• *****
  • 629
Failsafe when FPV vs. Pathplanned missions (using OPlink)
« on: January 01, 2020, 06:59:08 am »
So far I have mainly used failsafe to swop to an Attitude mode and put throttle to -100% make it fall out of the sky and hope for the best landing.
Understand how to set it up and what to expect.
Wiki is clear.

However, I am not sure when preparing for failsafe settings for FPV flights and for path planner waypoint mission flights.

1. case fpv, I want failsafe to RTB and not fall out of the sky.
Should I set the 'On failsafe change flightmode to'= any flightmode with RTB
AND keep the 'Channel input setting on failsafe'= to -100% for throttle?
Thinking that I don't want that but it does not matter whatever set to, since its an autonomous flight mode.

2. case PP, I want failsafe to just carry on the PP mission as nothing happened.
It will eventually come around and regain rc link when mission approaches the end waypoints.
Should I set the 'On failsafe change flightmode to'= The flightmode PathPlanner AND like above just ignore other settings.
I know if you change from PP mode to something else and then change back to PP again it will Restart with waypoint 1.
So I am worried on failsafe the mission will restart...

I am using Revo class flight controllers with OPlink for both rc control and telemetry.
That will mean (I think) when getting out of reach of radio link the failsafe will be triggered and receiver will just stop sending more data to the FC.

Re: Failsafe when FPV vs. Pathplanned missions (using OPlink)
« Reply #1 on: January 01, 2020, 08:54:10 am »
There is a setting that says whether VtolPathFollowerSettings flight modes use the transmitter throttle stick position or automatically adjust the throttle.  I would leave that in the automatic mode.  (ThrustControl=Auto)  With that I do recall that zero throttle in VtolPathFollowerSettings flight modes stops the motors where any other throttle stick position is just automatic throttle.  I could be wrong.  For failsafe setup, just configure the throttle in the middle and have ThrustControl=Auto.

I don't recall what fixed wing RTB (and other FW pathfollower modes) does if you move the throttle to zero.  I do know that non-zero positions are automatic throttle.  I would test it, but again, just configure the throttle failsafe to be in the middle and it's not an issue.  :)

Obviously the FC doesn't even know there is a failsafe if you are using RC failsafe to set switch and stick positions when out of RC range and your RC failsafe leaves the flight mode switch in the current position.

If your FC failsafe has some flight mode position with all the sticks in the middle, then there is basically no difference between being in range in that mode with those stick positions and being out of range.  PathPlanner won't see a mode change because there will not be a mode change, but there is also a setting for whether to start the waypoints over again.  FlightModeSettings->FlightModeChangeRestartsPathPlan

For either of these FC failsafes (FPV or waypoint) I would start with all configured failsafe stick positions in the middle, including throttle.  On failsafe, FPV should do RTB mode and waypoint should do waypoint mode.

I generally just set my last switch position to be the failsafe position with all sticks in the middle and before FPV I set that last position to be RTB.  Before waypoint I set the last switch position to be waypoint.

What would be handy is a code change so that failsafe does not change the flight mode if it is in waypoint mode with a valid set of waypoints loaded.  It would still use the failsafe stick positions though.  Then you would not have to change settings when switching between FPV and waypoint missions.  Of course there would be a setting to enable this new behavior and the default value would be to act like it did before (always change the mode when failsafe happens).

It would also be handy to read a waypoint mission from settings memory so you don't have to load it from GCS every time.  This would be very handy to always have available a "fly home and land and ignore the fact that I am switching the transmitter off" in case you get harassed and need to leave while claiming to not be flying.   8)

It's generally fairly easy and safe to test these "out of RC range" conditions by doing it all close by and switching your transmitter off.  Beware two things about switching your transmitter off:
- Remember that modern transmitters often have safety features like the one that requires you to have your throttle stick at zero before the transmitter will start talking.  Disable this and the other safety features that require other stuff like your flight mode switch to be in a certain position.
- If you use OpLinks for control and you use an unmodified RC transmitter with an "RC receiver to OpLink transmitter relay box" then be aware that switching only the RC transmitter off will cause the relay box to send a signal that moves all the sticks and switches to their max position, so you should switch the relay box off instead of the RC transmitter, but then beware that the relay box takes several seconds to boot up when you power it back on.  Test it all on the ground first.  :)
« Last Edit: January 01, 2020, 09:11:55 am by TheOtherCliff »


  • *****
  • 629
Re: Failsafe when FPV vs. Pathplanned missions (using OPlink)
« Reply #2 on: January 02, 2020, 04:46:08 am »
Thanks Cliff, its a lot more to this as I suspected.
Will test as safely as I can  :P