intuitively-with multiple degrees of freedom (DOFs) still remains a challenge. In this study, a control interface for an assistive upper-limb exoskeleton with five DOFs based on an intraoral tongue-computer interface (ITCI) for individuals with tetraplegia was proposed. Furthermore, we evaluated eyes-free use of the ITCI for the first time and compared two tongue-operated control methods, one based on tongue gestures and the other based on dynamic virtual buttons and a joystick-like control. Ten able-bodied participants tongue controlled the exoskeleton for a drinking task with and without visual feedback on a screen in three experimental sessions. As a baseline, the participants performed the drinking task with a standard gamepad. The results showed that it was possible to control the exoskeleton with the tongue even without visual feedback and to perform the drinking task at 65.1% of the speed of the gamepad. In a clinical case study, an individual with tetraplegia further succeeded to fully control the exoskeleton and perform the drinking task only 5.6% slower than the able-bodied group. This study demonstrated the first single-modal control interface that can enable individuals with complete tetraplegia to fully and continuously control a five-DOF upper limb exoskeleton and perform a drinking task after only 2 h of training. The interface was used both with and without visual feedback.