In recent years, people have paid more attention to the frequency conversion characteristics of stepper motors. Due to the non-uniformity of things change, the fixed frequency technology shows its limitations more and more, while the frequency conversion technology can well adapt to various randomly changing systems. This article is to introduce the frequency conversion characteristics of the stepper motor controlled by PLC, so that it is used in the let-off device of the textile machine. It is not uncommon to use programmable logic controllers (PLCs) to generate various step pulses to drive step motors to achieve various control and test purposes. Because of its low rotor inertia, high positioning accuracy, no cumulative error, and simple control, stepping motors have become one of the main actuators of industrial control, especially in positioning applications. But in recent years, people have paid more attention to its frequency conversion characteristics. Due to the non-uniformity of things change, the fixed frequency technology shows its limitations more and more, while the frequency conversion technology can well adapt to various randomly changing systems. PLC control of stepper motor PLC is a controller widely used in the field of industrial automation. Its functions are getting stronger and stronger, and its performance is getting more advanced. In order to cooperate with the control of stepper motors, many PLCs have built-in pulse output functions and set corresponding control instructions to control the stepper motors. Figure 1 is the output circuit of Panasonic FP0-C16T transistor output PLC structure. FP0-C16T PLC has two pulse output terminals Y0 and Y1. With different control methods, there are three types of pulse output. (1) These two pulse output terminals can be used as two single-phase pulse output terminals without acceleration and deceleration. They are mainly controlled by PLS and SPD1 instructions. The frequency range is 0Hz_10KHz, which can be output continuously or in pulse form. Output, can be output separately at the same time. (2) It can be used as a two-phase variable duty cycle continuous pulse output terminal. It is mainly controlled by PWM instructions. The duty cycle setting range is 0% _100%. The frequency setting Blower motor range is 0.1Hz_999.9Hz. (3) Can be used as two-phase pulse output with trapezoidal acceleration and deceleration, mainly controlled by PULS and SPD1 instructions. The frequency range is 0Hz_10KHz, and the acceleration / deceleration rate is 10Hz / 10ms_10KHz / 10ms. It can be output continuously or in the form of pulse train. Here again It is divided into two control modes, one is pulse + direction control (Y0, Y1 output pulse, Y2, Y3 output direction), and the other is forward and reverse pulse output (Y0 outputs CW pulse, Y1 outputs CCW pulse). If Y0 and Y2 are used for pulse and direction control, the control system is shown in Figure 2. If Y0 is used as the pulse output, the two-phase pulse output can be achieved by the method shown in Figure 3. The application of PLC-controlled stepper motor in the let-off device. The frequency conversion characteristics of the stepper motor controlled by PLC are used in the let-off device of the textile machine to well solve the problem of uneven tension in the warp yarn, resulting in product quality. Great progress. (1) Warp tension signal detection This device detects whether the fluctuation of warp tension meets the requirements by detecting whether the swing of the back beam exceeds the range. If the requirements are not met, the warp sending device is controlled to adjust. As shown in FIG. 4, when the tension of the warp yarn 2 fluctuates, the movable back beam 4 drives the tension sensing lever 5 to swing around the point O. When the detection piece 6 enters the effective area of the proximity switch 7, the proximity switch 7 sends a high-level signal. Based on this signal and the spindle position signal, the PLC-based controller starts the stepper motor 13 to drive the weaving shaft to send out warp yarns. The proximity switch 7 \u0026 rsquo; is a limit tension detection switch. When the warp tension is too large or too small, the detection piece 6 will block the high-level signal output from the proximity switches 7 \u0026 rsquo; and 7 \u0026 rsquo; to the controller, and the controller will turn off the loom for manual processing. The detection of the spindle position is to control the allowable time of the warp movement to avoid beat-up and ensure that the weft yarn can be tightened. human-machine interface, it can realize the visual operation of warp rewinding and weaving, change the keyboard input of the weft density, prevent driving and block, and automatically close the car alarm when abnormal conditions occur.
