Auto take-off

[Yuri Pederi]

Dear all,

I did auto take-off and first 20 meters the UAV was running along the runway but then suddenly turned left off the runway and we had to take over manually.

The runway heading is 12 degrees. The compass heading was around 0 and GPS heading was increasing to 11-12 degrees as the speed was going up. I assume that Desired heading was driven by Compass heading and autopilot tried to reduce GPS heading to Desired heading turning left that drove the UAV off the runway.

If i recalibrate the Compass to get the right heading will that fix the problem of slipping off the runway? Is there a way to offset the current compass calibration to adjust it to the right heading? Is there a way to set Desired heading manually in Horizon?

The log and vrs files are attached. Appreciate your help.

Regards,

Yuri

[Evan Schellenberg]

Hello Yuri,

As you mentioned, you will need the compass to give the right heading to prevent this problem. The desired heading locked on at 2 degrees during takeoff due to the incorrect compass heading.

You can replay the last compass calibration you did by opening the compassCal plugin, clicking File -> Replay calibration data, and then selecting the last calibration folder. This will let you repeat certain steps if you think they were not done well initially, or you can adjust the calibration values on the last step and test the results immediately to try and fix the bias.

There is currently no way to set a specific desired heading before takeoff.

If you have added any new equipment to the plane or repositioned any hardware that is affecting the compass reading it would be best to perform a full compass calibration.

Evan Schellenberg

MicroPilot Support

[Yuri Pederi]

Dear Evan,

Quick question: Is it possible to set desired heading from pre-defined runways to lock heading during take-off?

Regards,

Yuri

[Evan Schellenberg]

Hi Yuri,

The heading of the pre-defined runway will be saved in the runway heading field during takeoff, but that is only used for landing.

During takeoff, when the wait for speed state starts the current heading is locked onto for the Rudder from Heading loop. So it doesn't use a specific runway heading at that point.

Evan Schellenberg

MicroPilot Support

[Yuri Pederi]

Thanks Evan, this is clear now how it works. Do you think it's possible to customize Rudder from Heading loop? Can I feed runway heading in the loop during take-off instead of locked desired heading after reaching certain speed?

[Evan Schellenberg]

Hi Yuri,

With an XTENDER user code plugin on the autopilot that is definitely possible. But otherwise there isn't any normal way to do that.

The one possibility could be to use a thread in the fly file that checks the [tState], so it only runs when taking off, that sets [dHeading] to your desired heading repeatedly.

In a quick Horizon simulation test it seems the default UAV model/VRS is very sensitive and spins easily when the desired heading is changed from the initial heading.

You could try tuning the simulator VRS or model to test it there. To test this on your real UAV you could set the takeoff throttle to a low value in your VRS that is only enough to roll the UAV at a safe speed.

You should change the [offGroundAlgorithm] to make off-ground be manually controlled to prevent going into fly mode and switching to the Rudder from Y Accelerometer loop.

Have a pilot ready to take over and steer it in PIC if needed.

Evan Schellenberg

MicroPilot Support