IEEE Robotics & Automation Magazine - December 2017 - 118

Figure 1. The training for the Cybathlon. The VariLeg pilot Philip Wipfli had to learn how
to walk with an exoskeleton after training in basic skills like standing up, sitting down,
balancing while standing upright, and walking. The pilot also trained in more advanced
tasks, such as climbing stairs or walking a slalom. (Photo courtesy of the Swiss Federal
Institute of Technology in Zürich, Switzerland.)

The variable-stiffness actuation system is inspired by the capability of
human legs to vary their mechanical
properties, thought to be critical to
robust and versatile walking. This key
challenge was addressed by two consecutive student projects over two
years, and, even though the final prototype was only ready about five months
before the competition, we were able to
participate in the Cybathlon, which
made us very proud. Our pilots were
challenged with learning how to stand
and walk with the exoskeleton and with
employing their optimal capacity while
managing the shortcomings of a research prototype. Participation in the
competition was only possible through
an intensive training with three sessions a week, thanks to the great motivation, patience, and endurance of our
pilots (see Figure 1).
RAM: How was the team put together?
Schrade: The team was composed
of ten ETH students, studying mechanical engineering, electrical engineering, or health science and technology,
who applied for this challenging project as a practical semester program
offered in the final part of ETH Zürich's
bachelor's degree curriculum. The
team was coached by researchers
from the Rehabilitation Engineering
Laboratory and the Product Development Group Zürich. Our two prospective pilots were very excited to be
part of the team and to embark on
the Cybathlon adventure with us. We
met one of the pilots at an exhibition for rehabilitation technology,
where the VariLeg project was presented, and the second pilot was contacted through the personal network
of team members.

Figure 2. The pilot Philipp Wipfli crossing the tilted path obstacle at Cybathlon
2016 with the VariLeg exoskeleton. (Photo courtesy of the Swiss Federal Institute of
Technology in Zürich, Switzerland.)

Schrade: Two years before the Cybathlon, when we decided that we would
like to participate, we had no experience
in building powered lower-limb exoskeletons for people who are paraplegic.
There was no prototype that we could
118

IEEE ROBOTICS & AUTOMATION MAGAZINE

build our design on. Additionally, we
wanted an innovative solution for our
exoskeleton. We decided to include a
novel actuation system that could later
be used for research purposes. Hence,
the VariLeg concept was born.

DECEMBER 2017

RAM: What was the impact on your
pilot?
Schrade: Both pilots were excited
to participate in the competition and
to advertise the need to improve technology that can benefit people with a
spinal cord injury. They also appreciated being part of the development
team and sharing their feedback on
possible improvements for the device.

Table of Contents for the Digital Edition of IEEE Robotics & Automation Magazine - December 2017