Yesterday, what it seemed like a nice day to fly, it became the end to my IRIS+. I just started flying over a wheat field and suddenly the IRIS+ stopped responding telemetry commands, raised up itselft for about 50 meters, then flew away and went side until it crashed, like if a motor had stopped working.
The results: all the four legs got crashed, the chasis is all with scratches, the front red leds didn't turn on anymore and the GoPro Hero3+ housing scratches too. Fortunately the Gimbal was not installed.
I'm feeling pretty dissapointed now on the IRIS+ since I spent so much money on it. Today sent an email to Help department at 3DRobotics hoping for an explanation of what happened and looking forward for some kind of warranty.
Here is the video and the photo showing how the IRIS+ ended up so I wondering if you guys could notice something wrong on this attempt to fly.
First of all why does the Pixhawk allow tack off without a good GPS and or not level, if this will result in a possible crash.
Second, I had a similar experience with a Pixhawk hovering a short while switching to Loiter mode then just veering off to the side. I was able to recover by switching to Stable mode. After examining I found that the last time I made a change I inadvertently mounted the compass 90° off. Correcting this solved the problem.
To be clear with the compass 90° off the Pixhawk complained about compass not calibrated and accelerometer not calibrated and it took a few time to get every thing recalibrated in the compasse off configuration. So the Pixhawk detected something had changed and needed to be recalibrated. If a compass that is calibrated know where North is and certainly GPS knows North, why if there is a descripancy does the Pixhawk allow this configuration to fly.
I had a very similiar thing happen to me with an APM 2.5 and front mounted goprp recording video. Right before it hit the ground I saved it by putting it in stabilize mode. After looking at the logs it showed my position jumped by like 200meters. I have since covered my gopro with aluminum foil and metal duck tape.
I always start a flight in stabilize mode and then put it in loiter for about 20 seconds to see how good the gps is holding.
I would recommend flying around in stabilze mode and learning how to fly well. Make up some obstacles to fly around. If you not crashing you aren't trying hard enough. just flying low and trying to land where i want the craft it to go made me a better pilot. Also by props by the dozen or more.
Even commercial airline pilots say their autopilots go off abit. that is why a pilot is always watching.
Because you asked it to ignoring the warnings.
Definitely take off in "STABILIZE" mode. There are a couple key things that happen when you do so, one is "TRIM_THROTTLE" sets the F/C throttle mid-point (calculated automatically) when you take off with different weights (GoPro, no GoPro), second is that GPS location is ignored (for purposes of flight stability) as well as you get better Throttle Stick response (as opposed to the wide dead-band when in LOITER or ALT-HOLD.
Getting TRIM_THROTTLE or THR_MID set right will alleviate the FLIES-UP and away very fast (example above of Jim B's MR that hit the ceiling).
There are also other settings that differentiate between using GPS North for orientation (you have to be moving for this to work, it's really a PLANE setting, not COPTER) vs. Compass Orientation (if you are not moving, the only way to tell what direction the copter is pointed is via the compass).
I set COMPASS_LEARN to "1" (this allows the Pix to determine compass offsets from F/C during flight), COMPASS_ORIENT to "0" (this one sets the relationship between the compass and the pixhawk by # of degrees, they should be pointing the same direction), and COMPASS_USE to "1" (this one sets the copter orientation based on COMPASS not GPS). Lastly, COMPASS_AUTODEC should be set to "1". This will alleviate the "toilet-bowling" affect caused by MAGNETIC NORTH being at an angle that is not the same as TRUE NORTH (for example here in Las Vegas it is 11deg, in San Francisco it is 13.5deg, and over 16deg in Seattle. It is different everywhere around the globe).
Why is COMPASS_LEARN set to "0" by default? Is there a downside to setting to "1"? My other settings are as you state.
Also, what is considered "level" for takeoff? I guess I never considered actually looking at the flight data before takeoff and saying "it's not level enough" because there is no reference I'm aware of for determining that.
As for GPS lock, there are times when it is cloudy and pretty much poor flying conditions and I'll get 10-12 sat and 1.3 hdop, whereas today it was clear and couldn't get under 2.3 hdop until later in the day. The K-Index was 2. Other times it fluctuates too much then I call it a day, pack up and wait for a better GPS signal.
Soon (hopefully) I'll be receiving the Neo M8N GPS from CSGshop and it will be interesting to see how that works out. One would think since GPS glitching is a problem, the newer RTF MR's would have the better GPS modules.
I determine level take off when in stabilized mode, hover then center the sticks. If the craft doesn't float away to fast then I consider it leveled. If it floats away in one direction I power it off and find a level place to try again.
GPS signals are so weak and the gps radios have to be so sensitive just to receive the signal it's easy to swamp them with other rf.
That's pretty much what I do; have never taken off in Loiter.
I'm hoping for a response from Joe Dietrich on why he sets COMPASS_LEARN to 1. I have never questioned why it is disabled.
From the description for COMPASS_LEARN = "1", it states that it will automatically determine the OFFSETS for the compass (to the flight controller, I assume).
It is probably similar to the offsets you MANUALLY enter into NAZA V2 to identify the X, Y, and Z axis differences between the GPS Puck and the Flight Controller.
I noticed the first time I did a calibration for the Pix where you rotate the bird around all three axes, you could see the settings creating OFFSETS. Somehow, the Pix figures out (maybe improves) the OFFSETs each time you fly or start-up. That's the only reason I can figure you would want to set it to "1" vs. "0".
Are you using the 3DR uBlox GPS with Compass? Mine seems rock solid, I can put it into a yaw spin in either direction, and it just about spins like a top. Now I can say on my early start-up flights, the yaw spin wasn't as tight, but as I flew more, it definitely seemed to get better. I know on NAZA, if you don't have your offsets right, the bird won't spin like a top. I've had to help several people fix their NAZA offsets, and they saw really good improvements.
I agree the GPS HDOP is definitely a PITA when trying to get a lock for Pre-Arm. HDOP stands for High Dilution of Precision, and from the Wiki on it, "When visible navigation satellites are close together in the sky, the geometry is said to be weak and the DOP value is high; when far apart, the geometry is strong and the DOP value is low." So I guess we see why having 10 - 13 satellites if they're close together doesn't help the F/C.
Here's what you can do though, usually HDOP will get better over time (as satellites move). If you're not planning on flying in GPS based mode, such as LOITER Mode or AUTO (Nav using GPS), set your GPS_HDOP_GOOD setting at 250 to 350, at least you'll get past the GPS Pre-Arm check. Keep in mind that RTL (Return to Land) might not work so well though! However, as your M/R moves around, the HDOP will change (and will usually get better).
I have a question... you mentioned taking off in STABILIZE mode. Is that only available from Droid Planner or APM Planner? I'm still learning, and just found that mode this weekend (after reading tis post) in Droid Planner. Is there a way to program that to the Controller itself, as a switch?
Also the IRIS+ docs say to use the long legs when using STABILIZE mode, due to some possible GPS interference.
Stabilize should be switch select able from your TX
The IRIS+ does not use Stabilize as one of the TX modes. You would need to set that using mission planner which could mess up the switch labels that are on the TX.
Really, stab mode is not the standard TX mode? If so, that is poor judgement as it should be. As mentioned before you can never really rely on GPS and MAG. I always take off in stab mode. If copter reacts normally to inputs i gain altitude. When i decide to use loiter or auto for by example recording a movie or taking a picture, i hit the switch and check if loiter performs like it should. While doing so i still hold the switch so that i can immediately switch back to stab if something is out of my expectations. I am not a big fan of automated modes but they can be handy. And i never ever trust them. I think nobody should be allowed to fly an advanced UAV like the Iris without at least being comfortable flying in Stab and it is a real bonus if you can fly acro also.
I wonder if the decision to remove stab from the switches is not because of market pressure from DJI. If so, that is a poor decision to say the least. With the current negative perception of UAV's in the media we can ill afford stories like this one.