Skid-steer drives a robot by running the wheels or tracks on each side at different speeds and letting them scrub sideways to turn — a simple, rugged, tank-like scheme used by loaders, tracked robots, and rovers.
Skid-steer turns a robot the way a tank does: speed up the wheels on one side and slow the other, and the machine pivots — the wheels or tracks scrub sideways across the ground to make it happen.
Skid-steer is the "tank turn" of robotics: no steering wheels, no complex mechanism — just drive one side faster than the other and let the machine pivot. It's simple, tough, and everywhere in the rugged mobile-robot world.
How it works
The wheels (or tracks) are fixed straight ahead and grouped into a left bank and a right bank. Drive both sides equally and the robot goes straight. Drive the right side faster than the left and it curves left; drive them in opposite directions and it spins on the spot. To rotate, the wheels or tracks must skid sideways across the ground — hence the name.
Turn by unequal side speeds
No steered wheels — turning comes entirely from the left/right speed difference, with lateral scrubbing making the rotation possible.
Strengths
Mechanical simplicity. Just two motor groups, no steering linkage — cheap, robust, few failure points.
Zero-radius turns. It spins in place, great for tight spaces (like a differential-drive robot, which is essentially skid-steer with two wheels).
Great on tracks.Tracked robots use skid-steer naturally, spreading weight and gripping rough or soft terrain (mud, rubble, snow).
The catch: skidding
That sideways scrub is also the weakness. Skidding means:
Wheel odometry is unreliable. During turns the wheels slip, so counting rotations badly overestimates rotation — skid-steer robots lean heavily on an IMU and other sensors to know their heading.
High friction and wear. Scrubbing wastes energy and grinds tires/tracks and the ground beneath.
Turning is terrain-dependent. The same command turns differently on carpet vs gravel, complicating control.
Like other differential schemes it's nonholonomic — it can't move sideways.
Where you'll see it
Skid-steer loaders (the Bobcat), military and search-and-rescue tracked robots, planetary rovers, agricultural machines, and countless research robots — anywhere ruggedness and simplicity beat efficiency and precise odometry.
Why it matters
Skid-steer is the workhorse locomotion of rough-terrain and heavy mobile robots — dead simple, extremely robust, and the natural drive for tracks. Understanding its odometry pitfall is key to localizing these robots well.
