Automatic manipulators that can imitate certain functions of human hands and arms to grasp and carry objects or manipulate tools according to a fixed procedure. Manipulators are the first industrial robots and the first modern robots that can replace heavy human labor to mechanize and automate production, 1. to improve the automation of production processes, 2. to improve labor conditions and avoid personal accidents, and 3. to reduce manpower and facilitate rhythmic production. It can operate in harmful environment to protect personal safety, so it is widely used in machinery manufacturing, metallurgy, electronics, light industry and atomic energy, etc.