The applications of underwater vehicles have shown a dramatic increase in recent years, such as, mines clearing operation, feature tracking, cable or pipeline tracking and deep ocean exploration. According to different applications, the mechanical and electrical configuration and shape of an underwater vehicle are different. For instance, manipulators are necessary when doing mines clearing operation or some other tasks which need to deal with environment. If an underwater vehicle is used for underwater environment detection or observation, it is better to make this vehicle smaller and flexible in motion that it can go to smaller space easily. If the vehicle needs high speed moving in the water.
