The Chebyshev linkage, also known as Tchebycheff’s linkage,
consists of three links and is driven by the rocking motion
of the lower links (light grey). This motion makes the central
link (yellow) move so that its center (marked by the red pin)
follows a straight line. The motion continues to the point
at which the central link becomes vertical. The central link
needs to be the shortest of the three to prevent it from
colliding with the supporting structure (dark grey).