Features of different wheels and drive trains.

In our meetings we have been covering the features of each wheel and drive train, and how they pertain to the creation of a robot as a whole. Our reasoning for doing so is because it is the most important sub system of the robot. Without a drive train the robot wouldn’t be able to move at all.

When building a robot’s movement system, there are two primary trade offs: speed and torque. For example, if you have high speed but low torque you will be very maneuverable but have little pushing power. While if you have low speed but high torque, you won’t be very maneuverable but you will have strong pushing power.

When working with FRC robots there are 5 primary drive trains:
tank, swerve, slide, mecanum, and holonomic.

https://grabcad.com/library/frc-team-4926-tank-drive-1

Tank Drive:

  • Left and right wheels are driven independently.
  • Typically in sets of two (sometimes higher).
  • Strengths: simplicity, easy to drive, potential for high speed and torque.
  • Weaknesses: Less agile than other drive trains.
http://www.team221.com/upload/392-img_4573.jpg

Swerve/Crab Drive:

  • Wheels rotate on the vertical axis to control direction.
  • Strengths: Agile, potential for high speed and torque.
  • Weaknesses: Complex to build and program, extra motors required to rotate the robot’s frame.
Bison Robotics

Slide Drive:

  • Similar to tank drive but with extra wheels perpendicular to the rest.
  • Must use all omni wheels.
  • Strengths: Easy and cheap to design, build, and program.
  • Weaknesses: No potential for high torque and extra wheels/motors/gearboxes are needed for the robot to move sideways.
https://www.buildblitz.com/mecanum-drivetrain-options/

Mecanum Drive:

  • Similar layout to tank drive, but each wheel is driven independently.
  • Must use all omni wheels.
  • Strengths: Fairly easy to design & build. Agile.
  • Weaknesses: Expensive. No potential for high torque. Difficult to program / learn to drive. Requires extra gearboxes and the wheels are expensive.
http://hflrobotics.com/

Holonomic Drive:

  • 4 omni wheels positioned on 45 deg angle in the corners of the frame.
  • Must use all omni wheels.
  • Strengths: Fairly easy to design & build. Agile.
  • Weaknesses: Expensive. No potential for high torque. Difficult to program / learn to drive. Requires extra gearboxes and the wheels are expensive.

Team 1114 has a great page on the mobility of robots which goes into the math behind the drive trains and deeper into the motivations for picking a drive train: http://www.simbotics.org/resources/mobility.

Thanks for reading, have a good day.
http://team2583.org/blog/