Drive a Grizzly

Updating the Virtual Machine

Open a terminal window (Ctrl + Alt + T), and enter the following:

sudo apt-get update
sudo apt-get install ros-kinetic-grizzly-simulator
sudo apt-get install ros-kinetic-grizzly-desktop
sudo apt-get install ros-kinetic-grizzly-navigation

Running a Virtual Grizzly

Open a terminal window, and enter:

roslaunch grizzly_gazebo grizzly_empty_world.launch

Open another terminal window, and enter:

roslaunch grizzly_viz view_robot.launch

You should be given two windows, both showing a yellow, rugged robot (Grizzly!). The left one shown is Gazebo. This is where we get a realistic simulation of our robot, including wheel slippage, skidding, and inertia. We can add objects to this simulation, or even entire maps of real places.

_images/grizzlysim.png

This window below is RViz. This tool allows us to see sensor data from a robot, and give it commands (in a future post). RViz is a more simplified simulation in the interest of speed.

_images/grizzlyviz.png

We can now command the robot to go forwards. Open a terminal window, and copy the following:

rostopic pub /cmd_vel geometry_msgs/Twist "linear:
        x: 0.5
        y: 0.0
        z: 0.0
angular:
        x: 0.0
        y: 0.0
        z: 0.0"

In the above command, we publish to the cmd_vel topic, of topic type geometry_msgs/Twist. The data we publish tells the simulated Grizzly to go forwards at 0.5m/s, without any rotation. You should see your Grizzly move forwards. In the gazebo window, you might also notice simulated wheel slip, and skidding.