-- Copter descends very rapidly in a spiral pattern to a preset altitude above home -- -- CAUTION: This script only works for Copter 4.2 (and higher) -- this script waits for the vehicle to be changed to Guided mode and then: -- a) flies a spiral pattern using the velocity and acceleration control -- b) slows the spiral and stops at the preset altitude -- c) switches to RTL -- constants local copter_guided_mode_num = 4 -- Guided mode is 4 on copter local copter_rtl_mode_num = 6 -- RTL is 6 on copter local circle_radius_rate_max_ms = 1 -- radius expands at max of this many m/s local circle_radius_accel_mss = 1 -- radius expansion speed accelerates at this many m/s/s local accel_xy = 1 -- horizontal acceleration in m/s^2 local accel_z = 1 -- target vertical acceleration is 1m/s/s local speed_z_slowdown = 0.1 -- target vertical speed during final slowdown -- timing and state machine variables local stage = 0 -- stage of descent local last_update_ms -- system time of last update local dt = 0.01 -- update rate of script (0.01 = 100hz) local interval_ms = 1 -- update interval in ms local last_print_ms = 0 -- pilot update timer local auto_last_id = -1 -- unique id used to detect if a new NAV_SCRIPT_TIME command has started -- control related variables local circle_center_pos = Vector3f()-- center of circle position as an offset from EKF origin local circle_radius = 0 -- target circle's current radius (this is slowly expanded to circle_radius_max) local circle_radius_rate_ms = 0 -- target circle's radius is increasing at this rate in m/s local circle_angle_rad = 0 -- current target angle on circle (in radians) local target_alt_D = 0 -- target altitude in m from EKF origin (Note: down is positive) local speed_xy = 0 -- target horizontal speed (i.e. tangential velocity or horizontal speed around the circle) local speed_z = 0 -- target descent rate currently local target_yaw_deg = 0 -- target yaw in degrees (degrees is more convenient based on interface) -- create and initialise parameters local PARAM_TABLE_KEY = 75 -- parameter table key must be used by only one script on a particular flight controller assert(param:add_table(PARAM_TABLE_KEY, "FDST_", 6), 'could not add param table') assert(param:add_param(PARAM_TABLE_KEY, 1, 'ACTIVATE', 0), 'could not add FDST_ACTIVATE param') -- 0:active in Guided, 1:active in Auto's NAV_SCRIPT_TIME command assert(param:add_param(PARAM_TABLE_KEY, 2, 'ALT_MIN', 50), 'could not add FDST_ALT_MIN param') -- copter will stop at this altitude above home assert(param:add_param(PARAM_TABLE_KEY, 3, 'RADIUS', 10), 'could not add FDST_RADIUS parameter') -- target circle's maximum radius assert(param:add_param(PARAM_TABLE_KEY, 4, 'SPEED_XY', 5), 'could not add FDST_SPEED_XY param') -- max target horizontal speed assert(param:add_param(PARAM_TABLE_KEY, 5, 'SPEED_DN', 10), 'could not add FDST_SPEED_DN param') -- target descent rate assert(param:add_param(PARAM_TABLE_KEY, 6, 'YAW_BEHAVE', 0), 'could not add FDST_YAW_BEHAVE param') -- 0:yaw does not change 1:yaw points toward center -- bind parameters to variables function bind_param(name) local p = Parameter() assert(p:init(name), string.format('could not find %s parameter', name)) return p end local activate_type = bind_param("FDST_ACTIVATE") -- activate type 0:Guided, 1:Auto's NAV_SCRIPT_TIME local alt_above_home_min = bind_param("FDST_ALT_MIN") -- copter will stop at this altitude above home local circle_radius_max = bind_param("FDST_RADIUS") -- target circle's maximum radius local speed_xy_max = bind_param("FDST_SPEED_XY") -- max target horizontal speed local speed_z_max = bind_param("FDST_SPEED_DN") -- target descent rate local yaw_behave = bind_param("FDST_YAW_BEHAVE") -- 0:yaw is static, 1:yaw points towards center of circle -- the main update function function update() -- update dt local now_ms = millis() if (last_update_ms) then dt = (now_ms - last_update_ms):tofloat() / 1000.0 end if (dt > 1) then dt = 0 end last_update_ms = now_ms -- determine if progress update should be sent to user local update_user = false if (now_ms - last_print_ms > 5000) then last_print_ms = now_ms update_user = true end -- reset stage until activated in Guided or Auto mode if (activate_type:get() == 0) then -- activate_type 0: reset stage when disarmed or not in Guided mode if not arming:is_armed() or (vehicle:get_mode() ~= copter_guided_mode_num) then stage = 0 if (update_user and arming:is_armed()) then gcs:send_text(6, "Fast Descent: waiting for Guided") end return update, interval_ms end else -- activate_type 1: reset stage when disarmed or not in Auto executing NAV_SCRIPT_TIME command auto_last_id, cmd, arg1, arg2 = vehicle:nav_script_time() if not arming:is_armed() or not auto_last_id then stage = 0 if (update_user and arming:is_armed()) then gcs:send_text(6, "Fast Descent: waiting for NAV_SCRIPT_TIME") end return update, interval_ms end end if (stage == 0) then -- Stage0: initialise local home = ahrs:get_home() local curr_loc = ahrs:get_location() if home and curr_loc then circle_center_pos = ahrs:get_relative_position_NED_origin() circle_radius_rate_ms = 0 -- reset circle radius expandion rate to zero circle_radius = 0 -- reset circle radius to zero if yaw_behave:get() == 0 then -- yaw does not move so reset starting angle to current heading circle_angle_rad = ahrs:get_yaw() else -- yaw points towards center so start 180deg behind vehicle circle_angle_rad = ahrs:get_yaw() + math.pi if (circle_angle_rad >= (math.pi * 2)) then circle_angle_rad = circle_angle_rad - (math.pi * 2) end end target_yaw_deg = math.deg(ahrs:get_yaw()) -- target heading will be kept at original heading target_alt_D = circle_center_pos:z() -- initialise target alt using current position (Note: down is positive) speed_xy = 0 speed_z = 0 stage = stage + 1 -- advance to next stage gcs:send_text(5, "Fast Descent: starting") end elseif (stage == 1) then -- Stage1: descend -- get current position local rel_pos_home_NED = ahrs:get_relative_position_NED_home() -- increase circle radius circle_radius_rate_ms = math.min(circle_radius_rate_ms + (circle_radius_accel_mss * dt), circle_radius_rate_max_ms) -- accelerate radius expansion circle_radius = math.min(circle_radius + (circle_radius_rate_ms * dt), circle_radius_max:get()) -- increase radius -- calculate horizontal and vertical speed if (circle_radius < circle_radius_max:get()) then speed_xy = math.max(speed_xy - (accel_xy * dt), 0) -- decelerate horizontal speed to zero speed_z = math.max(speed_z - (accel_z * dt), 0) -- decelerate vertical speed to zero else -- calculate conversion between alt-above-home and alt-above-ekf-origin local home_alt_above_origin = 0 local home = ahrs:get_home() local ekf_origin = ahrs:get_origin() if home and ekf_origin then local dist_NED = home:get_distance_NED(ekf_origin) home_alt_above_origin = dist_NED:z() end -- calculate target speeds local target_dist_to_alt_min = -target_alt_D - home_alt_above_origin - alt_above_home_min:get() -- alt target's distance to alt_min if (target_dist_to_alt_min > 0) then local speed_z_limit = speed_z_max:get() speed_z_limit = math.min(speed_z_limit, math.sqrt(2.0 * target_dist_to_alt_min * accel_z)) -- limit speed so vehicle can stop at ALT_MIN speed_z_limit = math.max(speed_z_limit, speed_z_slowdown) -- vertical speed should never be less than 0.1 m/s when above ALT_MIN speed_z = math.min(speed_z + (accel_z * dt), speed_z_limit) speed_xy = math.min(speed_xy + (accel_xy * dt), speed_xy_max:get()) -- accelerate horizontal speed to maximum else -- below alt min so decelerate target speeds to zero speed_xy = math.max(speed_xy - (accel_xy * dt), 0) -- decelerate horizontal speed to zero speed_z = math.max(speed_z - (accel_z * dt), 0) -- decelerate vertical speed to zero end end -- calculate angular velocity local ang_vel_rads = 0 if (circle_radius >= circle_radius_max:get()) then ang_vel_rads = speed_xy / circle_radius; end -- increment angular position circle_angle_rad = circle_angle_rad + (ang_vel_rads * dt) if (circle_angle_rad >= (math.pi * 2)) then circle_angle_rad = circle_angle_rad - (math.pi * 2) end -- calculate target position local cos_ang = math.cos(circle_angle_rad) local sin_ang = math.sin(circle_angle_rad) local target_pos = Vector3f() target_pos:x(circle_center_pos:x() + (circle_radius * cos_ang)) target_pos:y(circle_center_pos:y() + (circle_radius * sin_ang)) target_alt_D = target_alt_D + (speed_z * dt) target_pos:z(target_alt_D) -- calculate target velocity target_vel = Vector3f() target_vel:x(speed_xy * -sin_ang) target_vel:y(speed_xy * cos_ang) target_vel:z(speed_z) -- calculate target acceleration local centrip_accel = 0 if (circle_radius > 0) then centrip_accel = speed_xy * speed_xy / circle_radius end target_accel = Vector3f() target_accel:x(centrip_accel * -cos_ang) target_accel:y(centrip_accel * -sin_ang) -- calculate target yaw if yaw_behave:get() == 1 then target_yaw_deg = math.deg(circle_angle_rad + math.pi) if target_yaw_deg > 360 then target_yaw_deg = target_yaw_deg - 360 end end -- send targets to vehicle with yaw target vehicle:set_target_posvelaccel_NED(target_pos, target_vel, target_accel, true, target_yaw_deg, false, 0, false) -- advance to stage 2 when below target altitude and target speeds are zero if (rel_pos_home_NED) then if (-rel_pos_home_NED:z() <= alt_above_home_min:get() and (speed_xy==0) and (speed_z==0)) then stage = stage + 1 end if (update_user) then gcs:send_text(5, string.format("Fast Descent: alt:%d target:%d", math.floor(-rel_pos_home_NED:z()), math.floor(alt_above_home_min:get()))) end else gcs:send_text(5, "Fast Descent: lost position estimate, aborting") stage = stage + 1 end elseif (stage == 2) then -- Stage2: done! stage = stage + 1 gcs:send_text(5, "Fast Descent: done!") if (activate_type:get() == 0) then -- if activated from Guided change to RTL mode vehicle:set_mode(copter_rtl_mode_num) else -- if activated from Auto NAV_SCRIPT_TIME then mark command as done vehicle:nav_script_time_done(auto_last_id) end end return update, interval_ms end return update()