At the RehaCare trade fair in September 2022, the Fraunhofer Institute for Manufacturing Engineering and Automation IPA presented so-called exoskeletons, which have so far been used primarily in industrial settings. They support people there during physically strenuous work, prevent incorrect posture and are thus intended to relieve muscles and joints. In the future, they could increasingly become an aid for people with certain physical disabilities, says Urban Daub, group leader of the Applied Biomechanics Research Group at the Fraunhofer Institute. Interview.
Mr. Daub, the term "exoskeleton" sounds somewhat technical to laypeople. What is behind it?
An exoskeleton is an assistance system that is worn directly on the body. It relieves the musculoskeletal system by providing additional power support. Our muscles and joints are designed for dynamic movements, such as walking. But if someone has to repeatedly lift heavy loads or keep the musculoskeletal system in an almost motionless position for a long time, the muscles can quickly become exhausted. This can be a risk for injury. Exoskeletons counteract this.
Where does this power assistance come from? Are exoskeletons powered by a motor?
Sometimes yes, sometimes no, there are passive and active systems. The most widely used industrial exoskeletons work passively. They have springs or expanders that are under mechanical tension and release their energy during certain body postures. As a result, they automatically add power during certain movements that would otherwise have to be provided by the muscles in the body alone. Certain areas of the body are thus specifically supported and relieved. There are other differences in this category; some systems have hard shells, for example, while some consist almost entirely of elastic bands and supports. The latter are the so-called soft exoskeletons or - this is the international term - "exosuits". However, there are also increasingly active systems that are electrically powered.
When does which system make sense?
It depends. If technical measures or a change in work processes are no longer sufficient to sufficiently relieve a person at work, exoskeletons can be a good additional option, whether active or passive. Active exoskeletons can be very useful, however, especially if a higher level of force is required for a job or if the support needed varies from person to person. This is because the exoskeleton can be adjusted much more precisely to the needs of the person or a specific activity. If, for example, weights vary greatly, i.e. packages weighing between two and 25 kilograms have to be moved, the support provided by active systems can be adjusted accordingly. Incidentally, part of our research is also very intensively concerned with such requirements.
You say that exoskeletons always support specific areas of the body. So there are different variants depending on whether someone works more with their arms or more from their legs, for example?
Yes, although most exoskeletons are designed to keep the upper body straight and upright - these are the "back exos" - or to take the load off the arms during overhead activities, these are the "shoulder exos". There are also systems for the neck, thumb or hand strength.
What kind of work do the back and shoulder systems support?
The systems for the back are used when heavy components or containers have to be lifted or put down, or when someone has to work in a forward-leaning posture for a longer period of time. A typical field of application for back exos is, for example, logistics, as already explained with the active systems: there, people often and frequently have to lift and carry heavy packages. The shoulder exoskeletons, in turn, help with activities in which the arms are held up for a long time, for example during assembly or welding work. (→ see video).
When is an exoskeleton considered "successful", and what all does it have to fulfill for this?
Users would say that the exoskeleton should weigh as little as possible, not be noticeable when worn, not be restrictive, and still provide as much support as possible. That sounds like the proverbial "egg-laying pillow" that has yet to be invented. Of course, this cannot be implemented so perfectly for technical reasons - so a few compromises are always necessary. That's why there are currently more than 100 different exoskeletons on the market: None of them is perfect in every respect, but each one solves very specific problems and applications very well for certain users. This in turn means that the most suitable exoskeleton must be found in each case.
So exoskeletons already exist in many different versions and for almost every application. Couldn't they then also be interesting for people for whom it is less a matter of preventing injuries, but for whom the supporting function is in the foreground - in other words, for people with a physical disability?
That is a very good thought. Exoskeletons could actually support people with disabilities in their working lives, sometimes even enabling them to participate in the first place. The exoskeleton manufacturers have also recognized this, i.e. that there is a completely different opportunity in the systems outside of industrial application. In my opinion, people with acquired or congenital physical disabilities could certainly benefit greatly from this in the future - and in some cases either be able to work again at all or be able to do so more easily.
Do you know of an example where this is already the case?
Yes, at the Rehacare fair we had a presentation in our symposium "Technical Assistance and Vocational Rehabilitation", which was about a museum employee who has a neurological disease. His job is to make scissors in the traditional way. In the museum business, the machines used for this are listed. Technical adaptations to them to make his work easier are therefore out of the question. For more than a year now, he has been using an exoskeleton in his work that supports his hand and thus helps him to compensate for the neurologically induced lack of strength. According to him, this enables him to perform his work better, longer and, above all, without pain. The museum thus retains a valuable employee - and he himself can continue to do his job.