Some assistive devices now go virtually unnoticed \u2013 eyeglasses for seeing nuances and details, for example, and hearing aids for perceiving the sounds around us. But others are more visible. That\u2019s the case for many of the assistive devices intended to restore mobility to patients who have lost it.<\/p>\n
These are the devices that Mohamed Bouri, a robotics engineer and head of EPFL\u2019s REHAssist research group, is working on. \u201cWhen I see a patient who can no longer walk, one of my main goals is to help them regain that capability,\u201d he says. He\u2019s developing exoskeletons for individuals who are paraplegic, suffer from a neuromuscular disease or have other kinds of mobility impairment. The exoskeletons are attached to the waist and legs, much like a pair of trousers. They\u2019re not intended to heal these patients, but rather to let them walk again and stand upright for hours \u2013 with all the social and health-related benefits that a vertical position brings.<\/p>\n<\/p>\n
Helping the paralyzed walk again <\/strong><\/p>\n The scientists and engineers at REHAssist are exploring various kinds of systems. One is TWIICE, an exoskeleton for people who are partially or completely paralyzed from the waist down but who have the use of their arms. It has two battery-powered motors on each leg that bend and extend the hip and knee joints. The exoskeleton\u2019s full weight \u2013 17 kilos \u2013 is supported by the structure itself with the help of the motors. \u201cIt\u2019s the lightest one in the world,\u201d says Bouri. \u201cPatients can use it to walk, climb stairs and go up and down ramps.\u201d Wearers control the device using crutches with integrated buttons that also help maintain balance. They can choose between several walking modes based on the desired speed and the surface they\u2019re on; each mode corresponds to a given magnitude of hip and knee movement. In short, the exoskeleton does all the work involved in displacing the wearer\u2019s legs.<\/p>\n \u201cExoskeletons aren\u2019t very complex in terms of design and robotics,\u201d says Bouri. \u201cThe technology is out there. The hard part is adapting the devices to the human gait and the needs of human patients while managing the system\u2019s weight, providing enough torque density for assisted walking and enabling effective control strategies. There are two \u201cdrivers\u201d to consider \u2013 the wearer and the exoskeleton itself \u2013 and they\u2019ve got to operate in synergy.\u201d<\/p>\n<\/p>\n A device for each pathology<\/strong><\/p>\n Bouri\u2019s research group has also teamed up with local neuromuscular research associations to develop exoskeletons specifically for patients with muscular disease. For instance, REHAssist is working with the Swiss muscular disease foundation and the French-speaking Switzerland association for neuromuscular disease to create exoskeletons that enable motorized abduction and adduction movements of the legs \u2013 allowing lateral leg movement \u2013 and assisted movements of the arms, in order to provide partial support while walking and improve balance. \u201cWhat\u2019s important for these associations is to delay the need for a wheelchair for as long as possible,\u201d says Bouri. Doctors have found that people with muscular disease quickly lose the use of their arms, meaning they can\u2019t manipulate an exoskeleton such as TWIICE ONE that involves crutches.<\/p>\n REHAssist is also designing systems to enable sports activities. Engineers have adapted TWIICE so that it can be used for ski mountaineering \u2013 in this case, wearers place a section of their lower leg into a standard ski mountaineering boot. In 2020, a parasport enthusiast was able to practice the sport using this system. Going further, the research group is developing a device for people with no particular pathology but who prefer not to walk for various reasons.<\/p>\n Of all the systems in the pipeline at REHAssist, TWIICE is the furthest along. An eponymous startup is in the process of setting up production facilities.<\/p>\n<\/p>\n Exoskeletons aren\u2019t very complex in terms of design and robotics. The hard part is adapting the devices to the human gait and the needs of human patients while managing the system\u2019s weight, providing enough torque density for assisted walking and enabling effective control strategies.<\/strong><\/p>\n\n