The tension controller is a kind of control instrument, which can directly set the tension value required to be controlled, and then input the signal of the tension sensor (generally at the millivolt level) as the tension feedback value. After the deviation is obtained by comparison, it is input to the PID and other controls. Processed by the controller, it is best to output to the peripheral actuator for control, and finally achieve the goal of the smallest deviation and the fastest system response.