81

Vehicles - MultiRotors / Re: GPS modes oscillations

« Last post by TheOtherCliff on June 24, 2022, 01:14:15 pm »

(see threads linked at bottom for details)

At least one of these is related to running OSD / telemetry.  Are you running one of these?  For a test, you could get it back to happening again and then try disabling OSD / telemetry.

Another is related to bad sensor (accels) calibration with an explanation that makes sense.  If you do a slow pirouette in VelocityRoam mode does it move away (say a meter or more) during the first 180 of the pirouette and come back as you approach completing the 360?

At least one of these (for me) only happens if the drone is facing south.  For you it may be a different direction.  For me that explains why it happens some times and not others.

If you turn off OSD and it goes away.  It appears that the way the high priority telemetry protocol (1ms-2ms window for reply) is coded, that it interferes with the high priority stabilization task, or that there is am OSD buffer full issue and it waits for room in the buffer.  There is a forum thread that discusses this.  It is just possible that it is caused by running too slow of a data rate for the amount of OSD / telemetry data that is being sent and increasing the data rate (just for a test if that makes your OSD / telemetry unusable).  I would have to refer to the thread for details; its been a while.

The slow one that happens with DJI Naza GPSs can be helped with a DJI GPS code patch (there is a forum thread that has code and binaries) that artificially removes the data smoothing that happens in the GPS.  Same issue can be seen with a Ublox GPS if you set the UbxDynamicModel to Pedestrian or the like, which does a lot more smoothing than Airborne 1-2-4G.  Maybe setting the GPS baud rate or report rate (UbxRate) too low might cause it too.

I have seen that the slow oscillation occurs in steps and that the steps are at the speed of the fast oscillation.

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so it seems the fast oscillation is caused by bad accel calibration (test in Attitude mode with neutral tx trims or just recalibrate accels)
and the slow one is caused by telemetry/OSD (low baud rate / buffer full ?) conflicting with stabilization (disable telemetry/OSD for a test)

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https://forum.librepilot.org/index.php?topic=4923.msg33063#msg33063
https://forum.librepilot.org/index.php?topic=4941.msg33301#msg33301

82

Vehicles - MultiRotors / GPS modes oscillations

« Last post by vgwit on June 24, 2022, 09:54:18 am »

It looks like attention to the progect is fading but have decided to post my experience nevertheless.

Have solved the problem with slow quad oscillation (toilet bowl) in GPS modes. It was caused by an interference/noise from Runcam2 camera to GPS module GN-801 that was sitting upon it. After moving the GPS by 5 cm back the problem has gone.

Now I'm focused on minimizing/removing fast oscillations in GPS modes. Its frequency is 5Hz and looks like it is the same as UbxRate setting in GCS. As these oscillations present in both PH and VR modes settings like ...VelPID hardly can help. Have tried to decrease HorizontalPosP but without obvious result. I'd try to decrease D part of  PID PH algorithm but can not find it. Only P part available.

Magnrtomeret calibration was repeated many times. No change.
Thanks for attention.

83

Applications - Autonomous Flight / Re: Voltage / Current Sensor Ground Issues

« Last post by TheOtherCliff on June 22, 2022, 02:41:28 pm »

Some ESC's BECs have two LM7805 5v regulators in parallel.  It has been my assumption that paralleling ESC's BECs would be similar to what is already going on inside a single ESC.  I know that this will put more load on one than another, due to manufacturing tolerances.  I leave my 4 ESC BECs connected in parallel and I can tell that one gets warmer than the others because it is the one actually being used (highest voltage) leaving the others basically switched off.

I have heard though, that it is not good to parallel switching BECs...

About: Current Sensor Ground Issues
Setting up a proper single point ground is one of the solutions I thought about and the correct way to do it.  Problem is that cheap sensors are leaving the BEC unpopulated now days, and that basically means a single ground is difficult to do (or requires adding a BEC at the current sensor for sake of the FC ADC).

If it was a simple matter of power wires with varying ground potential along the length; with sensor in one place and ADC ground in another, then a fix of having a current to voltage tweak seemed a simple fix.  I coded it up and it seems to work.  I will flight test it next flying session.

84

Applications - Autonomous Flight / Re: Voltage / Current Sensor Ground Issues

« Last post by jdl on June 22, 2022, 10:35:30 am »

Probably a ground loop issue here?

How many ground wires go to the flight controller? It should be only one ground wire! ESCs / servos should have only their signal wires connected to the FC.  Then there shouldn't be invalid voltage readings, regardless of current being drawn.

BTW, connecting together the +5V coming from BECs built in the ESCs is a key to disaster   Voltage sources shouldn't be wired in parallel. There are always minor differences in BEC voltages that may float with temperature and once the difference is big enough this will stress too much one of the BECs, causing more and more current to be drawn from one BEC to another in attempt to equilise the voltages, this will heat the BEC even further, causing bigger drift in its output voltage, etc... Finally the BEC temperature rises so much that it causes the ESC to enter thermal protection mode and the quad, presumably, to crash...


Shunt type current sensors we commonly use are not precise for small currents, I prefer calibrating them for typical in-flight currents (8-15A, for example). The easy and precise way is using a current/Ah meter, compare its readings to what the GCS reports for mAh used (via Oplink telemetry) and correct the calibration coefficient respetively.

Zero current trim should not be used with this type of sensors, it makes sense and is intended for hall effect current sensors (like ACS758LCB-100B).

To have best calibration results, telemetry should be via Oplink, and no USB cable connected.


https://rcecho.com/skyrc-rc-model-wm-010-high-precision-rc-hobby-battery-watt-meter-bk210/

85

Applications - Autonomous Flight / Re: Voltage / Current Sensor Ground Issues

« Last post by TheOtherCliff on June 22, 2022, 07:25:28 am »

My voltage readings are OK at low amps.

I am not able to get consistent low current readings either, even with trimming the zero current.  It changes with the day or the battery.

Do you use the BEC built into the current/voltage sensor to power the FC?

How much max current in your vehicle and what gauge power wires?

Thanks!

86

Applications - Autonomous Flight / Re: Voltage / Current Sensor Ground Issues

« Last post by karla on June 22, 2022, 03:48:29 am »

I usually have problems with inaccurate Amp readings but the Voltage normally okay.

87

Applications - Autonomous Flight / Voltage / Current Sensor Ground Issues

« Last post by TheOtherCliff on June 22, 2022, 12:40:18 am »

I have calibrated and tested my voltage / current sensor on the bench.  When I run the bench power supply variable voltage up and down, telemetry agrees with the voltage.  When I fly it (a 40 amp max total draw quad) the voltage is invalid.  I shows about 8 volts from a 12 volt pack.  I know this is wrong because my lipo alarm acts normally and does not come on till later in the flight when it should.

This is a cheap 90A sensor.  The power wires are 16 AWG which is too small.  That's one issue, but probably not the cause.

The sensor board has a BEC but I am not using it, so I presume I am getting a difference in ground between the FC where the ADC is (powered by ESCs BEC at the end of the power wires) and sensor board that is on the power wires closer to the battery.

Is this a standard problem?

I suppose I could use the sensor's BEC and disconnect both ground and +5V from the ESCs.

I am thinking of coding a current to voltage factor into the sensor flight code.  I think that would fix the issue too.

88

GCS General / Re: Saving PFD gadget to mpeg file..

« Last post by Marico on June 21, 2022, 02:15:29 pm »

I would bet that it is quite possible, especially in Linux.  I haven't ever done it though.  Maybe someone else can jump in here...

Yes, I forget say that I need this in Linux. 

Of course you could do a screen / desktop record.  The one I use allows full screen, window, or even a user defined rectangle as I recall.  I know, I would want to capture it more directly if I were doing it too.

I know but if it is possible in "native" way (gstreamer script?) It would be much better.

89

GCS General / Re: Saving PFD gadget to mpeg file..

« Last post by TheOtherCliff on June 21, 2022, 12:23:51 pm »

I would bet that it is quite possible, especially in Linux.  I haven't ever done it though.  Maybe someone else can jump in here...

Of course you could do a screen / desktop record.  The one I use allows full screen, window, or even a user defined rectangle as I recall.  I know, I would want to capture it more directly if I were doing it too.

90

GCS General / Saving PFD gadget to mpeg file..

« Last post by Marico on June 21, 2022, 10:14:17 am »

Hello,
is it possible to save PFD gadget animation with black background (during log playback) to a high resolution mpeg file? I need it for post process video editing/merging  with high resolution videos.  I read "New gadget" thread but it covers only mixing video input (USB camera etc) with PFD, not saving only PFD to a file....