Autolanding with Rangefinder - Parameter Setup Question

flyingw · August 14, 2018, 9:59pm

When using a rangefinder the documentation says you can set LAND_FLARE_SEC to zero if you only want to use altitude.

Similarly, can I also set LAND_PF_SEC to zero if I only want to use altitude?

Thanks,

Paul

Naterater · August 18, 2018, 5:10am

Yes. And if you set LAND_PF_ALT to zero, you just won’t have a pre-flare.

flyingw · August 20, 2018, 4:12pm

What exactly does this “Rangefinder engaged at 4.12m” message mean?

I have the pre-flare stage set at 3 meters and the flare set to 1.5 meters, both worked wiht this TFMini unit.

rngfnd-412

Note that the TFMini rangefinder comes alive at about 6 meters over grass.

Thanks,

Paul

kikislater · April 23, 2019, 5:33pm

May be related to this :

During the approach, the glide slope is actually calculated to pass through a point in front of the LAND waypoint. The distance in front is calculated as groundspeed * flare_alt / TECS_LAND_SINK, where flare_alt is LAND_FLARE_ALT, or LAND_FLARE_SEC times glide slope sink rate.

github.com/ArduPilot/ardupilot

Plane: Landing glideslope offset

opened 03:20PM - 01 Dec 18 UTC

Naterater

Plane

### Feature request **Is your feature request related to a problem? Please de…scribe.** Plane's traditional landing sequence is fundamentally flawed to achieve smooth flares and touchdowns at the landing waypoint. For a proper final approach, pre-flare, and landing, the landing will always be overshot, often based on the wind speed. The current approach is designed as more of a guided controlled crash sequence. Quite simply, this is because the glideslope is calculated on a line directly to the land waypoint. Pre-flares and flares only cause a reduction in descent rate, but they do not necessarily slow the forward speed by a proportional amount. For a properly configured landing, the glideslope must be targeted at a point before the touchdown point so that the pre-flare and flare can arrest the descent rate. This shows itself the most in reverse-thrust enabled landings. The glide slope is achieved with reverse thrust during the final approach to the land waypoint. Once the flare point is hit, the plane's throttle is reduced to zero, and that causes one of two things. #1 - The glideslope is continued to the touchdown point, and the plane is effectively crashed because of the increase in airspeed at the end of the landing in order to keep the steep descent. #2 - The plane flares properly, increases its pitch in order to slow the rate of descent, but lands well beyond the LAND waypoint. **Describe the solution you'd like** Add a parameter for the offset of the glideslope calculation that makes the glide target point in front of the touchdown point (land waypoint). Theoretically it could be a fake waypoint between the last waypoint and the LAND waypoint. Parameter should be named LAND_FLARE_DIST with a description: distance the glide slope is offset to achieve the landings that are not short or long. This would be much easier than changing TECS and other parameters in order to achieve consistent spot landings. **Describe alternatives you've considered** Offsetting the landing waypoint manually **Platform** [ ] All [ ] AntennaTracker [ ] Copter [X] Plane [ ] Rover [ ] Submarine **Additional context** _Add any other context or screenshots about the feature request here._