Closed loop stepper motor is the combination of stepper motor and closed-loop control, also known as hybrid servo. Because the open-loop control system of stepper motor has the disadvantages of low precision and step loss, the closed-loop control system of stepper motor can be used in the occasions with high precision requirements. This control mode is to directly or indirectly detect the position or speed of rotation (or load), and then through feedback The driving pulse sequence of the stepper motor is given automatically according to the position of the load or rotor. There are many ways to realize this control mode. In the situation of high precision, the combination of micro step driving technology and microcomputer control technology can achieve high position precision.