A cycloidal drive or cycloidal speed reducer is a mechanism for reducing the acceleration of an insight shaft by a particular ratio. Cycloidal speed reducers can planetary gearbox handle relatively high ratios in small sizes. [1]
The input shaft drives an eccentric bearing that in turn drives 
the cycloidal disc within an eccentric, cycloidal movement. The perimeter of this disc is geared to a stationary ring equipment and has a group of output shaft pins or rollers positioned through the face of the disc. These result shaft pins directly drive the result shaft as the cycloidal disc rotates. The radial movement of the disc is not translated to the output shaft.