kaist_webots: webots_run | webots_joy_demo | webots_controllers

The idea behind this package was to create a controller manager for Webots, similar to GazeboRosControllerManager. This would enable users to easily test different position, velocity, or force controllers with their simulation.

The launch file loads the 'webots_run' node which opens the specified world file in the Webots simulator, which in turn executes the controller binary.

At present, only a simple stand-alone P-controller has been implemented: joint_position_controller. The controller can be easily configured for new Webots worlds, allowing users to quickly test their model.

Tested with Webots 6.4.4 and ROS Fuerte.

• Author: David Butterworth.
• License: BSD

• Repository: kaist-ros-pkg

• Source: http://kaist-ros-pkg.googlecode.com/svn/trunk/kaist_webots/webots_controllers/

Joint Position Controller

A joint position controller for Webots, utilising the C++ API and simple P-control.

The controller configuration is defined in a yaml file, which includes the ROS topic for subscribing to commands for each joint, the joint's servo name in Webots, and the value of the P constant.
The webots_controllers_to_load parameter in the launch file specifies which controllers from the yaml file should be loaded.

Position commands are received on a ROS topic for each joint.
Current position and calculated velocity values are published on the /joint_states topic.
Force information is not checked due to a bug with Webots 6.4.4

Installation

Follow these instructions to install the kaist_webots stack.

Usage

A demo of the joint position controller is included, using ROS messages to control a simulated Puma 560 manipulator in Webots.

Run the demo:

$ roslaunch webots_controllers joint_position_controller_demo.launch

The Webots simulator should load with the Puma 560 in the home position.

If everything is working correctly, the following messages will be printed in the Webots console:

List the available joint controllers by opening a new shell console and running: $ rostopic list

To move one of the joints, you need to publish the desired position to the
/Puma560/SimController/<joint name>/command
topic.

For example, the base rotation joint is called 'waist'. To move that joint, run the command:

$ rostopic pub -1 /Puma560/SimController/waist/command std_msgs/Float64 -- 1.5

The joint will rotate 1.5 radians in the positive direction.
This command publishes one message to the ROS topic and the "--" indiciates that the next input is a number.

Controlling your own Webots robot arm

• Create a new Webots world and robot arm model. Assign each joint servo with a unique name.

• Ceate a new ROS package e.g. myrobot_sim_webots. See Creating a ROS Package

• Add the Webots .wbt world file to your package, in the /world directory

• Copy the webots_controllers source to the /src directory

• Edit CMakeLists.txt, using this package as an example. Note how the destination of the compiled binary is in the controllers/binary_name directory to suit Webots requirements, not the default ROS directory /bin

• Edit your Webots world file and specify the name of the controller binary file

• Create a new .yaml file in the /config directory, using this package as an example. This contains the name of the ROS topic for joint commands, the servo names from the Webots model, and the P constant for the position controller.

• Create a launch file in the /launch directory, using this package as an example. The webots_controllers_to_load parameter contains the controller names from the yaml file. The Webots world file is specified as an argument to the webots_run node

• Build your package: rosmake myrobot_sim_webots