This article introduces the composition and control principle of the rewinding machine control system, focusing on the implementation strategy of the Lenze9326 servo controller integrated with the CAN bus system and the variable torque taper tension control system. 1 Introduction In the production of wet-laid glass fiber mat, the rewinding machine is a downstream process. It is mainly used for spot-checking and inspecting the appearance quality of the mat rolls, removing substandard or defective parts; and rewinding mat rolls with uneven end faces. Since the width of the mat is fixed in thin-layer production, the rewinding machine is needed to cut it into different specifications according to customer requirements. It can also perform product heating and joining, providing the opportunity to combine small rolls into larger rolls to meet customer needs. 2 Rewinding Machine Control System The rewinding machine control system consists of a traction roller constant speed control system, a winding tension control system, an unwinding control system, and a PLC and control console. A schematic diagram of the control system is shown in Figure 1. 2.1 Constant Speed ​​Control System for Traction Rollers The constant speed transmission control system for traction rollers consists of a pair of traction rollers covered with rubber or coated with sandpaper, a servo controller FC1 (EVS9326-ES), a traction variable frequency motor M1, a traction reducer, a resolver, and a speed potentiometer R1. The linear speed of the traction rollers is the master speed of the rewinder, i.e., the machine speed, and must remain constant after being set. Slippage must be prevented between the traction rollers and the felt material. The traction rollers should have sufficient traction force to ensure adequate traction on the thin felt and to overcome the reverse torque of the longitudinal slitting blade and the metering wheel (which acts as a counter-rotating element). Once the diameter of the traction rollers and the reduction ratio of the reducer are determined, the rotational speed of the traction motor M1 is proportional to the linear speed of the traction rollers. [IMG=Figure 1 Rewinder Control Schematic Diagram]/uploadpic/THESIS/2007/11/2007111612000975976Q.jpg[/IMG] Figure 1 Rewinder Control Schematic Diagram 2.2 Take-up Shaft Tension Control System The take-up shaft tension control system consists of a take-up shaft, servo controller FC2 (EVS9326-ES), take-up motor M2, reducer, resolver, tension setting potentiometer R2, and taper setting potentiometer R3. According to product process requirements, this system adopts indirect tension control with tapered (gradually decreasing) tension winding, eliminating the need for a tension sensor and eliminating the need for calculations outside the controller. Satisfactory winding results can be achieved simply by setting the product's take-up tension, taper, and winding speed. 2.3 Unwinding Control System The unwinding control system consists of an unwinding shaft, a servo controller FC3 (EVS9323-ES), an unwinding motor M3, a reducer, a resolver, a pneumatic brake, and a coupling mechanism. During the unwinding process, a pneumatic brake is used to apply load to the unwinding shaft, generating tension on the felt web to ensure constant tension during unwinding. The system is equipped with a "return/forward" switch to allow the rewinder to perform forward or reverse winding. The braking and coupling effects are achieved by adjusting the compressed air pressure, typically around 2 bar. When the winding direction changes, the brake and coupling switches should be in the correct positions. Forward winding: brake on, coupling off. Reverse winding: brake off, coupling on. 2.4 PLC and Control Console This system is controlled by an S7-313 PLC. The winding tension, taper (tension coefficient), and winding speed are set via the control console to ensure satisfactory winding results. The winding control process is implemented inside the controller, and the PLC only performs logic control for the rewinding process. The rear end of the machine has an electric automatic deviation correction device to ensure neat edges of the roll material. The length controller on the control cabinet can set the roll length. The unit is also equipped with a fabric inspection lamp and a product heating docking device. [IMG=Figure 2 Controller FC1+FC2 CAN bus signal diagram]/uploadpic/THESIS/2007/11/2007111612014239942E.jpg[/IMG] Figure 2 Controller FC1+FC2 CAN bus signal diagram 3 Implementation of the winding control process 3.1 System bus CANbus control In this system, the traction roller servo controller FC1 and the winding shaft servo controller FC2 are both model EVS9326-ES. This controller integrates a CAN bus interface X4. X4 GND is the CAN bus reference potential; CAN LO is the CAN bus I/O low potential terminal; CAN HI is the CAN bus I/O high potential terminal. Connect the X4 terminals of the two 9326 controllers sequentially using a dedicated twisted-pair shielded cable, and connect 120Ω terminating resistors to the LO and HI terminals of the X4 terminals of controllers FC1 and FC2 respectively. To enable signal transmission between controllers FC1 and FC2, the following parameters need to be configured: CAN bus address setting: The CAN bus address is determined by C0350. The CAN bus addresses for controllers FC1 and FC2 are 1 and 2 respectively. CAN-IN2/OUT2 Address Settings: FC1: Main Drive C0350/000 CAN address = 1 C0354/003 IN2 addr2 = 257 C0354/004 OUT2 addr2 = 258 FC2: Winder Drive C0350/000 CAN address = 2 C0354/003 IN2 addr2 = 258 C0354/004 OUT2 addr2 = 257 Therefore, it can be seen that the CAN input of controller FC1 is the CAN output of controller FC2, and the CAN output of controller FC1 is the CAN input of controller FC2; similarly, the CAN input of controller FC2 is the CAN output of controller FC1, and the CAN output of controller FC2 is the CAN input of controller FC1. The CAN bus signal diagram of controller FC1+FC2 is shown in Figure 2. The event-triggered loop process data channels CAN-IN2 and CAN-OUT2 are internal function blocks of the 9326 servo controller. Under certain conditions, CAN-IN2 can receive data from another controller's CAN-OUT2. Both sending and receiving are 8 bytes of data, of which bytes 1, 2, 3, and 4 can be used for 32-bit binary signals, two quasi-analog signals, or a 32-bit double-word phase signal. Here, the input CAN-IN2 of FC2 is the output CAN-OUT2 of FC1. FC2: CAN-IN2.W1 is the traction roller speed, CAN-IN2.W2 is the winding diameter ratio, CAN-IN2.W3 is the winding diameter, and CAN-IN2.W4 is the torque rating compensation. The input CAN-IN2 of FC1 is the output CAN-OUT2 of FC2. FC1: CAN-IN2.W1 is the winding speed, CAN-IN2.W2 is the winding torque rating, and CAN-IN2.W3 is the winding diameter compensation. Through signal conversion and data processing of the function blocks shown in Figure 2, variable torque taper tension control in the rewinding process is achieved. In Figure 2, the speed setpoint signals X6/1 and X6/2 of controller FC1 come from the speed potentiometers on the control panel and can be arbitrarily set according to product requirements. The tension setting signal and taper setting signal of controller FC2 also come from their respective potentiometers on the control panel. This signal is a quasi-analog signal represented in decimal, with the unit being "%". For example, the machine speed is a percentage calculated with 100 m/min as 100%, and a negative sign is added according to the needs of signal flow graph calculations; for example, -60% indicates a speed of 60 m/min. 3.2 Signal Conversion and Data Processing For the main drive servo controller (FC1), the output signal MCTRL-PHI-ACT of the internal motor control function block MCTRL is the actual speed of the motor (rpm), and CAN-IN2.W1 is the speed of the winding drive motor (rpm). These two signals are used as the input terminals IN1 and IN2 of the arithmetic block ARIT1, respectively. After calculation, the winding diameter is obtained: d = main drive speed / winding drive speed × d[sub]min[/sub][%] / 100. For the winding drive servo controller (FC2), CAN-IN2.W2 is the winding diameter ratio y, y = winding speed / d[sub]min[/sub] 1. It is the input terminal IN1 of the arithmetic block ARIT1. The ARIT1 input terminal IN2 is the taper (HW). After arithmetic operation, a = HW × y is obtained; after addition operation by ADD1, the result is a + 1. The winding controller torque command M = M₀(a+1) M = M₀(HW×y+1) = M₀][HW×(d / dmin-1)+1] = M₀•HW •d / dmin+M₀•(1HW) ……① Figure 3 The winding torque process value M = F•d ……② From equations ① and ②, we know that: the winding controller tension command F = M₀•HW•1 / dmin+M₀•(1HW)/d = F₀•HW + F₀•(1HW)d/dmin…… ③ Where: M₀ = F₀•d_min M₀: Initial torque; M: Torque process value; H_W: Taper; d_min: Minimum roll diameter; d: Actual roll diameter; F₀: Set tension; F: Tension process value. The winding control process follows the above mathematical model for variable torque taper tension control. 4. Winding Characteristics Analysis For rewinding machines, to ensure the ideal rewinding effect of the felt roll, tension control during the winding process is particularly important, as the quality of tension control directly affects the rewinding quality of the product. In most cases, the tension is required to remain constant during the winding process. However, for wet-laid glass fiber felt, it is required that the inner tension be tight and the outer tension loose during the winding process, i.e., a gradually decreasing (tapered) tension control is adopted. It is required that the felt width tension gradually decreases as the winding diameter increases during the winding process from an empty shaft to a full shaft, and its taper value must meet the process requirements. Figure 3 shows the torque-diameter and tension-diameter curves for the variable torque taper tension control mode. As can be seen from the curves, this winding control is a variable torque, variable tension control. This means that the torque increases with increasing diameter and different taper settings, while the tension changes differently. When the taper coefficient HW = 100%, constant tension winding is used. When the taper coefficient HW ≤ 100%, tapered tension (gradually decreasing tension) winding is used. When the taper coefficient HW > 100%, increasing tension winding is used. After setting the taper coefficient HW, the winding torque increases linearly along different taper values, while the tension changes curvilinearly, either decreasing or increasing. For example, when the taper coefficient HW is set to 100%, tension attenuation means that the tension does not decrease when the diameter is exceeded, i.e., constant tension; when the taper coefficient HW is set to 70%, when wound to the maximum diameter, the final winding tension decreases by 30% compared to the set tension, meaning that the retained tension at the maximum diameter is 70% of the set tension; when HW is set to 0%, the winding tension at the maximum diameter decreases to 0; when the taper coefficient HW is set to 130%, the tension increases incrementally. Additionally, the servo controller has a torque compensation function to eliminate the interference on tension caused by radius changes. 5. Conclusion The main transmission points of the rewinder are the take-up roller and the traction roller. Ensuring the continuity of the thin felt and meeting the requirement of a tight inner and loose outer roll after rewinding requires automatically adjusting the winding control process based on the felt roll diameter and torque and tension control curves to achieve the "tight inner and loose outer" process requirement of the paper roll. This system has a simple configuration, complete functions, and advantages such as fast response, good stability, low failure rate, reliable operation, and easy maintenance. Its control principle and implementation method can be widely applied in related industries. Proceedings of the 2nd Servo and Motion Control Forum and the 3rd Servo and Motion Control Forum