EKF3: improve source switching (GPS<->NonGPS)

[rmackay9]

This is a list of issues to improve the EKF3 source switching that was added with PR: #14803

• support always aligning external system's heading to AHRS heading when not in use
• extend AP_NavEKF3::getVelInnovationsAndVariancesForSource to return innovations for:
  • wheel encoders
• add more lua scripts (like ahrs-sources.lua) to support automatic switching in more situations:
  • only GPS+T265 instead of GPS+T265+optical flow
• investigate why Rover EKF failsafe triggers when switching to GPS sources if GPS has been disabled for some time when it wasn't being used. I.e. switch to secondary source, set GPS_TYPE = 0, set GPS_TYPE = 1, switch to primary source.

Completed Items:

• allow aligning to AHRS when gps-for-yaw used (align code can't see difference between external nav and GPS-for-yaw) (PR)
• add more lua scripts to support automatic switching between GPS + optical flow (PR)
• extend AP_NavEKF3::getVelInnovationsAndVariancesForSource to return innovations for optical flow (PR)
• add support for switching source via MAVLink (PR) -- included in 4.2.0-dev
• split EK3_SRCn_YAW = 2 (external) into "External Nav", "GPS" and maybe "GPS for yaw", "GSF"
• remove need for AP_NavEKF_Source::setVelZSource (see PR: EKF: don't reset EKx_GPS_TYPE when GPS has no vertical velocity #15815, AP_NavEKF_Source: remove unused setVelZSource #15969)
• add lua script for GPS + wheel encoders (PR: AP_Scripting: add ahrs-source-gps-wheelencoders.lua #15932)
• add wiki page with setup instructions (linked from here)
• performance optimisation of AP_NavEKF_Source::configured_in_storage() using temp variable because once true it will always be true (see PR: AP_NavEKF_Source: optimise configured_in_storage #15874)
• check GPS + wheel encoders work (see issue: EKF3/Rover: wheel encoders + GPS data causes EKF failsafe #15125)

Relevant wiki pages:

• GPS/Non-GPS transitions

[diegodab]

Hello, does anyone know how to automatically switch between GPS and optical flow?

[rmackay9]

@diegodab,

Probably best to ask these sorts of questions in the Copter-4.1 forum but in any case, adding a lua script to support automatically switching between GPS and optical flow is still on the to-do list (see "GPS + optical flow" above). The best we have at the moment is a script that handles GPS, T265 and OpticalFlow (e.g. more than you want).

[diegodab]

@rmackay9 Hi, thank you for answering. The Lua script hat handles the GNSS, T265 and optical flow reports the following error:

$lua main.lua
lua: main.lua:47: attempt to index a nil value (global 'rc')
stack traceback:
main.lua:47: in function 'update'
(...tail calls...)
[C]: in ?

Does it work even though it gives that message when executing?

[yubo105139]

Please tell me, I need to switch t265 with gps automatically . Is there any way to achieve this?

[rmackay9]

@yubo105139,

Yes, on the GPS / Non-GPS Transitions page we have a link to a lua script that can do this.

[yubo105139]

@rmackay9
🙏 thanks!!!