Xtreme Robot Olympiad Programming with Sensors Dr. Peter Laz Associate Professor Department of Engineering University of Denver

Outline Microcontroller architecture Digital versus analog signals Line sensors Ultrasonic sensors Programming with EasyC

Robot Control We programmed the vehicle to perform specific actions Drive in a square “dead reckoning” By adding sensors, we can make the vehicle “smart” by making decisions based on the readings of the sensor

Digital versus Analog Digital signals Two levels: 0 or 1 Binary Analog signals Infinite number of levels Signals can be between 0 and 1000 Calibrate readings to physical meaning

Microcontroller Ports have different types of signals Analog 1-4 Digital 5-10 Motors Interrupts Analog/Digital Signals (Sensors)

Line Sensor Uses an Infrared (IR) LED emitter and detector to measure intensity LED = light emitting diode Distance of the sensor to surface will affect readings Emitter Detector Sensor

Ultrasonic Sensor Uses ultrasound to measure time for a pulse to bounce off of an object Time and known speed to sound  distance Sound waves must reflect off the object Difficulty with curved objects Emitter Detector Sensor Object

Exercises Download LinefollowerTest.ecp What reading corresponds to white? What reading corresponds to black? Test how distance from the surface affects the reading Download UltrasonicTest.ecp How does the reading vary with distance? How close can you get? What reading do you get with a curved surface?

The Grand Challenge Two competitions Autonomous maze Navigate through a maze using sensors and autonomous control Additional time bonus for stopping within 2” of the wall without touching it New adventure race with your team’s best driver

The Grand Challenge Teams will use the same vehicle for both competitions Exception different programs will be downloaded Autonomous maze 50 pts Adventure race50 pts

Line Follower Logic LeftRight LeftCenterRight Use multiple sensors together to make a “smart” line following robot What decisions are made based on the readings on the different sensors? Two Sensor Configuration Three Sensor Configuration

Line Follower Logic If both see line Then go _______ If left sensor sees line Then turn _______ If right sensor sees line Then turn _______ If no sensors see line Then _______ LeftRight Two Sensor Configuration

Line Follower Logic What sensor reading is on the line? How much do you turn? How fast can you go without losing the line? Develop a robust program Consider what to do if you lose the line Consider right angles and “T”s If … then …or If … then … else …

Exercises 1. Write a code to follow the line Use the test field to test your program Program and test 2. Develop a code to earn the stopping distance bonus 3. Make changes to your vehicle for the final mission Again, hanging bonus is in play

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