Winding tension control system

Abstract

The invention discloses a winding tension control system. The winding tension control system comprises a tension acquisition part and a motion control part, the tension acquisition part comprises a tension sensor, a tension amplifier and an analog quantity acquisition module; the motion control part comprises a PLC control module and a servo control module, the PLC control module further comprises a tension compensation unit, and controllable compensation of control tension is achieved through integration and differentiation; the PLC control module further comprises a rolling diameter calculator, the rolling diameter calculator compensates tension changes caused by radius changes, the tension changes caused by winding speed changes are compensated in an acceleration compensation mode, and the tension changes caused by inertia changes are compensated in an inertia compensation mode. According to the winding tension control system, the tension change problem caused by radius change, winding speed change and inertia change can be solved, higher adaptability of winding tension control is achieved, and therefore the dynamic performance of the winding process is guaranteed.

Description

Technical Field

[0001] The present invention relates to a winding tension control system, in particular to a winding tension control system suitable for winding conveying systems in industrial equipment such as coating, IC manufacturing, printing, and fiber winding, and belongs to the technical field of winding control. Background Art

[0002] The winding conveyor system is one of the common basic systems in industrial equipment such as coating, IC manufacturing, printing, and fiber winding. As the winding conveyor system develops towards high speed and high precision, tension control technology is extremely important. Taking the winding conveyor system of a vacuum coating machine as an example, due to the complex structure and many influencing factors of a large-scale winding conveyor system, the system parameters have strong coupling, nonlinearity, time-varying and uncertainty under different working conditions; among them, the winding tension control technology is the key technology in the vacuum coating machine. The accuracy and stability of the winding tension control directly affect the adaptability of the vacuum coating machine to the raw material film and the quality of the product. In the prior art, winding tension control usually uses a variety of methods including PID control to achieve precise control. On the one hand, the PID controller first compares the real-time data (such as temperature, pressure, speed, etc.) fed back by the sensor with the set target value and calculates the deviation. Then the PID controller adjusts the action of the actuator according to the deviation (such as adjusting the valve opening, motor speed, etc.) to gradually approach the target value. On the other hand, it usually includes setting appropriate PID controller parameters such as proportional coefficient, integral time, differential time, etc., which can adjust the control ratio through the proportional coefficient, adjust the deviation through the integral time, and suppress overshoot through the differential time. However, since the winding conveying system is a complex control object, especially in the process of film winding and unwinding, the dynamic characteristics of the winding and unwinding device usually change greatly, and it is difficult to ensure the dynamic performance of the winding process by using an ordinary PID controller, and it is difficult to ensure the stability of the dynamic characteristics under various usage conditions. A more adaptable control strategy is required. Summary of the invention

[0003] In view of the problems existing in the above-mentioned prior art, the present invention provides a winding tension control system, which can solve the tension change problem caused by radius change, winding speed change and inertia change, and thus achieve stronger adaptability of winding tension control, thereby ensuring the dynamic performance of the winding process.

[0004] To achieve the above purpose, the winding tension control system includes a tension acquisition part and a motion control part; the tension acquisition part includes a tension sensor, a tension amplifier and an analog quantity acquisition module, the tension sensor transmits the millivolt voltage signal to the tension amplifier, and the tension amplifier transmits the collected signal to the analog quantity acquisition module in the form of analog quantity; the motion control part includes a PLC control module and a servo control module, the PLC control module is used to convert the collected signal into a tension value, and after comparing it with the set comparison value, adopt a PID algorithm to output it to the servo control module, and the servo control module is used to control the tension change of each roller according to the tension control signal fed back by the PLC control module; it is characterized in that

[0005] The PLC control module also includes a tension compensation unit, which realizes controllable compensation of the control tension through integration and differentiation; the PLC control module also includes a reel diameter calculator, which compensates for the tension change caused by the radius change, uses acceleration compensation to compensate for the tension change caused by the winding speed change, and uses inertia compensation to compensate for the tension change caused by the inertia change.

[0006] Furthermore, based on the PID control principle, an adaptive PID algorithm is introduced, and the roll diameter setting, speed gradient algorithm and zero-speed tension holding are added: the roll diameter setting process is to output the set angular velocity through the input roll diameter value, and the angular velocity is adjusted by controlling the servo motor; the speed gradient algorithm realizes speed gradient through the corresponding algorithm method of decreasing or increasing the angular velocity at fixed time intervals; zero-speed tension holding is to keep the reeling and unwinding tension constant at zero speed.

[0007] Furthermore, the parameters of the adaptive PID algorithm are set as follows:

[0008] u k =K p ·e k +K j j=0+ΣK e j+K d (e k -e k-1 )

[0009] Where: u k is the output at time k, K p is the proportionality coefficient, e k is the deviation at time k, K i is the integration coefficient, K d is the differential coefficient, K j is a constant coefficient and j is a constant.

[0010] Furthermore, the tension sensor transmits the signal in the form of a millivolt voltage signal to the tension amplifier, and the tension amplifier amplifies the signal and transmits it to the analog quantity acquisition module in the form of an analog quantity.

[0011] Furthermore, before winding the base film, the tension sensor must first be zeroed and the span adjusted:

[0012] When calibrating the tension sensor to zero, when the roller being calibrated is not subjected to any external force, perform the zero span setting at the tension amplifier end. When the tension sensor displays that the zero span is completed, the tension sensor zero calibration is completed.

[0013] When adjusting the span of the tension sensor, first wind the rope at the end close to the tension sensor according to the film-threading direction of the winding, hang a weight at one end of the rope and keep the weight suspended in the air, and fix the other end of the rope on the roller shaft of a redirecting roller at the far end (the distance from the roller shaft where the tension sensor is located is greater than or equal to 6 rollers). After the weight is in a stable static suspended state, perform span adjustment on the tension amplifier when the roller is not subjected to any external force, and input the total weight of the weight as the span value.

[0014] Furthermore, a redirecting roller at the far end refers to a redirecting roller that is greater than or equal to 6 redirecting rollers away from the roller axis where the tension sensor is located.

[0015] Compared with the existing technology, the present winding tension control system can compensate for the tension change problem caused by radius change by adopting a winding diameter calculator, and solve the tension change problem caused by winding speed change by adopting acceleration compensation, while inertia compensation can solve the tension change problem caused by inertia change of the film collecting roller and the film unwinding roller. Compared with the conventional PID control strategy, the present winding tension control system can achieve stronger adaptability, thereby ensuring the dynamic performance of the winding process. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of winding of an embodiment of the present invention. DETAILED DESCRIPTION

[0017] The present invention will be further described below in conjunction with the accompanying drawings.

[0018] The winding tension control system comprises a tension acquisition part and a motion control part.

[0019] The tension collection part includes a tension sensor, a tension amplifier and an analog quantity collection module. The tension sensor transmits the millivolt voltage signal to the tension amplifier, and the tension amplifier transmits the collected signal to the analog quantity collection module in the form of analog quantity.

[0020] The motion control part includes a PLC control module and a servo control module. The PLC control module is used to convert the collected signal into a tension value, and after comparing it with the set comparison value, it uses the PID algorithm to output it to the servo control module. The servo control module is used to control the tension change of each roller according to the tension control signal fed back by the PLC control module. The PLC control module also includes a tension compensation unit, which realizes controllable compensation of the control tension through integration and differentiation. The PLC control module also includes a roll diameter calculator, which compensates for the tension change caused by the radius change, and uses acceleration compensation to solve the tension change problem caused by the change in winding speed, while inertia compensation solves the tension change problem caused by the inertia change of the film collection roller and the film release roller.

[0021] like Figure 1 In the embodiment shown, the raw material PET film or PE film is put in from the unwinding roller, redirected by the triple roller and then bypasses the redirecting roller equipped with the unwinding control tension sensor, and then bypasses the process roller A after passing through several follow-up redirecting rollers. After the film is plated at the process roller A, it switches to the other side for film coating at the process roller B, and after the film is plated at the process roller B, it passes through several middle follow-up redirecting rollers and then bypasses the process roller C. After the film is plated at the process roller A, the texture of the film changes because the surface of the film has been plated with copper ions. That is to say, the tension before the process roller A and the tension after the process roller A will change, thereby constantly affecting the tension fluctuation of the unwinding. The PID algorithm is used to control the unwinding tension to adjust the tension of the process roller A to stabilize the film. On the process roller C, the same surface as the previous process roller A is plated again, and then the process roller D is bypassed, and the same surface as the process roller B is plated again on the process roller D. During the coating process, the speeds of the four process rollers A, B, C, and D are the same. After the process roller D is plated (twice on both sides), it is wound into the winding roller through several follow-up redirection rollers, and finally formed into a film and made into a product on the winding roller. On the one hand, the tension and the film transmission speed should be kept at a constant value. Once the speed fluctuates, the thickness of the compound generated by the magnetron during the coating process will be inconsistent on the film. On the other hand, inappropriate tension will cause wrinkles on the film or even cause the film to break, and if the tension of the film is too small for the roller, it will cause the film to slip. Therefore, the winding tension control system must ensure that the speed and tension are controlled at the same time, but because the winding tension control system is composed of many roller subsystems, the subsystems affect each other, resulting in a very complex film tension control system. The change of tension value in a certain area will cause the tension change of the adjacent part, which will then cause speed fluctuations and other problems.

[0022] To solve the problem in the above specific scenario, a flange-fixed tension sensor with a measuring range of 0 to 500N is installed at a position where the interval between the unwinding rollers is no more than 3 follower redirecting rollers. The tension sensor uses electronic millivolt pressure difference detection and transmits the collected signal to the tension amplifier. A tension sensor is also set at the corresponding position on the unwinding roller side.

[0023] Before winding the base film, the tension sensor must first be calibrated and the span adjusted. Before calibrating the sensor and adjusting the span, fix the two flange-fixed tension sensors at both ends of the redirecting roller shaft. During installation, ensure that the roller shaft is not subjected to stress in different directions.

[0024] To calibrate the tension sensor, make sure that the roller being calibrated is not subject to any external force during the calibration process. Perform the zero span setting at the tension amplifier end. When the tension sensor displays zero span, the tension sensor zero calibration is completed.

[0025] To adjust the span of the tension sensor, prepare four 10kg weights and a rope. First, wind the rope at the end close to the tension sensor according to the film-threading direction of the winding. Hang four weights on one end of the rope and make the weights suspended in the air. Fix the other end of the rope on the roller axis of a farther redirecting roller (the distance from the roller axis where the tension sensor is located is greater than or equal to 6 rollers). After the weights are in a static suspended state and are stable, no external force can affect any roller axis. Perform span adjustment on the tension amplifier. Enter the total weight of the weights as the span value. In this embodiment, the total weight of the weights is 40kg×9.8N / kg=392N.

[0026] After all tension rollers equipped with tension sensors are calibrated, the base film is threaded and both sides of the rewinding and unwinding are wound, and the parameters of the winding tension PID are set (K p , K i , K d ).

[0027] The proportional link can proportionally reflect the deviation signal of the control system, that is, the output is proportional to the input deviation, which can be used to reduce the deviation of the system. The formula of this link is as follows:

[0028] u=K p ·e

[0029] Where: u is the output, K p is the proportionality coefficient and e is the deviation.

[0030] Assume that the winding tension needs to be adjusted to 100N, but the actual tension is 90N. The deviation e is 10. From the formula of the proportional link, it can be seen that when e is determined, K pThe larger the value, the greater the output u, that is, the greater the adjustment force of the tension, so that the target tension can be reached faster. p When the deviation e is larger, the output u is larger. It can be seen that in the proportional link, the proportional coefficient K p The larger the deviation e is, the shorter the time it takes for the tension adjustment to eliminate the deviation is.

[0031] In actual applications, if only the proportional link is controlled, it may cause static error problems in the system. Static error refers to the deviation between the target value and the measured value when the system control process tends to be stable. The integral link can integrate the deviation e. As long as there is a deviation, the integral link will continue to work, mainly used to eliminate static errors and improve the system's zero difference. After the integral link is introduced, the formula of the proportional + integral link is as follows:

[0032] u=K p e+K i ·Σe

[0033] Where: K i is the integration coefficient.

[0034] Assume that the winding tension needs to be adjusted to 100N, but the actual tension is 90N. The deviation e is 10, K p For a fixed value, if the output at this time can increase the large winding tension by 10N within 11 seconds, and the influence of the coating can reduce the winding tension by 10N within 1 second, that is to say, the effect of the output u is just offset by the external influence, which makes the deviation e always exist. As long as there is a deviation in the system, the integral link will continue to accumulate the deviation e. When the system deviation e is 0, it means that the target value has been reached. At this time, the accumulated deviation no longer changes, but the integral link is still in effect (often the greatest effect at this time), which can easily cause overshoot. Therefore, it is necessary to introduce a differential link to weaken the output in advance and suppress the occurrence of overshoot.

[0035] The role of the differential link is to reflect the changing trend of the system deviation, or the rate of change. It can introduce an effective correction signal in advance before the error occurs, which is conducive to improving the rapidity of the output response, reducing the overshoot of the controlled quantity and increasing the stability of the system. After the differential link is introduced, the formula of the proportional + integral + differential link is as follows:

[0036] u k =K p ·e k +K j j = 0 + ∑ K e j+K d (e k -e k-1 )

[0037] Where: u k is the output at time k; K p is the proportionality coefficient; e k is the deviation at time k; K i is the integral coefficient; K d is the differential coefficient; K j is a constant coefficient, j is a constant and has a fixed value for a specific system.

[0038] The differential link helps the system reduce overshoot, overcome oscillation, speed up the system response, and reduce the adjustment time, thereby improving the dynamic performance of the system. However, if the differential time constant is too large, the system will become unstable.

[0039] Based on the above PID control principle, in this embodiment, an adaptive PID algorithm is introduced, and after adding the roll diameter setting, speed gradient algorithm and zero-speed tension maintenance, a closed-loop tension control system with compensation technology and programmable controller as the control core, servo motor as the tension actuator, tension sensor to feedback film tension changes in real time can be realized. The details are as follows:

[0040] The winding diameter setting process is to output the set angular velocity through the input winding diameter value, and adjust the angular velocity by controlling the servo motor to keep the winding linear speed stable.

[0041] The speed gradient algorithm mainly realizes speed gradient by decreasing or increasing the angular velocity at a fixed time interval. The speed gradient adjustment module connects the data of the coil diameter input and the input linear velocity, converts the linear velocity into angular velocity through the internal calculation formula (this is the prior art and will not be described in detail), and calculates the angular velocity that should be increased at a fixed time interval based on the change data, and outputs it to the servo motor controller, thereby controlling the servo motor to change the speed and control the angular velocity change to ensure that the linear velocity is stable within the set speed range.

[0042] Zero speed tension maintenance means that at zero speed (that is, when the winding line speed is zero), the tension of the unwinding and rewinding is kept constant (user set value), so that the film is in a tightened state without relaxation. When starting the process, you only need to give the line speed to operate. No need to adjust the tension from the beginning, saving time. The zero speed tension maintenance module monitors the winding mechanism and starts when the speed is detected to be 0. The output signal control keeps the unwinding and rewinding tension constant and maintains it according to the input set tension.

[0043] The above process can be realized by setting the preset module in the controller of the vacuum coating equipment. For example, a corresponding module, a roll diameter setting module, is added, the output end is connected to the controller of the servo motor, an input box for inputting the roll diameter is added on the control panel, and the corresponding angular velocity control signal is output to the servo motor controller through the input roll diameter value, thereby controlling the size and change of the angular velocity.

[0044] The winding tension control system adopts a winding diameter calculator to compensate for the tension change caused by radius change, and adopts acceleration compensation to solve the tension change problem caused by winding speed change. Inertia compensation can solve the tension change problem caused by inertia changes of the film taking-up roller and the film unwinding roller. Compared with the conventional PID control strategy, it can achieve stronger adaptability of winding tension control, thereby ensuring the dynamic performance of the winding process.

Claims

1. A winding tension control system, comprising a tension acquisition part and a motion control part; the tension acquisition part comprises a tension sensor, a tension amplifier and an analog quantity acquisition module, the tension sensor acquires tension information and transmits the signal to the tension amplifier, the tension amplifier amplifies the signal and transmits it to the analog quantity acquisition module; the motion control part comprises a PLC control module and a servo control module, the PLC control module is used to convert the acquired signal into a tension value, and after comparing it with a set comparison value, adopts a PID algorithm to output it to the servo control module, the servo control module is used to control the tension change of each roller according to the tension control signal fed back by the PLC control module; it is characterized in that The PLC control module also includes a tension compensation unit, which realizes controllable compensation of the control tension through integration and differentiation; the PLC control module also includes a reel diameter calculator, which compensates for the tension change caused by the radius change, uses acceleration compensation to compensate for the tension change caused by the winding speed change, and uses inertia compensation to compensate for the tension change caused by the inertia change.

2. The winding tension control system according to claim 1, characterized in that: Based on the PID control principle, an adaptive PID algorithm is introduced, and the roll diameter setting, speed gradient algorithm and zero-speed tension holding are added: the roll diameter setting process is to output the set angular velocity through the input roll diameter value, and adjust the angular velocity by controlling the servo motor; the speed gradient algorithm realizes speed gradient through the corresponding algorithm method of decreasing or increasing the angular velocity at fixed time intervals; zero-speed tension holding is to keep the rewinding and unwinding tension constant at zero speed.

3. The winding tension control system according to claim 2, characterized in that: The parameters of the adaptive PID algorithm are set as follows: u k =K p ·e k +K j ·j=0+∑K e j+K d (e k -e k-1 ) Where: u k is the output at time k, K p is the proportionality coefficient, e k is the deviation at time k, K i is the integration coefficient, K d is the differential coefficient, K j is a constant coefficient and j is a constant.

4. The winding tension control system according to claim 1, characterized in that: The tension sensor transmits the signal in the form of a millivolt voltage signal to the tension amplifier, and the tension amplifier amplifies the signal and transmits it to the analog quantity acquisition module in the form of an analog quantity.

5. The winding tension control system according to claim 1, characterized in that: Before winding the base film, the tension sensor must first be zeroed and span adjusted: When calibrating the tension sensor to zero, when the roller being calibrated is not subjected to any external force, perform the zero span setting at the tension amplifier end. When the tension sensor displays that the zero span is completed, the tension sensor zero calibration is completed. When adjusting the span of the tension sensor, first wind the rope at the end close to the tension sensor according to the film-threading direction of the winding, hang a weight at one end of the rope and keep the weight suspended in the air, and fix the other end of the rope on the roller shaft of a redirecting roller at the far end (the distance from the roller shaft where the tension sensor is located is greater than or equal to 6 rollers). After the weight is in a stable static suspended state, perform span adjustment on the tension amplifier when the roller is not subjected to any external force, and input the total weight of the weight as the span value.

6. The winding tension control system according to claim 5, characterized in that: A far-end redirecting roller refers to a redirecting roller that is greater than or equal to 6 redirecting rollers away from the roller axis where the tension sensor is located.

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