Exo controller circuit cleaned up in new project box with new FSR trigger on walker handle

I’ve finished cleaning up the exo controller circuit, moving it from the breadboard to an Arduino proto shield. It also lives in a new project box (as seen above, positioned on top of the walker). The gray mini-din cable coming out of the side of the box through a mini-din panel mount port connects to the hip joint servo motor for communication.

To the right in the picture above is a new force sensitive resistor (the tab leads on the previous one wore off).

Here’s a broader shot of the walker and exo brace together:

Walker with exo controller in new enclosure

The goal of transferring the exo circuit away from the breadboard was to be able to test more thoroughly which I did do last night. I have some more video of the testing that I’m hoping to get up on YouTube and here soon. In getting the chance to test the device while walking last night, a few  thoughts struck me that I plan to further explore:

  • It seems that the actuation of the hip joint could be smoother and more effective by altering the design a bit. When the actuation occurs, there seems to be resistance as the knee rises. This is natural of course because of gravity but it seems that the device and the leg buckle also causing increased resistance. As the hip joint angle changes so does the distance from the top of the upper leg segment of the brace to the location of the leg. In other words, adding some sort of flexibility to the piece of the brace that straps to the upper leg might make the actuation more effective. One thought is putting the connection on a slider (i.e. a desk drawer sliding mechanism) so as the angle changes the upper leg could still be pulled up but where exactly the brace segment is attached to the thigh could change
  • The current thigh portion of the brace is somewhat of a longer segment that spans upwards of a foot along the thigh with two straps and rigid plastic behind this segment. In thinking about the above problem, it may be that this segment could be designed better perhaps so there is a strap further down right above the knee and another strap further up the thigh and not the larger plastic segment connecting the two.
  • The idea of incorporating should straps to the device as well as maybe a rigid back section keeps popping into my mind. Doing so would definitely offload some of the weight of the brace more effectively. As the device is worn right now the weight of it definitely adds strain over time which would be even more of any issue for users that are already weak in the lower body. Adding the back support would also add rigidity to the hip joint actuation and may in turn increase efficiency.
  • Knee joint articulation is necessary at this point. I’d like to try a purely mechanical approach to this harnessing the power of the hip joint servo as a way to keep the cost and weight down. We’ll see how well that turns out

Rehabilitation hip brace that I bought on eBay for $40

I mentioned in my last post that one  of the major challenges has been connecting the device to the body. It needs to be comfortable yet rigid. Thinking that using molded plastic to better make that connection would be a good approach, I scored this great hip brace off of eBay for $40. It has a molded plastic piece that goes around the waist and cinches with a Velcro strap. That top piece then has molded plastic hip cups or guards which, so far in testing with it, seem to keep the brace quite rigid on the body. It’s much better than just using the strapping as I was doing in the first prototype.

Here’s another pic of the back of the brace:

Back of Rehab Hip Brace

Now the question is how to mount the motor to the brace. I took the brace hinge apart to see what I might be able to reuse of that but I haven’t come up with anything concrete yet although I have a couple of ideas. I’ll post back here with my progress.

© 2011 OpenExo Suffusion theme by Sayontan Sinha