Avoid waypoint following during backtransition which can lead to strong banking (#22642)

* avoid waypoint following during backtransition
- if vehicle overshoots transition, make controller track the prev/current
waypoint line, this avoids large banking maneuvers that delay the transition further

Signed-off-by: RomanBapst <bapstroman@gmail.com>

* navigator: use SETPOINT_TYPE_LAND as setpoint type for VTOL_LAND waypoints
such that fixed wing position controller can distinguish from other types

Signed-off-by: RomanBapst <bapstroman@gmail.com>

* FixedWingPositionControl: split vtol backtransition logic into separate method

Signed-off-by: RomanBapst <bapstroman@gmail.com>

* review changes

Signed-off-by: RomanBapst <bapstroman@gmail.com>

* prevent loiter when approaching vtol backtransition and invalidate previous waypoint during mission landing

Signed-off-by: RomanBapst <bapstroman@gmail.com>

* removed unused parameter

Signed-off-by: RomanBapst <bapstroman@gmail.com>

* small renaming of transition mode

Signed-off-by: RomanBapst <bapstroman@gmail.com>

---------

Signed-off-by: RomanBapst <bapstroman@gmail.com>

src/modules/navigator/mission_base.cpp

@@ -574,10 +574,6 @@ void MissionBase::handleLanding(WorkItemType &new_work_item_type, mission_item_s
 			set_vtol_transition_item(&_mission_item, vtol_vehicle_status_s::VEHICLE_VTOL_STATE_MC);
 
 			new_work_item_type = WorkItemType::WORK_ITEM_TYPE_MOVE_TO_LAND_AFTER_TRANSITION;
-
-			// make previous setpoint invalid, such that there will be no prev-current line following
-			// if the vehicle drifted off the path during back-transition it should just go straight to the landing point
-			_navigator->reset_position_setpoint(pos_sp_triplet->previous);
 		}
 
 	} else if (needs_to_land) {

src/modules/navigator/mission_block.cpp

@@ -110,7 +110,8 @@ MissionBlock::is_mission_item_reached_or_completed()
 
 		if (int(_mission_item.params[0]) == 3) {
 			// transition to RW requested, only accept waypoint if vehicle state has changed accordingly
-			return _navigator->get_vstatus()->vehicle_type == vehicle_status_s::VEHICLE_TYPE_ROTARY_WING;
+			return _navigator->get_vstatus()->vehicle_type == vehicle_status_s::VEHICLE_TYPE_ROTARY_WING
+			       && !_navigator->get_vstatus()->in_transition_mode;
 
 		} else if (int(_mission_item.params[0]) == 4) {
 			// transition to FW requested, only accept waypoint if vehicle state has changed accordingly

src/modules/navigator/rtl_direct.cpp

@@ -310,6 +310,7 @@ void RtlDirect::set_rtl_item()
 			dest.alt = loiter_altitude;
 
 			setMoveToPositionMissionItem(_mission_item, dest, rtl_heading_mode);
+			_navigator->reset_position_setpoint(pos_sp_triplet->previous);
 
 			_rtl_state = RTLState::LAND;