# Swerve drive
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###### tags: `self-learing`

## What is swerve
“Swerve Drive” is a drivetrain that is specifically designed so that the robot can spin while traveling along any path across the terrain. With each wheel rotating while also pivoting on the vertical axes, the maneuverability is unstoppable.

Swerve drive bases can rotate and translate independently; they **can even spin while cruising straight ahead**.
## advantages
- Agility - true **2D drivetrain** in which drive direction may be divorced from chassis orientation
- Traction - in contrast to other holonomic drive systems, high traction wheels may be employed without negative consequence; furthermore drive force may be vectored in any desired direction
- Stealth - no need to telegraph intentions via chassis reorientation
- Flexibility - with the drive direction and power controlled independently to each wheel by software, multiple drive modes, including game-specific drive modes, become possible
- Minimal steering hysteresis - there is almost no need to overcome static friction in steering

## disadvantages
- Complexity - This isn't an easy drivetrain to execute
- Mass
- Time - CNC machining takes time; so does the assembly of complex mechanisms
- Cost - A normal swerve drive need 2 motor, and a standard drive train need 4 swerve, equal to 8 motor. Each swerve drive kit is about 300 USD, so it's really expensive. 
- **High use of IO port**
- Hard to drive - It need lots of time to practice to drive it well.

#### Reference:
* https://web.northeastern.edu/nurobotics/projects/swerve-drive/
* https://team1640.com/wiki/index.php/Swerve_Central
* https://botspace.github.io/differential-swerve-drive/
* https://photos.google.com/share/AF1QipPXM_Y7qwiZ8wTnx2qMfIFTv-MAgH-Di3VNoQ9GszyRalKVUCKWN8eY_2iAS4v8OA?pli=1&key=NmxTSHdxbEJrYWxoMzZJMU9MblRKMHhuV3dUWlRR
* https://compendium.readthedocs.io/en/latest/tasks/drivetrains/swerve.html