Tension control methods can generally be divided into two types: direct tension control and indirect tension control.
(1) Direct tension control: Also known as feedback control, can be further divided into two types, A and B. (A) Utilizing sensors such as tension meters to detect the actual tension, the measured value is used as a feedback signal to form a tension closed-loop system. The measured actual value is compared with the given tension, and the deviation generates a control effect, making the actual tension equal to the given tension. Depending on the sensor structure, it can also be divided into positional and feedback control. (B) Using a looper to establish tension, the looper quantity is measured to form a looper feedback control system, controlling the looper quantity to keep the product tension constant. This tension control method is suitable for high-precision, high-speed tension control applications, and has advantages such as high control accuracy and good real-time performance.
(2) Indirect tension control method: Also known as compensation control, it indirectly maintains tension stability by adjusting the parameters that affect tension stability to compensate for possible tension changes. That is, only a tension setpoint is given, without using a detector to collect the actual tension value. It does not form a closed-loop control of the tension, but indirectly controls the tension by controlling the current or excitation current of the controlled machine, i.e., the drive motor, so that the motor torque remains unchanged and the tension of the wound product remains constant.