AP_Scripting: example script to release gripper on thrust loss

libraries/AP_Scripting/examples/copter-release-gripper-thrust-loss.lua

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+--[[
+This script should only be used on multicopters
+The gripper is released when thrust loss is detected
+Note that thrust loss false positives are common meaning the gripper may be released unnecessarily
+--]]
+
+local MAV_SEVERITY = {EMERGENCY=0, ALERT=1, CRITICAL=2, ERROR=3, WARNING=4, NOTICE=5, INFO=6, DEBUG=7}
+
+local update_interval_ms = 100
+local thrust_loss_counter = 0
+
+function update()
+
+   -- return immediately if not armed
+   if not arming:is_armed() then
+      thrust_loss_counter = 0
+      return update, update_interval_ms
+   end
+
+   -- return if no thrust loss
+   if not MotorsMatrix:get_thrust_boost() then
+      thrust_loss_counter = 0
+      return update, update_interval_ms
+   end
+
+   -- return if vehicle is not descending (or cannot retrieve climb rate)
+   local vel_NED = ahrs:get_velocity_NED()
+   if vel_NED == nil or vel_NED:z() <= 0 then
+      thrust_loss_counter = 0
+      return update, update_interval_ms
+   end
+
+   -- vehicle is descending and thrust loss is detected
+   thrust_loss_counter = thrust_loss_counter + 1
+   if thrust_loss_counter < 10 then
+      return update, update_interval_ms
+   end
+
+   -- release gripper and warn user
+   if not gripper:released() then
+      gripper:release()
+      gcs:send_text(MAV_SEVERITY.WARNING, "Thrust loss, gripper released!")
+   end
+
+   return update, update_interval_ms
+end
+
+return update, update_interval_ms