15-494 Cognitive Robotics
Spring 2011
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Reference:

Cognitive Robotics: Lab 2 & Homework 1


Part I: Compile and Run a State Machine

  1. Compile the shorthand form of the Bark/Howl/Blink state machine in the file BarkHowlBlinkBehavior.cc.fsm, by copying it to your ~/project directory and then typing "make".

  2. Load the file ~/project/build/PLATFORM_LOCAL/TGT_CHIARA/BarkHowlBlinkBehavior-fsm.cc into a text editor and look at the code the stateparser generated from the shorthand description.

  3. Run the behavior on the Chiara. To do this, use "sendmycode" to send your tekkotsu-CHIARA executable to the Chiara. Remember that for the first run of the day you should use "sendtekkotsu" instead of "sendmycode".

  4. In the ControllerGUI, go to Root Control > Status Reports > Event Logger and select buttonEGID, stateMachineEGID, and stateTransitionEGID. Run the behavior and look on the Tekkotsu console to see the events scroll by.

Part II: Storyboard Tool

Review the Storyboard Tool chapter of the Tekkotsu tutorial, which you should have read prior to this lab.

Remember that you must run the Storyboard on your workstation, not on the robot! Follow the instructions in the Downloading a state machine model section of the Storyboard chapter to download the model of your Bark/Howl/Blink state machine and create an appropriate layout. Edit the layout to make it look like the diagram in the tutorial. Note: to move a link, click on it, and a tiny dot will appear in the middle of the arrow shaft. Click and drag on the dot to move the link. Save the layout when you're done editing it.

Run your state machine on the Chiara and generate an execution trace using the Storyboard tool.

Before leaving the lab today, hand in (via email to dst@cs.cmu.edu) a screen capture showing your layout and the execution trace. Include the names of everyone in your group. Note: you can get a screen capture by going to the Gnome pulldown menu and clicking on Applications > Accessories > Take Screenshot. If you just want to capture one window, you can run Gimp and click on File > Acquire > Screen Shot, then save the file as a JPEG or PNG image.

Part III: State Machine Programming

You should start this part in the lab, and finish it for homework. Your answers should be turned in as Homework 1, due Friday, January 28.

  1. Initializing a node's motion command. Write a simple state machine that waits for a green button press event. When the event occurs, it should flash the green LED for 1 second. How are you going to do that? First, look over the documentation for LedNode. You'll notice that a LedNode contains a motion command inside it, of type LedMC. Read the documentation on LedMC. The real work of calculating LED states is done by a parent class called LedEngine. Skim the documentation on LedEngine and you will find the cycle() and set() methods that were used in the Bark/Howl/Blink example. There are more. Find a method for flashing an LED. To determine the bitmask to use to access the green LED, look in the file Tekkotsu/Shared/ChiaraInfo.h. How will you get back from your LedNode to the node that waits for a button press?

  2. Smooth movement. You can use a HeadPointerNode to move the robot's camera to look at a specific point in space. It contains a HeadPointerMC motion command inside it. By chaining together a series of these you can produce a complex head movement that will look roughly the same no matter what configuration of head and neck joints your robot has. First you'll want to use HeadPointerMC's setMaxSpeed() method to slow down the motion so it doesn't jerk the robot's head around violently. (0.2 is a good setting) The first argument should be a joint number; set the max speed for both joint 0 (PanOffset) and joint 1 (TiltOffset). Then you can use the lookAtPoint method to point the camera.

    Write a behavior to make the robot nod its head "yes". On startup the behavior should move the head to a neutral position by looking at the point (5000, 0, 400). Then, after a 2 second pause, it should smoothly move the head down to (500, 0, -100), then back up to neutral, then down again, and then back up.

  3. Parallel programming. Write a behavior that flashes a repeating sequence of LEDs, red-yellow-green-blue, for 1 second each, over and over. Asynchronously, your behavior should play a series of three barks: barklow.wav, barkmed.wav, and yipper.wav, over and over. In response to a green button press, reverse both the sequence of lights and the sequence of nodes, and do it without losing your place in the sequence, e.g., if you're currently in the forward sequence and lighting the green LED, you would normally light the blue one next, but if you get a button press you immediately switch to the yellow LED and start running backwards; the sound should immediately switch too. Another green button press should switch the light and sound sequences back to their original order. Note: don't do anything weird like trying to dynamically change the structure of the state machine. Just write separate parts for the forward and reverse sequences and include appropriate transitions between them.

    After you have your behavior running correctly, use the Storyboard tool to generate a layout and an execution trace.

  4. Fork/join. Redo the sound and light sequence from the previous problem as follows. Instead of running asynchronously, each light has an associated sound: red is howl.wav, yellow is barklow.wav, green in ping.wav, and blue is toc.wav. Each LED should come on as the sound starts to play, and stay on until the sound finishes. As soon as the sound is done, you proceed to the next LED/sound pair. A green button press should reverse the sequence. Show your model and an execution trace.
What to hand in: your source code for all homework problems, plus a screen capture of the Storyboard showing your model and its exeuction trace, where requested.


Dave Touretzky and Ethan Tira-Thompson