TWIICE develops the world’s first exoskeleton for ski-touring

[Bobby Marinov]

Since his accident 10 years ago, Martin Loos never had the chance to go ski-touring anymore. His spinal cord injury made him paralyzed from the waist down. When he first discussed with TWIICE, he told the engineers: “I don’t care much about walking again, I get around just fine with my wheelchair. But if your exoskeleton could take me back to the fresh deep snow of the alps, that would be amazing.”

This is how team TWIICE set to the challenge of creating the world’s first exoskeleton for ski-touring. And within one month only. In March 2020 the project was first unveiled, showing Martin’s first steps in 45cm-deep powder snow. Thanks to Martin’s dedication and training, he could achieve new goals and climb the Gornergrat in Zermatt, facing the iconic Matterhorn. Discover the result in the video below:

Martin’s story, ascending the Gornergrat in front of the iconic Matterhorn in Zermatt.

WIITE is a variant of the TWIICE exoskeleton, allowing a person with a complete spinal cord injury to stand up, walk, and most importantly, ski tour. Thanks to its compatibility with standard ski touring boots, it can be worn by the wearer and used in conjunction with mountaineering skis. It then allows its user, despite a complete motor and sensory disability, to practice ski touring.

Who is this version of TWIICE for?

TWIICE WIITE is designed for individuals with so-called functionally complete paraplegia, i.e. who do not have the ability to control their muscles nor perception in the lower body. The user must, however, be able to use the upper body to manipulate the crutches used for balance and control of the exoskeleton. Thanks to its design flexibility and adaptability, the TWIICE exoskeleton can take into account certain user characteristics. These may include, for example, limited joint range of motion as a result of permanent sitting or increased spasticity requiring slower movements. These adaptations are essential to enable a greater proportion of users to benefit from this technology.

How is TWIICE used?

In order to ensure safe and reliable use, the exoskeleton is entirely manually controlled by the user. Each action is triggered by the brief press of an easily accessible trigger on the handles of the crutches held by the user. Other buttons allow the selection of different operating modes, corresponding to the various types of activities. The users’ testimonials attest to a feeling of confidence by this means. This provides greater predictability, which increases the user’s feeling of being in total control of their own limbs. A more autonomous behaviour by the exoskeleton could disrupt this symbiosis.

To check the status of the device, a brief “dashboard” is displayed on the screen of a watch connected to the exoskeleton and worn by the user. This indicates the selected activity, the remaining battery life, or various settings that allow the user to fine-tune the gait to adapt to the terrain in real time.

In the WIITE extension, the gait is designed for ski touring at different levels of slope and elevation. The current movements are adapted for slopes up to 40%. It should be noted that the exoskeleton is only suitable for ascent, the descent being performed on handi-ski for example. The use of the exoskeleton is always done with an accompanying person to assist the wearer whenever necessary. As for any sport, the wearer also wears a helmet as a precautionary measure.

How does TWIICE work?

TWIICE and, in extenso, WIITE is a structure articulated at the hips and knees that supports the torso, thighs and legs. The electric motors move the knees and hips in flexion and extension to reproduce the movements of walking or ski-mountaineering. The batteries, housed in the dorsal part of the device, provide the necessary energy for up to 2 hours of continuous use. Spare batteries, weighing less than one kilogram per set, can be carried in a separate backpack. A dedicated electronic system manages the movements of the exoskeleton by responding to the wearer’s instructions in a reliable and secure manner. Several layers of safety functions prevent the occurrence of dangerous events such as unexpected movements or battery depletion.

What is the difference between TWIICE and WIITE?

WIITE is an extension of TWIICE to expand the range of application possibilities to ski touring for people with a complete spinal cord injury. The core of the device is identical, allowing the components to be reused. For example, motors, batteries and electronics are kept between the two applications. As for each version of TWIICE, the morphology of the device is precisely customized to each user’s morphology for more comfort and maximized safety. Some parts have also been adapted to allow the device to be attached to standard ski boots.

Where did the idea for the WIITE project for ski touring come from?

TWIICE’s development philosophy is to listen and try to respond to the specific wishes of people with disabilities. Martin has always been passionate about mountaineering. However, his accident has not dampened his passion for the mountains. Also attracted by the engineering he is studying in Yverdon, it is through his father Roland, a graduate of EPFL, that he came to contact the project’s engineers.

During an initial discussion, his wish quickly became clear: ” For daily commuting in the city, my chair is a simple and sufficient solution. What would be great, however, would be to be able to ski tour again and return to that place dear to my heart, which is inaccessible in a chair”. Determined, Martin has had to adapt his winter sports for several years now. He can ski down the slopes perfectly with his handi-ski and has even taken part in group hiking excursions. But to go up, the need to be hoisted by his fellow climbers tainted his sense of freedom. “I would love to simply be standing on the snow without having the ground at my fingertips, while sitting on my handi-ski,” he says. A year later he challenged the designers with the fulfilled ambition to create his own trail in the powder snow.

How did the project come about?

Funded in part thanks to the support of the project’s technical partners, the development project was completed in record time, i.e. in one month, including the design and custom manufacturing of the adapted parts. By the third training session, Martin was already able to walk with the exoskeleton, skis on his feet, on the snowy Diablerets slope where he had learned everything as a child. It took him a little over a dozen sessions to reach the current level, requiring almost no external intervention.

In terms of technological partnerships, the motor manufacturer Sonceboz, based in the Bernese Jura, supplied the high-performance electric motors capable of developing high torque in a very compact volume. These components, the result of close collaboration between the REHAssist group at EPFL and the Jura mechatronics leader, are reused between the different exoskeletons of the TWIICE family, allowing for a rationalization of design efforts and production costs. The company Fischer Connectors, based in St-Prex and also sponsoring the project, has made available a custom-made version of the electrical connectors integrated in the exoskeleton. Their lightness and robustness are major assets for such a demanding application.

More recently, the closing of a strategic partnership with Bâloise Insurance and the support of the Fondation Avenir Plus have given the project a new turn. The newly founded startup is determined to make this product accessible to people who need it. The commercialization is planned for 2022, with a new service model, allowing affordable technology through resource sharing.

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