Modifying drone's pose (during sphinx simulation) with parrot-gz results in drone bouncing

[GCid]

Hello,

When using the command bellow to modify the drone’s pose (only its position) during sphinx simulation, it results in the model bouncing to randomly (as seen in this video).

parrot-gz topic -p "~/pose/modify" -m "position{x:0 y:0 z:0} orientation{w:0 x:0 y:0 z:0} name:'anafi4k_1::gimbal_2'"

I have tried:

• setting the z position to 0.2 instead of 0 (in case a glitch with the terrain happens during the modification, but the drone still bounces)
• changing the body’s position instead of gimbal_2
• resetting its position while hovering

In all cases the bouncing still happens.

In any case, are there any other ways to reset the drone’s position fast?

Thank you in advance.

[ocrave]

Hello,

With sphinx 1.9, you can use the handling plugin to update the position of the drone (see How to simulate a human operator physically interacting with a drone — Parrot-Sphinx 1.2.1 documentation).

This example updates the script parameter of the “calibration” plugin to move the drone 5 meters north (and 20 cm above the ground to prevent any collision):

echo '{"jsonrpc": "2.0", "method": "SetParam", "params": {"machine":"anafi4k", "object":"calibration/handling", "parameter":"script", "value":"[ { \"stop_condition_expr\": \"step_time > 1\", \"start_pose\": { \"x_expr\": \"0\", \"y_expr\": \"5\", \"z_expr\": \"0.2\", \"roll_expr\": \"val\", \"pitch_expr\": \"val\", \"yaw_expr\": \"val\" }, \"pose\": { \"x_expr\": \"0\", \"y_expr\": \"0\", \"z_expr\": \"0\", \"roll_expr\": \"start_val\", \"pitch_expr\": \"start_val\", \"yaw_expr\": \"start_val\" } }]"}, "id": 1}' | curl -d @- http://127.0.0.1:8383 | python -m json.tool

The script can then be executed with:

echo '{"jsonrpc": "2.0", "method": "TriggerAction", "params": {"machine":"anafi4k", "object":"calibration/handling", "action":"start"}, "id": 1}' | curl -d @- http://127.0.0.1:8383 | python -m json.tool

[GCid]

Thank you for your reply.
When I try to start the sphinx-dashboard, I get the following error:

Using JSON-RPC port 8383.
Error: Cannot connect to sphinx. Is Sphinx running?

When I start sphinx, I do receive the following message indicating that the parameter server has started:

[Msg] Publicized address: 127.0.0.1
[Msg] created parameter server on http:8383

As the title of the documentation you provided says, it is used to simulate an operator/move the drone. Is it a practical way to follow when I need to reset the drone’s position (move it instantly to a specific position inside the world) many times during a single simulation?

[ocrave]

That is a known issue with sphinx 1.9. To access the dashboard you have to open http://localhost:9002 in your web browser.

The handling plugin can be used multiple times during a single simulation.

A safer way to move the drone is by setting its initial_pose parameter:

echo '{"jsonrpc": "2.0", "method": "SetParam", "params": {"machine":"anafi4k", "object":"fwman/fwman", "parameter":"initial_pose", "value":"0 5 0.2 0 0 0"}, "id": 1}' | curl -d @- http://127.0.0.1:8383 | python -m json.tool

Then, you can call parrot-gz world -r to reset the world and the drone will be spawned at its new position.

[GCid]

I am aware of the parrot-gz world -r command, but it resets the whole world, which doesn’t help me in my case. I need to be able to reset only the position of a specific drone (I am simulating multiple drones at once).
As for the initial_pose you mentioned, it’s the same as setting its spawn_point inside the .world file, right?

[ocrave]

Yes, it’s identical to the spawn_point parameter. It lets you update the spawn_point of a drone when sphinx is running without having to restart it. But it requires a world reset.

[GCid]

I get the following output for both of the commands you provided:

  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   668  100   528  100   140   103k  28000 --:--:-- --:--:-- --:--:--  130k
Expecting value: line 1 column 1 (char 0)

When the second command is executed, the drone’s position isn’t changed.
I executed the commands with the following differences:

1. “machine”: “anafi4k_1” instead of “anafi4k” as I spawn it with a different name
2. curl -d @- http://localhost:9002 instead of curl -d @- http://127.0.0.1:8383, as I couldn’t launch sphinx dashboard

In case it helps, I am using Python 3.6.13.

[ocrave]

You must use http://127.0.0.1:8383. 9002 is the port of the web server (for the web dashboard), 8383 is the port of the server that listens for json-rpc requests like the ones above.

[GCid]

I see.
Works good now. Thank you very much!