First plunge to AQ with 80cm hex

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Re: First plunge to AQ with 80cm hex

Postby Trnquill » Tue Mar 18, 2014 10:31 am

The oscillation is gone! :) In short, the reason was not AQ firmware as I first suspected, but closed loop RPM mode of ESC32's.

I updated firmware to 6.9 and went out to give it a go. The oscillation was still there, I could see tips of the booms shake ever so slightly up and down. The shivers would come and go, sometimes shaking the whole copter all the way down to camera gimbal. I started to think if there was something else that could cause really fast oscillation and then I suddenly remembered someone saying something about tuning the PID (or PI?) of ESC32 closed loop RPM mode and how you should not start with closed loop mode in a new heli because you end up having multiple un-tuned PID's after each other. It's obviously hard to tune them one by one if all are active at the same time. So, I rushed inside to change ESC32 settings.

I tried first with my laptop running Windows XP but could not connect to the ESC32's. No matter what I did all qGroundControl said was "connected - unknown firmware version" and the settings boxes were left blank. I tried qGC 1.3 RC 1 and 1.3 "official", different USB ports, different baud rates but still nothing. Finally I gave up, fired up my desktop PC (running Windows 7) and was able to connect right away. Any idea why my XP machine could not connect? I was using the same cable and same qGC version both times.

I switched all the ESC32's to open loop mode and went outside. Nice stable humm (the motors actually "humm" since I'm running 380kv motors with 4S batteries, the RPM is nice and slow), no oscillation, no vibration, no "twittering" sound from the motors. Nice! Even the altitude hold got significantly better just by reverting back to open loop mode! Who knew!? I still have a lot of tuning to do with altitude hold, it tends to drop at a steady rate. But not as fast as when the ESC's were in closed loop RPM mode. Why's that?

Overall, 6.9 seems to respond slower to stick input and feels quite sluggish compared to 6.7 (both at default PIDs). I might raise the PIDs for agility a bit, but in general sluggish and slow movement is just good for an AP heli in my opinnion. It's just a tad too sluggish, so minor tuning is in order. :)

Ok, now I can continue building and finalizing the hex and my new brushless camera gimbal. I'll put up some pics as soon as they are ready and tested. :)
Trnquill
 
Posts: 159
Joined: Thu Jun 06, 2013 9:35 am

Re: First plunge to AQ with 80cm hex

Postby Trnquill » Sat Apr 05, 2014 8:09 pm

I grew tired hauling the huge hex around (it barely fit inside my car, even when folded up!) and decided to convert it to Y6. Here's a pic midway, after stripping off the arms and shortening three of them by 8cm:

Image

I was a bit surprised how much loosing three arms lost weight! I weighted the extra parts on the table after putting her back together as Y6 and total was 336g. That's more than 10% weight loss and the frame now weights 2150g with propellers, without batteries and camera gimbal.

I'm a bit embarrased to say I wired the ESCs wrong TWICE before managing to get her lift off the ground! :) Fortunately I was very gentle (and the ground was soft) and I only ended up doing very gentle rolls and flips on the ground because of the faulty wiring. But after the second fix all was wired up allright and I managed to do a tiny hop in the backyard. I'll do proper test flights later, when I have time.

Two things left me wondering:

1) My Futaba S.Bus receiver blinked red light every once in a while very rapidly (at least) before the last test flight. I started moving the antennas around with no effect. Finally I managed to get solid green light after plugging out XBee telemetry transceiver from AQ board. It was still powered but not transmitting. I have never had issues with radio quality, so the coming and going flickering red light gave me shivers! I don't know if I should move the XBee unit further away from receiver or something...

2) There was no logs from any of the test flights/hops from today! Not a single one even though I had the SD card plugged in and I plugged the power on and off like 10 times today. Thinking back the green LED was blinking slowly before arming, so AQ board actually told me it was not logging. I just forgot the slowly blinking green meant that. After seeing there was no logs I plugged the SD card back in and gave it one more go. Suddenly, AQ logged normally!
Trnquill
 
Posts: 159
Joined: Thu Jun 06, 2013 9:35 am

Re: First plunge to AQ with 80cm hex

Postby Trnquill » Sun Apr 06, 2014 12:17 pm

Gave her a go today. She flew kinda nervous and alt hold was loosing it's game every now and then (I even experienced one quite scarey sudden nod & drop in position hold mode), but that's to be expected when running the board in what is effectively a new frame without re-doing the calibso dance. I'll freeze my DIMU-AQ and then put it in this Y6 and go out to try the "tare" function. Can't wait to see how she flies! :)

I had to raise throttle scale factor from 0,5 all the way to 0,65 but that's the only adjustment I did for these test flights.

One question: looking at the logs all four front motors are clipping from start to finish. In the same time the back motors (5 & 6) are not clipping at all. I know my frame is not perfectly balanced BUT she is BACK heavy (because of the unbalanced and back heavy camera gimbal). So, it really baffles me how the front motors can be clipping but not the back motors. Any ideas? I am planning to try 5S instead of 4S and different propellers so clipping does not worry my too much at the moment. But the unevenness of clipping is puzzling!
Trnquill
 
Posts: 159
Joined: Thu Jun 06, 2013 9:35 am

Re: First plunge to AQ with 80cm hex

Postby Trnquill » Sun Apr 06, 2014 2:46 pm

Oh snap! I was just about to freeze the new AQ+DIMU board when I noticed the SD card slot is faulty! It does not lock the card in, just springs it back out again. Comparing the card slots of my two AQ boards I can see the slot in this new card is faulty. There's a tiny silver wire sticking out of the slot, on the left side where there's a metal tab and the spring mechanism. I can't use this board, let's hope Viacopter comes up with a good (and fast!) solution to fix this. :(
Trnquill
 
Posts: 159
Joined: Thu Jun 06, 2013 9:35 am

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