Shallow depth warning and avoidance using lua

geofrancis · November 17, 2021, 2:18pm

I was looking through the Lua examples and noticed this, would this work for boat depth?, im not sure how rover handles altitude information. if it can then it should be able to work as shallow water avoidance without much modification by just setting loiter or hold if the water gets too shallow along with sending a warning back to the ground station.

github.com

ArduPilot/ardupilot/blob/master/libraries/AP_Scripting/examples/terrain_warning.lua

-- height above terrain warning script

-- min altitude above terrain, script will warn if lower than this
local terrain_min_alt = 20

-- warning is only enabled further than this distance from home
local home_dist_enable = 25

-- must have climbed at least this distance above terrain since arming to enable warning
local height_enable = 10

-- warning repeat time in ms
local warn_ms = 10000


local height_threshold_passed = false
local last_warn = 0
function update()

  if not arming:is_armed() then

This file has been truncated. show original

geofrancis · November 17, 2021, 5:03pm

Ok that didn’t work. What should I use instead altitude.

hendjosh · November 17, 2021, 9:57pm

AP_Terrain is not available on Rover. So I dont see how that script will work for you without adding AP_Terrain to rover.

Someone could add AP_Terrain rover like sub has then if you had a rangefinder that script could work for you likely.

geofrancis · November 17, 2021, 10:46pm

is there a way of getting depth data in a lua script? it should just be a matter of swapping it in.

this looks like it works
local depth_under_boat = rangefinder:distance_cm_orient(25)

geofrancis · November 17, 2021, 11:48pm

I have made this lua script to display a warning if the depth is under 2m but its not running correctly, if someone could take a look at it I would be grateful.I’m just copy and pasting, I’m pretty useless at code lol.

ideally, I would like it to display a warning along with the current depth.
depth.lua (369 Bytes)

kiwiPaul · January 17, 2022, 8:53pm

Did you get any further with this ?
We’re doing mapping and water quality sampling - its going to get shallow !!
Ideally - if depth < 1m then STOP or Skip to next waypoint or something…

geofrancis · January 17, 2022, 11:01pm

Unfortunately not, I’m not a software developer so my abilities to make this work are limited. all the parts are there.

to switch the boat to loiter whenever it gets shallow it needs to do something like :

get_mode() - Returns current vehicle mode by mode_number
if mode = auto and rangefinder:distance_cm_orient(25) <1m then
set_mode(loiter) - Attempts to change vehicle mode to loiter
gcs:send_text(0, “SHALLOW WATER HALT” (depth))

@rishabsingh3003 @rmackay9 any assistance would be appreciated.

geofrancis · January 18, 2022, 3:02am

This is where I am at, I can’t get it to run there is an error on line 52,

essentially it’s just a modification of the terrain warning script but modified to work on the downward facing rangefinder. The idea is that if its in auto mode, and it gets shallow it will switch to loiter and send an alert to the ground station, essentially it restricts the minimum water depth it will work in auto mode. I haven’t had a chance to test my boat in the water, so it hasn’t really been a priority for me.

depth avoid.lua (1.6 KB)

https://raw.githubusercontent.com/ArduPilot/ardupilot/master/libraries/AP_Scripting/examples/terrain_warning.lua

Yuri_Rage · January 18, 2022, 4:56am

At a glance, the following lines 52/53 will probably get the script running:

  if (water_depth < water_min_depth) and (vehicle:get_mode() == 10) then    -- if mode is in auto 
	vehicle:set_mode(5) --set mode to loiter

I’ve never polled a rangefinder peripheral using onboard Lua, so I’m not much more help than this.

geofrancis · January 18, 2022, 11:21am

that’s running now thank you.

depth avoid.lua (1.6 KB)