ROS_tutorial

First Example

Brief Description

We give radius, linear velocity and direction of turtle's trajectory(uniform circular) to "/rvd_publisher" node.

Then "/rvd_publisher" node publishs "/uniform_circular_velocity" topic msg ("rvd_msg_example/msg/RVD" type) to "/rvd_subscriber" node. This node transforms "/uniform_circular_velocity" topic msg ("rvd_msg_example/msg/RVD" type) to "/turtle1/cmd_vel" topic msg ("geometry_msgs/msg/Twist" type) and publishs to "/turtlesim" node.

Launch file includes "/rvd_subscriber" node and "/turtlesim_node" (turtlesim package). We give "/uniform_circular_velocity" topic msg ("rvd_msg_example/msg/RVD" type) to "/rvd_subscriber" node.

Requirements

Ubuntu 18.04, ROS2 dashing version

To see results, follow:

git clone https://github.com/windust7/ROS_tutorial

Move rvd_msg_example and uniform_circle_turtle folders to src folder(which is at your workspace)

cd ~/(your workspace)
colcon build --symlink-install --packages-select rvd_msg_example
colcon build --symlink-install --packages-select uniform_circle_turtle
. ~/(your workspace)/install/local_setup.bash

To run each nodes, follow below at different terminal window:

ros2 run turtlesim turtlesim_node
ros2 run uniform_circle_turtle rvd_publisher -r 2 -v 2 -c 1
ros2 run uniform_circle_turtle rvd_subscriber

To run launch file, follow below at different terminal window:

ros2 launch uniform_circle_turtle rvd_to_twist.launch.py
ros2 topic pub --once /uniform_circular_velocity rvd_msg_example/msg/RVD "{ccwdirection: False, radius: 1.5, lin_vel: 5.0}"

Second Example

Brief Description

/agent_spawner node spawns a new turtle(/agent).

An original turtle(/turtle1) will be an obstacle and the agent has to move to targets in order without bumping into the obstacle. You can decide which points will be targets with config file.

Requirements

Ubuntu 18.04, ROS2 dashing version

To see results, follow:

git clone https://github.com/windust7/ROS_tutorial

Move dwa_turtle folders to src folder(which is at your workspace)

cd ~/(your workspace)
colcon build --symlink-install --packages-select dwa_turtle
. ~/(your workspace)/install/local_setup.bash

To run each nodes, follow below at different terminal window.

-x means initial x coordinate of /agent, -y means initial y coordinate of /agent, -t means initial theta of /agent.
If you don't give x, y, t or direction of .yaml file, default values are given.
If you give .yaml file's directory, you have to run last line at your workspace.

ros2 run turtlesim turtlesim_node
ros2 run dwa_turtle agent_spawner -x 1.0 -y 1.0 -t 0.0
ros2 run dwa_turtle dwa_planner __params:=src/dwa_turtle/param/config.yaml

At config.yaml, you can decide num_target, pick_target and etc.

If you give 3 to num_target, there will be 3 * 3 = 9 grids.

If you give 325 to pick_target, 325 = 0b101000101 and 1st, 3rd, 7th, and 9th grids will be targets(Consider each digit in a binary number).

Citation(Dynamic Window Planner)

Problem

I tried to run a launch file but when I tried:

ros2 launch dwa_turtle dwa_turtle.launch.py

The following error message appeared:

[ERROR] [launch]: Caught exception in launch (see debug for traceback): __init__() missing 1 required keyword-only argument: 'node_executable'

If someone find the reason or solution, please let me know(via e-mail or etc,,)

(Looks like my local environment is something wrong,, Maybe you will be able to run the launch file without that error message)