The device has little in common with the leg presses you see in gyms. Of course there is a seat and two pedals, but that is where the similarities end. Taking a seat on the Allegro (for Adaptive Leg Robot) means entering into the care of a unique, soft-robotic training partner. It is equipped with state-of-the-art industrial drive and safety components and a learning computer system. Human and machine work closely together – with astonishing results.
A pneumatic muscle is the core
Allegro is the brainchild of robotics experts Max Lungarella and Raja Dravid, founders of the company Dynamic Devices AG. They developed the first Allegro prototype in 2007 at the Artificial Intelligence Laboratory at the University of Zurich.
Their goal was to build a high-tech device for athletes, a highly dynamic machine that monitors and analyzes all workout sessions and makes suggestions for the next exercise. The core of the device is a pneumatic muscle that is able to deliver large forces to the pedals very quickly. This enables the machine to be used for a variety of challenging exercises.
Example: By pressing or pulling in with their legs, the user has to stay close to a line displayed on the screen. At the same time, the computer amplifies the effective forces, either gently or in the form of impacts. The user has to compensate these forces continuously, which is demanding but extremely effective. Not just the body is trained, but also the brain. “Our system supports this kind of dynamic interaction”, says Max Lungarella. The concept works even better than the two developers had at first imagined.
More or less by chance, the two discovered that their training system had great effects on patients with neuro-muscular disorders or orthopedic conditions. On the Allegro machine, a number of patients were able to move their legs again in ways that didn't seem possible. Stroke patients also made great progress in the restoration of their motor skills. These effects have now been corroborated in studies – a fact that motivated the developers of the soft-robotic training device to focus primarily on rehabilitation. This is where maxon motors enter the stage.
In order to certify the Allegro as a medical device, it needed a critical safety feature: an adjustable stop that prevents the press from going past a certain angle. This is to protect the patient, especially those who are no longer able to fully bend their knees. A brushless EC 45 DC motor takes care of the individual positioning of the safety stop. Absolute reliability is an important, if not the most vital criteria for the drive. “With a maxon motor, we can be certain that this requirement is being fulfilled”, says Lungarella. Other important points include the compact design and integrated electronics of the flat motor.
Successful combination of drive and controller
Another maxon flat motor, an EC 90 with an outside rotor, is in charge of automatic seat positioning. Dynamic Devices combined the brushless motor with a planetary drive and an ESCON 50/5 servo controller. maxon drives are a key component of this training device, providing comfort and safety to the patient.
Success through a playful approach
Despite being a relatively new company, Dynamic Devices has achieved considerable success. Engineers, scientists, physicians, and therapists have collaborated to create a training device that gives many patients new hope for an improvement of their motor abilities. The decisive factor is the training aspect, which was traditionally relegated to a relatively minor role in rehabilitation therapy. If you sit down on the Allegro, you can expect to be challenged. If users are motivated to become better and score higher, their performance improves faster. Motivation is important, and that is why Dynamic Devices focuses on a playful approach. When patients use the pedals to control a simulated penguin sliding down a hill on its belly, trying to score as high as possible, they almost forget about the physical effort.
Some hospitals and rehabilitation centers are already using the new robotics-based training with more soon to follow. The next step is an expansion into the entire Eurozone. In addition, Max Lungarella and Raja Dravid are working to make their soft-robotic training device even more intelligent.