Slippage Detection, after successful rescue Options

[garybeau]

Interesting concept - I wonder if such a system could be deployed so as to be far enough away from the ground to not risk being 'ground out' - but close enough to work well.

Could make an interesting science instrument as well actually - partway between PC and MI

Doug

I wasn't too sure how well it would work from several inches away, so I decided to give it a try. I took an optical mouse, removed the existing lens and mounted a lens from a webcam. Getting it focused was a problem because I had no visual feedback, I just kept moving it back and forth and adjusted the focus until the cursor on the screen started to move. It ended up working surprisingly well. I was able to get it work reliably from 3" to 24”. With the mouse in its original configuration, the cursor on the screen would move about 7" for every one inch of movement with the mouse. With the lens attached and held 12" away, the cursor on the screen would move 2" for every 20" I moved the mouse. It seemed pretty repeatable, when I moved the mouse back to it's original position, the cursor ended up back to where it started. The only drawback that I saw was that it took
quite a bit of light to work. This must be due to the high shutter speed (1500 fps)
In conclusion, I think the concept would work well for measuring ground speed. There would be a little variation due to the distance to the ground not at a fixed distance. The beauty of using something like this is you can get real time feedback on your movement and since all the computing is done on the chip you free up the main computer for more important task such as obstacle avoidance and route planning. I think if something like this was ever used on a rover, the best place to put it would be in the belly with a peephole pointing straight down to the ground where it would be protected from the elements. In order to get the light sensitivity up, the frame rate could be slowed way down. Doing a little math, it looks like there was about a 1:63 reduction in speed of the cursor. You could easily bring the frame rate down to 50 - 100 fps, which should increase the light sensitivity significantly. With a little bit of on chip software modification, I'm sure you could get it to output speed and direction instead of x,y position.
I don't think the images would be of much use to anyone. The image sensor is only 18x18 pixels. I'm sure someone at Nasa would want to stitch together a picture 18 pixels high x 6 kilometers long.

Gary