Starfish Project: Performance Tests and Results

Motion Tracking Testing and Results:

Although we could not get movement from all the legs due to several design limitations, we got a high-speed video of a few individual feet moving at 30fps, as displayed in this video link (Click *here* to access link). Using this video, we tracked the movement of a single foot on Kinovea. As seen in Figure [21], the feet moved in a sinusoidal-like fashion, the same pattern seen in a starfish. The peaks represent when the legs were moving the fastest (0.095m/s) and corresponded to when the motor pulled on the strings to pull the leg in the forward direction. The decrease in speed by about 0.08 m/s was the movement of the legs as the string relaxed to its original position, causing the leg to return before its next move. 

Figure 21: Kinovea Result Graph

In this graph, we see a repeating pattern of three movements, the first small peak (0-500ms), is when the string begins to pull the foot, as it starts to reach its full rest position. The large peak (500-1000ms) we see the full torque of the string acting on the foot. This is the time period in which the foot would take the step and the movement we expected/wanted is performed. The third and final movement in each pattern is seen at (2000ms), this is when the string has released enough that the foot starts to move back to initial position but does not fully reset. It is important to note that the foot was not on the table during this testing, but rather the feet were able to swing freely. This could be the cause of the relatively high velocity seen when the foot is moving and in the two separate periods of restoring movement. The full reset occurs at the first peak. In this graph this pattern repeats 4 times in 15000ms. This would mean that the starfish would take approximately 16 full steps in one minute, moving a distance of approximately 2.25 meters in one minute. 

Fashion Tape Adhesion Testing and Results:

In order to determine the adhesion strength of fresh fashion tape we set up an experiment shown in Figure [22]. This experiment determined the adhesion of the fashion tape by increasing the mass of the hanging mass, and therefore the tension of the string, until the fashion tape began to peel away from the surface it was in contact with. We determined that the fashion tape was able to withstand a force of roughly 0.3N before it began to peel away. We determined that this adhesive force was likely too great for our servos to overcome. To overcome this issue we think we could add grease or dust to the fashion tape in order to decrease the adhesion. We recommend testing the adhesion of the fashion tape in both of these conditions in order to determine their efficacy.

Figure 22: Adhesion Experiment Set-Up.

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