Abstract: This article mainly introduces the control principle of tension-controlled variable frequency winding. This technology can make the entire winding process in the textile industry very stable, avoiding excessive tension when using small rolls and loose yarn when starting large rolls. I. Introduction : The essence of constant tension control using a frequency converter is closed-loop vector control, that is, adding encoder feedback. For winding, the winding diameter changes from small to large. In order to ensure constant tension, the output torque of the motor must change from small to large. At the same time, corresponding torque compensation is required in different operating processes. That is, at the moment of starting small rolls, acceleration, deceleration, and stopping, and when starting large rolls, different torque compensations are required for different roll diameters. This makes the entire winding process very stable, avoiding excessive tension when using small rolls and loose yarn when starting large rolls. II. Application and process requirements of tension-controlled variable frequency winding in the textile industry 2.1 Disadvantages of traditional winding devices Textile machinery such as sizing machines, sizing and dyeing combined machines, and spinning machines all have a winding stage. Traditional winding uses mechanical transmission. Because coaxial transmission of machinery causes severe wear and tear on the machinery, it is understood that the average lifespan of machinery used for coaxial transmission is about one year. Moreover, it requires frequent maintenance, which is very troublesome, not only wasting manpower but also incurring high maintenance costs, causing a lot of inconvenience to customers. In particular, textile equipment is basically not allowed to be stopped midway after it is started. If an unexpected situation occurs and it needs to be stopped, it will cause a lot of waste. Under such circumstances, tension control frequency conversion winding has begun to gradually replace the traditional mechanical transmission system. 2.2 Process requirements of tension control frequency conversion winding (1) Maintain constant tension throughout the winding process. The unit of tension is: Newton or kilogram force. (2) When starting a small roll, the yarn should not break due to excessive tension; when starting a large roll, the yarn should not loosen. (3) The above situation should not occur during acceleration, deceleration, and stopping. (4) It is required to quantify the tension, that is, to be able to set the tension (unit of force) and to display the actual roll diameter. 2.3 Advantages of Variable Frequency Winding with Tension Control (1) Tension setting is set on the human-machine interface, providing a user-friendly operation. The unit is the force unit: Newton. (2) Advanced control algorithms are used: recursive calculation of roll diameter; linear increase of tension when hollow roll diameter is activated; application of tension taper calculation formula; dynamic adjustment of torque compensation, etc. (3) Real-time calculation of roll diameter with very high accuracy ensures good smoothness of the output torque of the winding motor. Furthermore, recursive calculation of roll diameter is added when calculating the roll diameter, so that the roll diameter can be corrected to the correct value when there is an operational error. (4) Because the rotational inertia of the winding device is very large, when the roll diameter increases from small to large, if the operator accelerates, decelerates, stops, and reactivates, it is easy to cause yarn breakage and loosening, which will directly affect the quality of the yarn. After the modification of variable frequency winding, the winding is very stable under the above conditions, and the tension is always constant. Moreover, after processing by PLC, some dynamic adjustment measures are added in specific dynamic processes, making the winding performance better. (5) It is very simple and inexpensive to modify the traditional mechanical transmission winding into frequency conversion winding. Basically, no modification is required to the original machinery. The modification cycle is short, and the installation and debugging can be completed in two or three days. (6) It overcomes the disadvantage of mechanical winding to mechanical wear and extends the service life of the machinery. It is convenient to maintain the equipment. [align=center] Figure 1 System composition and system block diagram[/align] III. Control principle and debugging process of frequency conversion winding 3.1 Calculation principle of winding diameter The winding diameter is calculated according to V1=V2. Because V1=ω1＊R1, V2=ω2＊Rx. Because the length of yarn that passes by the measuring roller in the same time is equal to the length of yarn that is wound up. That is, L1/Δt = L2/Δt, Δn1 * C1 = Δn2 * C2/i (Δn1 — number of revolutions of the traction motor per unit time, Δn2 — number of revolutions of the take-up motor per unit time, C1 — circumference of the measuring roller, C2 — circumference of the take-up head, i — reduction ratio). Δn1 * π * D1 = Δn2 * π * D2/i, D2 = Δn1 * D1 * i/Δn2, because Δn2 = ΔP2/P2 (ΔP2 — number of pulses generated by the take-up encoder, P2 — number of lines of the take-up encoder). Δn1 = ΔP1/P1. Taking Δn1 = 1, that is, when the measuring roller rotates one revolution, a signal is generated by the Hall switch and connected to the PLC. Then D2 = D1 * i * P2/ΔP2, thus the diameter of the take-up head is obtained. 3.2 Dynamic Process Analysis of Winding To ensure the smoothness of the winding process, constant tension must be maintained regardless of whether the roll is large or small, during acceleration, deceleration, activation, or stopping. Torque compensation is required. For the entire system to activate, the torque generated by static friction must first be overcome, referred to as static friction torque, which only acts at the moment of activation. During normal operation, the sliding friction torque generated by sliding friction must be overcome. Sliding friction torque exists throughout operation and its magnitude differs at low and high speeds. Different amounts of compensation are required. During acceleration, deceleration, and stopping, corresponding torque compensation is also necessary to overcome the system's inertia. The amount of compensation is proportional to the operating speed. The compensation coefficient differs at different speeds. These include acceleration torque, deceleration torque, stopping torque, and activation torque. After overcoming these factors, the load torque must also be overcome. This is calculated by dividing the real-time roll diameter by 2 and multiplying by the set tension, then converting the result to the motor shaft through the reduction ratio. This analysis reveals the torque compensation process throughout the entire winding process. Summary: The output torque of the motor = static friction torque (at the moment of activation) + sliding friction torque + load torque. (1) When accelerating, the acceleration torque should be added; (2) When decelerating, the deceleration torque should be subtracted. (3) When stopping, since the deceleration is controlled by the program to the set minimum speed, the compensation of the stopping torque is the same as the processing of the deceleration torque. 3.3 Torque compensation standard (1) Compensation of static friction torque Since the static friction torque only exists at the moment of activation and disappears after the system is activated, the compensation of static friction torque is to compensate by multiplying the calculated output torque of the motor by a certain percentage. (2) Compensation of sliding friction torque The compensation of sliding friction torque is effective throughout the entire process of system operation. The compensation is based on the rated torque of the winding motor. The amount of compensation is related to the running speed. Therefore, when processing in the program, the compensation should be carried out in segments. (4) Compensation of acceleration, deceleration and stopping torque The compensation is based on the rated torque of the winding motor, and the corresponding compensation coefficient should be relatively stable and not change much. 3.4 Formula calculation in the calculation (1) Given the hollow core roll diameter Dmin=200mm, Dmax=1200mm; the maximum linear speed Vmax=90m/min, the maximum tension setting Fmax=50kg (approximately 500 Newtons); the reduction ratio i=9; the speed limit is as follows: because: V=π*D*n/i (for the winding motor) => the winding motor speed is the fastest when the hollow core roll diameter is reached. So: 90=3.14*0.2*n/9=>n=1290r/min; (2) Because we know that when the frequency converter works at low frequency, the characteristics of the AC asynchronous motor are not good, the activation torque is low and nonlinear. Therefore, during the entire winding process, the winding motor should be kept away from working below 2HZ as much as possible. Therefore: the winding motor has a minimum speed limit. The calculation is as follows: for a four-pole motor, its synchronous speed is: n1=60f1/p=>n1=1500r/min. =>2HZ/5HZ=N/1500=>n=60r/min. When the maximum winding diameter is reached, the minimum speed during the entire winding process can be calculated. V=π＊D＊n/i=>Vmin=3.14＊1.2＊60/9=25.12m/min. When controlling tension, the speed must be limited, otherwise runaway will occur. Therefore, speed must be limited. (3) The calculation of tension and torque is as follows: If F＊D/2=T/I=>F=2＊T＊i/D For a 22KW AC motor, the rated torque is calculated as follows: T=9550＊P/n=>T=140N. m. So Fmax=2＊140＊9/0.6=4200N. (where P is the rated power and n is the rated speed). (4) Debugging process: ● First, perform self-tuning on the motor and read the stator inductance, stator resistance and other parameters of the motor into the frequency converter. ● Connect the encoder signal to the frequency converter and set the encoder line count on the frequency converter. Then, use the panel to set the frequency and start/stop control, and observe whether the displayed operating frequency fluctuates around the set frequency. Because when using infinite loop vector control, the operating frequency is always as close as possible to the set frequency as possible with reference to the speed fed back by the encoder, so the operating frequency oscillates around the set frequency. ● Set the values ​​of the hollow core diameter and the maximum diameter in the program. Calculate the maximum pulse quantity (P2) and minimum pulse quantity (P2) generated by the encoder added to the motor tail using the formula for calculating the diameter. Limit the speed of the winding motor by using the calculated maximum pulse quantity, because if the maximum speed is not limited when the frequency converter is used for tension control, the winding motor will run away if there is a yarn breakage or other situation. The minimum pulse quantity is to avoid the winding frequency converter operating below 2Hz, because when the frequency converter operates below 2Hz, the motor's torque characteristics are very poor and a jitter phenomenon will occur. ●Through the dynamic process of the entire winding process analyzed above, a certain torque compensation is performed at each stage with different roll diameters and different running speeds. The magnitude of the compensation can be set as a percentage of the rated torque of the motor. V. True Tension Control 5.1 Definition of Tension Control In simple terms, tension control means being able to control how much force the motor outputs, that is, how many Newtons it outputs. This is reflected in the motor shaft, which can control the output torque of the motor. 5.2 True tension control is different from a system that relies on the speed difference between two power points to form tension. The essence of adjusting tension by speed difference is PID control of tension, which requires the addition of a tension sensor. Moreover, the adjustment during the start-up, stop, acceleration, deceleration, and parking of large and small rolls cannot achieve the effect of true tension control, and the tension is not very stable. This will definitely affect the quality of the produced products. VI. Requirements of Variable Frequency Winding for Variable Frequency Drive Performance (1) The essence of variable frequency winding is to complete tension control, that is, to control the operating current of the motor, because the output torque of a three-phase asynchronous motor T=CmφmIa is proportional to the current. And when there is a sudden change in load, it can ensure that the mechanical characteristic curve of the motor is relatively hard. Therefore, a vector inverter must be used, and an encoder dead loop control must be added. (2) The inverters that can perform tension control frequency conversion winding on the market are mainly: Yaskawa, Emerson, Rentz, etc. Emerson TD3300 is a frequency converter dedicated to winding and unwinding. Delta's V+ series frequency converters are launching their own frequency converters dedicated to winding and unwinding. They summarize many of the main functions and parameters of the frequency converters dedicated to winding and unwinding and add their own algorithms, which have their own characteristics. In addition, Delta's nationwide warranty service can solve customers' worries. It should be a good choice for customers. About the author: Li Qiang (1978.11-) Male Senior Technical Engineer (FAE) of Delta Electronics Co., Ltd. Research direction: Provide customers with automation solutions, and complete system design using configuration software, human-machine interface, PLC, frequency converter and servo.