Diameter, Circumference, and Rotational Sensors

Robotics Academy 2002. All Rights Reserved.

Robotics Academy 2002. All Rights Reserved.

Geometry Review

The Radius is thedistance from thecenter of the circleto the outer edge.

The Diameter isthe distance across the circlethrough its center.It is twice the radius.

The Circumferenceis the distance allthe way around thecircle.C = x DiameterC = x 2 Radius.( = 3.14)

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!

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.

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 travel25.1 / 16 = 1.57 cm per sensor count.

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 cm2) 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