Erratic Robot

Description of Erratic
Bringup Erratic in Gazebo
Controlling the Erratic



Description of Erratic

The Erratic robot is a clone by Videre of the well known Pioneer2 robotic platform that's been around for more than 10 years.

Note: Until further notice, we will be using the erratic robot for Project 1. Remember that, You should not have anything to do with Gazebo once you finish Phase 1 until you are ready for Phase 3.




Bring up the Erratic Robot in Gazebo

Install the stack, Launch Gazebo & Teleoperate

  1. Install the erratic_robot stack:

    sudo apt-get install ros-cturtle-erratic-robot
  2. Launch gazebo with the erratic in an empty environment:

    roslaunch erratic_navigation_apps demo_2dnav_empty_map.launch
  3. Run the teleoperation node:

    rosrun erratic_teleop erratic_keyboard_teleop
  4. Have fun driving that bad boy around with the WASD keys! Press Shift to put the pedal to the metal.

Controlling the Erratic

Brief Description

Topics

/odom (nav_msgs/Odometry)

subscribe to this topic to receive updates on the robot's odometry. (units are meters, radians)

/cmd_speed (geometry_msgs/Twist)

publish speed commands for the left and right motors on this topic to control the robot's base.
linear.x: msg field for speed of left motor
linear.y: msg field for speed of right motor
forward speed: 0 < v <= 2.0 (max: 2.0)
reverse speed: -2.0 <= v < 0 (max: -2.0)

C++ / Python

There isn't much you have to know other than what is described in the brief summary above. You have to subscribe to /odom and publish motor commands on /cmd_speed.

You still have to download erratic_control_2-3-2011.zip because it contains the modified erratic_gazebo_plugins package that subscribes to /cmd_speed instead of /cmd_vel - the standard topic. Make sure you place the erratic_gazebo_plugins folder in your ROS_PACKAGE_PATH before /opt/ros/cturtle/stacks. Then source your ~/.bashrc file and run rosmake erratic_gazebo_plugins.

You can use this launch file: erratic_gazebo.launch to bring up the erratic in gazebo. ''(note: it refers to a texture in the erratic_control_example package, so I would suggest to put that folder in your ROS_PACKAGE_PATH as well...)

Matlab

  1. Download the code erratic_control_2-3-2011.zip.
  2. Unzip it.

    unzip erratic_control_2-3-2011.zip
  3. Put the erratic_control folder in your ROS_PACKAGE_PATH.
  4. Compile the erratic_gazebo_plugins package.

    rosmake erratic_gazebo_plugins
  5. Now let's run the example code. Let's launch gazebo, ipc & ipc_bridge. If everything loaded properly, you should see the gazebo window come up with the erratic at the center.

    roslaunch erratic_control_example bringup_erratic_with_controller.launch
  6. We will now run an example script in matlab that reads the odometry measurement and then sends dummy control signals to the left and right motors. Open erratic_control_example/control_erratic.m in matlab. Press F5 to run it.

    Try running the script again if you get an error. It doesn't always load properly the first time (I don't know why).

In gazebo, you should see the robot randomly choose new speeds for the left and right motors every 5 seconds.

http://www.youtube.com/watch?v=D2Pck5l51A0

A totally pointless video showing the robot responding to random motor commands.
Look. It moves.


The output should look like this:

[position]    x: -1.038 y: -8.720 z: 0.000 
[orientation] x: 0.000 y: 0.000 z: -0.970 w: 0.243
[command] right_motor: 0.018   left_motor: 0.323
---------------
[position]    x: -1.370 y: -8.724 z: 0.000 
[orientation] x: 0.000 y: 0.000 z: 0.893 w: 0.450
[command] right_motor: 0.018   left_motor: 0.323

......

[position]    x: -1.017 y: -7.245 z: 0.000 
[orientation] x: 0.000 y: 0.000 z: 0.577 w: 0.817
[command] right_motor: 0.090   left_motor: 0.059
---------------
[position]    x: -0.977 y: -7.094 z: 0.000 
[orientation] x: 0.000 y: 0.000 z: 0.649 w: 0.761
[command] right_motor: 0.090   left_motor: 0.059
---------------
[position]    x: -0.967 y: -6.942 z: 0.000 
[orientation] x: 0.000 y: 0.000 z: 0.716 w: 0.698
[command] right_motor: 0.090   left_motor: 0.059
---------------
[position]    x: -0.984 y: -6.793 z: 0.000 
[orientation] x: 0.000 y: 0.000 z: 0.776 w: 0.631
[command] right_motor: 0.090   left_motor: 0.059
---------------
[position]    x: -1.022 y: -6.663 z: 0.000 
[orientation] x: 0.000 y: 0.000 z: 0.825 w: 0.566
[command] right_motor: 0.374   left_motor: 0.385
---------------