Lab 2 LineFollowing FALL2010

Lab 2 LineFollowing FALL2010 - LEGO MINDSTORMS NXT Lab 2 In...

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NXT Lab 2 Page 1/9 LEGO ® MINDSTORMS ® NXT Lab 2 In Lab 1, the Tribot was commanded to drive in a specific pattern that had the shape of a bow tie. Specific functions were passed to the motors to command how the Tribot should move. However, what would happen if the desired path were changed? All of the movement function blocks in the program would have to be adjusted to account for the new path. This can become quite cumbersome, especially if the path changes frequently. What if the robot was designed so that it traced a line instead of following specific commands? The robot would still be able to follow the path that is laid out by the line, and the code would not have to be changed whenever the path changes. This is an example of a situation where a feedback system can be quite useful. This lab will demonstrate the practical use of a simple feedback control system. Lab Summary A. Use the LEGO MINDSTORMS NXT software to understand how the light sensor works B. Create a program that follows a line using digital sensor feedback C. Improve the line following program using analog sensor feedback D. Challenge L AB 2 F EEDBACK C ONTROL
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NXT Lab 2 Page 2/9 Part A: Understanding the Light Sensor 1. Open the MINDSTORMS NXT software on your computer 2. Open the light monitor VI ( Lab 2 Part A.vi ) 3. Power on the NXT and connect it to a USB port on your computer. 4. Run the VI and observe the waveform chart. Move the light sensor over different surfaces and observe the changes in value. 5. Click the Generate Light? control and observe how the values change. Questions: a) What is the average reading of the light sensor when it is detecting a white shade? b) What’s the reading for a black shade? c) How do the readings change when the Generate Light option is turned off? d) Based on your findings, what does this sensor specifically detect? e) With the Generate Light option turned on, try testing the light sensor on the different colors displayed on the Test Pad. Which colors produce some of the highest readings? f) Do you notice a pattern in these readings? What is it? Is the pattern different when the Generate Light option is turned off? g) Are there any colors that are completely different that produce the same reading? Do the readings match both when the sensor’s light is on and off? h) Test the light sensor on the different colored regions present on the competition course (i.e., white, blue, and black). Note the range of values observed for each color with the Generate Light op t ion bo th on and o f f . No te these ranges the c lass room ’s whiteboard. i) BONUS: Suppose there was a need for an application where the tribot had to distinguish between two different colors that causes the light sensor to produce the exact same readings. What could be done to improve the sensor’s ability to distinguish between these two colors? (Hint: The answer to question f) is a clue on how to solve this problem.)
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NXT Lab 2 Page 3/9 Part B: Using the Light Sensor as a Switch
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Lab 2 LineFollowing FALL2010 - LEGO MINDSTORMS NXT Lab 2 In...

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