Manual wheelchairs are naturally the most widely used worldwide due to their simplicity, affordability and ease of maintenance. On the other hand, people with more severe mobility limitations who cannot propel manual wheelchairs require motorized models. However, access to this type of wheelchair is limited, as these devices are more expensive to purchase and maintain, including batteries and other components.
With the aim of making motorized wheelchairs more accessible, a team of researchers from the Faculty of Mechanical Engineering (FEM) at Unicamp began a pioneering line of research many years ago. These efforts have now resulted in the creation of a motorization kit for manual wheelchairs, a device whose development has allowed the deposit, with the support and strategy of the Unicamp Innovation Agency (Innovates Unicamp), of three patents. The kit could benefit people who are unable to use manual devices, and could also be used in other sectors, such as, for example, in the motorization of robots to transport objects to hard-to-reach places.
“Our first experiment took place in the 1980s,” says FEM professor Franco Giuseppe Dedini. “At the time, we had contact with professionals from Hospital of Clinics [HC] at Unicamp and we were informed of the case of a woman who needed a wheelchair but could not move it. So, we developed a first version of this technology for the chair, powered by two car batteries, something quite advanced for the time. This was the first step in these long years of research and improvements until we arrived at the adaptable kit.”
Motorization kit
Professor Ludmila Correa de Alkmin e Silva, also from FEM and a member of the research group, adds that the team was concerned with creating a kit that could be easily adapted to manual wheelchairs and that, at the same time, was relatively affordable from an economic point of view. “We always aimed for a generalist system that could be adapted for use by many people, and not for a motorized wheelchair. à la carte , that is, capable of attending only to a particular case”, stated Silva.
According to the researcher, one of the challenges in perfecting the kit was to allow it to be used with the most diverse types of wheels and tires currently found on wheelchairs. There is a wide variety of wheels and tires available, which means that the dynamic behavior of the wheel-floor contact can be changed on a case-by-case basis, which directly influences the programming of the motorized system. “We had to perform numerous simulations on the behavior of the device, as we intended to define the equations and parameters of the contact between the wheel and the floor and insert them into the computer program,” she explained.
These simulations, which aimed to mathematically model the dynamic behavior of the system in each situation, resulted in the filing of one of the three patents provided by the project: the patent for a bench designed to test different types of wheelchair tires in contact with different types of surfaces. When the equipment was put into operation, a mathematical reading of the main parameters involved – force, moment, friction, etc. – was performed, allowing the dynamic modeling of its behavior and the subsequent programming of the motorized system software.
Guided by a joystick
One of the advantages of the device developed by FEM researchers is the ease with which it can be incorporated into various models of manual wheelchairs, as Dedini explains. “The user himself can attach and detach the motorized kit to a manual wheelchair quickly and easily. And the kit does not alter the original characteristics of the chair, which remains foldable.”
Furthermore, the motorized kit provides adequate performance in the most diverse conditions of use. “The management software allows the motorized wheelchair to correctly maneuver tight curves, which require a speed differential between one wheel and another. The system also reduces problems with loss of traction, as the power generated by the motor is transmitted directly to the floor,” said the professor.
To facilitate the operation of the motorized kit, a joystick-guided control panel was added. With this device, the wheelchair became more easily maneuverable. This motorized and joystick-guided assembly corresponds to the second of the three patents deposited with the support of Inova Unicamp and which are available for companies and institutions to license.
Control sensor
A natural evolution of the equipment would consist of serving people unable to handle a joystick, wheelchair users who live with total paralysis of all four limbs.
“To take this step forward, we developed a human-machine interface capable of emitting signals when the user performs some type of muscle contraction. In this case, eyebrow movement would be enough to emit these signals,” said Dedini.
The professor explained how this device works: “We included a sensor in the system that emits a signal when the user performs any type of muscle contraction. The user can attach this sensor to any part of the body to generate the signals. In the case of the kit, one idea is, for example, to use a band on the forehead to interpret the movement of the eyebrow. Based on this movement, the system interprets whether the user wants to click once or twice. This way, commands are sent to the motorized system by moving the eyebrow.”
This assistive human-machine interface device is the third patent filed by the FEM research group with support from Inova Unicamp. In addition to expanding the number of potential users of the motorized kit, the invention may also have other industrial applications. “But our main concern was to serve wheelchair users who cannot use conventional controls, such as joysticks, mice or keyboards,” added Dedini.
Future development
Dedini and Silva said that there are already plans to continue improving the kit with their teams at the Integrated Systems Laboratory (Labsin) at FEM. “We are working on improving several modules of the motorization kit. There are still challenges, such as improving battery consumption or optimizing the trajectory of the motorized wheelchair. We hope to implement these updates to the kit in the future,” said the professor.
The technology developed at Unicamp is available for licensing. More information about the invention can be found at Unicamp Technology Portfolio.
