This week my team finished constructing all five of our prototypes for a method of measuring the forearm rotation angle. All five have two separate markers gliding over a central cylinder that are pushed by the rotation of the wrist. The final locations of these two tabs reflects the angle through which the forearm was rotated. Each design approaches this method in a slightly different way. We went through a couple tests to determine which prototype worked the best.

We conducted a test of the force required to rotate the tabs using a spring scale through six trials for each device. One team member held the wrist attachment on an axle while another held the central ring from rotating. The third person pulled down on the device using the spring scale and measured the force needed to begin rotating the device. Our other test was of the precision of each of our prototypes. One team member tested each device five times by measuring his forearm rotation and recording the results. We then found the standard deviation of the results of all five trials to see how consistent each device was.

We used these results to score our prototypes in a Pugh Matrix and found that the internal tab design was the best method for tracking the forearm rotation. The design consists of a small plastic tab contained within a rail and pushed along by a small leg that sticks into the rail.

We spent the second half of Thursday and all of Friday beginning to work on the wrist attachment and the elbow attachment for our device. We hope to complete both of these blocks within the next week or so.