Chebyshev parallel motion

The Chebyshev parallel motion is a mechanical linkage designed to approximate rectilinear motion using a series of connected bars. Developed by Pafnuty Chebyshev, this three-bar linkage is a significant contribution to the field of theoretical mechanics.1

Linkages, in general, are systems of connected solid bars that form closed chains. When one bar is fixed, the movement of the others is constrained. The four-bar linkage is particularly common, capable of converting rotary motion into other forms of motion. Chebyshev's specific design aimed to achieve straight-line motion, a fundamental challenge in mechanical engineering, by providing a close approximation to it.21