1. Introduction With the advancement of textile machinery technology, the application of stepper and servo motor motion control systems is becoming increasingly widespread. Their functional diversity and product reliability are constantly improving, and they are gradually replacing ordinary motors. Furthermore, with the increasing maturity of programmable logic controller (PLC) technology, the complete integration of these two technologies to achieve automatic control of various complex movements and implement mechatronics is becoming a trend. A stepper motor is an actuator that converts pulse signals into linear or angular displacement. The output displacement of a stepper motor is proportional to the number of input pulses, its speed is proportional to the number of input pulses per unit time (i.e., pulse frequency), and its direction of rotation is related to the phase sequence of the pulses distributed to the windings of the stepper motor. Therefore, by controlling the number and frequency of command pulses and the phase sequence of the motor windings, the output displacement, speed, and direction of the stepper motor can be controlled. Stepper motors have good control performance; their starting, stopping, reversing, and any other changes in operating mode can be completed within a few pulses, and high control accuracy can be achieved, thus leading to their widespread application. 2 Stepper Motor Pulse Distributor In the application of programmable logic controllers (PLCs), stepper motors are common controlled objects. A stepper motor is a digital control element that directly receives pulse signals. Its rotation angle and speed are directly proportional to the number and frequency of the input pulses, respectively. Therefore, by controlling the number and frequency of pulses input to its coil windings, the rotation angle and speed of the stepper motor can be controlled. However, the input pulses still need to be distributed to the various windings of the stepper motor by a pulse distributor. The design of the pulse distributor is a very important and flexible issue when controlling a stepper motor with a PLC. It can be implemented in hardware or software. This article takes the Panasonic FP0-C16T PLC as an example to discuss several methods for implementing a stepper motor pulse distributor. [align=center][img=397,189]http://www.ca800.com/uploadfile/maga/plc2008-7/lyj-1.jpg[/img] Figure 1 Control Principle Wiring Diagram[/align] The hardware implementation wiring diagram of the stepper motor pulse distributor control principle is shown in Figure 1. Since the pulse distributor is implemented in hardware, the FP0-C16T only needs to provide a series of pulses. The FP0 series PLCs have pulse output and high-speed counter (HSC) functions, making it very convenient to control stepper motors using these functions. [align=center][img=397,249]http://www.ca800.com/uploadfile/maga/plc2008-7/lyj-2.jpg[/img] Figure 2 Control Ladder Diagram[/align] The output terminals Y0 or Y1 of various FP0 series PLC models have pulse output functions, with a maximum output pulse frequency of 10kHz. The specific output pulse frequency can be programmed in software. The pulses output by Y0 or Y1 are distributed to the phase windings of the stepper motor via the pulse distributor. Simultaneously, Y0 or Y1 is connected to the input contacts of the pulse. When a set value is reached, an interrupt occurs, switching the pulse frequency of Y0 or Y1 to the next parameter. Y2 or Y3 is the direction control signal. When VCC is 5V, R is short-circuited; when VCC is 12V, R = 1kq (≥1/8W); when VCC is 24V, R = 2kq (≥1/8W). Figure 2 is the ladder diagram for implementing this control. dt100～dt106 are general-purpose registers that store the output pulse frequency and number. The parameters given in the ladder diagram are an initial output pulse frequency of 500Hz, a maximum frequency of 5000Hz, and a pulse count of 10000. 3 Software Stepper Motor Pulse Distributor Design 3.1 Electrical Principle Design [align=center][img=397,336]http://www.ca800.com/uploadfile/maga/plc2008-7/lyj-3.jpg[/img] Figure 3 Hardware Wiring Diagram[/align] Figure 3 is the hardware wiring diagram of the software-implemented stepper motor pulse distributor PLC and the stepper motor. The stepper motor operates in the most common three-phase six-step energizing mode. k0, k1, and k2 are the forward, reverse, and stop control switches, respectively, connected to the input relays x0, x1, and x2 of the PLC; the output relays y0, y1, and y2 of the PLC are connected to the three-phase windings a, b, and c of the stepper motor, respectively. There are many methods for implementing pulse distribution in software; three implementation schemes are discussed here. 3.2 One of the software implementation schemes [align=center][img=397,726]http://www.ca800.com/uploadfile/maga/plc2008-7/lyj-4.jpg[/img] Figure 4 Ladder diagram of software scheme 1[/align] The ladder diagram is shown in Figure 4. The stepper motor operates in a six-phase energizing mode, meaning the energizing sequence of the three-phase windings is: forward rotation: a-ab-b-bc-c-ca; reverse rotation: a-ac-c-cb-b-ba. In this scheme, the clock can be generated by designing a clock generator using the timer in the PLC, or by using the PLC's internal 0.01s, 0.02s, 0.1s, 0.2s, 1s, and 2s clocks, which are generated by the PLC's special internal relays R9018, R9019, R901a, R901b, R901c, and R901d, respectively. For convenience, the PLC's special internal relay R901a (0.1s pulse relay) is used here as the control clock. Relays r0 and r1 are activated in both forward and reverse directions respectively; the 16-bit shift register (relay) wr1 generates six cycles of forward and reverse rotation. The contacts r10-r15 of the shift register are combined with r0 and r1 to energize the output relays y0, y1, and y2 in the aforementioned forward and reverse sequence. 3.3 Software Implementation Scheme Two [align=center][img=397,650]http://www.ca800.com/uploadfile/maga/plc2008-7/lyj-5.jpg[/img] Figure 5 Ladder Diagram of Software Scheme 2[/align] The ladder diagram is shown in Figure 5. In this scheme, switches x0 and x1 are used for forward and reverse start control, and k2 is used for stop. The clock still uses the special internal relay 901a 0.1s pulse relay in the PLC as the control clock. Using a 16-bit shift register (relay) wr1, six cycles required for forward and reverse rotation are generated. The contacts r10-15 of the shift register (relay) are combined with the contacts of the forward and reverse control relays r0-r1. Using advanced data transfer instructions in the PLC, the required control word (see attached table) is directly output to the PLC's output terminal, causing the output relays y0, y1, and y2 to be energized in the aforementioned forward and reverse sequence. 3.4 Software Implementation Method Three [align=center][img=397,687]http://www.ca800.com/uploadfile/maga/plc2008-7/lyj-6.jpg[/img] Figure 6 Ladder Diagram of Software Scheme 3[/align] The ladder diagram is shown in Figure 6. The function of the control switches and the clock remain as described in Scheme Two. In this scheme, the R9013 utilizes the initial 0n pulse relay during startup. Upon power-up, the output control word is sent to the PLC's general-purpose data registers dt0~dt7. Based on the forward/reverse control requirements, the PLC's lookup register ix (initial value: 0 for forward rotation or 5 for reverse rotation) is used as the initial pointer for the output control word. Using the instruction [f0 mv ,ixdt0, wy0], the required control word is directly output to the PLC's output terminal. Then, the value of ix is ​​modified to energize output relays y0, y1, and y2 in the aforementioned forward/reverse sequence. R900B is a comparison equality flag. 4. Application Case [align=center][img=397,170]http://www.ca800.com/uploadfile/maga/plc2008-7/lyj-7.jpg[/img] Figure 7 A stepper motor control system based on a hardware implementation scheme was designed and successfully applied to the transformation of the electrical control system of a domestic carding machine. The block diagram of its electrical control system is shown in Figure 7. This electrical control system, through PLC control of the stepper motor, solves the difficulties of complex relay control systems in domestic carding machines, such as low reliability, insufficient control precision, numerous fault points, and complicated wiring. It can conveniently control the carding machine according to its process requirements and can also determine the electrical parameters of the carding machine, including the start-up time and speed of the cylinder and doffer, based on the type of fiber spun and the product quality requirements. Furthermore, the system has advantages such as reliable performance, high control precision, simple operation, stable operation, and no noise, improving the mechatronics integration level of the carding machine and fully meeting the user's requirements. 5 Conclusion Programmable logic controllers (PLCs) can be used to easily control the speed and position of motors, reliably operating stepper motors to complete various complex actions. The application of a PLC-based stepper motor control system on domestically produced carding machines has improved the mechatronics level of these machines. More importantly, it lays the foundation for improving the stability and reliability of the entire cotton spinning process, ensuring continuous, synchronous, and stable operation. This keeps the uniformity of long, medium, and even short segments of the output sliver within a stable range, thus guaranteeing the stability of yarn quality. The successful application of the PLC-based stepper motor control system on domestically produced carding machines demonstrates that this control system can be applied to the upgrading of other domestically produced traditional textile equipment, providing valuable reference for domestic textile mills upgrading their equipment.