Swerve Drive

What it is

Swerve drive uses (almost always) four independently controlled modules, one near each corner. Each swerve module has two motors: a drive motor that spins the wheel and a steer (azimuth) motor that rotates the whole wheel assembly to any angle. By coordinating all four modules, the robot can translate in any direction and rotate at the same time. This is true holonomic, omnidirectional motion.

Why it dominates

• Omnidirectional movement without turning the chassis lets a robot strafe to a scoring position while keeping its shooter or intake aimed.
• Superior maneuverability and traction compared with skid steer, because the wheels never have to scrub sideways.

Real COTS modules

Swerve is hard to build from scratch, so nearly all teams buy modules:

• Swerve Drive Specialties MK4 / MK4i / MK4n — the MK4i moves the steer motor inboard for a lower profile; the MK4n is only about 4" on its narrow side, enabling wide intakes between the modules. They support NEO, NEO Vortex, Falcon 500, and Kraken X60 (the large-diameter CIM does not fit).
• WestCoast Products Swerve X / Swerve X2 — the X2 is gear-driven with no belts in the module and advertises single-bolt wheel swaps; it supports 550, 775, CIM, NEO, and Kraken X60 motors.
• REV MAXSwerve — REV's compact, spline-input module built around the ION ecosystem.
• The Thrifty Bot (TTB) Thrifty Swerve — a lower-cost module popular for its value.

Required sensors

Each module needs an absolute encoder on the steering axis (e.g., a CTR Electronics CANcoder, a REV Through Bore Encoder, or a WCP encoder) so the robot knows each wheel's angle on power-up. A robot-level gyro/IMU such as the Pigeon 2.0 provides heading for field-oriented driving.

Trade-offs

• Cost and complexity. Eight motors plus four absolute encoders, more wiring, and significantly more programming (each module runs its own closed-loop control for steering).
• Maintenance. More parts to inspect and maintain between matches.

Swerve rewards teams that can support the software and electrical workload. If your programming team can deliver field-oriented control reliably, swerve is a major competitive advantage.