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Apr 17, 2013, 01:31 AM
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webcam vision busted

After much fabrication & debugging, webcam vision was busted again. Machine vision in ambient light is a high shutter speed affair. Monocopters need a high frame rate to reconstruct an oval from a high shutter speed. The webcams aren't fast enough to do it in ambient light, although they could do slow shutter speed tracking in total darkness.

Since it was about a common vision system for all vehicles, that eliminated webcams from any vehicle. For the low frame rate vehicles, the boardcams can still do 640x240 to get the same depth perception as a webcam. 640x240 wasn't possible for the raspberry pi, but is possible for a PC.

1 week of development was necessary to discover what wouldn't work. A far cry from simply recompiling the board cam code, the code which worked in January suddenly can't fly anymore.

The ground based autopilot is a 7 year old ocean of benign bugs, like why does video only come in at 40fps if the beacon rate is 25Hz? Why is the current position scale way off? Why does target altitude get offset after takeoff? Why does the pitch detection sometimes invert or show a blob at 0,0? They have no bearing on why it doesn't fly.

In the single board computer sighting department, it's a credit card sized quad core 1.7Ghz

For all the attention arducopter is giving to augmenting GPS with the accelerometer, extremely tight vibration isolation, & extermely tight PID calibration, that solution only appears to work in the absolute deadest weather. The more practical way to get the last bit of stability is machine vision. These 1.7Ghz ARMs can get really good results from downward optical flow.

There's been an explosion in single board computer ventures.

Everyone wants to quit their day jobs, maybe get a huge venture capitol investment. Few will become the next Chris Anderson. The bad experience with the raspberry pi predicts similar disappointment with the other ventures. The quad core 1.7Ghz from Korea especially doesn't add up. Those quad core ARMs usually only do 1.7Ghz in single core mode, then downscale to 1.3Ghz or worse in quad core mode. Then your power supply has to be spot on, minimum ripple.
Last edited by Jack Crossfire; Apr 17, 2013 at 04:52 AM.
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