mirror of https://github.com/ArduPilot/ardupilot
73 lines
2.7 KiB
Markdown
73 lines
2.7 KiB
Markdown
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# Copter Loiter Brake
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This script implements an emergency change to BRAKE mode in copter if
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you are in LOITER mode and break a terrain altitude limit. The script
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is useful when flying in LOITER mode in steep terrain.
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# Parameters
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The script adds the following parameters to control it's behaviour.
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## TERR_BRK_ENABLE
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This must be set to 1 to enable the script.
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## TERR_BRK_ALT
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This is the terrain altitude threshold for engaging BRAKE mode. The
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onboard terrain system must be enabled with TERRAIN_ENABLE=1 and
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terrain must have either been preloaded to the vehicle (see
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https://terrain.ardupilot.org ) or be available from the ground
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station over MAVLink.
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Make sure you set sufficient margin to cope with obstacles such as
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trees or any local towers or other obstacles.
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## TERR_BRK_HDIST
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This is the distance from home for the BRAKE checking to be
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enabled. The default of 100 meters is good for most operations. This
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threshold allows you to take over in LOITER mode for low altitude
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operations and takeoff/landing when close to home.
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## TERR_BRK_SPD
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This is a speed threshold BRAKE checking to be enabled. If both the
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horizontal speed and the descent rate are below this threshold then
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BRAKE will not be engaged. This defaults to zero which means no speed
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checking is performed.
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You should set this to a small value if you want to be able to recover
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from BRAKE mode by climbing straight up in LOITER mode. A value of 0.5
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m/s is recommended. The value needed will be dependent on the amount
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of noise there is in your velocity measurement and how gusty the wind
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is, but 0.5 should work in most applications.
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If you set this value then to recover in LOITER mode you should raise
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the throttle stick to demand climb before you switch back to LOITER
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mode. The positive climb rate means BRAKE will not re-engage.
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# Operation
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Install the lua script in the APM/SCRIPTS directory on the flight
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controllers microSD card. Review the above parameter descriptions and
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decide on the right parameter values for your vehicle and operations.
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Make sure TERRAIN_ENABLE is 1 and you should preload terrain data for
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the flight area from https://terrain.ardupilot.org
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It is strongly recommended that you set TERRAIN_SPACING=30 and preload
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the SRTM1 terrain data for 30m horizontal resolution of terrain data.
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When the system engages you will see a message like this
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"Terrain 29.2m - BRAKE"
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where in this example you are 29.2m above the terrain.
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To recover you could use GUIDED mode, or RTL (make sure you have set
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RTL_ALT_TYPE to terrain) or if you have set TERR_BRK_SPD to a positive
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value then you could raise the throttle stick and switch back to
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LOITER mode.
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If the system is continually giving false positives then set
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TERR_BRK_ENABLE to zero to disable.
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