Worst flight ever with p4p I'm still shaking, no control but got it landed

[F3honda4me]

The tracker doesn't change with location. Certainly, if a tracker is added then a calibration should be done.

I'm assuming that regional effects such as a nearby mountain range loaded with iron could cause the declination to change. Within the confines of the compass dance the field isn't distorted because the scale of the regional effects are so much larger than the compass dance. It's just that the field is coming from the wrong direction. But this regional declination can't be determined from the compass dance for the same reason that the global declination can't be determined from the compass dance. To detect and compensate for any declination during a compass dance it would be necessary to place the AC in a true north heading and then tell it that it's heading is true north. Since this isn't part of the dance declination can not be determined from a compass calibration.

It's debatable if the geomagnetic inclination is used to correct IMU data. I would suppose the opposite is true. But, nevertheless, the same type of argument apples here. I.e. the craft would have to be placed in a known orientation while the magnetometer data is taken. This also is not part of the compass dance. At this point I always refer to an experiment I did where the P3 was calibrated upside down; first step inverted, second step nose up. Flew fine - didn't fly off to China upside down.

The only purpose of a calibration that consists of a P3-like compass dance is to detect and then compensate for the distortions caused by the AC itself; also called the hard iron effects. Detecting and compensating for regional effects just isn't possible with compass dance.

This is also what my research had led me to believe, and why I had also used some of Bud's post in my initial post. If it's incorrect, can someone explain how the craft can determine magnetic deviation since it requires the compass to know where true north is?


PS. I'm greatly enjoying this polite discussion.

 

[Kman]

I've always calibrated the compass if i traveled more than 100 miles from the location the last place I did a compass calibration.

I forgot to do a compass calibration when I was in Lake Tahoe two weeks ago. App said everything was fine but when I took off with my P4, it wouldn't hover in place. More like circling and jumping around in a 4 foot circle. Flying around was a bit touchy. Landed and did a compass cal. No issues.

I never trust the app when it comes to compass calibrations.

 

[BudWalker]

I've always calibrated the compass if i traveled more than 100 miles from the location the last place I did a compass calibration.

I forgot to do a compass calibration when I was in Lake Tahoe two weeks ago. App said everything was fine but when I took off with my P4, it wouldn't hover in place. More like circling and jumping around in a 4 foot circle. Flying around was a bit touchy. Landed and did a compass cal. No issues.

I never trust the app when it comes to compass calibrations.

This would be a perfect opportunity to have a closer look. Would it be possible to get the .DAT from both of these flights? To see how to retrieve the .DAT look here. You can actually select both of those flights in DJI Assistant 2 and it will produce a file with a name something like DJI_ASSISTANT_EXPORT_FILE_2017-01-08_19-45-02.DAT that has both of those flights. It'll be large so you'll need to use something like Dropbox or Google Drive and post the link here. When you use DJI Assistant 2 don't select the Vision Modules or the .DAT will be even larger than it needs to be.

 

[Kman]

This would be a perfect opportunity to have a closer look. Would it be possible to get the .DAT from both of these flights? To see how to retrieve the .DAT look here. You can actually select both of those flights in DJI Assistant 2 and it will produce a file with a name something like DJI_ASSISTANT_EXPORT_FILE_2017-01-08_19-45-02.DAT that has both of those flights. It'll be large so you'll need to use something like Dropbox or Google Drive and post the link here. When you use DJI Assistant 2 don't select the Vision Modules or the .DAT will be even larger than it needs to be.

I've flown a bunch since then. Would they still be there?

 

[BudWalker]

I've flown a bunch since then. Would they still be there?

That's hard to say. If it were a P3 I could give you a pretty good idea based on the total number of battery on minutes since those flights. The real answer is you'll have to use DJI Assistant 2 to see if they are still there.

 

[ianwood]

The tracker doesn't change with location. Certainly, if a tracker is added then a calibration should be done.

I'm assuming that regional effects such as a nearby mountain range loaded with iron could cause the declination to change. Within the confines of the compass dance the field isn't distorted because the scale of the regional effects are so much larger than the compass dance. It's just that the field is coming from the wrong direction. But this regional declination can't be determined from the compass dance for the same reason that the global declination can't be determined from the compass dance. To detect and compensate for any declination during a compass dance it would be necessary to place the AC in a true north heading and then tell it that it's heading is true north. Since this isn't part of the dance declination can not be determined from a compass calibration.

A tracker is an example of a "hard iron" deviation i.e. it is a magnetic field that is built into the craft and moves with it. This is detected as part of the compass calibration.

Local mineral deposits is an example of a "soft iron" deviation (not declination) i.e. a magnetic field that is in the local area but does not move with the craft. This is also detected as part of the compass calibration.

As for declination, you don't have to point at true north to find it. One method is to use a local lat / lon lookup table based on the 2015 survey. Pixhawk has been doing this since forever. Another is an adaption that takes place in first flight following the calibration. This is how it was done on the P2. It's likely the P4 uses elements of both.

It's debatable if the geomagnetic inclination is used to correct IMU data. I would suppose the opposite is true. But, nevertheless, the same type of argument apples here. I.e. the craft would have to be placed in a known orientation while the magnetometer data is taken. This also is not part of the compass dance. At this point I always refer to an experiment I did where the P3 was calibrated upside down; first step inverted, second step nose up. Flew fine - didn't fly off to China upside down.

Compass data is used in a lot of places. Common in AHRS. Like I said, look no further than the gimbal and the influence bad compass data has on it. Also look at orientation twitch in the Inspire 1 when in areas of high electromagnetic influence. That you calibrated upside down and it didn't go bonkers simply means the algorithm used could tolerate that for some reason.

And it's not based on inclination. Determining absolute orientation (IMU can only do relative) involves reading all 3 axes of the compass to determine the vector to the center of the earth applying offsets as needed from the calibration, declination and inclination as needed. It is then used in common sensor fusion algorithms to correct gyro drift and accelerometer noise.

The only purpose of a calibration that consists of a P3-like compass dance is to detect and then compensate for the distortions caused by the AC itself; also called the hard iron effects. Detecting and compensating for regional effects just isn't possible with compass dance.

This is not true. Soft iron is also adjusted for as I believe is localized variations in inclination. It's a pretty commonly used method in AHRS.

 

[BudWalker]

A tracker is an example of a "hard iron" deviation i.e. it is a magnetic field that is built into the craft and moves with it. This is detected as part of the compass calibration.
Local mineral deposits is an example of a "soft iron" deviation (not declination) i.e. a magnetic field that is in the local area but does not move with the craft. This is also detected as part of the compass calibration.
.

Exactly. I was responding to your assertion that a tracker is a reason to calibrate since the location was changed (from the east to west coast). Maybe a misunderstanding on my part.

As for declination, you don't have to point at true north to find it. One method is to use a local lat / lon lookup table based on the 2015 survey. Pixhawk has been doing this since forever. Another is an adaption that takes place in first flight following the calibration. This is how it was done on the P2. It's likely the P4 uses elements of both.
.

Exactly my point. Declination isn't being found by a compass calibration.

Compass data is used in a lot of places. Common in AHRS. Like I said, look no further than the gimbal and the influence bad compass data has on it. Also look at orientation twitch in the Inspire 1 when in areas of high electromagnetic influence. That you calibrated upside down and it didn't go bonkers simply means the algorithm used could tolerate that for some reason.
.

Don't see the relevancy here. Compass data is used lots of places. But, that has nothing do with the fact that declination and inclination can't be determined by the compass dance.

And it's not based on inclination. Determining absolute orientation (IMU can only do relative) involves reading all 3 axis of the compass to determine the vector to the center of the earth applying offsets as needed from the calibration, declination and inclination as needed. It is then used in common sensor fusion algorithms to correct gyro drift and accelerometer noise.
.

I'm not sure what's not based on inclination. Absolute pitch and roll orientation can be determined from the IMU, Heading, can't though. Magnetometer data is used to correct heading data (albeit slowly with the P3). The lower frequency magnetometer data can't really by used to correct the higher frequency accelerometer data. But, what's the point here? It still remains that declination and inclination can't be determined by a P3 compass calibration.

This is not true. Soft iron is also adjusted for as I believe is localized variations in inclination. It's a pretty commonly used method in AHRS.

Here again, you're right, compass data is used all kinds of ways for different purposes. But, declination and inclination can't be determined by a P3-style compass dance.

 

[Jason Porembski]

Oh!!!! feel for you too matey, they may have changed things inside and if they have they are unlikely to say they have, have a fly when you can and see what it flys like, bet it will be stable.

They have to tell you. They actually email you an invoice telling you what's going to be fixed.


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[Snowwolf]

Just an update, p4p arrived with DJI Netherlands today.

 

[Beebeach]

They have to tell you. They actually email you an invoice telling you what's going to be fixed.

This is the actual quote from the DJI repair report:
"warranty unit tested oke no problems found could be a environment issue" which isn't giving me a lot of confidence. I haven't had a single event-free flight, and it's not a handling issue as my previous P4 flew perfectly for over 50 hours.

I need to quit work early and go out and do a few test flights today. If they haven't repaired anything, my confidence is at rock bottom...

 

[Snowwolf]

Just an update, DJI on Wednesday said they were conducting damage assessment, allow 1 to 2 days, still on same, I'm not pushing them, it gets sorted when it sorted, just thought I would let you all know how it's going.

 

[Jason Porembski]

Any updates?


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[Snowwolf]

Any updates?


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Any updates?


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As above Jason, I will get in touch with DJI on Monday, see if any news

 

[Jason Porembski]

Gotcha. I figured something may have been updated on Thursday or Friday. Fingers crossed!!!


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[Snowwolf]

Gotcha. I figured something may have been updated on Thursday or Friday. Fingers crossed!!!


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It still says the same thing on there repair site, saying they are checking it out and to wait one or two days, that was Wednesday

 

[John Locke]

Must be something different then. Was there some kind of compass dance? Or was it just point it magnetic north and tell the craft?

Yes, refer to post 149. Lots of spins and rotations, but the dance was relevant to magnetic North, a much different dance versus DJIs dance which doesn't ask where North is.

 

[swhoward1971]

I'm new and just got on here. Could the issue be you were in the path of a microwave tower. I operate cranes and on some if the boom tip is in the path it can make the computer go haywire.

 

[Snowwolf]

I'm new and just got on here. Could the issue be you were in the path of a microwave tower. I operate cranes and on some if the boom tip is in the path it can make the computer go haywire.

I checked all around the area and I can't see any towers about.

 

[iflyhelis]

So, were you in "ATTI Mode" at that time? If so, kiss your satellites good-bye.

You also had magnetic interference from that metal fence.

Have you flown in that location before?

Remember, these little electronic birds are so "Twitchy" They need the correct procedures done before each flight. If your DJI Go App looks like it is happy, then, you should be able to fly your mission. But! With all of the crap that is going on with keeping your TX/RX/Bird/Battery at the same level of software, it makes it very hard to swallow that pill!

I have had 2 funky things happen to me so far, first a prop spun off. (I now use the tool to loosen as a tightening tool) The other funk was, I hit auto-land on the cellphone (By mistake) & I was beyond 20 meters. It went up to my RTH height of 100 meters. I tried to cancel it by moving the UP/Down lever (Left Stick) that didn't work at all. I stayed calm even though my Drone was climbing towards a 17,000 volt power line.

I fought off the altitude change & then it started sliding towards some bushes at about 2 feet off of the ground.

I must have over-reacted & rolled it over up-side down.

One prop damaged, Drone fly's fine!

Kurt

Hi all
I decided to have a fly today, lovely bright sunny day very minimal wind, before flight it was taking its time finding satellites but eventually it did and said I could take off, once up in the air the bird was totally out of control, it was the worst 10 minutes flight I have ever had, all sorts of warnings were coming up on the screen but I could not take my eyes off the drone as I was having great difficulty keeping it from flying away, sometimes I was full throttle from keeping it drifting away, then all of a sudden it would accelerate fast and needed to full throttle in opp direction, lots of things were happening on screen and with the drone, I did eventually get it back down on the ground, how I don't know, luckily I have flown planes for many years and always fly atti mode with the drone very often in case of flights like I just had, I had a P4 previous to the p4p and have done 160 full flights with no issues, 140 flights being with the P4 so I am pretty good and check everything before a flight.

I have the data log of what has happened in the link below and hoping someone can have a look at it to find out what went wrong.

I have had a look at the flight I done on the iPad Pro which I use, I am running the latest software and firmware, I have taken a few snap shots from the flight, one warming was un paved airport but that is untrue, here are is a snap shot of the screen, I had 14 satellites on take off but looking at the flight on iPad it kept losing them, also it looks like it has only recorded half the flight and only recorded from when I walked to a new position I was getting a lot of warnings of gimbal yaw reached end point
Here is the flight data file folder link and a video from my ipad on how it was flying.

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https://www.dropbox.com/sh/jomjd ... I6KAvSoRn3iDEa?dl=0

 

[Snowwolf]

I was in P mode, it was the first IMU I had flown in that are, I have never had any issues with flying around fences and cars, if it was the metal fence that caused the problem, would it not go away when the drone was 400 ft up in the air ?
My drone is arriving back from DJI on Monday