I finally bit the bullet and ordered the 3DR kit. #excited
I should preface all of this with the fact that I'm not a hardware guy, software guy, r/c guy, hax0r extraordinaire, FAA commander, or anything that would make me particularly qualified -- I ordered the kit, followed the instructions, and happen to have an experienced quad flyer friend to bounce questions off of.
To start, my experience with the ordering system was lacking -- multiple kits "in-stock" but nothing could be added to my cart because one of the items in the kit was not in-stock. I could see this being an issue if it were a major component, but it was the velcro battery strap. So if you cannot delay shipment until said part arrives, and you won't let me add the kit to my cart, then you really don't have any in-stock.
Kit arrives and I spend the next two and a half days or so building the 3DR per the instructions in the wiki. It wasn't really all that difficult, just a lot of tedious work - checking, double checking, oops and fixing, etc. Issues that I had included the instructions not matching the hardware I was sent. Cables weren't the same colors, parts were off, etc.
After the main frame assembly was complete there was a very noticeable "arch" on two of the arms. If oriented in "plus" mode instead of "x" mode you would notice that the left and right arms were both angled backwards by several degrees, while the fore and aft arms formed a straight line in relation to each other. The left/right arms had to be measured and drilled out a bit to make them straight. Poor QC imho.
It was also interesting to see that 3DR was shipping bullet connectors as from my research they are notoriously sketchy. Not that it's a show stopper, but "sketchy" is not a word I want to use for any components going into a fairly expensive flying device. Replaced all the bullets with dean connectors which seem to be pretty stable. (also per the rec of my quad flyer friend)
The configuration of everything seemed to be pretty straight forward with no major or noticeable glitches. Once the beast was built it was time to see if it would fly!
Flying started slowly until I could get a feel for how this thing works. I can say that after a few minor adjustments it was picture perfect! Hovered well, responded well, and seemed to generally be a rock solid performer. I was definitely stoked to fly more. I drained one battery in testing.
Day 4: I head to the quad flyer buddy of mine's house and we head out to a HUGE field to play around and for me to learn a bit more. Drained another battery and everything seemed grand - and then...
After putting in the second battery (3rd battery that's ever been used) I start noticing a little glitch -- the controls don't seem to respond, but only for a second. The quad is hovering nicely, bank right, nothing - being a newb I'm not sure what's going on as everything else has been spotless. Bank right again and we're back. This happened a couple times in various spots, but nothing major.
We then do a vertical assent, which I've done a couple previously, but this time was different, much different. I "gas" it to probably 75% throttle and the quad shoots straight up, fast, I let off the throttle and nothing happens. The quad continues to climb and no controls will work! There was a 2-3mph cross wind and the quad climbed and was blown sideways FOR MILES. A more or less fresh 2650mah nano-tech battery carried this bitch further than I could see it until it was nothing more than a black dot across the grey sky. Nothing worked, nothing stopped it. Gone.
I have no means of locating the craft let alone troubleshooting wth happened - could it have been a bad board? bad radio? software malfunction? short? I'm not trying to lay blame on 3DR or anything, but there are a lot of assumptions made in the assembly instructions, stuff that's just plain not there, and if I didn't have an experienced pal assisting there would have been a lot of unanswered questions. Heh, at this point there still are.
So my take away from this is - WTF. I completely lost the quad I just paid 600$ for, spent 2 days building, have flown twice - barely, and have no clue as to why it decided to full throttle to the stratosphere. There appeared to be zero issues with any of the equipment, all fresh batteries, and much to the bewilderment of my experienced friend who commented that he's never seen that happen before.
So the two flights I got out of this device were awesome and I was told it was handling very well and looked spot on. Irrelevant at this point I suppose as I don't even have a handful of busted parts to scavenge from. I lost the entire craft, a brand new battery, and radio gear.
Can anyone here contribute to conversation regarding the possibility that bad solder joints could have helped enable the motors to stay in full throttle?
Well, I think one major problem is the use of standard ESCs of which we have no control over the firmware. That said, a Bad solder joint would have to produce a PWM signal (vibrations just right) that is basically impossible.
The ESCs do have a function though of masking what would normally be a momentary loss of input and stay for a second or so at the last throttle position. We actually need this to some extent with our system because the APM puts out PWM pulses only in the main loop which runs reportedly about 200Hz. Thus by basic design of the system, we need the ESC to maintain throttle for short periods of time. This is why there is a rather large push to make our own ESC in which we control the firmware and specifically time functions of input like this. Further, pure digital input would work much better in the system, without the requirement to send out discrete PWM signals. Trust me, this change alone would improve damatically performance of the entire main loop and code.
If you want to prove this to yourself, plug an ESC into the throttle channel of the radio receiver (Remove the prop for safety!!!), Spin it up and then unplug the ESC signal cable and it will continue to run for a short time with obviously no signal input at all.
That said, a bad solder joint ALSO doesn't make a valid input signal to the PPM either, so not exactly what I would consider a remote possiblity of being a cause. No signal input must equal no throttle. Of course you can do some no prop testing to prove this too, but use a servo on the ouputs of the APM as I stated and proved, the ESCs will mask loss of output from the APM.
Sorry to hear about your quad! Based on my experience it sounds like the R/C gear lost link and it held the last good data it received which was high throttle. If you're using a Turnigy 9x that would make sense, I've had the 9x drop out at really low range before. Any idea where it could have come down? Maybe you could put up a notice somewhere to contact you if it's found... depending on where/how it landed you might be able to recover a lot of stuff from it.
I can't say for sure because I switched to a spektrum after I had the signal drop I mentioned above over a year ago. That time I was also flying a carbon fiber quad and I thought maybe the CF (which shields RF pretty well) may have been part of the cause.
That said, a lot of people have used the 9x without problems.. whether that's because they keep the quad really close or because they are using ER9x I'm not really sure. Fortunately for whatever reason flyaways like this don't seem to be happening much or at least no one mentions it in the forums if they do.
Usually when people talk about failsafe they mean that the receiver detects loss of signal and goes to a predefined output, not freezing the last known output. Usually then you would set the output to be switching into RTL mode or just killing the throttle so it doesn't fly away. The cheapest solution is probably to switch to the FrSky module mentioned in your link above, that one has a normal failsafe feature that can be set to RTL.
Essentially, this is the fixed-wing airplane setting. It is usually combined with a slight roll to go in a circle. If the radio is lost, the engine "coasts" until the battery runs out. The plane just glides in a circle to the ground.
In a copter of course, a stuck full-throttle or even mid-throttle will send it to the moon, and a slight roll (I think the default on mine was 10deg), would send it off to the side too.
So, you flew a copter with the failsafe settings for a fixed-wing. Again, not blaming you because I did the _exact_ same thing 3 times in the last two months. Apparently I'm not only a newbie pilot, I'm a slow learner because I didn't get it until the third accident.
I have added a warning about failsafe to the wiki here:
"failsafe modes for signal loss.."
and another warning about avoiding high altitude and speed before testing auto modes and failsafes, here:
"Avoid flying at high speed or high altitude"
"Avoid sudden or extreme control deflections"
(this last one unrelated to your accident, but very much a part of mine ;-))
Hey, sorry about your lost copter again, but at least we can use this experience to help future droners. Thanks for posting it.
What a horrible experience, so sorry!
i have crashed my quad 3 times, each time because of too much altitude + wind + loss of control - it seems to be the recipe for disaster.
I know this will not be much comfort, but it is precisely because of this scenario that I worked on porting "geo-fencing" to the ArduCopter. The goal is to have an automatic fence that does not allow your copter to go too far and will automatically return it if it does (if GPS is working).
I'm considering putting "Property of X - reward if found" on the bottom of the quad, in case it gets lost. Then again, I am wondering if that note just provides someone with contact details for a lawsuit if it damaged property or worse when landing.
Best thing is to buy a cheap GPS GSM tracker of ebay, then if something bad happens, you can always use that to locate your lost UAV
Bad solder won't induce runaway ESCs, not setting a failsafe will!
What was the expected behaviour of the throttle channel in the event of a loss of signal??
If you can't answer that before you fly then you should not be flying, also make sure you test that function, props off before your first test flight. Its non negotiable. Setting of failsafes is very radio dependant so consult your manual!
Harsh words I know and a hard lesson learnt. Console yourself in the knowledge that 5 years ago multicopter levelling only boards started at $1000
You did'nt enable the simplest failsafe, the one included with the radio. Every RC flyer should have the throttle channel set to close in the event of loss of signal.
Its a building block of RC flight, nothing to do with autopilots.
Yes your quad would drop like a rock but at least you would find the bits.
By having a flyaway you have no idea what your quad hit when it fell. Perhaps if it had your name and address on it somebody might come knocking on your door with a claim.
Of course UAS can fly off, its your responsibility to make sure it does not.
The amount you spend on the radio gear, is directly proportional to what you stand to loose with what you are flying. $50 radios are great for $50 machines.
Bummer dude. I have to say that I have read quite a few stories like that. This sport just isn't plug-n-fly yet, it really is for developers and tinkerers at the moment.
If it's any consolation, a lot of people crash and burn their first few times. Thanks for bringing up the potential 9x problem though. I've got one and should probably do a lot more testing of failure conditions.
It's too bad the autopilot didn't have more sophisticated failure handling. But I don't know how much you can really expect the autopilot to do when flying in manual mode.
Bummer to hear but, go look for it. I've found mine after what seemed hopeless fly-away, a friend 3 times.