Abstract: This paper discusses a novel constant tension winding system that employs direct torque control. In this system, there is no need for winding diameter measurement and tension measurement. Instead, winding diameter and torque information are obtained through calculation to achieve constant tension control.
Keywords: Torque control; Roll diameter calculation; Constant tension control
Abstract：This paper describes, is a new type of constant tension winding system, using the direct torque control mode, in which the system do not need to link with the roll diameter measurement links and tension measurements links, using the calculation method to know the information of the roll diameter and the information of the torque diameter, to achieve constant tension control mode.
Key words: Torque control; Roll diameter calculation; Constant tension control
1. Introduction In modern industrial production, especially in papermaking, textiles, and metal products manufacturing, tension regulation of winding machine speed is the most common method. In traditional torque control modes, because the radius of the winding roller gradually increases, it is difficult to ensure a constant winding tension, resulting in compromised product quality. Therefore, only by employing a constant tension control mode during the winding process can high product quality be guaranteed.
2. System Introduction This paper discusses a winding system for a large-scale twisting machine. It utilizes the direct torque control mode of a frequency converter to achieve constant tension winding control, eliminating the need for tension detection, winding diameter detection, and a tensioning frame synchronization device. The required torque and winding diameter are directly calculated internally by the programmable logic controller (PLC), providing a simple method that avoids the need for constant winding diameter detection.
In typical variable frequency drive (VFD) control, the VFD operates in speed control mode. To ensure constant tension, a tension detection component is essential. This component feeds back the detected tension to the VFD for PID control. Constant tension control requires constant torque, but during winding, the radius of the winding reel continuously increases, necessitating a gradual increase in motor torque (torque equals the ratio of tension to radius). The instantaneous winding diameter is calculated. Given the relatively constant tension, the instantaneous motor torque can be obtained. Its core characteristics are: firstly, through winding diameter and torque calculations, the PLC transmits this constantly changing torque to the VFD; secondly, speed limiting is used to control the VFD's output frequency, stabilizing the motor's linear speed and thus achieving constant tension.
In the application system, DP communication enables the transmission of torque setting and speed limiting information between the PLC and the frequency converter.
3. Calculation of roll diameter and torque
(1) Calculation of the winding diameter: During the operation, it is assumed that the drawn wire is very thin (0.22mm), and the gaps generated during winding can be ignored. According to the principle of constant volume, at a certain moment during operation, the volume of the wire on the take-up reel is:
In this system, the radius of the take-up reel gradually increases as the take-up length increases. To maintain constant tension, the change in torque must be proportional to the change in reel diameter.
Therefore, at a certain moment, the magnitude of its torque can be calculated in the programmable controller using this formula, and then this value is sent to the frequency converter via DP communication.
4. Application Examples
In the winding process of large twisting machines, torque control is used for the winding motor to improve product quality. The connection between the touchscreen, programmable controller (PLC), and frequency converter in this system is shown in Figure 2. In this system, the motor tension and speed limit frequency can be set on the display screen. The PLC reads these two digital values, calculates the torque, and converts the tension into an analog signal, which is then sent to the frequency converter. When the frequency converter executes this instruction, the motor operates under constant torque. When the winding diameter increases, the PLC calculates the diameter and torque, sends the new analog signal to the frequency converter, and the frequency converter executes the new instruction. Through continuous calculation, the torque of the winding motor increases with the increase in winding diameter, ensuring constant tension.
5. Conclusion
Compared to speed control winding, torque control winding is simpler, primarily because it eliminates the need for a tensioner synchronization mechanism. Furthermore, the powerful computing capabilities of the programmable controller (PLC) are used to calculate the winding diameter and torque, further simplifying the system hardware by eliminating the need for diameter and tension detection. Compared to variable tension control, constant tension control produces significantly higher quality products, making it more suitable for winding finished products. The use of the DP bus facilitates convenient and rapid information exchange between the inverter and the PLC.
References
[1] Wang Hongbo, Application of PLC in Constant Tension Control System, Journal of Shunde Polytechnic, 2007.6, 20-22
[2] Wang Zejuan. Several Schemes for Synchronization and Constant Tension Control Systems. Hebei Textile, 2008, No. 3, pp. 49-51.
[3] Shen Hongwei Research on constant tension control system without tension sensor Combined Machine Tool & Automated Machining Technology 2003.11 87-88
