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Biomedical engineering

Enhanced mobility

System will enable the severely paralyzed to drive a wheelchair with their facial muscles

An indispensable part of the lives of people with impaired mobility, the wheelchair has evolved a great deal in the past decades. At first, the only models observed on the streets were hand-powered. These days, joystick-controlled motorized chairs are a common sight. Now, a team of researchers at the Federal University of Uberlândia (UFU), in partnership with colleagues from the University of Lorraine in France and in parallel with other research groups around the world, are trying to raise this means of locomotion to a new technological level.

The team is developing a system that will enable users to control and command a wheelchair using the electrical signals generated by their muscles and brain activity, as an option for people with forms of paralysis so severe that they cannot even move a joystick.

The Brazilian group, headed by engineer Alcimar Barbosa Soares at UFU’s Biomedical Engineering Laboratory, is working to define the technologies that will be applied in detecting and processing the muscular or neural control signals. They are also building virtual and augmented reality environments. The French are developing controls and navigation for the new “smart” wheelchairs, and they are collaborating with the UFU researchers to create virtual systems to be used for training.

According to Yann Morere from the University of Lorraine, the main advantage in the partnership is that it brings together complementary skills. “The people at UFU are experts in acquiring and analyzing human signals, and doing so in virtual and augmented reality,” he says. “Our specialties are wheelchairs, communication devices, mobile robotics and assistive technology.”

Soares says that when the work began, they had to choose the best way to develop a chair with the specifications and potential applications that the project requires. Should they build a chair from scratch or use a commercially available model? Their choice, with a view towards easier technology transfer, was to use an available chair with a higher number of sensors and systems that could meet the team’s preliminary requirements.

The initial studies that paved the way for the project began four years ago as a spin-off from a partnership between the Brazilian and French research groups for developing augmented communication technologies for people with neuromotor disabilities. The European group provides support in alternative communication, mobility, accessibility, and cognitive domains, for example.

Soares says that back then, the two groups started a project to enable patients with late-stage amyotrophic lateral sclerosis (ALS) — who had lost practically all motor control, including speech — to communicate using specially designed software. British physicist Stephen Hawking is a well-known sufferer of this degenerative disease that gradually paralyzes every muscle in the body. The project was funded by the Coordinating Agency for the Improvement of Higher Education Personnel (Capes) and by the French Committee for the Evaluation of Academic and Scientific Cooperation with Brazil (Cofecub, according to the French acronym for Comité Français d’Evaluation de la Coopération Universitaire avec le Brésil).

Safe navigation
Developing control systems for wheelchairs in order to improve the lives of these patients was a natural sequel to the groups’ initial research. “Our goal now is to create a locomotion device with enough on-board intelligence to allow it to be controlled by the brain or by neuromuscular commands, and navigated safely and effectively,” says Soares. “We hope to have the first neuromuscularly controlled equipment available for patients in about two or three years.”

At this initial stage, the idea is to have users control their wheelchairs through the electrical signals generated by their facial muscle movements. Later, the research will move toward brainwave-mediated control. The first step is to find a muscle in the severely paralyzed person that still retains minimal function, that is, which is still able to contract, even if only weakly. “Then we put surface sensors on that region and they capture signals from the electrical activity associated with the muscle’s contraction,” Soares explains. “These signals are sent to a computer to be processed and transformed into a command for the wheelchair.”

Muscles in action
For people with cerebral palsy, or patients with late-stage ALS but who still have functional facial muscles, a number of commands can be programmed. “Biting down with both masseters [the cheek muscles used to for chewing] can represent an order for the chair to move forward,” Soares exemplifies. “Biting down more strongly on the left side can mean that the chair should turn left. And so on.”

For this to occur, the patient must be trained to master these commands. “We’re also developing virtual and augmented reality systems — a mix of real images and virtual objects — that will allow the real wheelchair to be operated in a virtual, and therefore safer, environment,” Soares reveals. “Sensors connected to the users’ skin capture their neuromuscular commands, which are then transmitted to control the wheelchair.”

Electrodes connected to the patient’s body in a room in Brazil capture the signals, which are processed and transformed into commands and uploaded via the internet to the laboratory in France. There, they are transformed into control signals for the real wheelchair, which moves by itself around the laboratory. “The chair, in turn, is equipped with cameras that capture the images, which are transmitted to Brazil and shown on a computer screen in front of the patient or through special 3D glasses,” Soares explains. “This way, users can feel like they are moving around in the French laboratory, as if they are really there.”

Morere says that they also intend to establish usage parameters custom-tailored to each user, such as maximum speed and acceleration, the dead zone around the joystick’s central position, and delayed start-up. “We also want to try out new functionalities that are completely safe, but that don’t have the limitations of the heavy materials used in smart-wheelchair prototypes.”

Although a great many people worldwide suffer from motor disabilities severe enough to impede locomotion and even the use of conventional wheelchairs, the two research groups have not yet assessed the potential market for the equipment they are developing. But their work will continue nonetheless. They have already completed tests with one volunteer and the results were encouraging. “At this time, we have strong expertise in the development of control systems based on neuromuscular control,” says Soares. “We are now starting research aimed at developing brain-computer interfaces that will enable ‘mental’ control over the equipment’s navigation.”