Copter GCS failsafe

[Randy Mackay]

 

     We have this issue in the AC issues list which suggests that we should trigger a GCS failsafe after the vehicle and ground station lose contact for more than 5 seconds even if the user has not been using the virtual sticks to control the copter:

              https://github.com/diydrones/ardupilot/issues/705

 

     What I worry about is false positives leading to unexpected RTLs or LANDs because it will mean if you’ve ever connected telemetry and then disconnect it, it will attempt an RTL.

 

     To fight against this it has the regular checks we have for other failsafes:

1.       If in manual flight mode (Stabilize, ACRO) with throttle at zero it will disarm immediately

2.       If very close to home it will simply LAND

 

     Basically  I’m wondering, do we really want to consider telemetry as critical even if it’s not being used to fly the vehicle using rc-overrides?

 

     I guess we need to consider situations like Guided mode where the GCS is controlling the vehicle but it’s not through the rc-overrides.  In these cases though I think the user can retake control with the transmitter.  If the vehicle is out of transmitter range then it should already have triggered a radio/throttle failsafe.

 

-Randy

[Charles Taylor]

It would be great to have the option of lost telemetry to trigger RTL. Having flown in FAA COAs for a few years they did make us setup our autopilot this way. The aircraft could still be flown by a RC Tx like arducopter yet it was a requirement.

[Bill Bonney]

Hi

I think GCS Failsafe should work the same as plane. If you lose the link, copter loiters then RTL/Land depending on setting. If you don't want that don't enable the GCS failsafe. 

The telemetry radio is generally the better range, so what you are suggesting means you only have RC radio range support as the dominant throttle failsafe. 

Bill

--------------------------------------------------------
bill bonney - mobile software developer

communis technologies

billb...@communistech.com

skype: maninvan 

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[Robert Lefebvre]

I say no.  Absolutely not.  At least not with as simple of a decision structure as you've laid out.  It'll be another failsafe that I have to turn off.

If the GCS is not being used to control the aircraft in some way, whether guided mode, or a long-range no-RC auto mission, then there's no justification for it to RTL or autoland just because the datalink stopped.  

The decision needs to be based on whether or not the GCS linke is Mission Critical.  So:

RC-Over-ride.

Guided mode with no RC Link

Auto mode with no RC Link

Those are the ones I can think of.  Otherwise, no.

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[Bill Bonney]

@Rob: I'm not quite sure what/who you are saying 'no' too. 

Anyway, to try and clarify the use cases 

1. GCS Failsafe - When enabled, the vehicle will trigger a Loiter for a period then RTL/LAND on connection lost. (There's an extra mode to continue if in Auto for Plane)

2. RC_OVERIDE Failsafe. - When enabled and the user is controlling the vehicle via telemetry radio, trigger a Loiter for a period then RTL/LAND on connection lost to the GCS.

Connection lost is determined by receiving heartbeat packets from the the GCS.

I see the issue with guided mode, since the telemetry radio is supposed to have longer rnage, but if you send it to a point you can no longer communicate with, how to bring it back. ie. when it's reached its destination, or when it looses contact.

Bill

[Robert Lefebvre]

It was directed mostly at Randy. 

I definitely don't want the existing GCS Failsafe expanded as described, because then I'd have to turn it off too.  Currently, it's useful for a loss of RC-Over-ride.  The lack of Loiter period before an auto-land is a real problem in our implementation.  The only time it's an acceptable risk, IMO, is if RC-override control is lost.

Airplanes are different, because you have time to react before the thing comes in for a landing the way you have done it.  Our current system for copter is akin to making an airplane suddenly nose-dive and crater with no warning every time it failsafes.

[john...@gmail.com]

>Our current system for copter is akin to making an airplane suddenly nose-dive and crater with no warning every time it failsafes.

The dreaded Outback challenge F/S rules in other words.. :)

[Paul Riseborough]

Not quite the same thing - the cratering resulting from going into land mode for a copter should be minimal - you replace the props and fly again. Mind you if it happens over a lake....

On Monday, 28 April 2014 03:49:54 UTC+10, robert.lefebvre wrote:

I Our current system for copter is akin to making an airplane suddenly nose-dive and crater with no warning every time it failsafes.

[Robert Lefebvre]

Or over trees, a fence, etc.  

Or if it's a Tradheli and you're over anything but smooth level ground, it pretty much results in a complete re-kit.  

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[Mike Lawrence]

I think that there should be GCS, THROTTLE, RC_OVERIDE, and GUIDED failsafe. All with the option to disable separately.

FS options should be the same, with a few mods. LOITER/CIRCLE(optional unlimited) then RTL/LAND, unless AUTO.

If using Tx, some may still want GCS_FS. I disable it.(false positive?/range issues_More often w/Rover than Copter)

If using virtual sticks, RC_OVERIDE_FS, w/options above, as well as ability to return to Tx. (Only if Throttle_FS is enabled?)

Regarding Guided/FollowMe, I think it should have a separate FS. GCS_FS would have you covered, but if Guided to a point beyond GCS range, I think there should be an option to continue(like for AUTO) then enable FS once WP has been reached.

I usually disable GCS_FS, but would like that protection during FollowMe. If my Telem. gets disconnected, Tx is across the field, currently copter stays at its last known FollowMe WP, no problem. But FS would be a nice 'option' at that point, while keeping GCS_FS disabled.

Not sure if any of this makes sense to you guys, just a few ideas from someone that has never seen code,(blink,helloworld) and rarely looks at his logs. I prefer to spend my time on the sticks.

Mike

[Glenn Gregory]

Hi Randy,

What was the consensus about this GCS Failsafe issue?

I believe the current functionality is very misleading. If you look up the FS_GCS_ENABLE parameter the description is "Controls whether failsafe will be invoked (and what action to take) when connection with Ground station is lost for at least 5 seconds". This implies if you have it set to 1 "Enabled always RTL" that if you lose the connection to the GCS it will initiate a RTL. There is no mention anywhere of this only works if RC Override is active.

It seems the simple solution would be if this parameter is enabled then you activate a RTL/Land or Auto continue as described even during normal operating modes i.e Auto, Guided etc. The parameter should be set 0 as default so as Rob mentioned you don't have to disable another failsafe and it would function the same as it currently does for the majority of users (who don't use RC override features).

The more involved method would be adding another parameter for GCS failsafe in guided mode as others have mentioned. But this method still leaves the functionality of FS_GCS_ENABLE as is which is miss-leading.

This came about as a friend tested this functionality believing if he set the FS_GCS_ENABLE parameter to 1 and flew a guided mission and lost comms that it would RTL. He asked me to look into why and once I checked the code I realised it requires the failsafe.rc_override_active flag to be set.

Thanks,

Glenn

[Craig Elder]

Hi Glenn

I just updated the parameter description to indicate that the GCS failsafe is only active when RC_OVERRIDE is being used to control the vehicle.

https://github.com/diydrones/ardupilot/commit/f7d0a930c20dc265d67a4f6f084e26798c63de9a

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[Glenn Gregory]

Thanks Craig.

That description is what Mission Planner and APM Planner 2 use correct? 

It should also be changed on the wiki also: 

http://copter.ardupilot.com/wiki/5819-2/

http://copter.ardupilot.com/wiki/arducopter-parameters/

[Randy Mackay]

Glenn,

I think there's good consensus that the GCS failsafe should work as you describe (where the failsafe triggers when we lose contact in Guided mode even if RC-overrides aren't being used).  It's on the to-do list but we just need someone to make the code changes.

-Randy

[Craig Elder]

Gary, those documents plus the Planners will automatically be updated