Motionalong

Motionalong is a term used to describe movement of a physical object along a prescribed trajectory or path, typically constrained to a curve in space or spacetime. In practice, motionalong emphasizes adherence to a route rather than arbitrary steering, often incorporating smooth acceleration and deceleration profiles.

The word is a portmanteau of motion and along; it appears in robotics, computer graphics, and control theory as a descriptive label for path-following behavior. It is not a formal mathematical term with a single canonical definition across all disciplines, though it is used to distinguish following a path from free roaming.

In a simple model, a motionalong path is described by a parametric curve γ: [0,T] -> R^n, with state x(t) constrained to x(t) ≈ γ(s(t)). The control input u(t) is chosen to keep x(t) on γ while respecting constraints on speed, curvature, and acceleration. Techniques include projecting commanded velocity onto the tangent of γ, using guidance laws, or employing trajectory tracking controllers.

In robotics and autonomous systems, motionalong is used for lane keeping, aisle following, or drone inspection routes; in computer animation it guides cameras or characters along precomputed routes for consistent framing; in virtual reality it helps with guided tours or scripted experiences.

See also: Path following, trajectory tracking, motion planning, curve fitting.