19 - 21 FEBRUARY 2020



Walking with robots - creating a tailored fit exoskeleton with 3D scanning

The R&MM's lower leg exoskeleton with 3D printed interfaces. Image 2: The Artec Eva scans from knee to foot in just ten minutes.

The more you walk with your robot, the faster you are going to recover. That's what the users of lower leg exoskeletons in a select few rehabilitation centres around the world are being told. They are used to help people with paraplegia to walk again, motors generating forces like torque to move the human leg via an interface and spring. But typically, there are problems surrounding fit and comfort which can discourage patients from persevering.

That's where a certain Belgian University Research Group comes in.

"The problem with interfaces in lower leg exoskeletons is that they slip, so the actuation system is trying to provide torque to the leg, and the interface is trying to move the leg, and because the connection isn't perfect, the interface is moving and slipping over the skin without actually moving the leg. This is a problem we wanted to stop," explains Kevin Langlois, of the Free University of Brussels' Robotics & Multibody Mechanics (R&MM) research group. "The way we wanted to do that was instead of interacting with soft tissue; we wanted to interact with bony prominences. This is why we turned to 3D scanning technology."

R&MM, almost a year ago, began using an Artec Eva scanning system as it sought to ditch the 'one-size-fits-all' approach, and focus on tailored fits. It identifies this as a gap in the research already carried out - so far, most research has concerned the actuation and control of the robot. An exoskeleton transfers energy from robot to human, but if the interface does not fit properly, much of that energy is lost, and that also means soft tissues can be damaged and unpleasant burning sensations can compromise comfort. A simple ten-minute 3D scan from the knee down to foot is the first step of a solution that works to solve these issues.

Mesh leg.

With the digital information gathered, R&MM can process the data within the Artec Studio 3D software, design the orthotic, in this case, the interface, to fit the patient, and then proceed to print it on an Ultimaker 3. It's a process said to be much quicker and more cost-effective than the traditional plaster moulding method, and one generating better results too.

It's the enabler for R&MM to set about an exoskeleton that interacts with the bony prominences of the leg: the malleolus, the tibia, and the femoral condyle. These are bony projections at the ankle, shin, and the femur, and by pushing forces through these areas the soft tissue is protected, and a stiffer connection is achieved. It serves to assist people with paraplegia in regaining locomotory capabilities quicker and safer. The exoskeleton R&MM is also developing has an assistance paradigm which can lower its workload as the patient becomes more independent. It will initially provide 120-newton meters of torque - the standard amount a healthy human generates at the ankle when walking - and come down as their walking ability improves.

The Artec Eva scans from knee to foot in just ten minutes.

Langlois is currently adding the finishing touches to the paper that will cover the intricacies of the exoskeleton project and its potential impact. He told TCT he sees robotic devices of this kind being adopted in other settings, away from medical, such as occupations which require heavy lifting. He also highlighted the benefits of having the Artec Eva scanner, of which he believes to have used for only 10 hours in 12 months. Applied intermittently, it is testament to the speed and accuracy of the device, which has been a small cog with a big impact.

"We believe that we have found a way to achieve a stiffer connection to the human body and that way is to interact with bony prominences, and the way you can do that is by using customized solutions using 3D scanning," Langlois says. "The main goal here was to reduce migration which will lead to increased comfort and increased efficiency. Already it's a promising result."

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