The past two weeks at the Columbia Robotics Lab we’ve built a mini version of our differential-drive base. It works pretty smoothly, and it’s a nice design touch because it compacts two degrees of freedom into one mechanism. However, it might be too complex of a system and cable-driven mechanisms can grow more unreliable with time as the cables stretch — and self-tensioning cables might be too much. Sometimes it’s better to follow the K.I.S.S. motto. We’ll see how it works out on the larger scale. I’ve also been CADing a lot of the arm, getting the exact specs down so we can start ordering parts — in fact, the project just received a National Science Foundation grant, which is great news. Now we have a bit more leeway, whereas before we had a limited budget. One way to make good use of the NSF grant is to simply make or buy a pricey arm, but this could defeat the purposes of the project (i.e. creating an inexpensive arm that people can actually purchase reasonably). We might still purchase an arm, but another good use of the grant might be to allow us to create more prototypes as we refine the design. I think going through multiple “drafts” of a design, like drafts of a piece of writing, is always an important part of the process.
Today I went on a “field trip” from the Robotic Lab to the wheelchair clinic near 168th St. It was a fun excursion — my team and I got to ride around on an electric wheelchair, gather specs, and ask doctors questions about what kind of activities an arm like ours will need to perform for paraplegics and other potential users. This will help finalize the design of the robot in terms of its reach and its strength. We’ll also be able to think about how best to create a mounting system for the arm which is adjustable to work on most electric wheelchairs — this will be the next focus in the project as we prepare to order parts. In fact, a similar project to ours, Kinova’s JACO arm, just opened a new site. The video is neat and worth a look. We’ll be in contact with the wheelchair clinic and revisiting in the future as we complete designs and build our prototypes.