Mobile robots: the fundamentals
How the machine turns
Differential
Two driven wheels steer by speed difference. Simple, cheap and reliable: forward, reverse, spin on the spot and turn, but no sideways travel. Underride models with D in the code are differential, such as the JS-U1000-DLP.
Dual steer / omni
Steerable drive wheels allow travel forwards, sideways and diagonally, plus spinning on the spot, so there is no turning round in narrow aisles, at the cost of complexity and price. Underride models with S in the code are omnidirectional, such as the JS-U2500-SLP, and the whole autonomous forklift series is omnidirectional.
Single steer
One steered drive wheel with castors, the arrangement used on many conventional forklifts. Strong capacity but a large turning radius, so aisles must be wide.
Ackermann
Car-like steering, suited to long bodies travelling straight at speed. The parking robot uses servo drive with Ackermann steering and two differential drive wheels.
Aisle width decides it. Wide enough, and differential or single-steer is the economical answer; too narrow to turn around, and you need omnidirectional.