Weird hovering / landing / takeoff issue P3P

dmiles · May 12, 2018

A buddy of mine brought me his P3P, looking for some help.

It seems that it all of a sudden developed what he thought was a hovering issue. Not really toilet bowl, just drifts left right, up down more than usual. Other than that, it flies normal at altitude. It's really noticeable indoors, so I put on a known good vision module, no change.

First thought is magnetic interference, but when I fly my P3P in the exact same location, there is a huge difference. The other issue is landing and takeoff. When you land, it's like there is no landing assistance. It always wants to bounce. And when you let it idle after landing, the idle speed is not stable. Sometimes it will almost shut down, and then other times it will raise the front end of the drone by itself, without touching the sticks. And if you try to take off while it's doing this, it will just drift off in one direction until it hits something, or the motors shut down because you had the throttle pulled down to zero as soon as it started to drift. It's not a matter of taking off to slowly, I've been flying phantoms for 4 years now, and I've had it happen to me 3 times with this bird at least.

Here is what I have done so far:
Swapped vision module
Forced new firmware update, and verified with log file
Calibrated IMU, twice
Calibrated compass in yard, no metal, twice

I suspect a motor issue, but I do not want to start swapping motors with my unit. Vision module was easy, but motors are further than I want to go if I'm shotgun troubleshooting. He would buy new motors, but would rather have something else than a gut feeling to go on first.

Here is a link to my Google drive that contains a dat file. This was just hovering in my yard, and right at the end was one of those times I tried to take off, and it just shot over to the right, barely off the ground, until I killed the motor.

FLY307.DAT

I don't know how to turn these dat files into those nice graphs I see here, but I would sure like to know how to do that. Any help anyone could lend would be most helpful. Thanks.

quaddamage · May 13, 2018

It's nice to see proper description of an issue. No need of pulling tongue.

I am a bit confused by the beginning of that log. Usually after boot the GPS module reports 0 satellites, then that number goes up. Here it starts at 10 satellites. The GPS module is not even able to say whether they're GPS or Glonass sats, but already reports there's 10 of them. Then the number goes down to 6, then up again.

Meta4 · May 13, 2018

dmiles said:
It seems that it all of a sudden developed what he thought was a hovering issue. Not really toilet bowl, just drifts left right, up down more than usual. Other than that, it flies normal at altitude. It's really noticeable indoors

If it drifts around when in VPS range but hovers properly up higher that sounds like the issue is the VPS trying to lock onto an unsuitable surface with no distinct pattern or texture (like grass, plain concrete or carpet) or insufficient lighting.
Look at what the ground surface looks like.
The simple test is to switch the VPS off and see if that makes a difference.

BudWalker · May 13, 2018

dmiles said:
A buddy of mine brought me his P3P, looking for some help.

It seems that it all of a sudden developed what he thought was a hovering issue. Not really toilet bowl, just drifts left right, up down more than usual. Other than that, it flies normal at altitude. It's really noticeable indoors, so I put on a known good vision module, no change.

First thought is magnetic interference, but when I fly my P3P in the exact same location, there is a huge difference. The other issue is landing and takeoff. When you land, it's like there is no landing assistance. It always wants to bounce. And when you let it idle after landing, the idle speed is not stable. Sometimes it will almost shut down, and then other times it will raise the front end of the drone by itself, without touching the sticks. And if you try to take off while it's doing this, it will just drift off in one direction until it hits something, or the motors shut down because you had the throttle pulled down to zero as soon as it started to drift. It's not a matter of taking off to slowly, I've been flying phantoms for 4 years now, and I've had it happen to me 3 times with this bird at least.

Here is what I have done so far:
Swapped vision module
Forced new firmware update, and verified with log file
Calibrated IMU, twice
Calibrated compass in yard, no metal, twice

I suspect a motor issue, but I do not want to start swapping motors with my unit. Vision module was easy, but motors are further than I want to go if I'm shotgun troubleshooting. He would buy new motors, but would rather have something else than a gut feeling to go on first.

Here is a link to my Google drive that contains a dat file. This was just hovering in my yard, and right at the end was one of those times I tried to take off, and it just shot over to the right, barely off the ground, until I killed the motor.

FLY307.DAT

I don't know how to turn these dat files into those nice graphs I see here, but I would sure like to know how to do that. Any help anyone could lend would be most helpful. Thanks.

FLY307.DAT isn't an actual flight. There isn't a motor start. Take a look here for help on picking the right .DAT.

dmiles · May 13, 2018

BudWalker said:
FLY307.DAT isn't an actual flight. There isn't a motor start. Take a look here for help on picking the right .DAT.

That's interesting. The reason I picked this file is because all I did was try to take off while it was idling as I described earlier, (motors slow down, then rev up on their own). It shot to the right, and I immediately pulled back on the throttle to kill the motors. There is really no other choice at that point. So I selected this dat file because it was the last one with yesterday's date on it, and I figured it would make it simpler to analyze. I don't know at what point it terminates a dat file, or when it starts a new one.

I have no problem selecting and retrieving the dat file, and running it through datcon. Where I run in to a problem is what to do with that spreadsheet full of numbers. I don't know what to do with all that data. If I did, I would sift through it myself, and be able to focus in on the issue before I call for help. The only spreadsheet software I've used is Open Office Calc. I do have access to Excel, just wondering if Excel would give me a more useful representation of all that data.

Anywho, not at all doubting your analysis of the data. I have been around these forums long enough, and done enough reading to know that all you guys that responded are the best there is at figuring this stuff out, that's why I took the time to retrieve the data, and call for help. I appreciate it, and I can tell you my buddy and his son do as well. To me, the biggest issue is landing, and figuring out what the heck is going on with those motors while idling, and then trying to take off after landing. I did try turning off VPS, and it made no difference. Also, when I fly my own P3P over the exact same area, it doesn't drift nearly as much.

Also, I don't seem to see the issue where it shoots off to one direction on the initial takeoff....only seems to do it once you have landed, and then try to take off again. So I could be like the doctor that when you tell him it hurts when I do this, and he says don't do that. He is actually able to use it the way it is, it's just obvious to me that there is an issue with this bird, and it's one I have never seen before.

There was only one other dat file generated yesterday, while I was doing this. It is much larger, so I zipped it. There is a lot more hovering, but no actual flight at altitude. Here is the link, and thanks again guys.

FLY306.zip

BudWalker · May 13, 2018

dmiles said:
That's interesting. The reason I picked this file is because all I did was try to take off while it was idling as I described earlier, (motors slow down, then rev up on their own). It shot to the right, and I immediately pulled back on the throttle to kill the motors. There is really no other choice at that point. So I selected this dat file because it was the last one with yesterday's date on it, and I figured it would make it simpler to analyze. I don't know at what point it terminates a dat file, or when it starts a new one.

I have no problem selecting and retrieving the dat file, and running it through datcon. Where I run in to a problem is what to do with that spreadsheet full of numbers. I don't know what to do with all that data. If I did, I would sift through it myself, and be able to focus in on the issue before I call for help. The only spreadsheet software I've used is Open Office Calc. I do have access to Excel, just wondering if Excel would give me a more useful representation of all that data.

Anywho, not at all doubting your analysis of the data. I have been around these forums long enough, and done enough reading to know that all you guys that responded are the best there is at figuring this stuff out, that's why I took the time to retrieve the data, and call for help. I appreciate it, and I can tell you my buddy and his son do as well. To me, the biggest issue is landing, and figuring out what the heck is going on with those motors while idling, and then trying to take off after landing. I did try turning off VPS, and it made no difference. Also, when I fly my own P3P over the exact same area, it doesn't drift nearly as much.

Also, I don't seem to see the issue where it shoots off to one direction on the initial takeoff....only seems to do it once you have landed, and then try to take off again. So I could be like the doctor that when you tell him it hurts when I do this, and he says don't do that. He is actually able to use it the way it is, it's just obvious to me that there is an issue with this bird, and it's one I have never seen before.

There was only one other dat file generated yesterday, while I was doing this. It is much larger, so I zipped it. There is a lot more hovering, but no actual flight at altitude. Here is the link, and thanks again guys.

FLY306.zip

This one doesn't seem to have a fly away incident that you've been describing. But, it does show the motors not idling after you've "landed" it. The quotes are because, although it's sitting on the ground the P3 doesn't think it's landed. Here's an example where this happened

The leftFront is idling but the other three are still trying to level the P3. Note, that the P3 doesn't even think it's near the ground at this point. Isn't this normal behavior?

Re your question about how to do the plotting you could try CsvView which can be obtained here.

dmiles · May 13, 2018

Thanks @BudWalker . I admit to being a bit confused, but couldn't the activity starting at 69.187 represent a flyaway situation? The drop to 0 rpm at aprox. 84 sec. would be what I would expect to see, given that I immediately pulled the throttle to zero. So if only 3 motors are responding, couldn't that account for the flyaway? Also, what defect would cause the bird not to know it is on the ground?

Just to recap, here is a description of the flyaway situation:

The bird has been landed, and it's sitting on the ground, idling.

The motor speeds seem to drift. They may drop, almost to zero, or they may increase, even to the point of lifting one end off the ground, with fingers off the sticks. I have recalibrated the controllers, and it does it with 2 different controllers (his and mine, both the same behavior)

If you try to takeoff, instead of moving straight up, it moves to one side, at relatively high speed, (I have seen backwards movement as well) just inches off the ground.

At that point, the only option is to pull down on the throttle, hopefully shutting off the motors, before it hits something.

At altitude, flight seems normal.

dmiles · May 13, 2018

OK guys, the CsvView is what I was looking for. You have created a monster.

I have a new dat file. In this file, there are 2 normal takeoffs, hovers, and landings. After the second landing, while the bird is idling on the ground is where the fun begins. At 124 sec., the right back motor control signal goes flat at a constant value of 14.67, while the other three start to increase. This is what I was talking about when I said the motor speeds would start to increase on their own until it would start to lift one side of the bird off the ground.

When the throttle is increased to try to take off in this condition, that is when the flyaway happens. I was hoping it was the motor, because that would be an easy, cheap replacement. But it looks like the issue is whatever is causing that pwm signal for the right back motor to go flat. The motor just appears to be doing what it's told. It's weird that when throttle is applied, the right back pwm signal responds, and starts to look normal again.

I suspect that the failure is something in the motor control circuitry for the right back motor, but I don't know enough about how that is done on the P3P to say for sure. If anyone knows of any information on how this is done, please point me in that direction. As always, any input is appreciated, and thanks again.

FLY309.zip

BudWalker · May 13, 2018

dmiles said:
Thanks @BudWalker . I admit to being a bit confused, but couldn't the activity starting at 69.187 represent a flyaway situation? The drop to 0 rpm at aprox. 84 sec. would be what I would expect to see, given that I immediately pulled the throttle to zero. So if only 3 motors are responding, couldn't that account for the flyaway? Also, what defect would cause the bird not to know it is on the ground?

Just to recap, here is a description of the flyaway situation:

The bird has been landed, and it's sitting on the ground, idling.

The motor speeds seem to drift. They may drop, almost to zero, or they may increase, even to the point of lifting one end off the ground, with fingers off the sticks. I have recalibrated the controllers, and it does it with 2 different controllers (his and mine, both the same behavior)

If you try to takeoff, instead of moving straight up, it moves to one side, at relatively high speed, (I have seen backwards movement as well) just inches off the ground.

At that point, the only option is to pull down on the throttle, hopefully shutting off the motors, before it hits something.

At altitude, flight seems normal.

The bird has been landed, and it's sitting on the ground, idling.
But, by your description they aren't idling.
The motor speeds seem to drift. They may drop, almost to zero, or they may increase, even to the point of lifting one end off the ground,
Doesn't the plot show the behavior you're describing?

I don't think it's a defect that the P3 didn't know it's on the ground. It's not as smart and waits for the IMU data to say it isn't descending when the control inputs would be causing it to descend if it were not on the ground. You know it thinks it's landed when the motors stop. The eventLog stream shows it didn't think it had landed until 83 secs.

-.062 : 4051 [M.Start]REQ_RC_NORMAL
-.062 : 4051 [Ctrl<2>] REQ_RC_COMMAND ENGINE_START ctrl_engine_start
-.042 : 4052 [IOC.CL ] -95.0 Degree
-.042 : 4052 [TO.ALT ] 80.624916
.658 : 4087 32.5888239 -83.7081114 100.62 Home Point
1.698 : 4139 [LED] changed: set home
1.958 : 4152 [Ctrl<2>] REQ_RC_COMMAND ASST_TAKEOFF_HOLD ctrl_asst_takeoff
3.198 : 4214 [LED] changed: normal led
4.078 : 4258 CTRL reset all by assisted takeoff finish
4.098 : 4259 [Ctrl<1>] REQ_RC_NORMAL ATTI_HOLD ctrl_gps_atti
83.098 : 8209 [M. Stop]landing.RC_Thr

Kinda looks to me like full negative throttle caused it to descend until it touched the ground. But the negative throttle was released before the P3 could see the negative throttle and not descending. The next negative throttle was at 81 secs and was long enough for the P3 to see the negative throttle and not descending.

BTW, the full negative throttle is coincident with a small amount of positive rudder.Maybe the throttle isn't being pulled straight back.

OK guys, the CsvView is what I was looking for. You have created a monster.

dmiles · May 13, 2018

BudWalker said:
The bird has been landed, and it's sitting on the ground, idling.
But, by your description they aren't idling.
The motor speeds seem to drift. They may drop, almost to zero, or they may increase, even to the point of lifting one end off the ground,
Doesn't the plot show the behavior you're describing?

I don't think it's a defect that the P3 didn't know it's on the ground. It's not as smart and waits for the IMU data to say it isn't descending when the control inputs would be causing it to descend if it were not on the ground. You know it thinks it's landed when the motors stop. The eventLog stream shows it didn't think it had landed until 83 secs.

-.062 : 4051 [M.Start]REQ_RC_NORMAL
-.062 : 4051 [Ctrl<2>] REQ_RC_COMMAND ENGINE_START ctrl_engine_start
-.042 : 4052 [IOC.CL ] -95.0 Degree
-.042 : 4052 [TO.ALT ] 80.624916
.658 : 4087 32.5888239 -83.7081114 100.62 Home Point
1.698 : 4139 [LED] changed: set home
1.958 : 4152 [Ctrl<2>] REQ_RC_COMMAND ASST_TAKEOFF_HOLD ctrl_asst_takeoff
3.198 : 4214 [LED] changed: normal led
4.078 : 4258 CTRL reset all by assisted takeoff finish
4.098 : 4259 [Ctrl<1>] REQ_RC_NORMAL ATTI_HOLD ctrl_gps_atti
83.098 : 8209 [M. Stop]landing.RC_Thr

Kinda looks to me like full negative throttle caused it to descend until it touched the ground. But the negative throttle was released before the P3 could see the negative throttle and not descending. The next negative throttle was at 81 secs and was long enough for the P3 to see the negative throttle and not descending.
View attachment 98812

BTW, the full negative throttle is coincident with a small amount of positive rudder.Maybe the throttle isn't being pulled straight back.

OK guys, the CsvView is what I was looking for. You have created a monster.

So you think that this is normal? Because it doesn't act like any P3P I've ever flown, and I've flown several.

BudWalker · May 13, 2018

dmiles said:
So you think that this is normal? Because it doesn't act like any P3P I've ever flown, and I've flown several.

I don't actually know since I've never done this with my P3P. I always pull the throttle back until the motors quit.The behavior seems normal to me given that the P3P doesn't think it's landed. The question you should be asking is why the P3P doesn't think it's landed. You'll need to use DatCon to see the eventLog stream which will show if the P3P thinks it has landed.

dmiles · May 13, 2018

BudWalker said:
I don't actually know since I've never done this with my P3P. I always pull the throttle back until the motors quit.The behavior seems normal to me given that the P3P doesn't think it's landed. The question you should be asking is why the P3P doesn't think it's landed. You'll need to use DatCon to see the eventLog stream which will show if the P3P thinks it has landed.

So if it doesn't think it has landed, then it's sitting on the ground trying to maintain level flight. That would explain why the first takeoff is always good. It would also explain the rough landings. I'll have to look into this further I guess.

BudWalker · May 13, 2018

@dmiles One other thing I noticed and forgot to mention. It's not always the leftBack that is slowest and flatlined. It can also be the leftFront and rightFront.

dmiles · May 13, 2018

Soooooo, I'm embarrassed. If you land but do not shut down the motors, the P3 doesn't know you landed. I tried the same thing with my P3P, and it does the exact same thing. In over 4 years of flying Phantoms, I never knew this. Thanks for your time, sorry to have wasted it. I did learn a lot, so hopefully it wasn't a total waste. It looks like there is actually nothing wrong with my buddies P3P after all. Now he claims it's better since we did the IMU calibration. Who knows, the first time we did it I did the IMU test, and it did say it was required. Looks like we just made up the other problem.