Blogs

So the equatorial mount naturally avoided gimbal lock without any crazy rules.  The mane question is if it's fast enough.  The takeoff move is so fast, it's not likely to keep up.  The alt/az was far enough away to not need to be fast.

So the solution to the equatorial to spherical transformation was once again a quaternion rotation, just like the inertial navigation.  You can invest a lot of effort into a discrete cosine transform, but the quaternion is intuitive.  Then, the position calculation was the same as the alt/az mount rotated on its side.

After another round of bug tracking, the USB ports on the laptop's right side turned out to not support the webcam, while the USB port on the left side was the only one that worked.  It was full blown lack of packets, even in isochronous mode.  Yet another fine point to remember.


Webcam failure
Vision could always be counted on to hit another failure point.  So the problem is the ND filter makes everything look red.  It could handle old 100W CFL's, but the new 100W CFL's pointed at the camera showed up as red & the 150W CFL's flooded it red.  More tweeking or abandonment is required.  A full range search with a known red marker might be required.  Vision is an absolutely horrid, complete bodge.

So Marcy 2 would capture video, but only fly in a dark room or a room with only lights pointed away, which defeats the purpose of capturing video. It would be as practical as a vicon copter capturing IR video.

Board cam.
The board cam with maximum shutter speed does a better job, but won't get the required smearing without its own ND filter, turning everything red.

There are more techniques, like requiring the blob to be a square or rectangle.  Marcy 2 will require certain conditions, like not pointing lights at the camera & only flying indoors, away from windows or vicon cameras.

By the time sonar made its last appearance

http://www.rcgroups.com/forums/showthread.php?t=1069292

it was really solid.  Its only problems of note were related to Marcy 1 being too unstable to stay in the sonar's limited range & no way of pointing the transmitter straight down.

Modern Marcy aircraft are so stable, they may work.  Modern, centrifugal mounting may get it pointed straight down.  It would be a lot cheaper than vision.  A dedicated sonar system, with dedicated radios & micros might do it.  The servos & fabrication make vision real expensive.

The PIC wasn't fast enough to do the required sampling rate, so it had a lot of aliasing & crosstalk.  The op-amps didn't have a high enough frequency range.  Doing the processing on a PC added a lot of latency.

Sonar using high quality, discrete preamps, a dedicated radio with no latency, all the processing done in microcontrollers & a fast ARM on the ground might outdo vision in cost & range.  It would solve the problem of takeoff being out of vision range.

In the sonar department, the STM32F4 is so expensive, a completely analog solution with PIC for purely timing is more attractive.  It was using a comb filter, integral, smoothing & short term maximum in software.

A reasonably priced analog circuit could only do a threshold & rely on the transducer's narrow band rejection.  The blog posts showed a lot of aliasing & background noise.  The PIC would have to set the threshold based on the false positives between pulses & time the threshold crossings, but it couldn't sample the waveform.

It might work, because the low sample rate & crosstalk were the mane problems.  The comb filter made it more directional.