ardupilot/libraries/AP_Scripting/examples/plane_ship_landing.lua

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-- support takeoff and landing on moving platforms for VTOL planes
local PARAM_TABLE_KEY = 7
local PARAM_TABLE_PREFIX = "SHIP_"
local MODE_MANUAL = 0
local MODE_RTL = 11
local MODE_QRTL = 21
local MODE_AUTO = 10
local MODE_QLOITER = 19
local NAV_TAKEOFF = 22
local NAV_VTOL_TAKEOFF = 84
local ALT_FRAME_ABSOLUTE = 0
-- 3 throttle position
local THROTTLE_LOW = 0
local THROTTLE_MID = 1
local THROTTLE_HIGH = 2
-- bind a parameter to a variable
function bind_param(name)
local p = Parameter()
assert(p:init(name), string.format('could not find %s parameter', name))
return p
end
-- add a parameter and bind it to a variable
function bind_add_param(name, idx, default_value)
assert(param:add_param(PARAM_TABLE_KEY, idx, name, default_value), string.format('could not add param %s', name))
return bind_param(PARAM_TABLE_PREFIX .. name)
end
-- setup SHIP specific parameters
assert(param:add_table(PARAM_TABLE_KEY, PARAM_TABLE_PREFIX, 3), 'could not add param table')
SHIP_ENABLE = bind_add_param('ENABLE', 1, 0)
SHIP_LAND_ANGLE = bind_add_param('LAND_ANGLE', 2, 0)
SHIP_AUTO_OFS = bind_add_param('AUTO_OFS', 3, 0)
-- other parameters
RCMAP_THROTTLE = bind_param("RCMAP_THROTTLE")
ALT_HOLD_RTL = bind_param("ALT_HOLD_RTL")
Q_RTL_ALT = bind_param("Q_RTL_ALT")
TRIM_ARSPD_CM = bind_param("TRIM_ARSPD_CM")
TECS_LAND_ARSPD = bind_param("TECS_LAND_ARSPD")
Q_TRANS_DECEL = bind_param("Q_TRANS_DECEL")
WP_LOITER_RAD = bind_param("WP_LOITER_RAD")
RTL_RADIUS = bind_param("RTL_RADIUS")
FOLL_OFS_X = bind_param("FOLL_OFS_X")
FOLL_OFS_Y = bind_param("FOLL_OFS_Y")
FOLL_OFS_Z = bind_param("FOLL_OFS_Z")
-- an auth ID to disallow arming when we don't have the beacon
local auth_id = arming:get_aux_auth_id()
arming:set_aux_auth_failed(auth_id, "Ship: no beacon")
-- current target
local target_pos = Location()
local current_pos = Location()
local target_velocity = Vector3f()
local target_heading = 0.0
-- landing stages
local STAGE_HOLDOFF = 0
local STAGE_DESCEND = 1
local STAGE_APPROACH = 2
local STAGE_IDLE = 2
local landing_stage = STAGE_HOLDOFF
-- other state
local vehicle_mode = MODE_MANUAL
local reached_alt = false
local throttle_pos = THROTTLE_HIGH
local have_target = false
-- square a variable
function sq(v)
return v*v
end
-- check key parameters
function check_parameters()
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--[[
parameter values which are auto-set on startup
--]]
local key_params = {
FOLL_ENABLE = 1,
FOLL_OFS_TYPE = 1,
FOLL_ALT_TYPE = 0,
}
for p, v in pairs(key_params) do
local current = param:get(p)
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assert(current, string.format("Parameter %s not found", p))
if math.abs(v-current) > 0.001 then
param:set_and_save(p, v)
gcs:send_text(0,string.format("Parameter %s set to %.2f was %.2f", p, v, current))
end
end
end
-- update the pilots throttle position
function update_throttle_pos()
local tpos
if not rc:has_valid_input() then
tpos = THROTTLE_LOW
else
local tchan = rc:get_channel(RCMAP_THROTTLE:get())
local tval = (tchan:norm_input_ignore_trim()+1.0)*0.5
if tval >= 0.40 then
tpos = THROTTLE_HIGH
elseif tval >= 0.1 then
tpos = THROTTLE_MID
else
tpos = THROTTLE_LOW
end
end
if tpos ~= throttle_pos then
reached_alt = false
if landing_stage == STAGE_HOLDOFF and tpos <= THROTTLE_MID then
landing_stage = STAGE_DESCEND
gcs:send_text(0, string.format("Descending for approach (hd=%.1fm h=%.1f th=%.1f)",
get_holdoff_distance(), current_pos:alt()*0.01, get_target_alt()))
end
if landing_stage == STAGE_DESCEND and tpos == THROTTLE_HIGH then
gcs:send_text(0,"Climbing for holdoff")
landing_stage = STAGE_HOLDOFF
end
end
throttle_pos = tpos
end
-- get landing airspeed
function get_land_airspeed()
if TECS_LAND_ARSPD:get() < 0 then
return TRIM_ARSPD_CM:get() * 0.01
end
return TECS_LAND_ARSPD:get()
end
--[[
calculate stopping distance assuming we are flying at
TECS_LAND_ARSPD and are approaching the landing target from
behind. Take account of the wind estimate to get approach
groundspeed
--]]
function stopping_distance()
-- get the target true airspeed for approach
local tas = get_land_airspeed() * ahrs:get_EAS2TAS()
-- add in wind in direction of flight
local wind = ahrs:wind_estimate():xy()
-- rotate wind to be in approach frame
wind:rotate(-math.rad(target_heading + SHIP_LAND_ANGLE:get()))
-- ship velocity rotated to the approach frame
local ship2d = target_velocity:xy()
ship2d:rotate(-math.rad(target_heading + SHIP_LAND_ANGLE:get()))
-- calculate closing speed
-- use pythagoras theorem to solve for the wind triangle
local tas_sq = sq(tas)
local y_sq = sq(wind:y())
local closing_speed
if tas_sq >= y_sq then
closing_speed = math.sqrt(tas_sq - y_sq)
else
-- min 1 m/s
closing_speed = 1.0
end
-- include the wind in the direction of the ship
closing_speed = closing_speed + wind:x()
-- account for the ship velocity
closing_speed = closing_speed - ship2d:x()
-- calculate stopping distance
return sq(closing_speed) / (2.0 * Q_TRANS_DECEL:get())
end
-- get holdoff distance
function get_holdoff_radius()
if RTL_RADIUS:get() ~= 0 then
return RTL_RADIUS:get()
end
return WP_LOITER_RAD:get()
end
-- get holdoff distance
function get_holdoff_distance()
local radius = get_holdoff_radius()
local holdoff_dist = math.abs(radius*1.5)
local stop_distance = stopping_distance()
-- increase holdoff distance by up to 50% to ensure we can stop
holdoff_dist = math.max(holdoff_dist, math.min(holdoff_dist*2.5, stop_distance*2))
return holdoff_dist
end
-- get the holdoff position
function get_holdoff_position()
local radius = get_holdoff_radius()
local heading_deg = target_heading + SHIP_LAND_ANGLE:get()
local holdoff_dist = get_holdoff_distance()
local ofs = Vector2f()
ofs:x(-holdoff_dist)
ofs:y(radius)
ofs:rotate(math.rad(heading_deg))
local target = target_pos:copy()
target:offset(ofs:x(), ofs:y())
return target
end
function wrap_360(angle)
local res = math.fmod(angle, 360.0)
if res < 0 then
res = res + 360.0
end
return res
end
function wrap_180(angle)
local res = wrap_360(angle)
if res > 180 then
res = res - 360
end
return res
end
--[[
check if we have reached the tangent to the landing location
--]]
function check_approach_tangent()
local distance = current_pos:get_distance(target_pos)
local holdoff_dist = get_holdoff_distance()
if landing_stage == STAGE_HOLDOFF and throttle_pos <= THROTTLE_MID and distance < 4*holdoff_dist then
gcs:send_text(0, string.format("Descending for approach (hd=%.1fm)", holdoff_dist))
landing_stage = STAGE_DESCEND
end
if reached_alt and landing_stage == STAGE_DESCEND then
-- go to approach stage when throttle is low, we are
-- pointing at the ship and have reached target alt.
-- Also require we are within 2.5 radius of the ship, and our heading is within 20
-- degrees of the target heading
local target_bearing_deg = wrap_180(math.deg(current_pos:get_bearing(target_pos)))
local ground_bearing_deg = wrap_180(math.deg(ahrs:groundspeed_vector():angle()))
local margin = 10
local distance = current_pos:get_distance(target_pos)
local holdoff_dist = get_holdoff_distance()
local error1 = math.abs(wrap_180(target_bearing_deg - ground_bearing_deg))
local error2 = math.abs(wrap_180(ground_bearing_deg - (target_heading + SHIP_LAND_ANGLE:get())))
logger.write('SLND','TBrg,GBrg,Dist,HDist,Err1,Err2','ffffff',target_bearing_deg, ground_bearing_deg, distance, holdoff_dist, error1, error2)
if (error1 < margin and
distance < 2.5*holdoff_dist and
distance > 0.7*holdoff_dist and
error2 < 2*margin) then
-- we are on the tangent, switch to QRTL
gcs:send_text(0, "Starting approach")
landing_stage = STAGE_APPROACH
vehicle:set_mode(MODE_QRTL)
end
end
end
--[[
check if we should abort a QRTL landing
--]]
function check_approach_abort()
local alt = current_pos:alt() * 0.01
local target_alt = get_target_alt()
if alt > target_alt then
gcs:send_text(0, "Aborting landing")
landing_stage = STAGE_HOLDOFF
vehicle:set_mode(MODE_RTL)
end
end
-- update state based on vehicle mode
function update_mode()
local mode = vehicle:get_mode()
if mode == vehicle_mode then
return
end
vehicle_mode = mode
if mode == MODE_RTL then
landing_stage = STAGE_HOLDOFF
reached_alt = false
elseif mode ~= MODE_QRTL then
landing_stage = STAGE_IDLE
reached_alt = false
end
end
-- update target state
function update_target()
if not follow:have_target() then
if have_target then
gcs:send_text(0,"Lost beacon")
arming:set_aux_auth_failed(auth_id, "Ship: no beacon")
end
have_target = false
return
end
if not have_target then
gcs:send_text(0,"Have beacon")
arming:set_aux_auth_passed(auth_id)
end
have_target = true
target_pos, target_velocity = follow:get_target_location_and_velocity_ofs()
target_heading = follow:get_target_heading_deg()
-- zero vertical velocity to reduce impact of ship movement
target_velocity:z(0)
end
-- get the alt target for holdoff, AMSL
function get_target_alt()
local base_alt = target_pos:alt() * 0.01
if landing_stage == STAGE_HOLDOFF then
return base_alt + ALT_HOLD_RTL:get() * 0.01
end
return base_alt + Q_RTL_ALT:get()
end
function update_alt()
local alt = current_pos:alt() * 0.01
local target_alt = get_target_alt()
if landing_stage == STAGE_HOLDOFF or landing_stage == STAGE_DESCEND then
if math.abs(alt - target_alt) < 3 then
if not reached_alt then
gcs:send_text(0,"Reached target altitude")
end
reached_alt = true
end
end
end
--[[
update automatic beacon offsets
--]]
function update_auto_offset()
if arming:is_armed() or math.floor(SHIP_AUTO_OFS:get()) ~= 1 then
return
end
-- get target without offsets applied
target_no_ofs, vel = follow:get_target_location_and_velocity()
-- setup offsets so target location will be current location
local new = target_no_ofs:get_distance_NED(current_pos)
new:rotate_xy(-math.rad(target_heading))
gcs:send_text(0,string.format("Set follow offset (%.2f,%.2f,%.2f)", new:x(), new:y(), new:z()))
FOLL_OFS_X:set_and_save(new:x())
FOLL_OFS_Y:set_and_save(new:y())
FOLL_OFS_Z:set_and_save(new:z())
SHIP_AUTO_OFS:set_and_save(0)
end
-- main update function
function update()
if SHIP_ENABLE:get() < 1 then
return
end
update_target()
if not have_target then
return
end
current_pos = ahrs:get_position()
if not current_pos then
return
end
current_pos:change_alt_frame(ALT_FRAME_ABSOLUTE)
update_throttle_pos()
update_mode()
update_alt()
update_auto_offset()
ahrs:set_home(target_pos)
local next_WP = vehicle:get_target_location()
if not next_WP then
-- not in a flight mode with a target location
return
end
if vehicle_mode == MODE_RTL then
local holdoff_pos = get_holdoff_position()
holdoff_pos:change_alt_frame(ALT_FRAME_ABSOLUTE)
holdoff_pos:alt(math.floor(get_target_alt()*100))
vehicle:update_target_location(next_WP, holdoff_pos)
if throttle_pos == THROTTLE_LOW then
check_approach_tangent()
end
elseif vehicle_mode == MODE_QRTL then
vehicle:set_velocity_match(target_velocity:xy())
target_pos:alt(next_WP:alt())
vehicle:update_target_location(next_WP, target_pos)
if throttle_pos == THROTTLE_HIGH then
check_approach_abort()
end
elseif vehicle_mode == MODE_AUTO then
local id = mission:get_current_nav_id()
if id == NAV_VTOL_TAKEOFF or id == NAV_TAKEOFF then
vehicle:set_velocity_match(target_velocity:xy())
local tpos = current_pos:copy()
tpos:alt(next_WP:alt())
vehicle:update_target_location(next_WP, tpos)
end
elseif vehicle_mode == MODE_QLOITER then
vehicle:set_velocity_match(target_velocity:xy())
end
end
function loop()
update()
-- run at 20Hz
return loop, 50
end
check_parameters()
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-- wrapper around update(). This calls update() at 20Hz,
-- and if update faults then an error is displayed, but the script is not
-- stopped
function protected_wrapper()
local success, err = pcall(update)
if not success then
gcs:send_text(0, "Internal Error: " .. err)
-- when we fault we run the update function again after 1s, slowing it
-- down a bit so we don't flood the console with errors
return protected_wrapper, 1000
end
return protected_wrapper, 50
end
-- start running update loop
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return protected_wrapper()