update mission after changing home position

[Drone-Lab]

Solved Problem

fix the bug which cause drone can't finish mission after changing home altitude.Update mission after changing home position.

Summary

This state management bug will result in the drone being unable to reach the waypoint and thus continuing the mission.And continues to drift irregularly near the waypoints.

Details

1. When the drone is executing a mission, PX4 calculates the distance between the drone and the current target waypoint, and checks if it has reached the vicinity.

   Here calculates the distance.
   

   PX4-Autopilot/src/modules/navigator/mission_block.cpp

   Lines 197 to 201 in 8b96cd5

   	dist = get_distance_to_point_global_wgs84(_mission_item.lat, _mission_item.lon, mission_item_altitude_amsl,
   	_navigator->get_global_position()->lat,
   	_navigator->get_global_position()->lon,
   	_navigator->get_global_position()->alt,
   	&dist_xy, &dist_z);

   
   When mission altitude mode is Relative to Launch mission_item_altitude_amsl=mission_item.altitude + home_alt

   And here checks whether it is less than the acceptable radius.
   

   PX4-Autopilot/src/modules/navigator/mission_block.cpp

   Lines 394 to 396 in 8b96cd5

   	if (dist_xy >= 0.0f && (dist_xy <= acceptance_radius || passed_curr_wp) && dist_z <= alt_acc_rad_m) {
   	_waypoint_position_reached = true;
   	}

2. When the drone is executing a mission, if the user modifies the home point to a new location (with a different altitude), the value of 'dist' will immediately change based on the new home point's altitude (which determines the check for whether the drone has reached the waypoint). However, the current actual executed 'mission_item' does not get updated.

   This will result in a discrepancy between the actual executed target of the drone and the checked completion target, causing the drone to start randomly oscillating near the waypoint.

Verification

We added some debug output to watch the drone's state change,and found every time the user changes the home point, 'dist_z' (altitude) also changes accordingly, but the 'mission_item' does not.

Temporary Patch

There are currently two patching approaches based on the expectations for how the drone should operate after modifying the home point:

1. After changing the drone's home point altitude, the currently executed mission target should also change immediately
2. Once the mission is uploaded and completed, the 'mission_item' should no longer change, even if the home altitude changes; the waypoint altitude should remain relative to the altitude at the time of mission upload

Impact

• This vulnerability could be exploited by attackers for covert attacks
• When a benign user modifies the home point while the drone is executing a mission, the drone may oscillate, come into contact with surrounding obstacles, and ultimately crash
• Modifying the home point to a new location during the mission execution will result in the drone randomly drifting near the next waypoint. This could lead to collisions and crashes.[Bug] Modifying home during Mission execution affects UAV's current Item completion detection #22576

can.t.reach.waypoint.mp4

Some bugs prevent you from directly viewing the video.You can download and check this vedio.

Solution

• Add an update for the current setpoint altitude when the home point is changed.

Test coverage

• Simulation/hardware testing logs:https://logs.px4.io/plot_app?log=0488b27d-6137-481a-9bb1-1b084777b2de

[Drone-Lab]

@bkueng Following your advice, I utilized _navigator->get_home_position()->update_count.

[Drone-Lab]

Resolved Conflict Code

[Drone-Lab]

@KonradRudin Looking forward to receiving your advice.

[KonradRudin]

Thansk for the bug fix. Looks fine to me, just extend it for the previous and next as well.

[Drone-Lab]

@KonradRudin How about this modification?

[KonradRudin]

Thanks for the changes. Looking good for me, but there seems to be a conflict we recent changes. If you rebase it on newest main, i can approve.

[Drone-Lab]

Thanks for the changes. Looking good for me, but there seems to be a conflict we recent changes. If you rebase it on newest main, i can approve.

@KonradRudin Thank you for your feedback! I've addressed the conflict and rebased the changes on the latest main branch.

[Drone-Lab]

@bkueng it's ready to merge

[bkueng]

Can you run make format, commit the result & rebase? CI should then pass.

[Drone-Lab]

Can you run make format, commit the result & rebase? CI should then pass.

@bkueng OK ，I have finished it.