New Tutorial: Multi-Agent Coordination Tutorial Now Available!

[aditjha]

There is a new tutorial posted on the MuSHR website! This tutorial is Multi-Agent Coordination Planner for Multi-Goal Tasks. We hope this is useful for many and let us know if there are any questions. Below is a link to the tutorial in case.

https://mushr.io/tutorials/coordination/

[Lilly-yang]

Hi,

First of all, thank you for writing this detailed tutorial. I learned a lot from it.

It just I encountered an error when running the last step init_planner.launch. Here are screenshots.
Mushr_coordination.launch

init_planner.launch

rviz

Could you please help me to find out why init_planner closes after publishing all these plans for these 4 cars (of course, the cars in rviz didn't move either)?

I also found that after launching the multi_teleop.launch file provided in the tutorial, I can only see one car in rviz. I found another file with the same name in the nhttc_ros repository which allows four carts to be displayed in rviz successfully. The latter launchs one more nhttc_pose_init node than the former, and it seems that without nhttc_pose_init the carts cannot be displayed in RIVZ (but I don't know why).

Thank you!

[sidtalia]

Hi @Lilly-yang!

1. Init-planner closes after publishing the plans because once the plan has been published, it (the planner) is no longer required. This is because the system (at the moment) does not consider re-planning.

2. The purpose of nhttc_pose_init is to initialize the poses for the cars. The reason why you may be seeing only one car in rviz when you launch multi_teleop.launch from mushr_sim is that all of them are being "plopped" on the same coordinate (origin), thus it looks like its just one car. In nhttc_pose_init, the cars are plopped at different locations, which is why you see them separately.

3. The cars don't move after the init-planner closes because the init-planner node is only responsible for publishing plans. The multi_teleop.launch file being referred to in this tutorial belongs to the mushr_sim repository, which means it does not contain the local-navigation system provided by nhttc_ros and is only used to bring the cars into the "arena". I believe the tutorial needs to be updated to point to the correct launch file for multi-agent navigation. In order for the cars to move, you need to launch the multi_teleop.launch in nhttc_ros. If I remember correctly, you should launch the nhttc_ros node before launching the planner. This is because the nhttc_pose_init
   simply starts the cars off at some pre-determined location, whereas the init_planner node sets the cars on the appropriate start points.

Regards,
Sidharth T.

[Lilly-yang]

Hi Sidharth,

Thanks for your reply.

The multi_teleop.launch file I launched is from nhttc_ros. But it still can't move these cars. All controller nodes are dead after publishing plans. The steps I have done are as follows:

roslaunch mushr_coordination mushr_coordination.launch
roslaunch nhttc_ros multi_teleop.launch
rviz
roslaunch mushr_coordination init_planner.launch

(cars_file:=4cars.yaml tasks_file:=4cars4tasks5x3.yaml)

[sidtalia]

Hi @Lilly-yang,

Could you try the following:

roscore
(new tab)
roslaunch nhttc_ros multi_teleop.launch
wait for a few minutes till you see this output:
[ INFO] [1621678112.116392844]: node started
[ INFO] [1621678112.116614789]: carrot_goal_ratio: 1.000000
[ INFO] [1621678112.116632550]: max_ttc: 6.000000
[ INFO] [1621678112.116642780]: solver_time: 20
[ INFO] [1621678112.116653036]: obey_time:1
.......
(it would look similar to what has been shown above, though it may contain more fields. Note that this can take a while (~1 minute).
(new tab)
rosrun rviz rviz  (or just rviz)
roslaunch mushr_coordination mushr_coordination.launch
(wait for it to initialize, the new tab)
roslaunch mushr_coordination init_planner.launch

The nhttc ros nodes tend to die out when launched around the same time as the rviz, so try waiting for the node to start (the info messages will indicate that it has started).

Regards,
Sidharth T.

[sidtalia]

Hi @Lilly-yang,

Thank you for waiting, I was trying to reproduce this bug in a VM with the same OS and lower specs.
I noticed that I was running an older version of mushr_sim and mushr_base, hence the earlier comment about using mushr_sim's map_server.launch.

1. I then updated the mushr_sim, mush_base, and vesc (if you already have vesc just make sure it is on master. I don't think this is the source of the problem though). Remember to catkin_make after updating

2. I ran the nhttc_ros nhttc_demo.launch as well as the multi_teleop.launch, and in both cases, the system ran without an issue (as in I got to the info messages that indicate that the node has started).

I assume that you're facing this bug even though your mushr_sim, mushr_base and nhttc_ros are up-to-date (on master). If that is the case and you're still facing issues, could you try running the following:

roslaunch mushr_sim single_car.launch
roslaunch mushr_base map_server.launch

and see if this creates an issue (it could be a different issue). Please also note the RAM usage when you launch these two nodes, I expect RAM usage to be around 1 GB.

Regards,
Sidharth T.

[Lilly-yang]

Hi @naughtyStark ,

Today I tried again to launch nhttc_ros/multi_teleop.launch, and this time the 'node started" msg was successfully displayed.

I noticed that after I had tried launching many nodes. Even if no node is running, multi_teleop.launch gets stuck at 'log file: *.log' like before. In this case, I reboot the laptop and rerun it, and the nodes start again successfully. I don't know why.

After multi_teleop.launch is launched well(i.e. the node is started). I launched the mushr_coordination nodes. The good news is that car1 moved. But the other three still didn't move. Their controllers died after the path was published. recording screen.

I also tried launching these two nodes.

roslaunch mushr_sim single_car.launch
roslaunch mushr_base map_server.launch

only a warning popped up when launching single_car.launch

and in rviz it showed up like this:

I checked the RAM usage while I launched nhttc_ros + mushr_coordination and mushr_sim + mushr_base. It's about 4G/62.6G.

[sidtalia]

@Lilly-yang could you try running the commands from the multiagent navigation tutorial (the one that uses nhttc_demo.launch) and see if they work? I am not sure why the other agent nodes are crashing.

Regards,
Sidharth.

[Lilly-yang]

I have tried the multi-agent navigation tutorial before the Multi-Agent Coordination tutorial. It worked fine, except that the two cars didn't move simultaneously. You can check it out here.

[sidtalia]

@Lilly-yang
Hi, I am not sure why it isn't working on your system as expected. At this point, I would suggest running this VM image from the quickstart tutorial and then cloning the required repositories and seeing how that works out.

Please note that I may take a little longer to respond to queries. Our team is currently working on a docker version which should be out soon (can't say when exactly) and that may make things easier. Hopefully the VM approach works for you, given that you have ample computer power and RAM.

Regards,
Sidharth.