Robotics Class 2011/Assignment 1

From HacDC Wiki

Note: This assignment assumes you have already installed ROS as well as the supplemental ROS package named irobot_create_2_1, an excellent ROS package that serves as a ROS driver for the iRobot Create robot series.

Write a ROS node that subscribes to the "sensorPacket" topic (a message of type irobot_create_2_1/SensorPacket), and uses values from within this message to represent the emotional state of the robot. You will then publish the robot emotional state via publishing a message of type robot_emotions/EmotionalState with the topic name "robot_emotions".

In order to start publishing the "sensorPacket" at home without a robot, you will need to check out the irobot_sensor_simulator ROS package, available from the HacDC ROS repository (several of you already installed it):

cd to where you store your downloaded ROS packages

svn co

rosmake irobot_sensor_simulator

Once the make is done, you can start up the simulator by typing:


rosrun irobot_sensor_simulator

Note that this node will not produce any output. It will just sit there. If you do a "rostopic list" at this point, you will see a sensorPacket topic, and you can display it using "rostopic echo sensorPacket".

In order to start modifying the values to test your emotion generator, you will need to run the ROS dynamic_reconfigure reconfiguration GUI interface. This will provide the GUI interface illustrated in class that allows you to modify values in the sensorPacket. You can start the reconfigure GUI by typing:

rosrun dynamic_reconfigure reconfigure_gui

You will need to select irobot_sensor_simulator from the drop down box and you should then be presented with boxes and sliders that let you change the values of the sensor packet in real time.

Note that these sliders allow you to configure the values of the sensors in an arbitrary fashion. However, of course, there is a nominal state of the robot defined by having a fully charged battery and being properly oriented with its base firmly on the floor.

A powerful feature of ROS is the ability to create archives, or "bag files" that contain sensor data that can be played back. A bag file containing messages of type irobot_create_2_1/SensorPacket has been created and can be downloaded here. After downloading this bag file, it can be played back using the rosbag package, which should be installed by default:

rosbag play 2011-06-08-20-32-02.bag

This bag file was recorded with a full battery charge with the robot on the floor. At a point in the middle, the wall sensor was triggered with a piece of paper (the wall sensor signifies when the Roomba detects a wall to its right side which is useful for wall-following). Near the end of the bag file, the robot was lifted off the floor, causing the states of wheel drop and cliff sensors to change.

In order to obtain the definition of the robot_emotions/EmotionalState message, you will need to check out the robot_emotions ROS package from the HacDC ROS repository:

cd to where you store your downloaded ROS packages

svn co

rosmake robot_emotions

You can explore the structure of the two above message types by using rosmsg show in the following way:

rosmsg show irobot_create_2_1/SensorPacket

rosmsg show robot_emotions/EmotionalState

Assignment Hint: The robot_emotions ROS package contains, in addition to the definition of the robot_emotions/EmotionalState message, a complete (but very simple) solution to the homework. Feel free to investigate it if you need help. If you want to try running the emotion generator provided within the robot_emotions package, just type (after doing the rosmake robot_emotions above):

rosrun robot_emotions

After typing this, a "rostopic list" command will show a new topic called robot_emotions, just as the assignment asked for.

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