The term unicycle is often used in

robotics Robotics is an interdisciplinary branch of computer science and engineering. Robotics involves design, construction, operation, and use of robots. The goal of robotics is to design machines that can help and assist humans. Robotics integrate ...

and

control theory Control theory is a field of mathematics that deals with the control of dynamical systems in engineered processes and machines. The objective is to develop a model or algorithm governing the application of system inputs to drive the system to a ...

to mean a generalised cart or car moving in a two-dimensional world; these are also often called "unicycle-like" or "unicycle-type" vehicles. This usage is distinct from the literal sense of " one wheeled robot bicycle". These theoretical vehicles are typically shown as having two parallel driven wheels, one mounted on each side of their centre, and (presumably) some sort of offset castor to maintain balance; although in general they could be any vehicle capable of simultaneous arbitrary rotation and translation. An alternative realization uses a single driven wheel with steering, and a pair of idler wheels to give balance and allow a steering torque to be applied. A physically realisable unicycle, in this sense, is a

nonholonomic system A nonholonomic system in physics and mathematics is a physical system whose state depends on the path taken in order to achieve it. Such a system is described by a set of parameters subject to differential constraints and non-linear constraints, ...

. This is a system in which a return to the original internal (wheel) configuration does not guarantee return to the original system (unicycle) position. In other words, the system outcome is

path-dependent Path dependence is a concept in economics and the social sciences, referring to processes where past events or decisions constrain later events or decisions. It can be used to refer to outcomes at a single point in time or to long-run equilibria ...

See also