I've got twin EasyStars, one with AttoPilot and one with ArduPilot. I had them both out today to begin the process of benchmarking the two autopilots against each other. Two interesting things happened, one scary, the other exhilerating:
1) It's quite windy at our field these days and I've been having trouble with the the current ArduPilot navigation algorithms, so I set out to try various PID settings. I put the EZ in autonomous mode and just started watching it hunt for waypoints, usually ineffectually, while keeping an eye on the ArduStation to diagnose the problem. I kept the plane at a pretty high altitude, and after looking at the screen a bit too long I looked up for the plane and it was gone!
I could still hear the motor, but it was nowhere in sight. I switched it into RTL mode and scanned the skies. Nothing! And the motor got fainter and fainter. Argh! Panicked, I booted up the laptop, switched the Xbee to the Sparkfun adapter and plugged it in, opening up a EVDO wireless Internet connection and loading the ArduStation software to see if I could find the plane on the moving map.
At this point, the plane had been gone for at least ten minutes, and I was sure it had gone out to sea or to another county, but when I called up the moving map, I was delighted to see that it was still in the air, still moving and apparently right overhead! My eight-year-old son started scanning the sky right overhead and with his great eyes he saw it, at a tremendous altitude. Eventually I could see it, too, and I switched to manual, cut the throttle and put it in a dive. A minute later it was landing right in front of us. Whew!
I'm not sure why altitude hold didn't work, but RTL sure did. If we hadn't had the wireless telemetry, I would have assumed the plane was gone and driven off. Many minutes later, it would have gently returned to earth right where we'd been standing. Yay Xbee! BTW, while replaying the video from the flight, I could hear that the RC system was losing its signal really often, with the ESC rebooting and all sorts of scary stuff. I could also hear the 1Hz buzz of interference from the Xbee module. I'm wondering if the Xbee or RF noise from ArduPilot is messing up my RC system. More testing required...
2) I also tested AttoPilot in the other EasyStar. Yesterday's trials had shown that the default gains were way to high for the EZ, so I'd brought them down from the default 10 to 7. Putting it in the air, it was clear that was too high, too, so I brought them down to 5. That turned out to be perfect, and I let it fly circles overhead.
It was eye-opening. Dean has written navigation algorithms that put ours to shame, The EZ didn't just sorta-circle or do random figure eights overhead, it sped around in perfect 100m radius circles, like a protractor. Wow. We've got a lot of work to do to equal that. Next weekend I'm going to have it do the T3 contest, and I think you'll be impressed.
BTW, here's the rest of the UAV fleet that I'll be benchmarking over the next month or two:
1) EasyStar with ArduPilot 2.3 (EM406)
2) Superstar with ArduPilot 2.3 (uBlox 5)
3) EasyStar with AttoPilot 1.8
4) EasyGlider with ArduPilot 2.3 (uBlox 5)
5) Funjet with Paparazzi Tiny 2.1
6) Superstar with UAV DevBoard 2
I've retired the old PicoPilots and my first gen Lego Mindstorms autopilots. I'm also sticking to park flier aircraft, so nothing that I can't hand launch and land in grass for now (that means no Predators or big trainers)