Peter BarkerandClaude Opus 5
805fa9f8d0
guided_above_terrain_posvelaccel_sub.lua integrates its position target
forward by the time since the last callback. When a callback arrived
later than 2/RUN_HZ it substituted 1/RUN_HZ for the real interval:
if (dt > 2.0 / RUN_HZ) then
dt = 1.0 / RUN_HZ
end
so a callback 243ms late advanced the target by 50ms and the remaining
193ms was discarded. The position target then falls behind the clock,
and the vehicle - which tracks that target accurately - covers less
ground than the commanded speed implies.
Measured from a failing Sub.GuidedAboveTerrain run under autotest at
--parallel=16, over the 60 simulated seconds the test watches:
GUIP updates 1047 at 17.2Hz (nominal 20Hz)
late callbacks 76 of 1047 (7.3%), worst 243ms
time discarded 5.82s, so 55.08s integrated of 60.90s elapsed
distance 27.90m of an expected 30.00m, +-1.00m -> failed
The dataflash shows the loss is upstream of the controller, not in it:
the script commanded 0.495m/s and the position controller achieved
0.442m/s against a desired 0.443m/s - it tracked what it was given to
within 0.001m/s, and what it was given was slow.
Cap the step at a fixed MAX_DT instead, so ordinary jitter is
integrated honestly and only a real stall is bounded. Pinning the
simulation speedup was tried first and is not a fix: at
context_set_speedup(10) the run still lost ground, reaching 28.93m,
because it reduces how often callbacks are late without changing what
happens when they are.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
AP_Scripting
Enabling Scripting Support in Builds
Scripting is automatically enabled on all boards with more than 1MB of flash space. The following example enables scripting, builds the ArduPlane firmware for the Cube, and uploads it.
waf configure --board=CubeBlack
waf plane
waf plane --upload
To run SITL you can simply use the sim_vehicle.py script which will wrap the configuration, compilation,
and launching of the simulation into one command for you.
Tools/autotest/sim_vehicle.py -v ArduPlane
Once you have a vehicle flashed with scripting you need to set the SCR_ENABLE parameter to 1 to enable scripting and reboot.
Adding Scripts
The vehicle will automatically look for and launch any scripts that are contained in the scripts folder when it starts.
On real hardware this should be inside of the APM folder of the SD card. In SITL this should be in the working directory (typically the main ardupilot directory).
An example script is given below:
function update () -- periodic function that will be called
local current_pos = ahrs:get_location() -- fetch the current position of the vehicle
local home = ahrs:get_home() -- fetch the home position of the vehicle
if current_pos and home then -- check that both a vehicle location, and home location are available
local distance = current_pos:get_distance(home) -- calculate the distance from home in meters
if distance > 1000 then -- if more then 1000 meters away
distance = 1000; -- clamp the distance to 1000 meters
end
SRV_Channels:set_output_pwm(96, 1000 + distance) -- set the servo assigned function 96 (scripting3) to a proportional value
end
return update, 1000 -- request "update" to be rerun again 1000 milliseconds (1 second) from now
end
return update, 1000 -- request "update" to be the first time 1000 milliseconds (1 second) after script is loaded
Examples
See the code examples folder
Working with bindings
Edit bindings.desc and rebuild. The waf build will automatically re-run the code generator.
Lua Source Code
The Lua 5.3.6 source code is vendored in lua/. This is a customized
version of the official
distribution. Where possible,
differences have been marked of the code.
Lua (not including modifications) is distributed under the terms of the MIT license.