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ROS2 spawn controllers (

asked 2021-03-27 09:20:48 -0500

RandyD gravatar image


For my mecanum robot, i'm trying to build everything using ROS2. Currently i'm at the point where i implemented a hardware interface class for controlling the motors and reading the sensors.

Following the documentation on ros2_control github, i'm at the point where i need to run "ros2 contol load_start_controller", where i'm testing with the diff_drive_controller before implementing a custom controller for mecanum drive.

I can't find any information on how to automatically spawn the controller in ROS2 so i don't have to run the ros2 control load_start_controller every time i launch my robot nodes.

Can the controller be defined in the URDF as we do with hardware interface or can the controller be spawned trough python launch files?

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You certainly can start the controller in your launch file. At the very least, anything that can be run from the commandline can be run from a python launch file by adding an ExecuteProcess action to your launch description. Something to the effect of: return LaunchDescritpion([... ,ExecuteProcess( cmd=['ros2', 'control', 'load_start_controller', 'differential_drive_controller'], output='screen' ])

shonigmann gravatar image shonigmann  ( 2021-03-30 11:38:48 -0500 )edit

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answered 2022-01-17 21:44:15 -0500

To start a controller immediately you should add a spawner node to your launch file. You can even control if controller should be started or only configured on the beginning using the flag "--stoppped" to only load and configure a controller.

joint_state_broadcaster_spawner = Node(
    arguments=["joint_state_broadcaster", "--controller-manager", "/controller_manager"],
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answered 2021-03-27 13:11:40 -0500

RandyD gravatar image

updated 2021-03-27 13:12:55 -0500

As workaround i duplicated the "ros2_control_node.cpp" into my mecanum_control package and added the following code above the executor->add_node / executor->spin();

// Load the controllers
std::vector<std::string> start_controllers;
std::vector<std::string> stop_controllers;
controller_manager_node->load_controller("joint_state_controller", "joint_state_controller/JointStateController");
controller_manager_node->load_controller("mecanumbot_drive_controller", "mecanumbot_controller/MecanumbotDriveController");

controller_manager_node->switch_controller(start_controllers, stop_controllers, 1, controller_manager_msgs::srv::SwitchController::Request::BEST_EFFORT);
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This approach is suboptimal. If you want to control this from a different node, then ok, but ros2_control_node if definitely misused for this.

destogl gravatar image destogl  ( 2022-01-17 21:46:12 -0500 )edit

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Asked: 2021-03-27 09:20:48 -0500

Seen: 616 times

Last updated: Jan 17