Lab 1: Robot Control and Using tf in ROS

CSE 468/568: Robotics Algorithms 1
CSE 468/568 Lab 1: Robot Control and Using tf in
ROS
The objective of this assignment is to get started with robot simulation in ROS, and use
tf to relate the coordinate system of one robot with the other.
Before you get started, please make sure you have done the following:
• Complete ROS tutorials 1 through 12 (in Section 1.1 Beginner) and be able to write
a simple publisher and subscriber in ROS
Simulation Setup
In this section, you will learn about launch files. Create a package named lab1 that
depends on std msgs rospy roscpp. Download the world and launch files for this assignment from here. It contains three files - playground.world and playground.pgm
which together form the initial stage world, and lab1.launch that is the initial launch
file.
Please read the roslaunch tutorial to understand the roslaunch file. Drop the world files
and the launch files in the appropriate sub-directories in the new package. Test to see if
you can launch stage using the launch file by running the command
$ roslaunch lab1 lab1.launch
Note:
• You might need to re-run the path commands after creating the package for roslaunch
to identify the new package lab1.
• You don’t need to run roscore when you use roslaunch. However, you do need
to have roscore running when you use rosrun
Evader Controller
In this section, you will write your own controller. Familiarize yourself with the given
robot by checking the information it publishes and subscribes. The robot also has a laser
range finder attached to it. Move the robot by dragging it with your mouse pointer to
face a wall. Monitor the output of the laser by using rostopic echo in the command
line. You should be able to understand the output of the sensor from the stage world file
and its output you observed.
CSE 468/568: Robotics Algorithms 2
Write a controller node that drives the robot straight at a constant speed of 2m/s. When
the robot is close to an obstacle, the robot should stop, turn in a random new direction,
and drive at the same speed. Create a new launch file evader.launch that adds the
execution of this node to what was in the earlier launch file.
Pursuer-Evader
Read through the tf tutorial. Publish the coordinate frame of the robot wrt the global
frame. Create a new world file with a second robot called pursuer, and drop it into the
world close to the first robot. Write a controller node for the pursuer that subscribes
to the tf messages from the evader, and follows the evader by going to the spot it was
at from one second before. Create a third launch file pursuer-evader.launch to run
the new world with the two robots, the evader controller, and the pursuer controller as
separate nodes.
Submission Instructions
You will submit lab1.tar.gz, a compressed archive file containing the lab1 folder. The
folder should contain the two world files and the pgm file in an appropriate sub-folder, two
launch files evader.launch and pursuer-evader.launch in an appropriate sub-folder,
and two controllers - one for the evader and another for the pursuer in an appropriate
sub-folder. The folder should compile if I drop it into my catkin workspace and call
catkin make. Please take care to follow the instructions carefully so we can script our
tests, and not have to dig into each submission. Problems in running will result in loss
of points.
Please use the submit script for submission using the syntax
$ submit cse468 lab1.tar.gz
or
$ submit cse568 lab1.tar.gz
depending on whether you are taking cse468 or cse568 respectively.
Details on the usage of the submit script can be found here.