1. Diameter, Circumference, and Rotational Sensors Robotics Academy 2002. All Rights Reserved.

2. Geometry Review The Radius is the distance from the center of the circle to the outer edge. The Diameter is the distance across the circle through its center. It is twice the radius. The Circumference is the distance all the way around the circle. C =  x Diameter C =  x 2 Radius. (  = 3.14)

3. Robotics Academy 2002. All Rights Reserved. Circumference Question: When this robot’s wheels make one revolution, how far does the robot travel? Answer: One circumference of the wheel!

4. Robotics Academy 2002. All Rights Reserved. Rotational Sensors The rotational sensor can measure the rotation of the wheels. By measuring the rotation of the wheels, and knowing the diameter of the wheels, we can measure and control how far the robot travels. Remember: The rotational sensor has 16 counts per rotation.

5. Robotics Academy 2002. All Rights Reserved. Example The diameter of this wheel is 8 cm. C =  x D. That means its circumference is 8 x 3.14 = 25.1 cm. The rotation sensor has 16 counts per rotation. That means the robot will travel 25.1 / 16 = 1.57 cm per sensor count.

6. Robotics Academy 2002. All Rights Reserved. Let’s Solve Some Problems 1) How far will the robot travel if it goes for 48 rotation sensor counts? ANSWER: 1.57 cm / count x 48 counts = 75.4 cm 2) How many wheel rotations is 48 sensor counts? ANSWER: 48 / 16 counts per rev. = 3 rotations 3) How many sensor counts should the robot go if you want it to travel 1 meter (100 cm)? ANSWER: 100 / 1.57 cm per count = 63.7 counts