AP_Scripting: add Plane autoland applet

libraries/AP_Scripting/applets/UniversalAutoLand.lua

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+--[[ Upon Arming , creates a four item mission consisting of: NAV_TAKEOFF, DO_LAND_START,Final Approach WP opposite bearing from HOME of heading used during takeoff, at TKOFF_ALT or SCR_USER3 above home, SCR_USER2 or 2X TKOFF_DIST, and a LAND waypoint at HOME and stops until next disarm/boot. SCR_USER1 is used to enable or disable it.
+--]]
+
+--local variablees
+
+SCR_USER_EN = Parameter("SCR_USER1") -- enable this script
+local FIN_WP_DIST = param:get("SCR_USER2") -- distance of final wp from HOME
+local FIN_WP_ALT = param:get("SCR_USER3") --- altitude of final wp from HOME
+local TKOFF_ALT = param:get("TKOFF_ALT")
+local TKOFF_DIST = param:get("TKOFF_DIST")
+
+-- make sure you have a reasonable final angle if someone does not change defualts other than SCR1_USER to enable
+if FIN_WP_ALT < TKOFF_ALT then FIN_WP_ALT = TKOFF_ALT end
+if FIN_WP_DIST < TKOFF_DIST then FIN_WP_DIST = 2 * TKOFF_DIST end
+
+FRAME_GLOBAL = 3
+NAV_WAYPOINT = 16
+NAV_TAKEOFF = 22
+NAV_LAND = 21
+DO_LAND_START = 189
+
+function create_final_approach_WP(i,bearing,dist,alt) --index,degs,m,m
+   local item = mavlink_mission_item_int_t()
+   local loc = ahrs:get_home()
+   loc:offset_bearing(bearing,dist) ---degs and meters
+
+   item:seq(i)
+   item:frame(FRAME_GLOBAL)
+   item:command(NAV_WAYPOINT)
+   item:param1(0)
+   item:param2(0)
+   item:param3(0)
+   item:param4(0)
+   item:x(loc:lat())
+   item:y(loc:lng())
+   item:z(alt)
+   return item
+end
+
+function create_takeoff_WP()
+   local item = mavlink_mission_item_int_t()
+   local loc = ahrs:get_home()
+
+   item:seq(1)
+   item:frame(FRAME_GLOBAL)
+   item:command(NAV_TAKEOFF)
+   item:param1(15)
+   item:param2(0)
+   item:param3(0)
+   item:param4(0)
+   item:x(loc:lat())
+   item:y(loc:lng())
+   item:z(TKOFF_ALT)
+   return item
+end
+
+function create_land_WP()
+   local item = mavlink_mission_item_int_t()
+   local loc = ahrs:get_home()
+
+   item:seq(4)
+   item:frame(FRAME_GLOBAL)
+   item:command(NAV_LAND)
+   item:param1(15)
+   item:param2(0)
+   item:param3(0)
+   item:param4(0)
+   item:x(loc:lat())
+   item:y(loc:lng())
+   item:z(0)
+   return item
+end
+
+function create_do_land_start_WP()
+   local item = mavlink_mission_item_int_t()
+
+   item:seq(2)
+   item:frame(FRAME_GLOBAL)
+   item:command(DO_LAND_START)
+   item:param1(0)
+   item:param2(0)
+   item:param3(0)
+   item:param4(0)
+   item:x(0)
+   item:y(0)
+   item:z(0)
+   return item
+end
+
+function update()
+  if not arming:is_armed() then --if disarmed, wait until armed
+    mission_loaded = false
+    return update,1000
+  end
+
+  if not mission_loaded then --if first time after arm and enabled is valid then create  mission 
+    local home = ahrs:get_home()
+    local location = ahrs:get_location()
+    if location:alt() > (home:alt() + param:get("TKOFF_LVL_ALT")*100) then
+        local yaw = ahrs:get_yaw()
+        mission:set_item(2,create_do_land_start_WP())
+        mission:set_item(3,create_final_approach_WP(3,math.deg(yaw)+180,FIN_WP_DIST,param:get("TKOFF_ALT")))
+        mission:set_item(4,create_land_WP())
+              mission_loaded = true
+    end
+  end
+  return update, 1000
+end 
+
+gcs:send_text(5,"Loaded TKOFF/RTL/Land Mission'.lua")
+if SCR_USER_EN:get() == 1 then 
+   if not mission:set_item(0,create_final_approach_WP(0,0,0,0)) then
+         gcs:send_text(0, string.format("Failed to create HOME WP, investigate!")) --something's really  wrong!
+   end
+mission:set_item(1,create_takeoff_WP())      
+return update, 5000
+else
+gcs:send_text(0, string.format("Script disabled by SCR_USER1"))
+return
+end
+

libraries/AP_Scripting/applets/UniversalAutoLand.md

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+This script is intended to allow eady, unpre-planned operation at any location with the protection of a do-land-start autoland sequence for failsafes that accounts for takeoff direction (ie wind direction). Final approach objects must be considered before you launch.
+
+If enabled by SCR_USER1 =1, setups up an autotakeoff waypoint as first waypoint and upon Arming , adds mission items consisting of:  DO_LAND_START,Final Approach WP opposite bearing from HOME of heading used during takeoff, at TKOFF_ALT or SCR_USER3 above home,  and at SCR_USER2 or 2X TKOFF_DIST, and a LAND waypoint at HOME and stops until next disarm/boot.
+
+In use you just arm and switch to AUTO, and switch to other flight modes after takeoff is completed.....relatively assured that a failsafe (assuming defaults for FS) will result in an autolanding in the correct direction. You can also just switch back to AUTO or RTL to do an autoland. 
+
+Caveats: be sure you have tested and setup autoland and TKOFF parameters. Setting SCR_USER2 and 3 for a good glide on a final approach is recommended. RTL_AUTOLAND =2 is recommended also.