Wheel odometry by drive type#

Seven ways to drive a wheeled robot, and how far you can trust the wheels on each.

Not every robot slips like the skid-steer in Wheel odometry. How far you can trust wheel odometry comes down to one question: do the wheels have to slip for the robot to move or turn?

Here are the seven main drive types for wheeled ground robots, from most to least trustworthy.

1. Differential drive#

Home robots, robot vacuums, TurtleBot.

Two driven wheels turn independently, with a free caster wheel at the front or back. The robot turns by running the two wheels at different speeds, so nothing has to slip.

Forward: ✅ reliable
Turning: ✅ reliable, once calibrated
Weak spots: crossing onto carpet, and the small jolt when the caster swings around.

2. Ackermann (car-like)#

Self-driving cars, farm vehicles, large field robots.

The front wheels steer and the rear wheels push. The wheels are set up to roll through a turn, so they slip very little.

Forward: ✅ reliable, from the rear wheel encoders
Turning: ✅ good, if the steering angle is measured accurately
Weak spots: it can’t turn in place, and slip grows at high speed or on slippery ground.

3. Swerve#

FRC robots, some industrial AGVs.

Every wheel has its own drive motor and its own steering motor. Each wheel can always point the way the robot is moving, so slip stays low.

Forward and sideways: ✅ good
Turning: ✅ good
Weak spots: only as good as the measured module angles, and it is complex and expensive.

4. Omni wheels#

Some education and competition robots.

Small free rollers sit around the edge of each wheel, so the robot can move in any direction.

Forward, sideways, turning: 🟡 fair
Weak spots: the rollers slide sideways by design. Part of that sliding is normal motion, but how much depends on the floor.

5. Mecanum wheels#

Warehouse robots, some AGVs, competition robots.

The rollers sit at 45°, so the robot can slide sideways.

Forward: 🟡 fair
Sideways: ❌ poor
Turning: 🟡 fair
Weak spots: very sensitive to the floor. On carpet or dusty floors the rollers slip, and sideways moves drift badly.

6. Skid-steer#

Field robots like the Clearpath Husky.

Four wheels, no steering, turning like a tank. To turn, the wheels have to scrub sideways across the ground.

Forward: 🟡 fair to good
Turning: ❌ poor
In short: fine when driving straight, don’t trust it in turns.

7. Tracked#

Field, mining, search-and-rescue and military robots.

Skid-steer taken to the extreme. The long contact patch means turning is all slip.

Forward: 🟡 fair, good in good conditions
Turning: ❌ very poor
In short: it tells you whether the robot is moving, forward or back, and roughly how fast. Take the turn rate from the IMU.

Summary#

Drive type	Forward	Sideways	Turning	Overall trust
Differential	✅	—	✅	⭐⭐⭐⭐⭐
Ackermann	✅	—	✅	⭐⭐⭐⭐⭐
Swerve	✅	✅	✅	⭐⭐⭐⭐
Omni	🟡	🟡	🟡	⭐⭐⭐
Mecanum	🟡	❌	🟡	⭐⭐
Skid-steer	🟡	—	❌	⭐⭐
Tracked	🟡	—	❌	⭐

— means the robot can’t move that way, so its sideways speed is taken as 0.

Note

The rule: the less a design needs to slip, the more you can trust its wheel odometry. On differential and Ackermann robots, slip is a fault. On mecanum, skid-steer and tracked robots, slip is part of how they move.