Nav2 and costmap_2d nodes

asked 2022-12-16 02:49:34 -0500

updated 2022-12-16 02:51:44 -0500

Hi all,

I'm trying to figure out how Nav2 is structured and I was searching for the launch files for the costmap_2d nodes that handle the local and the global cost maps.

I found that the nodes are not launched, but they are incorporated in the planner server or the control server that uses them.

For example here is where a node is declared inside the planner server: https://github.com/ros-planning/navig...

Is there a reason for this hard-coded design when there is a powerful tool in ROS2 like IPC (Intra Process Communication) to be used?

For a personal exercise, I also tried to create my launch file for a costmap_2d node that subscribes to a 2D lidar scan and generates the local cost map... without success because it seems that the costmap_2d node does not work like any other nodes (for example, the namespace and node name parameters in the launch file are ignored). But this is a topic for another eventual thread...

answered 2022-12-19 17:53:41 -0500

stevemacenski

8272 ●34 ●503 ●129 https://www.linkedin.c...

updated 2022-12-19 17:54:48 -0500

Low-latency, direct-memory access is important for environmental models so that delays in communication don't result in collisions since it takes non-zero time for the data to be communicated over the network - reducing emergency situation response time.

It could have been in a separate process, but there wasn't a strong reason to do so. But there are compelling reasons why not to do so.

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Hi Steve, thanks for the reply. This makes sense, but I think that it would also be useful to use it in a non-"hardcoded" way, by launching it as a standalone node, for example for assisted teleops that don't require path planning.

Myzhar ( 2022-12-20 02:48:20 -0500 )edit

There is also a stand-alone node option! Its just not launched by default but there is totally that option available and folks do use it.

stevemacenski ( 2022-12-21 12:27:33 -0500 )edit

That's true, but it's not working as expected. The issue has been reported, but never fixed:

Myzhar ( 2022-12-21 13:13:56 -0500 )edit

There were pull requests clearly merged from that request.

stevemacenski ( 2022-12-21 19:12:58 -0500 )edit

I tested it in ROS2 Humble and I faced the same issue:

```

local_costmap_node = Node(

    package="nav2_costmap_2d",

    executable="nav2_costmap_2d",

    name="local_costmap",

    namespace=namespace,

    arguments=[],

    parameters=[

        # YAML file

        local_costmap_config

    ],

    output="screen",

)

```

name and namespace are ignored.

Myzhar ( 2022-12-22 03:40:06 -0500 )edit

@Myzhar have you tried compiling nav2_costmap_2d from source? It takes time for changes to make it into deb packages, and even most of a year after the PR mentioned by steve an inspection of the latest package manifest reveals that the deb doesn't have the desired fixes.

chives_onion ( 2023-07-26 10:55:34 -0500 )edit

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