I am new to ardupilot and running a 3DR hex kit, mostly stock with xBee telemetry ,5000mah 4S 50C batteries, and Spektrum DX7 controller. Here are some stats to whet your appetite for my post:

Number of test flights:2

Number of successful test flights:0

Number of broken props:12

Trips to emergency room: 1

Successful uses of any flight mode but stabilize:0

Number of times I have had to kick a quad out of the air doing “rtl” towards my co-pilot at 1m from the ground: 1

I’m going to say right off the bat that most of these errors likely occurred between the copter and the controls (i.e me), however the copter flies well in stabilize mode, and seems to be well tuned there. 

My configuration files are attached, but the major changes were:

-Geo-bound and max alt. failsafes: 20m radius, 30m height, failsafe to RTL

-Comm error and low battery, set to RTL. Comm error was set by “binding” my DX7 with a PWM of 1050 on the throttle, which is 200 below my lowest throttle setting. So, when the controller is turned off (or comm disrupted) throttle input falls to the bound value, and the failsafe is engaged.

The copter has the following issues:

In stabilize mode, pitch and roll are reversed. This I feel is a fairly straightforward error, but my mappings seem to be reversed

In loiter and Alt Hold, the copter will not stay aloft. In alt hold (engaged at~3m), the throttle will oscillate, and the copter will oscillate, but slowly come to land. Loiter will cut throttle slightly and settle in to land.

The copter will take off sporadically. We are calling this “killer”mode. The we flew the copter to the geo-bound, it was doing an RTL and coming back towards us. I switched to alt hold, with zero throttle, and the copter fell out of the sky (definitely my fault..i Think). We went to the copter after it crashed, assuming that the system was disarmed (also my fault). Approximately 1 minute after the crash, the copter took off into one of us, causing a serious hand injury. There was no external input on any PWM channel, and it appears the system thought it was in RTL mode. But, would ardupilot take off in RTL mode if the props weren’t already spinning?

The copter will fly directly at us at 1m altitude. I had set up the geo bound on the mission planner software, and confirmed that the copter was shown to be at the centre of the 20m geo bound. I changed my channel mappings to stabilize->RTL->loiter in order to test my RTL functionality. I started to take off in stabilize mode, and when we reached ~1m altitude the copter pitched on its side and came directly at us, again with no external pwm input. Looking at the logs, I dropped throttle as soon as the copter pitched (ch3 PWM went to low), but the autopilot throttle continued to increase and oscillate, and the flight mode went to “unkown”. Also, at the same time as the pitch, the satellites dropped from 10 to 6, and the GPS eph (position accuracy) went from 175->375. Looking on mission planner, the location of the copter was wrong, and it thinks it was about 200m away from the home position. So, my assumption is that the GPS accuracy went down, it thought it was well outside of the geo bound, and tried to RTL back to home (even though it was at home already). However, I thought that RTL had to achieve a certain altitude before moving, and so am confused why it did RTL at this altitude. There is the minimum altitude setting, which I will now set, however I have heard that there are some issues with this setting (such as spontaneous takeoffs, which I don’t want to encourage, as above) I’ve included the telemetry from this test flight. The killer mode happened on the last flight.

Can I set a “kill all” failsafe? I can see the reason to set failsafes to RTL in order to try to preserve the copter, however I woudl like to have a failsafe that I can send which will disable everything, in those cases that the things that the copter is flying towards (ie. me) are more important than the copter itself. With the way my failsafes are set at the moment, turning off the controller would keep the copter in RTL.

So, overall, I would really appreciate help in getting this system going safely. At the moment I am pretty wary about flying my aerial lawn mower again until I have the safety settings done properly. It is not acceptable for the copter to take off, or fly quickly in arbitrary directions. these things are dangerous.

Thanks!

Tags: 2.5, APM, GPS, Safety, flight, tuning

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Nice, you have discovered that what you thought was a toy, is actually a dangerous machine, comparable with an upside down lawnmower.  Too bad you had to learn that the hard way.  Reading a bit before flying could have helped, but I understand that some are eager to fly.

It's actually pretty simple.  In stead of RTL set your receiver failsafe to "stabilise mode" and 0 throttle.  This will cause your copter to fall out of the sky if you turn off transmitter or loose link.

Configure your tx to have a switch that sets mode channel to stabilise and throttle to 0 and you have your kill switch.

Now you are always safe : if you have rc link, you can kill it with the kill switch.  If you loose RC link it will be killed by the receiver.  

Ow and if it comes flying towards you fast, don't bother with kill switches and stuff.  Just RUN ! 

Another happy customer!

Not sure O Drone Savant, it seems my taking a few days off away and not logging in often enough has disqualified me. Oh, and obviously, my lack of enthusiasm for the viability of the featured product here probably did not help.

I sold my APM because I did not trust it, after extensive bench testing, I decided it was dangerous, I guess I can no longer be a moderator. I dislike everything about my experience with 3DR products and the terrible customer service. This site could have been the authority in the hobby we are pursuing, it is turning into a commercial biased farce, I have lost all respect when Mr. Admin started poking into my moderating habits so I personally couldn`t care less. I will check in from time to time until they ban me for good. Until then, what happens here is of no concern to me since I have lost all respect anyways. At this point, my only regret is the amount of time I wasted here. On the bright side, I met some cool people, most of which, like you,  have seen the light and fly real flight controllers with an actual future. 

It's a shame that you feel that way Olivier and whilst it's quite clear that you've already made up your mind about your future on this site, it was mentioned during the process that you could always talk to the guys in charge of that process if you had any queries.

As for the 3DR component, I think we've all made comments about 3DR at some point.  Some of us have then taken those comments to them or Chris directly in a hope to get things resolved.  This is crowd sourced after all.  However, the site (myself included) would be very interested in your opinions and thoughts of other flight controllers (or components) if you do start using them - just like i'm interested in Drone Savant's sites and comments.  There are things to learn all along the way - no matter how much experience we have, and for many people this isn't the only site referenced.

However, I encourage you to talk to Thomas or Josh, or happy for you to talk to me via PM, but can we please respect the original posters post and keep it on topic.

Merci,
David.

Hi David,

In order not to pollute this post any further and drift off topic, I sent you a PM instead.

Regards, 

Maybe in documentation that would be good to add a section "bad experiences", with experience and solution. Before buying anything I always search bad experience on youtube, a good way to prepare ourself !

See http://code.google.com/p/arducopter/wiki/AC2_Pitfalls

I can see an extra thing to add: if you have crashed or landed, and not within 2m of your RTL location be careful to make sure you have really disarmed your copter before approaching.

See http://code.google.com/p/arducopter/wiki/AC2_Failsafe for setting how fail safes works and how to configure how it works
All this fancy fail safe stuff is nice, but the best safe thing you can do is be a good pilot. Learn how to fly in stabilize mode. I mean really know how to fly in stabilize mode. Be able to land, fly level, fly low, fly high. You have to be able to recover when things go wrong. Once you got manual flight down, then move to alt hold. Keep in mind that alt hold is the bases for loiter, RTL and auto modes. If you can't fly alt hold you can't do the other modes. I also fly in simple mode in all my flight modes. This way I don't have to be concerned about my copter's orientation. I've been where you are now. I've had some crazy things happen with my copter. I've had it crash and then take off. I've had it flip 90 degrees and try and give me a hair cut. Thank god I've never gotten hurt or worse yet hurt someone else. With alt hold you need to get vibration down and have a good zAccel graph if you are flying firmware 2.9.1.
Good luck and fly safe.
Richard
P. S. my copter is still a toy. A dangerous toy if I'm not careful.

Sounds like you have some understanding of what this thing is supposed to do. I'd agree with Richard... learn it in it's most basic mode first. In fact, I would suggest that when you have maybe 20 perfect flights in a row in stab/simple mode without any incident, you could move forward with some confidence. 

Mick

Rob,

     Sorry to hear about your troubles.

     Just had a quick look at your logs and a few things I saw:

  • did you skip the radio calibration in the mission planner's config area or perhaps not move all the sticks, switches while doing the calibration?  The min/max values for all channels except 3 (throttle) is 1499/1500.  I would expect this means that your copter has very little roll, pitch, yaw or even flight mode control....or maybe this is not the correct tlog..that's also possible.
  • you should leave geofencing off.  i'm wondering how you turned it on, or which wiki page you referred to because we removed it from the mission planner until it's more stable and reliable.
  • you should set your INS_MPU6K_FILTER parameter to 20 using the mission planner's Config, Advanced Params, Adv Parameter list screen (remember to press "write params" after changing the number)

HI Randy, 

  I did a proper calibration, and when flying the copter flew pretty well in stab. It was very responsive around the centre, and so I set a 30 Expo on my DX7 to reduce sensitivity around dead centre, and it works pretty well. However, I just checked it again, and the adavanced params list showed what you saw. So, I re-did the calibration, and now it has proper values. Any ideas of why I was able to fly? What effect will re-doing calibration have on flight performance? 

I have turned geo-fence off. When I looked up failsafes previously, the wiki didn't state that this functionality was removed  and I assumed that this was best practice (esp. after hearing some flyaway stories). I activated it through the adv. param list. 

 I have set the filter parameter. Was this on one of the guides that I missed? If so could you point me to it to make sure there are not any other best practices defaults that I missed?

Also, could you clarify the automatic disarm procedures for the APM? Why did the copter, after sitting with no props spinning, stay armed for this long? I have heard on other platforms that you can set the props to spin slowly when the system is armed... is this possible on the APM? I'll clarify now that my assumption is that it is always armed, and will verify with telemetry before approaching, and will disconnect the batteries whenever I am within arms reach of the copter. 

Thanks!

Rob, I'm glad it wasn't worse.  Richard and Mick have it right, aside from whatever setup issues there might be. Do one thing at a time, until it works correctly and you are thoroughly comfortable, and only then move on to the next. Flying in plain stabilize should be first, meaning you can control the aircraft in any orientation. If you have little prior RC experience that can take a while, but it can and should be fun and in itself rewarding. Next is altitude hold, including throttle stick management while entering and leaving, and during, that mode. Then loiter. When all of that is working and comfortable you can start messing around with RTL. And so on. Sooner or later just about any RC aircraft will do something unexpected, for internal or external reasons. If you have basic manual flying skills and the confidence that comes with them such events are often barely noticeable or will get a "nice save" comment from a fellow pilot. If you haven't got those skills, the outcome is always a crap shoot.

Also, a specific safety tip: Any crashed electric RC aircraft should be assumed to be armed and dangerous. Approaching the craft, if it looks flight-worthy, is best done with a jacket or blanket in hand to toss at it if it gets frisky before you reach it. The immediate desired action is to disconnect the main battery.   On multicopters this can mean reaching in among a bunch of props. The bad news is that multicopter props can go from zero to a gazillion RPM faster than you can blink. The good news is that they have negligible torque at startup. So, you want your hands/arms either firmly touching the props or well within their arc, so that should they start they can't actually spin. Do this in a way that also holds the multicopter down, because if it starts up you don't want the props on the other side flipping it into your face.  Also, once you're committed you don't want to pull back should it all of a sudden fire up; just follow through with the disconnect. Make this your standard everyday method for disconnecting the mains and it will be automatic when needed. An alternative is to carry trauma dressings in your tool kit, as anyone who has seen prop injuries will tell you that band-aids will not be sufficient.

   

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