Start core ROS processes

• Start roscore
• Start rxgraph

Make a robot teleop process

Get teleop_twist_keyboard:

cd ~/ros_workspace
git clone http://www.cse.unsw.edu.au/~cs3431/teleop_twist_keyboard.git
cd teleop_twist_keyboard
rosmake

(That is a local cache of code available here: http://brown-ros-pkg.googlecode.com/.)

Start a Simulation

rosrun stage stageros `rospack find stage`/world/willow-erratic.world

Note this is using one of the simulated worlds that comes with ROS. Details on the ROS integration of stage are on the ros wiki: http://www.ros.org/wiki/stage. That page lists the ROS topics published and subscribed to. The .world file describes the world to simulate.

Start a visualisation: (the simulation is showing us the 'real world' - this visualisation will show us what the robot's sensors see.)

rosrun rviz rviz

note that you cannot see anything. I am assuming in these notes that you last started rvis using the config file /opt/ros/diamondback/stacks/laser_drivers/sicktoolbox_wrapper/sick_test.vcg. If not, then use the file menu to open that config.

The robot's laser and the simulation's laser have slightly different names. In global options, change the Fixed frame and Target frame each from /laser to /base_laser_link. In the laser scan section, change the Topic from /scan to /base_scan. Remember from the tutorials that ROS allows you to rename things on the command line. We could also have copied and edited the sick_test.vcg config file.

You should now see the laser scan in rviz.

Drive the simulated robot around using the keyboard and look at what the simulated laser sees.

Look at the rxgraph output and note that the teleop_twist_keyboard node is publishing commands on the /cmd_vel topic the same way the joystick was last week. (If someone wants to write a better keyboard teleop, that would be cool.)

You can also use rostopic echo /base_scan to see the simulated laser output.

Making your own world

Look at the stage documentation for world files at http://playerstage.sourceforge.net/doc/Stage-3.2.1/group__model__position.html. Build your own simple world with a couple of circular pillars of different sizes and a robot with a laser on it. The example world files that come with stage are also useful (e.g the /opt/ros/diamondback/stacks/simulator_stage/stage/world/willow-erratic.world file used above). Note that an object's shape is specified by a bitmap. A bitmap of a circle is available at http://www.cse.unsw.edu.au/~cs3431/Circle.png.

Drive around your world.