Abstract : The welding wire winding machine is one of the key pieces of equipment in welding wire production, and its control directly affects the quality of the welding wire. Currently, most winding machines use zero-degree angle winding, resulting in low reliability. An angle-controlled winding system achieves automatic winding and smooth reversing. The combination of an angle sensor and a digital AC servo motor enables constant and variable angle winding control. Practice shows that this improves the winding quality and production efficiency of the machine, with an angle detection resolution of 0.09°. Keywords : PLC; Servo motor; Angle sensor; Welding wire winding system 0 Introduction Currently, most similar domestic equipment uses vertical winding (the welding wire is perpendicular to the take-up shaft), making the equipment susceptible to interference, resulting in frequent shutdowns and uneven welding wire tension. An automatic winding system based on hysteresis angle control can improve the accuracy and performance of the winding. Angle closed-loop control using a programmable logic controller (PLC) enables the welding wire to be wound at high speed on the I-beam at a fixed hysteresis angle β. The PLC detects the angle value and compares it with the set value. The deviation causes the PLC to send a pulse signal to the servo motor to drive the linear unit to move, so that the deviation tends to zero, so that the welding wire can be wound with a fixed lag angle. The human-machine interface is used to complete the input of equipment data and real-time monitoring. The design realizes the control of the automatic wire laying system that tracks the normal speed outside the reversing zone, quickly catches up to the synchronous speed tracking after the reversing switch is activated, and forms a new lag tracking after the welding wire reaches the edge of the H-beam. It meets the requirements of automatic and smooth wire laying of the wire laying system [1>-[2>]. 1. Process principle of layer winding The structure of the automatic wire laying device is shown in Figure 1. The wire laying device adopts lag angle wire laying. The servo motor pushes the wire laying device to lay the wire at a certain angle through the roller screw and slide rail. In the inner diameter area of ​​the take-up H-beam, when laying the wire from one side to the other, the entire area is divided into two areas: general tracking and reversing tracking. The fixed lag angle tracking mode is used in the general tracking area, and the variable angle tracking mode is used in the reversing zone. Because the welding wire automatically winds in the opposite direction when it reaches the edge of the I-beam, it is not allowed to wind the wire ahead of its original angle during this process. Otherwise, gaps will appear between the welding wires, defects will appear in the next layer, and the winding will be forced to stop. Therefore, angle detection and control in the reversing area is crucial. [align=center] Fig1 Automatic Arranging Welding Wire System Fig2 The Change Process of Angle in reversing Area The reversing switch automatically generates a direction indicator for the linear unit's movement. The left reversing switch sets the right movement indicator and resets the left movement indicator; the right reversing switch sets the left movement indicator and resets the right movement indicator. The rising edge of the take-up and reversing switches will reverse the left and right movement indicators of the linear unit. Taking the right reversal of the take-up wire as an example, when the right reversal switch is activated, the linear unit advances rapidly at 6 times the base speed until β≤0; as the main motor continues to rotate, the linear unit continues to track at the base speed. When the welding wire is wound close to the rightmost loop of the H-beam reel, the linear unit stops, and at the same time, the right-moving flag of the linear unit is reset and the left-moving flag is set. The left reversal of the take-up wire is similar to the right reversal of the take-up wire. When the take-up wire moves to the left, the angle α is maintained ≤ center angle + lag angle; when moving to the right, the angle α is maintained ≥ center angle - lag angle. The angle change process in the reversal zone is shown in Figure 2. 2 Control System Structure and Working Principle 2.1 Control System Structure [align=center] Fig3 The Control System for Arranging Welding Wire Fig4 The Control Block According to the wiring principle of the wiring device, the control system must first complete the real-time detection of the wiring angle. The design uses a digital angle sensor implemented by combining a 1000-line incremental encoder with a PLC program to detect the real-time angle of the wire laying. The sensor resolution is 0.09°, which meets the requirement of detecting the angle of the welding wire with a minimum diameter of 0.8mm as it wraps around the spindle. The tracking of the normal and reversing areas of the linear unit is realized by the action of the proximity switch. The servo motor is controlled by the output pulse of the PLC to drive the operation of the linear unit [3]. 2.2 Working principle of the linear unit The traveling speed of the linear unit should match the spindle speed. The rotational angular velocity N (revolutions/second) of the spindle is calculated by the speed sensor installed on the spindle. The axial moving speed of the welding wire on the H-beam is V = N * Φ, where Φ is the wire diameter in mm and V is in mm/s. In order to keep the wire laying mechanism synchronized with the moving speed of the welding wire on the spindle, that is, to keep a fixed lag angle, the advancing speed of the linear unit should be equal to V. To ensure accurate synchronization of the lag angle, the travel speed of the linear unit should be equal to V plus the output value of the angle loop (offset). V is converted into the rotational speed of the servo motor (pulse number/second) as follows: Pulse rate = M * N * Φ / d (pulse/second) (1) Where, N is the rotational angular velocity of the main shaft (revolution/second), Φ is the wire diameter (mm), M is the number of lines per revolution of the encoder of the servo motor, and d is the lead of the roller screw (mm/revolution). According to the calculation formula of the given pulse rate of the servo motor in Equation 2-1, its value range is 0～25000 P/S, so the upper limit of the output saturation of MV should be set to 2500 P/S. 3 Programming based on angle control 3.1 Cable angle detection [align=center] Program1 Angle Measuring Program1 Angle detection Program2 Master Speed ​​Measuring Program2 Master speed detection [/align] The hardware high-speed counter adopts a 4x frequency multiplication working mode, and the zero-return function of the angle sensor is implemented in the interrupt service routine. As shown in Program 1. 3.2 Spindle speed detection adopts the M-method, which calculates the spindle speed by interrupting at fixed times (unaffected by the PLC program scanning time), i.e., the spindle speed is calculated from the counting pulse value of the photoelectric encoder every 0.4 seconds. See Program 2. 3.3 Closed-loop control of lag angle layer winding: This part of the program is the core of the layer winding machine control system software, and the flowchart is shown in Figure 5. [align=center] Fig5 Program Flow Block for winding by layer 4 Conclusion The author's innovation lies in using an angle-controlled automatic wire guide, which ensures uniform tension and smooth commutation of the welding wire layer winding, resulting in a low equipment reversal rate and significantly improved welding wire quality. Applications in several engineering projects demonstrate that the angle sensor is accurate and highly sensitive, and the linear unit provides stable lag angle tracking and accurate commutation, greatly improving the system's stability and reliability. References : 1 Wang Shumei, Zhang Dongliang. Control system of wire winding machine based on C8051 F005 [J]. Measurement and Control Technology, 2006, 25 (6): 77-78 2 Fang Tianhong, Gong Min. Design and development of single-chip microcomputer control system for fully automatic winding machine [J]. Journal of Shenyang Institute of Technology, 2004, 23 (3): 36-37 3 Yu Kelong. Motion analysis and control of winding machine wire laying mechanism [J]. Mechanical Manufacturing and Automation, 2005, 34 (3): 102-103 4 Yu Jing. Research on a new type of digital angle sensor [J]. Microcomputer Information, 2007, 1-1: 163-165