Robotics Basics (Mechanical)

Wheels

There are four main types of wheels used for FRC:

Standard Wheels

Standard wheels are exactly what you’d expect them to be: wheels. They may differ in their traction used, however, ranging from a hard plastic to a soft rubber.

Pros: simple to drive and program, allow for simple drivetrain (some wheels on the left, some on the right)

Cons: average mobility (can only travel in two directions)

Omni Wheels

An omni wheel contains many smaller, perpendicular wheels that allow the wheel to travel in more than just two directions.

Here’s a video showing omni wheels in action:

Pros: increased mobility

Cons: low traction, more challenging drivetrain design (some wheels in front, back, left, and right)

Mecanum Wheels

Mecanum wheels are just like omni wheels, except their inner rollers are placed at an angle. This allows the wheels to provide the same mobility advantage as omni wheels, while also being mounted on the robot in a standard configuration.

Here’s a video showing mecanum wheels in action:

Pros: increased mobility, allow for simple drivetrain (some wheels on the left, some on the right)

Cons: low traction, harder to program for

Pneumatic Wheels

Pneumatic wheels are just like standard wheels, but they’re filled with air. This allows them to provide much greater traction than all of the above wheel types.

Pros: good traction, allow for simple drivetrain (some wheels on the left, some on the right)

Cons: generally slower-moving, average mobility (can only travel in two directions)

Drivetrains

Tank drive
Slide drive
Swerve drive

Tank drive means that some wheels are placed on the left and some on the right.

Slide drive is the same as a tank drive, but it includes another central wheel that allows for moving in more than two directions. This drivetrain requires omni wheels.

Swerve drive uses standard wheels that can independently turn, allowing for both great mobility and no decrease in traction. However, it consists of many parts that can fail, and it’s an expensive design.

Pneumatics

Pneumatics deals with the control of pressurized air. With pneumatics, we can push and pull objects using a fairly large amount of force.

Air compressor
Air tank

The air compressor compresses air into the air tank at an acceptable pressure. Pressurizing too much is dangerous and against the rules. Pressurizing too little would make the air less effective (lower pressure means lower pushing/pulling force).

Solenoid
Pneumatic cylinder

We program solenoids to control when air flows into or out of pneumatic cylinders. When air flows into a pneumatic cylinder, the piston rod pushes out, and when air flows away, the piston rod is retracted.