A CW Posted at 2018-4-25 10:44
Totally agree Hallmark.

I'd also add that flying at night (as in this case) massively impacts on the VPS - the drone lost VPS 5 seconds into the flight as couldn't see/detect the ground so OPTI was ineffective too. Adding that to a compass failure upon take off due to not checking the compass reading and taking off next to a car and you're set for a fly away. Also, the home point was set after take off and I believe the recommendation is to wait for 11 sats to be received as a minimum for a true GPS/GLONASS lock - not 10 (reducing in number) as in this case.

There was a huge mountain to my one side (the one the drone crashed into) so half the sky was blocked was probably the reason for the 10 sats.

Just as a side note. More than half my flight time has been at night. Night time to me is everyone else's day time. I do everything at night. So Im not too worried about flying at night. So i understand the circumstances. I always have to deal with a shorter battery life due to it being colder at night.

Also this wasn't my first flight of the night. I already made one flight that was probably about a mile or slightly more. It was a freshly charged battery to being with. The 2nd flight is where it crashed.

2wenty Posted at 2018-4-26 09:20
There was a huge mountain to my one side (the one the drone crashed into) so half the sky was blocked was probably the reason for the 10 sats.

Just as a side note. More than half my flight time has been at night. Night time to me is everyone else's day time. I do everything at night. So Im not too worried about flying at night. So i understand the circumstances. I always have to deal with a shorter battery life due to it being colder at night.

I see - definite fault with the compass for sure.

HedgeTrimmer Posted at 2018-4-26 08:15
But when it clears magnetic interference compass will then move to  correct heading which you would think was great. But No, what happens is  IMU is then conflicted and confused because of this sudden movement by  compass,

I can go along with first part.  But sudden compass change conflicting with output single axis (Yaw) of Inertia Measurement Unit, should be dealt with firmware of drone.  The drone should have slowly rotated left or right, then stopped rotating.

Believe it or not but first check flight log, every stick movement made by controller was registered and aircraft acted as it should, it’s very easy to see thisin the flight log.
I’m not quite sure why it doesn’t report going to Atti mode, but MavAir is the first dji aircraft that doesn’t report this why I honestly don’t know, but when I look at flight log, look at controllers stick movements and pitch and roll of aircraft then it can only be said that aircraft was capable of being controlled by the pilot.
Admittedly it would have been very difficult , but first course of action when this happens should be to pull throttle down until aircraft hits the ground.

If you have read your manual you will be aware that when Aircraft goes to Atti mode speed will be increased, I don’t believe it’s a safety issue, surely safety in a case like this comes long before we seen the outcome.
Pilot at night decides he wants to take some photographs he launches his aircraft with battery not charged fully he launches 6 feet from his car on the side of a road see where I’m going here, all pilots of these aircraft must take some responsibility and all of those points are clearly marked in the manual and reading the manual is the first and most important thing any responsible person should do.

All dji aircraft run on basically the same technology and 99% of users don’t have problems using it .

hallmark007 Posted at 2018-4-26 16:51
Believe it or not but first check flight log, every stick movement made by controller was registered and aircraft acted as it should, it’s very easy to see thisin the flight log.
I’m not quite sure why it doesn’t report going to Atti mode, but MavAir is the first dji aircraft that doesn’t report this why I honestly don’t know, but when I look at flight log, look at controllers stick movements and pitch and roll of aircraft then it can only be said that aircraft was capable of being controlled by the pilot.
Admittedly it would have been very difficult , but first course of action when this happens should be to pull throttle down until aircraft hits the ground.

every stick movement made by controller was registered and aircraft acted as it should,

Except for aircraft flying away.  That was not commanded according to pilot and not by flight log.


not quite sure why it doesn’t report going to Atti mode

A programming mistake in firmware.  One that fails to warn pilot that drone has switched modes and it will now take different technique to fly.  That would be another Safety issue.


Pilot at night decides he wants to take some photographs he launches his aircraft with battery not charged fully

Non issue.  The log shows plenty of power for short flight.  Battery showed over 2/3rds charged.  Fact drone was able to accelerate so rapidly and still have plenty of battery power proves it.  Pointing to a battery with 68% charge as some sort of safety issue is non-sense.


he launches 6 feet from his car on the side of a road see where I’m going here

Whether that could have caused a problem is unknown.  Manual only warns about calibrating compass near a car.

hallmark007 Posted at 2018-4-26 16:51
Believe it or not but first check flight log, every stick movement made by controller was registered and aircraft acted as it should, it’s very easy to see thisin the flight log.
I’m not quite sure why it doesn’t report going to Atti mode, but MavAir is the first dji aircraft that doesn’t report this why I honestly don’t know, but when I look at flight log, look at controllers stick movements and pitch and roll of aircraft then it can only be said that aircraft was capable of being controlled by the pilot.
Admittedly it would have been very difficult , but first course of action when this happens should be to pull throttle down until aircraft hits the ground.

but when I look at flight log, look at controllers stick movements and pitch and roll of aircraft then it can only be said that aircraft was capable of being controlled by the pilot.  

Assuming something else was not wrong with drone.  If you do more than look at flight log, actually analyze it.  You would see the Yaw of IMU was not confused, as you mentioned.
Yaw was relatively steady until 10 seconds into flight, then only changed for about 1.2 seconds.  First entry is at 10.0 seconds, and last at 11.2 seconds.

            

-107
-108.5
-110
-110.2
-109.7
-108.9
-108.2
-108.9
-109.1
-108.9
-107.7
-107.3

     

        
        

The drone pilot is not at fault here.  The drone's compass malfunctioned 6.1 seconds after take off and drone may have (or may not have) changed into ATTI mode.  The manual says drone will on compass failure, but logs do not show that.  

I am sorry to hear the accident. Had you contacted our support to report this case? If you haven't, I suggest contacting them to start a case first. You can contact us at http://www.dji.com/support.

The reason for me not crashing it into the ground was in was over a sheer cliff. I wanted my drone and most importantly the SD card.  When it took off on its own I did try and fight it for a second and nothing happened. So I then stopped trying to control it since I couldn't tell exactly direction it was going, I didn't want to make it worse and fly it further off the cliff. I also let off so I could run full speed after it and keep a visual since some brush was about to block my view. After a short run it looked like it wasn't going to make it back to road height so I tried to lift it (pulled down, inverted controls). Im not sure if it even did anything. From what I noticed it never went into Atti mode and I never had any amount of control. Could be my yaw control is turned way down so I can get smooth panning shots. Either way, it should never fly like this on its own. Its a massive safety risk. and I never got a magnetic warning. I have also fly around cars and metal a lot and never had any issue at all. And Ive flown pretty far from a launch at 20% battery. I will never be worried about 68%. Its just never going to happen. Its borderline toy, not a passenger plane full of people.  I mean, even if the thing fell out of the sky because of a low battery I would happily take responsibility, but I still don't understand what the battery has to do with this. I would like to know a real way to stop this if it even happens again. Technically it should of moved far away enough to lose the interference and stabilize according to what you guys are saying and it never did. It went pretty far away from the car. From the looks of it, it flew its own course, my input did nothing to change its direction. It looks like a perfect arc to me.

I filed a report online and Im mailing in the drone and controller. I guess we shall see what DJI has to say. Just really bummed I was pressed to get another Mavic Pro when theres rumors of a new one around the corner. A $1000 isn't the type of money I can throw around.

rwynant V1 Posted at 2018-4-24 12:55
Here's what I'm seeing......... ( not a professional by any means, but I do fly Pro jobs )

68% start.....3.9v/cell    First off that is NOT 68%    ( Always start your flight with fully charged batteries )

This is absurd.

rwynant V1 Posted at 2018-4-25 08:19
Look,  I am truly sorry this happened to you,  but the reality is the software seemed to think you had a battery that was holding 68% down to 67%......when INFACT you were at 3.6v/cell which is closer to 10-12%....................... 12 seconds in the air and your load dropped available voltage to 3.6/cell

Basically you installed a dead battery.  

Wow, this is even more absurd.

HedgeTrimmer Posted at 2018-4-26 17:52
but when I look at flight log, look at controllers stick movements and pitch and roll of aircraft then it can only be said that aircraft was capable of being controlled by the pilot.  

Assuming something else was not wrong with drone.  If you do more than look at flight log, actually analyze it.  You would see the Yaw of IMU was not confused, as you mentioned.

So the pilot has no responsibility for envoirment he flies in, he has no responsibility for prechecking before flying, he has no responsibility for flying at night in a country that outlaws flying at night, if the chicken came first he laid a bad egg here.

Read your manual, because this is typical of someone after the crash wants to lay the blame at someone’s else’s door.
I may take a very pragmatic view here, you will also see that aircraft compass problem began 1 SECOND AFTER LAUNCH NOT 6.1 AFTER TAKE OFF, AIRCRAFT NEEDS TO BE IN THE AIR AFTER TAKEOFF, you can also see aircraft moving forward in the immediate few seconds after take off with no yaw input from OP, (remember was not using mode 2 to control sticks) but I checked the log and if you look at them you will see as I’ve already explained everything OP done was carried out correctly by the aircraft.
You also need to check post #22 to read what I thought happened here, other stuff I mentioned here was simply to point out how this can occur and what develops as a result , it’s very clear that simply because aircraft could not fly higher than 16ft that gps was a knock on , I believe if we could see flight played back we would see very little gps bars lit up if any at all, there is a procedure to all of this and  it’s my belief that aircraft crashed before this took place.

One other thing I never blamed OP for this crash, you seem more adept to make a decision on this but when you do it would appropriate to read log correctly, I just pointed out what I think happened, it will be up to dji to decide the outcome.

Blame doesn't empower you. It keeps you stuck in a place you don't want to be because you don't want to make the temporary, but painful decision, to be responsible for the outcome of your own life.

HedgeTrimmer Posted at 2018-4-26 08:15
But when it clears magnetic interference compass will then move to  correct heading which you would think was great. But No, what happens is  IMU is then conflicted and confused because of this sudden movement by  compass,

I can go along with first part.  But sudden compass change conflicting with output single axis (Yaw) of Inertia Measurement Unit, should be dealt with firmware of drone.  The drone should have slowly rotated left or right, then stopped rotating.

I can go along with first part.  But sudden compass change conflicting with output single axis (Yaw) of Inertia Measurement Unit, should be dealt with firmware of drone.  The drone should have slowly rotated left or right, then stopped rotating.

I absolutely agree with you on that. Moreover, since the drone had detected the compass failure it should have stopped taking its readings into consideration relying only on the IMU and GPS for stabilization (visual sensors apparently could not work in the dark). Unfortunately, the log doesn't seem to provide raw readings from the sensors (like real flight recorders do) so it is extremely difficult to judge whether the problem was in the wrong readings or in the algorithm that processed them.

asaw Posted at 2018-4-27 03:34
I can go along with first part.  But sudden compass change conflicting with output single axis (Yaw) of Inertia Measurement Unit, should be dealt with firmware of drone.  The drone should have slowly rotated left or right, then stopped rotating.

I absolutely agree with you on that. Moreover, since the drone had detected the compass failure it should have stopped taking its readings into consideration relying only on the IMU and GPS for stabilization (visual sensors apparently could not work in the dark). Unfortunately, the log doesn't seem to provide raw readings from the sensors (like real flight recorders do) so it is extremely difficult to judge whether the problem was in the wrong readings or in the algorithm that processed them.

You need to know how these aircraft work first, it’s not about how you would like to see them work, it’s the way they actually work and it’s the same for Mavic Pro phantom inspire and MavAir,

These aircraft are programmed to drop gps in favour of compass, because they simply cannot fly without compass but can with compass.
If you think that you cannot get magnetic interference without app warning you, then you are being mislead, for instance start your aircraft in your hand, then place on a manhole made of steel it will in most cases let you take off, we see it time and time again with people starting their aircraft on the way out of their house then placing on the ground close to interference, and this is how problems start.

Also aircraft and telemetry recognized compass problems less than 1 second after take off, not 6.1 seconds as poster above would like you to believe .

hallmark007 Posted at 2018-4-27 03:51
You need to know how these aircraft work first, it’s not about how you would like to see them work, it’s the way they actually work and it’s the same for Mavic Pro phantom inspire and MavAir,

These aircraft are programmed to drop gps in favour of compass, because they simply cannot fly without compass but can with compass.

These aircraft are programmed to drop gps in favour of compass, because they simply cannot fly without compass but can with compass.

Well, I agree that it is, probably, a good idea to prefer compass over sat nav, but I strongly disagree that these aircraft cannot fly without a compass. My RC helicopters fly perfectly without a compass using only an IMU (3- or 6-axis gyro as they call it). Adding a correctly working GPS to it (which in our case wasn't diagnosed as faulty) would allow a fully autonomous flight, although, not as stable as with a compass. In theory.

asaw Posted at 2018-4-27 04:04
These aircraft are programmed to drop gps in favour of compass, because they simply cannot fly without compass but can with compass.

Well, I agree that it is, probably, a good idea to prefer compass over sat nav, but I strongly disagree that these aircraft cannot fly without a compass. My RC helicopters fly perfectly without a compass using only an IMU (3- or 6-axis gyro as they call it). Adding a correctly working GPS to it (which in our case wasn't diagnosed as faulty) would allow a fully autonomous flight, although, not as stable as with a compass. In theory.

Your RC helicopter may well fly without compass, I’m not talking about that, I’m talking about these dji drones and how they work, if you think you can fly it without compass then you might try it and let us know how you get on, I for one would be interested to know how it goes for you.
But I believe there are no built in algorithms built into dji drones and it has been discussed many times on this forum to no avail, to transfer to gps/IMU only to fly your aircraft.
We have seen in MavAir for the first time in any dji drone the inclusion of second directional compass to cope with loss of gps, which is very rare.

hallmark007 Posted at 2018-4-27 04:47
Your RC helicopter may well fly without compass, I’m not talking about that, I’m talking about these dji drones and how they work, if you think you can fly it without compass then you might try it and let us know how you get on, I for one would be interested to know how it goes for you.
But I believe there are no built in algorithms built into dji drones and it has been discussed many times on this forum to no avail, to transfer to gps/IMU only to fly your aircraft.
We have seen in MavAir for the first time in any dji drone the inclusion of second directional compass to cope with loss of gps, which is very rare.

I’m talking about these dji drones and how they work

Do you imply that you know at least how they are supposed to work? If so, please explain to us what stands in the way of these drones flying without compass just like RC helicopters.

if you think you can fly it without compass then you might try it and let us know how you get on,

We are discussing such a case, aren't we? I mean this thing didn't fall out of the sky the very moment it lost compass but continued flying and even accelerated rushing towards the mountain instead! My point is that it had all the necessary information to have done much better than that.

asaw Posted at 2018-4-27 05:35
I’m talking about these dji drones and how they work

Do you pretend that you know at least how they are supposed to work? If so, please explain to us what stands in the way of these drones flying without compass just like RC helicopters.

I have explained, now maybe it’s your turn to tell us how to fly it without compass and how this was controlled.

The best way I can explain this is. If you put your Aircraft on the ground in normal circumstances, start it up, then lift it up and turn it 90 degrees to the right both your compass heading and IMU will remain at 0.
If you put your Aircraft on the ground and there is magnetic interference only the heading of your compass will change, your aircraft will still take off. But when it clears magnetic interference compass will then move to correct heading which you would think was great. But No, what happens is IMU is then conflicted and confused because of this sudden movement by compass, so you receive IMU exceptional heading warning, your aircraft cannot deal with data conflict so decides to switch to Atti mode dropping gps in favour of compass simply because aircraft can fly without gps but not compass.

With regards to what your saying maybe you will tell us how, this is my thinking of what your talking about.

The compass tells the drone which direction it's facing. The GPS data is used to find the latitude/longitude location.
Bear in mind that in a fluid such as air, Course (path across ground) and Heading (direction nose is pointed) are often different. Only in dead calm conditions would they be the same.
Same as a boat subject to the water currents or a car 'drifting'.

GPS only knows direction if it is moving. Take a handheld GPS and stop. You can turn the GPS and it will only display the proper direction after you start moving again. You need a compass to know what direction you are facing if you aren't moving.

It seems simple but look at it this way:

You're blindfolded standing on a Segway in the middle of a dynamic obstacle course. You've got a group of 12 people standing around you to give you verbal directions on which way to go. Some of them see you clearly while some see a blurry version and some may be looking at you via mirrors etc. All of them are yelling at you turn left, turn right, speed up, slow down, back up.... You're trying to listen to everyone while navigating an obstacle course that is constantly moving around you. You have to calculate which ones are collectively telling you correct info and which ones to disregard. All while someone else is remotely trying to drive your Segway.

All of this is done "behind the curtain" while we are trying to learn to fly and not crash into things

hallmark007 Posted at 2018-4-27 06:43
I have explained, now maybe it’s your turn to tell us how to fly it without compass and how this was controlled.

The best way I can explain this is. If you put your Aircraft on the ground in normal circumstances, start it up, then lift it up and turn it 90 degrees to the right both your compass heading and IMU will both move together 90 degrees and no problems.

OK, on flying without a compass. The problem here is to stabilize orientation - the pitch, roll, and yaw angle velocities - at first and then the position in space (latitude, longitude, height, and heading). To fully stabilize pitch and roll it is enough to know the accelerations along two axes determining the horizontal plane and corresponding angular velocities. To stabilize yaw the angular velocity along the vertical axis is needed. The IMU provides accelerations and angular velocities along all three axes, so there is more than enough information to stabilize the angles. This is what “gyros” in RC helicopters do. But as everyone knows flying an RC helicopter is much harder than flying any of the DJI drones. Because simpler “gyros” in helicopters only stabilize angular velocities, more advanced ones also stabilize pitch and roll relative to the horizontal plane. But they don’t stabilize the aircraft position in space: if there is a gust of wind it can easily blow the helicopter away and the pilot must always be ready to compensate for that. DJI drones add GPS and various other sensors (ultrasonic/infrared/vision/etc) to fix aircraft relative to the ground as precisely as possible. Vision sensors, for example, yield velocities which is enough information to stop the AC from arbitrarily moving in space. Note that these are not the absolute values of latitude and longitude but rather some values proportional to their derivatives. And still, these are just enough to adequately stabilize the aircraft’s position in the absence of GPS data (when flying indoors for example). It is basically the same thing with the compass. You only need a compass to know the “absolute value” of heading. But in order to adequately stabilize yaw, you only need to know the yaw rate, which is given by the IMU (and which should equal the first derivative of heading). If your compass malfunctions you still have two IMUs that give you the corresponding angular velocity. In fact, yaw angle in RC helicopters is the most stable one. So this is how you fly without a compass. If you want to automatically navigate without a compass using GPS you do it in the same manner as you navigate without a compass in your car: you choose an arbitrary direction and then compensate for errors. You don’t need to know your heading beforehand.

hallmark007 Posted at 2018-4-27 06:43
I have explained, now maybe it’s your turn to tell us how to fly it without compass and how this was controlled.

The best way I can explain this is. If you put your Aircraft on the ground in normal circumstances, start it up, then lift it up and turn it 90 degrees to the right both your compass heading and IMU will both move together 90 degrees and no problems.

But No, what happens is IMU is then conflicted and confused because of this sudden movement by compass, so you receive IMU exceptional heading warning,  

Not in the logs posted.  Perhaps DJI can see that with their flight log analyzer.

HedgeTrimmer Posted at 2018-4-27 09:56
But No, what happens is IMU is then conflicted and confused because of this sudden movement by compass, so you receive IMU exceptional heading warning,  

Not in the logs posted.  Perhaps DJI can see that with their flight log analyzer.

If you put your Aircraft on the ground and there is magnetic  interference only the heading of your compass will change, your aircraft  will still take off.

At this time, there is no proof of magnetic interference.  If there had been, the drone should request Compass Recalibration, which has happened when there was magnetic interference.

I will again suggest, the drone Pilot return to where it all happened.  Check area with a regular compass or handheld GPS with digital compass to see if there is magnetic interference.
Realizing the drone Pilot may not be able too, because of distance or only visiting area as part of a trip.

hallmark007 Posted at 2018-4-27 01:14
So the pilot has no responsibility for envoirment he flies in, he has no responsibility for prechecking before flying, he has no responsibility for flying at night in a country that outlaws flying at night, if the chicken came first he laid a bad egg here.

Read your manual, because this is typical of someone after the crash wants to lay the blame at someone’s else’s door.

So the pilot has no responsibility for envoirment he flies in, he has no  responsibility for prechecking before flying, he has no responsibility  for flying at night in a country that outlaws flying at night, if the  chicken came first he laid a bad egg here.

I never said that.  What I did point out was you were grasping a straws - when you went down path of pointing at pilot for starting a flight with battery that was not absolutely fully charged.  

hallmark007 Posted at 2018-4-27 01:14
So the pilot has no responsibility for envoirment he flies in, he has no responsibility for prechecking before flying, he has no responsibility for flying at night in a country that outlaws flying at night, if the chicken came first he laid a bad egg here.

Read your manual, because this is typical of someone after the crash wants to lay the blame at someone’s else’s door.

you will also see that aircraft compass problem began 1 SECOND AFTER LAUNCH NOT 6.1 AFTER TAKE OFF, AIRCRAFT NEEDS TO BE IN THE AIR AFTER TAKEOFF,  

You are correct.  The compass problem began 1 second after takeoff from ground.  The 6.1 seconds is from start of flight log.
Still not proof of magnetic interference.  

hallmark007 Posted at 2018-4-27 01:14
So the pilot has no responsibility for envoirment he flies in, he has no responsibility for prechecking before flying, he has no responsibility for flying at night in a country that outlaws flying at night, if the chicken came first he laid a bad egg here.

Read your manual, because this is typical of someone after the crash wants to lay the blame at someone’s else’s door.

One other thing I never blamed OP for this crash,

Except you wrote: Pilot at night decides he wants to take some photographs he launches his  aircraft with battery not charged fully he launches 6 feet from his car  on the side of a road see where I’m going here,

hallmark007 Posted at 2018-4-27 06:43
I have explained, now maybe it’s your turn to tell us how to fly it without compass and how this was controlled.

The best way I can explain this is. If you put your Aircraft on the ground in normal circumstances, start it up, then lift it up and turn it 90 degrees to the right both your compass heading and IMU will both move together 90 degrees and no problems.

GPS only knows direction if it is moving. Take a handheld GPS and stop. You can turn the GPS and it will only display the proper direction after you start moving again.  

You are preaching to Choir.  Some of us have been working with GPS long before DJI and drones.  

Ironically, in this case the drone flew off on its own accelerating ever faster.  GPS (which according to posted log was being used) would have indicate both movement and increasing speed.  Which the IMU would have collaborated.  

Put another way, even though drone didn't know which way it was facing because of compass failure, there was no reason for drone to fly X direction and increase its speed.

HedgeTrimmer Posted at 2018-4-27 09:56
But No, what happens is IMU is then conflicted and confused because of this sudden movement by compass, so you receive IMU exceptional heading warning,  

Not in the logs posted.  Perhaps DJI can see that with their flight log analyzer.

Again I never said this happened but I know how these aircraft work which you obviously don’t.

HedgeTrimmer Posted at 2018-4-27 10:01
If you put your Aircraft on the ground and there is magnetic  interference only the heading of your compass will change, your aircraft  will still take off.

At this time, there is no proof of magnetic interference.  If there had been, the drone should request Compass Recalibration, which has happened when there was magnetic interference.

If you have been reading the thread you would know that his drone is out of action, and to do what you are saying is just nothing short of ridiculous.

HedgeTrimmer Posted at 2018-4-27 10:05
So the pilot has no responsibility for envoirment he flies in, he has no  responsibility for prechecking before flying, he has no responsibility  for flying at night in a country that outlaws flying at night, if the  chicken came first he laid a bad egg here.

I never said that.  What I did point out was you were grasping a straws - when you went down path of pointing at pilot for starting a flight with battery that was not absolutely fully charged.

When did I say pilot had started with less than 100% battery, yes I did in my last post to you, but still never blamed or clutched at straws or never posted wrong information because I forgot to read the log properly.

HedgeTrimmer Posted at 2018-4-27 10:16
One other thing I never blamed OP for this crash,

Except you wrote: Pilot at night decides he wants to take some photographs he launches his  aircraft with battery not charged fully he launches 6 feet from his car  on the side of a road see where I’m going here,

If you think this is good preparation for flight that’s your prerogative, but there are plenty around here who would like best advice.
We can all see accidents waiting to happen, except you maybe.

HedgeTrimmer Posted at 2018-4-27 10:28
GPS only knows direction if it is moving. Take a handheld GPS and stop. You can turn the GPS and it will only display the proper direction after you start moving again.  

You are preaching to Choir.  Some of us have been working with GPS long before DJI and drones.  

There is no doubt about it what you know could be written on the back of a postage stamp.
I just realized today that you are the guy that said drone photography was not real photography, something else you fit on the back of that stamp.

Anyone who feels he has to big himself up here usually is lacking something.

asaw Posted at 2018-4-27 09:21
OK, on flying without a compass. The problem here is to stabilize orientation - the pitch, roll, and yaw angle velocities - at first and then the position in space (latitude, longitude, height, and heading). To fully stabilize pitch and roll it is enough to know the accelerations along two axes determining the horizontal plane and corresponding angular velocities. To stabilize yaw the angular velocity along the vertical axis is needed. The IMU provides accelerations and angular velocities along all three axes, so there is more than enough information to stabilize the angles. This is what “gyros” in RC helicopters do. But as everyone knows flying an RC helicopter is much harder than flying any of the DJI drones. Because simpler “gyros” in helicopters only stabilize angular velocities, more advanced ones also stabilize pitch and roll relative to the horizontal plane. But they don’t stabilize the aircraft position in space: if there is a gust of wind it can easily blow the helicopter away and the pilot must always be ready to compensate for that. DJI drones add GPS and various other sensors (ultrasonic/infrared/vision/etc) to fix aircraft relative to the ground as precisely as possible. Vision sensors, for example, yield velocities which is enough information to stop the AC from arbitrarily moving in space. Note that these are not the absolute values of latitude and longitude but rather some values proportional to their derivatives. And still, these are just enough to adequately stabilize the aircraft’s position in the absence of GPS data (when flying indoors for example). It is basically the same thing with the compass. You only need a compass to know the “absolute value” of heading. But in order to adequately stabilize yaw, you only need to know the yaw rate, which is given by the IMU (and which should equal the first derivative of heading). If your compass malfunctions you still have two IMUs that give you the corresponding angular velocity. In fact, yaw angle in RC helicopters is the most stable one. So this is how you fly without a compass. If you want to automatically navigate without a compass using GPS you do it in the same manner as you navigate without a compass in your car: you choose an arbitrary direction and then compensate for errors. You don’t need to know your heading beforehand.

Again I’m talking about how it is now, not what you think is a better option, there are many around here that have really credible ideas about what could or should be done to these drones to make them safer and better and yes this should be debated and discussed and I have plenty of ideas as to how all this can be improved, but this is not what you or OP bought into, and that’s what’s being discussed here, I have said how these aircraft work I expected that you would have a different position on that, and that’s what I wanted to hear not how it should be done but how it is done at present.

hallmark007 Posted at 2018-4-27 11:37
Again I’m talking about how it is now, not what you think is a better option, there are many around here that have really credible ideas about what could or should be done to these drones to make them safer and better and yes this should be debated and discussed and I have plenty of ideas as to how all this can be improved, but this is not what you or OP bought into, and that’s what’s being discussed here, I have said how these aircraft work I expected that you would have a different position on that, and that’s what I wanted to hear not how it should be done but how it is done at present.

I said how these things are generally approached in aviation because I have a background in aviation. DJI UAVs should be no different. But how they are implemented in reality only their creators can tell.

hallmark007 Posted at 2018-4-27 11:19
Again I never said this happened but I know how these aircraft work which you obviously don’t.

Well you did, and more than once.

hallmark007: it’s the magnetic interference that causes problem with compass and the compass puts IMU out of whack,

hallmark007 Posted at 2018-4-27 11:20
If you have been reading the thread you would know that his drone is out of action, and to do what you are saying is just nothing short of ridiculous.

Also said to start with compass.  He could also take along another drone.
What have you got against trying to find out?

Ever heard of - The lady doth protest too much, methinks

hallmark007 Posted at 2018-4-27 11:24
When did I say pilot had started with less than 100% battery, yes I did in my last post to you, but still never blamed or clutched at straws or never posted wrong information because I forgot to read the log properly.

hallmark007 - Pilot at night decides he wants to take some photographs he launches his aircraft with battery not charged fully

There you go, with trying to blame pilot.  Clutching at straws.  
As for reading logs properly, at least I can admit my mistakes.  See YAW in logs and your claim of confused IMU.  

hallmark007 Posted at 2018-4-27 11:37
Again I’m talking about how it is now, not what you think is a better option, there are many around here that have really credible ideas about what could or should be done to these drones to make them safer and better and yes this should be debated and discussed and I have plenty of ideas as to how all this can be improved, but this is not what you or OP bought into, and that’s what’s being discussed here, I have said how these aircraft work I expected that you would have a different position on that, and that’s what I wanted to hear not how it should be done but how it is done at present.

No what you are doing is trying to defend a narrative.  Pushing claim there was magnetic interference, without good evidence of.
Internal compass never showed it needed calibration prior to lift off, which is common sign of magnetic interference.

Ironically, one test that could easily be done to show magnetic interference, you have dismissed as ridicoulous.  

hallmark007 Posted at 2018-4-27 11:29
There is no doubt about it what you know could be written on the back of a postage stamp.
I just realized today that you are the guy that said drone photography was not real photography, something else you fit on the back of that stamp.

I just realized today that you are the guy that said drone photography was not real photography,

Not what I said, and made very clear to you several times.  The disgrace is upon you.

hallmark007 Posted at 2018-4-27 11:29
There is no doubt about it what you know could be written on the back of a postage stamp.
I just realized today that you are the guy that said drone photography was not real photography, something else you fit on the back of that stamp.

There is no doubt about it what you know could be written on the back of a postage stamp.

hallmark007: Vision position sensors on Mavic and MavAir are both the same , ultra  sonic sensor is used to measure barometric pressure and to help aircraft  maintain its current position.

hallmark007 Posted at 2018-4-27 11:27
If you think this is good preparation for flight that’s your prerogative, but there are plenty around here who would like best advice.
We can all see accidents waiting to happen, except you maybe.

We can all see accidents waiting to happen, except you maybe.  

Especially when you ignore things that don't fit your narrative of accident...

How about you provide evidence that there was Magnetic Interference that was subtle enough as not to cause drone before launch to detect Interference, yet was strong enough to cause compass to give a false reading till drone reached 5.9-feet, then have drone decide that the change in magnetic field was so drastic as to declare Compass Failure.


Being you can see accidents waiting to happen...
Please go into why the DJI's firmware decided that drone needed to start moving faster and faster till it crashed.  And why that problem was not dealt with.

HedgeTrimmer Posted at 2018-4-27 13:51
We can all see accidents waiting to happen, except you maybe.  

Especially when you ignore things that don't fit your narrative of accident...

So,  since I've been off flying......this thread appears to have turned into a Kludge!

Everyone jump in and try to define................Kludge  ( ask Siri )

Anyway,  DID either of you....Hedge and Hall see the voltage mathmatics?  Did you EVEN consider what was said? And shown as a Mathematical answer?   If there is NOT enough POWER to drive all systems....then,   Jump in here and ANSWER THAT QUESTION. JUST THAT QUESTION.

ANSWER that question.......there does NOT need to be any BS, personal opinions, jumping down someone throat......simply answer the question asked......IF YOU DON'T KNOW......Then STFU

And PLEASE stop ( what I and others see as attacking each other ) There are many things at play here, and we all have touched on them.......understand....IT'S NOT JUST 1 THING

It's a forum,  it's bouncing ideas, and possibilities off each other..........That's all.

Randy
Vice President
www.sefsd.org     The first AMA Club in the US to have a designated RotorPlex for Drone Racing and Helo activities.

HWCM Posted at 2018-4-26 22:44
Wow, this is even more absurd.

HWCM

Please see post# 35

And please,  if you can give us all a different outcome.  It's straight math.  There is no other outcome for the available power.

Oh I almost forgot.......  WOW

Randy

HedgeTrimmer Posted at 2018-4-27 13:51
We can all see accidents waiting to happen, except you maybe.  

Especially when you ignore things that don't fit your narrative of accident...

It was in Atti mode I’m not responsible for that with all your knowledge could yo nothave worked it out.