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
+
+
+FRAME_GLOBAL = 3
+NAV_WAYPOINT = 16
+NAV_TAKEOFF = 22
+NAV_LAND = 21
+DO_LAND_START = 189
+
+TAKEOFF_PITCH = 15
+
+local function wrap_360(angle)
+   local res = math.fmod(angle, 360.0)
+    if res < 0 then
+        res = res + 360.0
+    end
+    return res
+end
+
+local function wrap_180(angle)
+    local res = wrap_360(angle)
+    if res > 180 then
+       res = res - 360
+    end
+    return res
+end
+
+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(alt)
+   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(TAKEOFF_PITCH)
+   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_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 and home and location:alt() > (home:alt() + param:get("TKOFF_LVL_ALT")*100) then
+        local yaw = ahrs:get_yaw()
+        mission:set_item(3,create_final_approach_WP(3,wrap_180(math.deg(yaw)+180),FIN_WP_DIST,FIN_WP_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 FIN_WP_DIST == 0 or FIN_WP_ALT ==0 then
+      gcs:send_text(0, string.format("Must set SCR_USER1 and 2 values!"))
+      return
+   end
+   mission:clear()
+   local item = mavlink_mission_item_int_t()
+   item:command(NAV_WAYPOINT)
+   mission:set_item(0,item)
+   mission:set_item(1,create_takeoff_WP(param:get("TKOFF_ALT"))) 
+   mission:set_item(2,create_do_land_start_WP())     
+   return update, 1000
+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 easy, 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, to SCR_USER3 above home,  and at SCR_USER2 distancee, and a LAND waypoint at HOME and stops until next disarm/boot. Warnings are given if the SCR_USER values are not set.
+
+In use you just arm and switch to AUTO, and then switch to other flight modes after takeoff is completed to fly around.....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 SCR_USER1/2 parameters. Setting SCR_USER2 and 3 for a good glide path on a final approach is required (be aware of possible obstructions when using). Values of 400 meters distance and 55 meters altitude work well for typcial 1m wingspan/1 kg foam planes. RTL_AUTOLAND =2 is recommended also.