CS81 Lab4: Scribbler Robot

Due by noon next Wednesday

In this lab you will use a real robot in the physical world. You will directly program the robot to do specific tasks, such as find its way out of a maze. Do an update81 to get the starting point files for this lab.

Scribbler robot and the Fluke

The Scribbler robot base has the following capabilities:

The robot has an attachment called the Fluke which provides additional capabilities:

Try to locate all of the sensors on the Scribbler and the Fluke.

Connecting to the Scribbler robot

In order to use your robot you'll need to do the following:

  1. Check that a bluetooth adapter is inserted into your computer.
  2. Turn on the robot. Notice what number robot you are using. You will need to use this number when setting up communication with the bluetooth adapter.
  3. Type the following where NUM is replaced with the number of your robot.
    % python
    >>> from myro import *
    >>> init("/dev/rfcommNUM")

If you get the following error message:

Serial element not found. If this continues, remove/replace serial device...
Check for the following problems:

After a successful connection you will see a message like this (the name may be different) and your robot will emit a series of beeps:

You are using fluke firmware 2.9.1
You are using scribbler firmware 1.0.2
Hello, I'm Scribby!

The Scribbler robot uses 6 AA batteries, and only works well when it has enough power. The first command you should run each time you begin using the robot is to check its current battery level:

>>> getBattery()
If the battery level is below 6.2, replace the batteries. Put the old batteries into the small green battery recycling bin.

Controlling the Scribbler robot interactively

The Scribbler is controlled through a python library called Myro. Read through the Myro reference manual trying the commands interactively in the python interpreter as you go. Not all of the commands will work as described.

For example, the speak command turns a string into spoken words that will be output through the computer's speakers, not from the robot. Some computers do not have speakers so you will not hear anything. Some computers do have speakers, but the volume control is set very low.

Focus your attention on the commands that move the robot and read the sensors.

Escaping from a maze

After you've tried all of the Myro commands interactively in python, explore the obstacle detection sensors available to you in more detail. You'll need these sensors in order to program the robot to escape from a maze. There are IR sensors on both the scribbler and the fluke. Which ones work more reliably to detect obstacles? Feel free to grab an extra wooden block and bring it back to your desk to more easily test the robot. Read about the setIRPower command in the Myro reference manual. You may need to tweak the power setting of the Fluke's IR sensors in order to get reasonable values for obstacle detection.

Edit the program escape.py in your current lab directory. Using Myro commands, write a program that will cause the robot to find its way out of a maze like the one that is set up at the front of the lab. One option is to use a wall following approach.

Once your robot can successfully escape, move on to the next section.

Drawing with the Scribbler

One of the challenging aspects of using physical robots in the real world is that their movements are not always reliable. We will test the reliability of the Scribbler by drawing geometric figures.

Get a big piece of white paper. Insert a pen into the Scribbler's pen port and put it on top of the paper. As the Scribbler moves it will draw a line.

  1. Issue a command to make the robot move forward at full speed for one second. Stop the robot. Then issue a command to move backward at full speed for 1 second. Pick up the robot and look at the pen marks. Does the robot traverse the same trajectory? Does it travel the same distance in both directions? Measure the length of the line drawn by the robot when moving for one second. In the file draw.py in your current lab directory, write a function called travel(distance) to make the robot travel the given distance. You may use inches or centimeters as your units. Test the robot a few times to see how accurate the line is.

  2. Study the turning behavior of your robot. Based on your observations write a function called degreeTurn(degrees) that will make the robot turn the specified degrees.

  3. Using the functions travel and degreeTurn write a function called square(size) to draw a square. Save the paper for a good square drawn by your robot.

  4. Using the same functions write a function called star(size) to draw a five-point star as shown below. Save the paper for a good star drawn by your robot.

  5. Suppose you would like to create a vacuuming robot. The robot is given the dimensions of a rectangular area and must travel through the entire area as efficiently as possible. Write a function called vacuum(length, width) that uses your travel and degreeTurn functions to traverse the entire area. You can test your program by using the white paper (which is 4ft wide) with a pen in the Scribbler to see how well the robot covers the area. Save the paper for a good vacuuming path executed by your robot.


When you are done, run handin81 to turn in your completed lab work. Also write your name(s) on the saved drawings made by your robot, staple them together, and turn them into me.