Orange plate performs planar motion without rotation.
Its upper surface is kept always horizontal thanks to 4 bevel gear drive of equal tooth numbers driven by a motor. Pink gear is fixed.
Sliding joints between green and yellow bars and between grey shafts allow radial displacements of the orange plate that are controlled by violet actuator.
4 bevel gear drive can be replaced by 4 screw gear drive in another embodiment of this mechanism.
This mechanism can be applied for manipulator of polar coordinate system.
Disadvantage: the actuator is not base-mounted.