Input: blue slider moving along a stationary runway thanks to grey cylinder.
Ouput: violet slider moving along a brown rotary runway. This motion can be performed even when the brown runway rotates.
Yellow round rack that can only move vertically is in mesh with two pink pinions.
Rotation of the brown runway is controlled by a motor (not shown) through the brown gear.
The mechanism can be used for controlling planar motion of a point that belongs to the violet slider based on the polar coordination system..