In fact, planetary gear reduction is the principle of gear reduction. It has a gear with a fixed axis position called the sun gear, and a gear with a variable axis at the edge of the sun gear, that is, the gear that rotates and revolves is called the planetary gear, and the planetary gear has a supporting part called the planet carrier, which transmits the power to the shaft and then to other gears. They consist of a group of several gears. There is only one prime Mover, and this epicyclic gear train is called a planetary gear train.