Orange plate performs planar motion without rotation.
The plate direction is kept unchanged thanks to a parallelogram mechanism driven by a motor. Distances between two revolute joints on the yellow conrod and between two revolute joints of the orange plate are equal.
Motion of the orange plate along sliding joint between green bar and pink bar is controlled by two green cylinders.
This mechanism can be applied for manipulator of polar coordinate system.
Disadvantage: the cylinders are not base-mounted.