[Penthane]

Hi people, I've got an interesting but annoying problem to solve. Anybody care to help?

I'm building a larger drone for finding lost small ones   We fly at a very wet piece of land and we loose much precious flying time wading through ankle deep water, searching for 250 drones. So I need Pos.Hold, a gimbal and manual control over camera pitch. I use 6ch RX's, so ch1-4 for motors, 5 for flight mode and 6 for gimbal pitch.

I started with just a basic drone: Revolution FC, ext. Ublox GPS+Mag, 450 frame, 4x 2216 1250kv, 4x LittleBee 40A, 2x2200mAh/3s with a 2A BEC (will be replaced by a 3A UBEC, when it arrives) and 1045 props shortened to 9". 1045 Hovered unstable and though the drone will not auto-land through it's own wash, it hovers very stable with 9"props.

After setup, I made some 10 flights without any trouble. Drone was stable, smooth, easy to fly. Pos.Hold and RTB worked 100%

Then it was time to make a gimbal and  stick it on the drone. Instructions on the internet were clear and it took only 5, 10 minutes tops, to get it to work. And 30 more to get it to move the right way

As I needed ch6 for manual gimbal pitch control, I had to switch arming procedure from acc.0 to any of the stick moves. As soon as I saved, Config Error went red: INS13 not selected. But INS13 IS selected and has a green light, as have all the other Health page items. If I remove all Assisted Control, Config Error goes green too. So I have ALL green, but if I select Ass. Control, Config Error goes red.

Quad-X: https://photos.app.goo.gl/ssk7DCpPSfFag6xu7
GPS/Mag is some 9" away from any high power cables and 11" from the motors. Revolution is lifted up and away from power cables about 2" too. And it's almost 6" from the motors. Both Mags calibrate fine at about 1-3%. Most wires have been twisted.

Screenshot of GCS is attached.
I have tried two different version of LP-Next. Wiped the Revo several times in a row and started all over. No cigar!
So, what am I missing?

[karla]

No cigar :0 that's terrible!
I am sure Cliff will come by in some hours and give you a great answer on how to solve this.
Meanwhile, if you are around, you can tell what version of LP you use and upload the config file?

[Penthane]

Ahhh, forgot to attach them.
I have tried Next 735 and Next 782. I don't notice any difference.

[karla]

When the system health is complaining about your configuration (stabilized1), I noticed you have GPS assist activated at the same time the Thrust control is set to AltitudeVario - I think these two should not be mixed. The assist will take care of the altitude and much more. When leave the sticks it should work like pos hold.

Not sure here, but I would try to set it to manual and the GPS assist setting will still take take care of it.

I also noticed you have the Flight mode switch set for channel 5 but you also have the gimbal Roll set for channel 5, how will that work without a conflict?
 

[Penthane]

Hi Karla,

- "GPS assist activated at the same time the Thrust control is set to AltitudeVario"
    As far as I know, AltitudeVario only determines the way your throttle works. Instead of CruiseControl, which 'feels' like the throttle of an airplane (more Throttle on the TX = more Thrust), AltitudeVario works more like the 'Collective' of a 3D-helicopter; centered it doesn't rise or descend. If you want up, you push up. If you want down, you pull down. And I have had TC to CruiseControl. No difference. Config Error stays.

- When leave the sticks it should work like pos hold.
     It does! But AltitudeHold is done through barometer sensor, not by GPS. I think. Maybe a mix of both on INS13. GPS can be some 15-20" off. Not really a problem for position, but for altitude it's a bit much.

- I would try to set it to manual and the GPS assist setting will still take take care of it.
     Don't think so. Manual Throttle is for airplanes. All motors of your drone will run the same speed on Manual Throttle and thus you will have no stabilisation. You can NEVER use Manual Throttle on a drone. Unless you tie it to your bicycle and let it push. Which is great fun by the way You'd be surprised what 10LBS thrust on your bike does.

- I also noticed you have the Flight mode with set for channel 5 but you also have the gimbal Roll set for channel 5, how will that work without a conflict?
     Flight Mode on CH5 from TX to RX (Input). Gimbal Roll on CH5 from FC to gimbal (Output / Gimbal page). Input and Output are totally seperated by the FC.
Example: Usually you have Throttle on CH3 on your TX. But from FC to motors (output), you use CH 1-4. On airplanes You have Throttle on CH3 (Input) as well, but output to motor is always on CH4 (unless you have twin motors with differential steering, then you need two output CHs). But they are mostly just conventions. If you want, you can change them. Most times on an airplane, Roll (ailerons) use CHs 1 and 6 (one for each servo). But if you  want, you can use CH 5 and 6 or 1 and 5 just as easy. The FC doesn't care. It's Fly-by-Wire; you tell the FC what you want it to do on the Input side and the FC autonomously acts accordingly on the Output side. So what you tell the FC to do (TX to RX), can never conflict with what the FC is ordering it's motors to do.

But I might be wrong, cause (FC-controlled) airplanes is my main 'business'. I'm mainly building this quad for searching downed vehicles. My mates fly helis and 250-racing drones mainly and especially the 250s are hard to find sometimes. But you'd be amazed how much time it took to find my 5' span, bright yellow and orange airplane. We fly in a pretty rough area. There isn't much room to fly here in the West of The Netherlands. It's a small country, with a lot of people. And the no-fly-zones of Schiphol (main airport) and a few others, cover most of the country. Cops don't usually make a fuss, as long as you stay away from flying above other people, roads, animals, buildings, etc., etc.. That's why we fly over a marsh-like area. So, boots and search-drone are mandatory

[karla]

Hi,
NL, nice.
I agree with your reasoning and can't see anything wrong with it.
Also tried to swop around with settings but GPS assist on then Config error what ever setting.
Need to wait for the oracle to pass by here and drop some light on the matter.

[TheOtherCliff]

1045 props shortened to 9". 1045 Hovered unstable and though the drone will not auto-land through it's own wash, it hovers very stable with 9"props.

1045 are a bit too large for typical sized 1250KV motors, but I wouldn't expect it to be unstable.  It sounds like your PIDs need tuning, especially if it won't descend through it's downwash.  Might I suggest you try AutoTune for that, but make sure your props are well balanced before that.
https://librepilot.atlassian.net/wiki/spaces/LPDOC/pages/25657377/AutoTune
(skip down to the simplified instructions, it really isn't too bad)

There is a scary and dangerous procedure you can do to use the Output page "Test Outputs" to run one motor at a time to full power to check prop balance.  DO IT WITH PROPS OFF until you fully understand the Home and End keys and left and right arrow to control the currently selected slider.  Props must be on to test correctly.  This is dangerous, but it will give good information about props balance.
https://librepilot.atlassian.net/wiki/spaces/LPDOC/pages/12058743/ESC+Calibration

If I remove all Assisted Control, Config Error goes green too. So I have ALL green, but if I select Ass. Control, Config Error goes red.

I didn't see any of the obvious problems with your setup.  The one thing to remember is that you don't use GPS assist with a GPS flight mode.

I had problems building that version (probably old machine needs newer QT) so I can't load that UAV file.

Found it.  At least one problem.  You have it set as a Custom aircraft type.  It must be a Multirotor to use GPS Assist.

GPS/Mag is some 9" away from any high power cables and 11" from the motors. Revolution is lifted up and away from power cables about 2" too. And it's almost 6" from the motors. Both Mags calibrate fine at about 1-3%. Most wires have been twisted.

Problems in these areas would cause flight problems, but not config error before even flying.

But AltitudeHold is done through barometer sensor, not by GPS. I think. Maybe a mix of both on INS13. GPS can be some 15-20" off. Not really a problem for position, but for altitude it's a bit much.

All of the GPS's we modelers use have much worse vertical accuracy and better horizontal accuracy.  INS13 uses both GPS and Baro for altitude.  Baro does not give repeatable altitude from day to day when for instance a weather front is moving through.  Basically, GPS gives initial altitude (more accurate from day to day), and Baro takes it from there (more accurate in the short term).  The place where this is a problem is trying to use the same waypoint flight plan on different days.  I always figure that the flight plan needs to be 3-4 meters above the ground to never have a problem.

[Penthane]

1045 are a bit too large for typical sized 1250KV motors

According to incuded manual sizes 8" - 10" are fit for this motor. Should give 1.3kg thrust on a 1045. I ran it on 8047s, the props I usually use on the xa2212 1400kv for my airplanes, but they are too small for this motor. So I took the 1045's and made them into bullnosed 9" blades.

Might I suggest you try AutoTune for that, but make sure your props are well balanced before that.

They have been balanced on a magnetic prop balancer.  It is possible that there is some inbalance in the motors. Maybe as a last resort I'll try the 'test output' trick.

I didn't see any of the obvious problems with your setup.  The one thing to remember is that you don't use GPS assist with a GPS flight mode.

I know. Pos.Hold and RTB have GPS 'built in', so it would be double GPS assist.

At least one problem.  You have it set as a Custom aircraft type.  It must be a Multirotor to use GPS Assist.

Cliff, you're great! That's it! As soon as I setup the gimbal ... Config Error!
But I need to set output CH 5 and 6 to Camera Roll and Camera Pitch and I can only do that in Custom setup or do I?
As soon as I click on [Save] in Multirotor Tab, Gimbal setup is gone. So, I have a none GPS flying drone with gimbal or a GPS flying drone without gimbal?
Haven't got a lot of time. Doing this 'in between', so I'll search the internet later for instructions on Gimbals and GPS assist.

Thanks, at least I now know what to search for.

[Penthane]

GOT IT! 

This is what happened:

Ev'rytime I Saved on the Multi-copter Tab, my gimbal-settings were wiped.
Instructive video on YT said to set CH 5 and 6 on Output Tab to 1050 and 1950 to be able to select CH 5and 6 in Gimbal-settings.
Problem was that in Output Tab, All but CH 1-4 were greyed out.
So this is what worked for me:

1- Go to Vehicle Configuration. Custom Tab. Set CH 5 and 6 to Camera Roll and Camera Pitch. Save. If GPS Assist is set anywhere in Flght Mode Switch Settings, Config Error will light up red.

2- Go to Output Config and set both CH 5 and 6 to 1050 and 1950. Put the sliders on 1500. You can tune that later.

3- Go to Gimbal Config and enable gimbal. Set Output channel for Roll and/or Pitch (5 and 6)

4- Go back to Vehicle Config, Multi-rotor Tab and click Save

5- Go back to Output Config and repeat the steps in 2 and 3

6- Tune the Output and Gimbal config

There should be no Config Error now and GPS assist is possible on Stabilized. It's possible to put GPS-assist on PosHold too. It adds an active break if PosHold is activated.

Now I can go ahead with the FPV-gear I just received

Thanks again for the support!

[TheOtherCliff]

May I suggest that VelocityRoam (a GPS mode that is just PositionHold when sticks are centered and doesn't need GPS Assist) is a good equivalent to Attitude+GPSAssist.  It's what I use on my photography quads.

If your configured max speed is 10 m/s, then e.g. holding half stick in any direction makes it fly at 5 m/s in that direction, regardless of wind.  With wind and Attitude+GPSAssist you have to compensate for the wind while moving.  Attitude+GPSAssist is Attitude mode that only goes into PositionHold if the sticks are centered, but I confess that I haven't actually tried it.    Then there are other GPS modes where e.g. forward is always north or always away from the takeoff location, or left and right just temporarily deviate from the direction you were flying when you entered the mode, etc.

Taking off in Attitude and switching to VelocityRoam is best though.  GPS location drifts a little, so a slow takeoff can allow it to think it needs to move sideways before being fully in the air.  It drags along the ground a little and may tip over.

[Penthane]

Cliff, I tried all flight modes a few years ago. I like Absolute Position for if -or better when-  I loose orientation and ofcourse my guardian angel failsafe: RTB. With some, like VelocityRoam and Stabilized+GPS I didn't see much difference. But I faintly remember that there wás a difference and I liked Stabilized better, but don't ask me why, cause I really don't know anymore. It's one of those things; you make a choice and stick with it for years, without remembering why you chose one over the other. I will check out VR vs Stabilized again... when it's nice and warm outside, COVID19 has gone and I have some more time again.