Continuing from Soft-Robotic Exoskeleton…
With the new and exciting idea at hand we also suddenly had quite a few assumptions to verify before the project could be assumed to have any sort of potential. This provided a great risk of running into a dead-end quickly after initiating the project.
In order to lower our risk a little I decided to do a preliminary study of the concept alone, prior to the actual mid-term project starting. This fitted nicely with the 3-week semester part in January.
As one of the great benefits of DTU all students are able to walk up to any professor and ask if they could be interesting in starting a course teaching a particular topic. These kind of custom courses can be started by anyone as long as there is someone who can and will supervise you and that the topic is found to fit into your studies.
By chance I heard about DTU Playware and that they were working with rehabilitation. I got in touch with David Johan Christensen who is associate professor at DTU, formerly at MIT Media Labs, and having worked a lot with robotics. I told him about my idea and he agreed to supervise my project, and eventually also supervise the bigger mid-term project if we wanted. Due to past experience with my supervisor from the 3D-printed animatronic head, David Bue Pedersen, I also asked him if he wanted to supervise and eventually we ended up with two super cool supervisors, both for my individual 3-Week course and for the mid-term team-project.
Talking to David Johan Christensen, it turned out that Center for Playware had recently initiated a collaboration with Center for Spinal Cord Injury at Glostrup Hospital, Denmark. They were already using exoskeletons for rehabilitation and it seemed the timing was just perfect.
We arranged that I should prepare a presentation for the Hospital for the beginning of my course. On the first day of the 3-week course we went to visit the Center for Spinal Cord Injury and I presented my idea. They were super excited about it and suddenly the project had funding!
The 3 weeks progress super fast, I was busy busy testing all sorts of things, hacking and having a really good time! Starting out with balloons, caulking guns and bicycle valves:
Nope.. wasn’t a good idea
Testing the straightening-force of a long balloon. None… 
Building the valve for easier handling and using less hands for holding on to everything:
Valve assembly: Bicycle valve, caulking-gun-tip, a balloon and a random piece of rubber tubing
Valve assembled
and eventually ending up with braided cable-routing tube surrounding a bicycle tube.
By inflating the inside tube, the diameter would expand, påushing out on the braided tube which contracts in length, when the diameter increases. In this way I made a linear pneumatic actuator.
Eventually it turned out that such actuator already existed and was called a McKibben-type Pneumatic Artificial Muscle. Good thing, then the concept was approved of and I continued in that direction.
The main challenge for me was to figure out whether the concept could provide enough lifting power to lift an arm, and how to approach reaching such forces. In the end I found a solution that seemed to work and I wrote a report on all my findings.
At the date of writing: Sadly, but also quite nicely, I cannot publish the report just yet as we are currently playing around with a potential patent for some of our recent findings. It is still very uncertain whether we will proceed with it or not, but to be safe, I’d rather say too little than too much right now.
However, it is the plan that we wrap up the project with an article, which will hopefully be fully published somewhere. More info will appear on this blog eventually 🙂
…To be continued in part 3, the mid-term project
Jakob Welner 