Draw frame system overview
In the process of becoming a roving and a spun yarn, the sliver is stretched by a hundred times, and the unevenness in a short range will affect the quality of the yarn in a long range. The carding and drawing process before the roving is a key process to improve the unevenness of the sliver and thus significantly improve the quality of the yarn. The drawing process is in the last step of improving the unevenness of the sliver, and the effect of the autoleveling control will directly affect the yarn quality. For the autoleveling of the draw frame, the main drafting motor, the auxiliary drafting motor and the can motor need to be controlled. The effect of autoleveling depends mainly on the speed ratio between the main drafting motor and the auxiliary drafting motor. Reasonable adjustment. The can motor needs to start and stop synchronously with the main drafting motor and the auxiliary drafting motor according to a certain speed. The can motor drives the rotation of the can to ensure that the sliver is evenly wound in the can, and the speed control precision is on the sliver. There is no major impact on quality, so the rapid and precise control of the main drafting motor and the auxiliary drafting motor should be the focus of the study.
Overview of Bonner PLC and HMI
American Bonner is an internationally renowned expert in sensing and automation technology. The company's BSP01 series PLC and THM series man-machine interface are especially suitable for use in textile machinery.
The BSP01 series of programmable logic controllers are compact, high performance, feature-rich, and powerful. The A series is a high-performance controller with high computing speed, large program capacity, more application commands, and higher pulse output. And high speed counting function. The PLC can expand up to 3 communication ports and has three special network communication functions: Computerlink, Datalink and remote input and output functions. The THM man-machine interface has excellent performance, beautiful appearance and complete product range. In addition to the basic functions of monitoring, operating, and storing data, it also supports communication with most brands of controllers, PLCs, and inverters. It has a wide range of applications in all areas of factory automation and process automation.
Autoleveling control system structure
In the autoleveling control of the high-speed draw frame, the sliver is detected and the corresponding detection point reaches the shift point, and there is a delay process in the middle. The precise control of this delay process is a key factor in determining the effect of open-loop autoleveling control. This delay is much longer than the auto-leveling control cycle, so the system is a typical pure lag and large delay. This delay is related to the system speed, but the model of the system is unknown, so it is difficult to adopt the Smith predictive delay method. If the traditional timing query method is adopted, the CPU spends a lot of time on the query, the system runs inefficiently, the precision is not high, and the length of the segment that can be controlled by the autoleveling cannot be reduced. The hardware can be used to trigger interrupts under equal displacement conditions to achieve accurate speed-independent delays, greatly improve CPU efficiency, and achieve auto-leveling control of the draw frame.
The hardware structure of the draw frame autoleveling is shown in Figure 4. The control system is the master-slave control structure, the industrial computer is the main, and the PLC is the auxiliary. The main control functions: the autoleveling of the sliver is realized in the industrial computer. The PLC mainly realizes the logic control of the system, such as automatic cylinder change, which simplifies the control program of the industrial computer and improves the reliability of the system. General industrial computer, Bonner BSP01 series PLC, two servo drives and 1 inverter are controlled by communication; the touch screen and PLC communicate through serial port, the thickness of the sliver is measured by three pressure sensors, and through the industrial control computer The data acquisition card in the collection is used for autoleveling control.
Control points
The control method of the autoleveling of the draw frame can be divided into three forms: open loop, closed loop and hybrid loop. The open loop system is targeted and uniform, suitable for short segment unevenness, the closed loop system is suitable for long segment unevenness, the hybrid ring system can have long and short segment unevenness, but the mechanism is complex and the manufacturing precision is very high. The drawing process has a very important control function for controlling the yarn weight unevenness and the weight deviation index, and has high requirements for the uniformity of the uniformity.
The inspection structure of the draw frame is shown in Figure 5. R1, R2, and R3 represent the front roller (driven by the main draft motor), the rear roller (driven by the auxiliary draft motor), and the feed roller (via the transmission mechanism: The pulley and R2 maintain a constant speed ratio). S1, S2, and S3 are three sliver thickness sensors, S3 is used for open loop control, S2 is used for closed loop control, S1 is used for spectral analysis, and B is a bell mouth. Mainly through the reasonable adjustment of the speed ratio of R1 and R2 to achieve the purpose of self-leveling. In order to improve the unevenness of the sliver and facilitate the speed regulation, the speed of R1 is kept constant, and the autoleveling is achieved by adjusting the speed of R2. Because the analog motor is used to control the drafting motor, changing the voltage output to R2 can adjust the speed of R2 to achieve autoleveling.
The quality of the sliver depends on two points: one is the synchronism of the main and auxiliary drafting motors and the can motor, and the other is the reasonable speed ratio between the three. The reasonable speed between the three is obtained by the control strategy described later. The synchronization of the three depends on the fast response of the hardware and the rationality of the software. The characteristics of the hardware have been described above.
For the draw frame, the open loop control can eliminate the dead zone, but the impact on the interference from the drafting system is powerless, the stability of the system is weak; the closed loop control can suppress the influence of the interference, and the system has strong robustness. But can not eliminate the dead zone.
The control process of the draw frame is a nonlinear, dynamic process that is susceptible to external disturbances (draw waves, noise, etc.) and it is difficult to establish a unified mathematical and physical model. Therefore, in order to eliminate the dead zone, reduce the influence of interference, and improve the stability of the system, this paper adopts a hybrid control mode of short open loop and long closed loop, as shown in Figure 6.
The purpose of the open loop is to avoid the dead zone and obtain the control basic amount uo. The purpose of the closed loop is to suppress the interference, and the control correction amount Δuc is corrected to control the basic amount uo. Therefore, the open loop controller and the closed loop controller are the core of the draw frame control system.
Process configuration analysis
1. Reasonable selection of the total drafting ratio: The drawing range of the draw frame is large, 5 to 15 times. In actual production, the total drafting multiple should be reasonably selected according to the actual process conditions and quality requirements. Because the deviation of the pitch of the additional uneven fibers during the drawing process increases with the increase of the draw ratio, the increase of the shift deviation will inevitably affect the draft quality, and therefore, the actual production The selection of the total drafting ratio should not be too large. Generally speaking, 6 joints are less than 7 times, and 8 joints are more than 10 times. Otherwise, it will not be good for improving the sliver dryness.
2. The setting of the tampon quantitatively: although the drafting mechanism is more reasonable and the adaptability to the quantitative determination of the sliver is large, the quantitative configuration of the sliver should not be too large to avoid delamination between the strips due to excessive quantification of the sliver. , affect the quality of sliver.
3. Reasonable selection of the main drafting area roller spacer: usually using the cradle spring pressure form. Under the premise of ensuring sufficient pressurization, in order to minimize the floating stroke of the shorter fibers, improve the drafting quality of the main drafting zone, and improve the dryness of the sliver, the main drafting zone is slightly smaller. Mastering is appropriate. When spinning a fiber with a good length uniformity, the roller spacing of the main drafting zone can be appropriately enlarged.
4. Reasonable configuration of the rear zone roller spacer and the rear zone drafting multiple: the main function of the rear zone drafting is to make the fed strips slightly tensioned, so that the fibers are straightened, so that the strands have a certain degree of tightness into the middle zone, and then After entering the main drafting zone, the central zone can stably draw and improve the drafting quality. The draw ratio in the back zone and the back gauge of the back zone have a significant influence on the sliver dryness, and can be optimally combined with the pressurization pressure, fiber properties and the type of the spun product.
5. Select the position of the pressure bar: the position of the pressure bar is determined by the amount of forward and backward movement of the two rubber rollers. When the process is actually configured, the position of the pressure bar can be optimized according to the production conditions.
6. Reasonable determination of the entrance size of the cotton tray: The size of the entrance of the cotton tray should be determined according to the quantity of the sliver and the number of feeds. In general, 8 to 14 mm when combined, and 9 to 13 mm when 6 are combined. It can be adjusted at any time according to the actual situation to ensure that the feeding sliver does not overlap or is not scattered.
to sum up:
As a leader in the automation industry, Bonner will use decades of product development and application experience, combining Bonner's traditional advantages: photoelectric sensor series, industrial intelligent indicator series, etc., with Bonner PLC controller and HMI people. The machine interface is integrated with these products, such as detection and signal transmission, to provide users with simple, complete, powerful, stable, reliable, safe, flexible and open solutions, widely used in water treatment, metallurgy, oil and gas, coal, cement, printing, In the demanding on-site environment of steel, electronics, automobiles, subways, textile machinery, etc., it provides complete, simple, open, integrated and flexible automation solutions for machine builders and end users.
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