maxon Story

Technical assistance systems: High-tech and sport combined

TU Berlin RISE Exoskelett Copyright Christian Kielmann 20240229-5436TU Berlin RISE Exoskelett Copyright Christian Kielmann 20240229-5430

The Cybathlon 2024 is just around the corner and the newcomer team RISE from the Technical University of Berlin is working flat out to finalize its exoskeleton for paraplegics: a current look at the progress, challenges and cooperation with partners.

Normally, field hockey players chase the puck across the ice in the Swiss Arena in Kloten, Canton Zurich in Switzerland. But from October 25 to 27, it will once again be transformed into a center for technological innovation: the Cybathlon 2024 is coming up.

At the international competition organized by ETH Zurich, people with physical disabilities will compete in disciplines relevant to everyday life, supported by high-tech assistance systems. 77 teams from all over the world have registered this year. The RISE (Research and Innovation in Student Exoskeleton Development) team from the Technische Universität (TU) Berlin is competing for the first time with its exoskeleton.

140 students involved in the exoskeleton

"The Cybathlon was always the dream! In October 2022, together with the student initiative 'Socially Engaged Engineers', we launched RISE as a practical module at TU Berlin to enable people with spinal cord injuries to stand up and walk," says Lukas Schneidewind. He is team leader and research assistant at the Department of Medical Technology at the Institute of Machine Design and Systems Engineering at TU Berlin.

A total of 140 students worked enthusiastically over four semesters on the development and construction of a robotic exoskeleton. The majority of the members come from engineering disciplines such as mechanical engineering, electrical engineering and electronics as well as control engineering and simulation. However, non-technical knowledge is also in demand: from biomechanics to user interface and user experience, design, psychological aspects, sponsorship acquisition and public relations.

"Transdisciplinary work is enriching"

"The project workshop allows us to break out of the very focused teaching environment at university and work in a transdisciplinary way - just like later in our professional lives," says Magnus Meyer, co-leader of the RISE team and Human Factors Master's student at TU Berlin.

Interdisciplinary thinking is relevant in the case of the exoskeleton for another reason: after all, the human is directly connected to the machine. Meyer describes the interaction with the paraplegic pilots as a highlight, as the team receives direct feedback on the user-friendliness and practicability of its development.

Direct human-machine interaction

In discussions with companies and potential partners from industry, the students quickly realized how diverse the field of exoskeleton applications is. "Many people often associate exoskeletons with making work easier, for example to relieve the backs of employees on production lines, which follow the movements of the user," says Magnus Meyer.

Meyer continues: "In our case, however, it not only provides relief, but as a powered orthosis it completely replaces the muscle strength of the legs (hip, knee and ankle muscles) and guides the limbs in an ergonomic movement." Lukas Schneidewind adds: "The fact that the technical requirements for such a system, which is used to mobilize paraplegics, are very different from other systems was and still is a major communication challenge."

Another challenge for the RISE team is to constantly update the appropriate technical requirements for the system with the findings from the training sessions. In order to optimally reproduce the natural walking movement with an exoskeleton and to be able to control the center of gravity when walking, appropriately flat gears and motors are needed that lie close to the body.

Special requirements for the technology

The students therefore installed brushless EC frameless Dynamique torque drives in sizes 65 and 85 mm from maxon in the hip and knee joints. The BLDC motor kits with internal rotor technology were specially developed for so-called robot joints, i.e. joints in the robotics environment.

They are particularly powerful, robust and compact. "We deliver these new drives without ball bearings; the user stores the rotor and stator unit themselves," says Falko Simon, Area Sales Manager at maxon. He adds: "The drive also achieves high torques of up to 300 Nm, which is required for short periods when people are kneeling or climbing high steps. This makes it perfect for use in the Cybathlon."

Another special feature is that the maxon motors and the gearheads from the manufacturer Ovalo, a subsidiary of Nabtesco Europe, form a single unit. Falko Simon: "The gearboxes have a so-called pancake shape and we have integrated our DT drives into the gearboxes. The whole thing is virtually one product, which means we have created an extremely flat unit." Thanks to the open and collaborative atmosphere, it was possible to find pragmatic solutions within just a few weeks, says Lukas Schneidewind. Falko Simon adds: "The students were also very eager to learn about our expertise as an industrial partner, which was fun."

Future prospects: crutch-free exoskeleton

The students are currently in the final stages of implementing the software and adapting the individual movement patterns before the final training sessions with the two pilots for the Cybathlon begin. Looking to the future, team leader Schneidewind already has specific goals: "We now have an initial basis, but in the long term we can definitely still downsize. At around 80 kilograms, the exoskeleton is currently a very heavy system, but it can climb a high step effortlessly, for example. Existing systems cannot do this without holding on tightly. Working without crutches is the big goal."

But for now, the team is looking forward to the Cybathlon. "If we can complete some of the tasks, we will have already achieved a huge success - and that within two years, whereas other teams have been at it for over ten years."

Image Copyrights: Christian Kielmann

Author: Nora Nuissl

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