Cascade control method for a film blowing machine and a film blowing machine using the method

Abstract

The present invention provides a cascade control method for a film blowing machine, comprising: setting a set speed Vup_set of an upper haul-off roll (S10); determining an actual speed Vup_act of the upper haul-off roll (S20); calculating an actual speed Vlow_act of a lower haul-off roll according to the actual speed Vup_act of the upper haul-off roll and a first set tension Tlow_set_1 of a lower haul-off tension roll determined by a lower haul-off PID controller (S30); calculating an actual speed Vwind_act of a winding roll according to the actual speed Vlow_act of the lower haul-off roll and a second set tension Twind_set_2 of a winding tension roll determined by a winding PID controller (S40). The present invention realizes synchronous adjustment of the actual speeds of the lower haul-off and winding by the upper haul-off, reduces the tension fluctuations of the lower haul-off and winding when adjusting the upper haul-off speed, and maintains the stability of the tension. The present invention also provides a film blowing machine using this cascade control method.

Description

Technical Field

[0001] The present invention relates to a cascade control method, and more particularly to a cascade control method for a film blowing machine and a film blowing machine using the method. Background Art

[0002] A film blowing machine is a machine that heats and melts plastic particles and then blows them into a film. A film blowing machine generally includes an upper traction mechanism, a lower traction mechanism, and a winding mechanism. There are two consecutive tension controls between the upper traction and the lower traction, and between the lower traction and the winding mechanism of the film blowing machine. Adjusting one of the tensions will affect the other tension, causing tension oscillation, resulting in the film being stretched and deformed, or the tension being relaxed, causing uneven winding. Summary of the Invention

[0003] The purpose of the present invention is to provide a cascade control method for a film blowing machine, which can keep the tension between each mechanism constant.

[0004] The present invention provides a cascade control method for a film blowing machine. The film blowing machine includes an upper traction roller, a lower traction roller, a lower traction tension roller, a lower traction PID controller, a winding roller, a winding tension roller, and a winding PID controller. The cascade control method for a film blowing machine sets the set speed Vup_set of the upper traction roller; determines the actual speed Vup_act of the upper traction roller; calculates the actual speed Vlow_act of the lower traction roller according to the actual speed Vup_act of the upper traction roller and the first set tension Tlow_set_1 of the lower traction tension roller determined by the lower traction PID controller; and calculates the actual speed Vwind_act of the winding roller according to the actual speed Vlow_act of the lower traction roller and the second set tension Twind_set_2 of the winding tension roller determined by the winding PID controller.

[0005] The cascade control method for a film blowing machine provided by the present invention can make the tensions of the upper and lower traction and winding form a cascade relationship on the basis of speed synchronization between the upper traction, the lower traction, and the winding, meeting the requirement of keeping their tensions constant when adjusting the traction speed or the tension size. In this way, the film blown by the film blowing machine will not be deformed and the winding will be flat.

[0006] In a schematic embodiment of a cascade control method for a film blowing machine, the actual speed Vup_act of the upper traction roller is determined by the following steps: the actual speed Vup_act of the upper traction roller is determined by increasing or decreasing with a ramp function based on the set speed Vup_set of the upper traction roller, that is: Vup_act = kf(Vset), where k is a constant within 0.01 - 5.

[0007] In a schematic embodiment of a cascade control method for a film blowing machine, the actual speed Vlow_act of the lower take-up roller is calculated by the following steps: Assign the actual speed Vup_act of the upper take-up roller to the set reference speed Vlow_set_ref of the lower take-up roller; Set the first set tension Tlow_set_1; Determine the first PID speed Vt1_pid of the lower take-up tension roller according to the first set tension Tlow_set_1, where the first PID speed is a function of the first set tension, that is: Vt1_pid = f(Tlow_set_1); and Determine the actual speed Vlow_act of the lower take-up roller according to the set reference speed Vlow_set_ref of the lower take-up roller and the first PID speed Vt1_pid, that is: Vlow_act = Vwind_set_ref +

[0008] Vt1_pid. The actual speed of the lower take-up roller is based on the actual speed of the upper take-up roller. On this basis, the output of the tension PID control is superimposed to realize the speed adjustment of the lower take-up, ensuring the stability of the overall tension control of the film blowing machine.

[0009] In a schematic embodiment of a cascade control method for a film blowing machine, the actual speed Vwind_act of the winding roller is calculated by the following steps: Assign the actual speed Vlow_act of the lower take-up roller to the set reference speed Vwind_set_ref of the winding roller; Set the second set tension Twind_set_2; Determine the second PID speed Vt2_pid of the winding PID controller according to the second set tension Twind_set_2, where the second PID speed is a function of the second set tension, that is: Vt2_pid = f(Tlow_set_2); and Determine the actual speed Vwind_act of the winding roller according to the set reference speed Vwind_set_ref of the winding roller and the second PID speed Vt2_pid, that is Vwind_act = Vwind_set_ref +

[0010] Vt2_pid. The actual speed of the winding roller is based on the actual speed of the lower take-up roller. On this basis, the output of the tension PID controller is superimposed to realize the winding speed adjustment, ensuring that the actual speed of the winding roller is synchronized with the actual speed of the lower take-up roller, reducing the deviation of the tension PID control, and enhancing the stability of the winding tension.

[0011] The present invention provides a film blowing machine controlled by the above cascade control method, including: a pair of upper take-up rollers, a pair of lower take-up rollers, a pair of winding rollers, a lower take-up tension roller located between the upper take-up roller and the lower take-up roller, a lower take-up PID controller for controlling the lower take-up tension, a winding tension roller located between the lower take-up roller and the winding roller, and a winding PID controller for controlling the winding tension roller.

[0012] In a schematic embodiment of the film blowing machine, the film blowing machine further includes a pair of intermediate drawing rollers, and the intermediate drawing rollers are located between the upper drawing roller and the lower drawing tension roller.

[0013] The film blowing machine provided by the present invention satisfies constant tension through the cascading relationship among the upper drawing, the lower drawing and the winding, and the blown film will not be deformed and the winding is flat. Brief Description of the Drawings

[0014] The present invention will be described in detail below in conjunction with the drawings and specific embodiments. Among them:

[0015] Figure 1 Shown is a schematic diagram of a schematic embodiment of the film blowing machine;

[0016] Figure 2 Shown is a schematic diagram of a schematic embodiment of the cascading control method for the film blowing machine;

[0017] Figure 3 Shown is a schematic diagram of a schematic embodiment of the cascading control method for the film blowing machine;

[0018] Figure 4 Shown is a schematic diagram of a schematic embodiment of the cascading control method for the film blowing machine;

[0019] Figure 5 Shown is a schematic diagram of another schematic embodiment of the film blowing machine. Detailed Description of the Embodiment

[0020] In order to have a clearer understanding of the technical features, purposes and effects of the invention, the specific embodiments of the present invention will now be described with reference to the drawings. In the drawings, the same reference numerals represent components with the same or similar structures but the same functions.

[0021] In this document, "schematic" means "serving as an example, instance or illustration", and any illustration or embodiment described as "schematic" in this document should not be interpreted as a more preferred or more advantageous technical solution.

[0022] In this document, "first", "second", etc. are only used for distinguishing from each other, rather than indicating their importance.

[0023] The various numbers in this document are not strict mathematical and / or geometric limitations, and also include the errors that can be understood by those skilled in the art and are allowed in manufacturing or using, etc.

[0024] Figure 1The figure shows a schematic diagram of a schematic embodiment of a blown film machine. The blown film machine includes an upper traction roller 10, a lower traction roller 20, a lower traction tension roller 22, a lower traction PID controller 24, a winding roller 30, a winding tension roller 32, and a winding PID controller 34. The lower traction tension roller 22 is located between the upper traction roller 10 and the lower traction roller 20. The lower traction PID controller 24 is used to control the lower traction tension roller. The winding tension roller 32 is located between the lower traction roller 20 and the winding roller 30. The winding PID controller 34 is used to control the winding tension roller. When the blown film machine is working, the film sequentially passes through the upper traction roller 10, the lower traction tension roller 22, the lower traction roller 20, the winding tension roller, and the winding roller.

[0025] Figure 2 The figure shows a schematic diagram of a schematic embodiment of a cascade control method for a blown film machine. As Figure 2 shown, the cascade control method for a blown film machine includes:

[0026] S10: Set the set speed Vup_set of the upper traction roller;

[0027] S20: Determine the actual speed Vup_act of the upper traction roller. The actual speed Vup_act of the upper traction roller is determined by increasing or decreasing based on the set speed Vup_set of the upper traction roller with a ramp function, that is: Vup_act = kf(Vset), where k is a constant within 0.01 - 5;

[0028] S30: Calculate the actual speed Vlow_act of the lower traction roller according to the actual speed Vup_act of the upper traction roller and the first set tension Tlow_set_1 of the lower traction tension roller determined by the lower traction PID controller;

[0029] S40: Calculate the actual speed Vwind_act of the winding roller according to the actual speed Vlow_act of the lower traction roller and the second set tension Twind_set_2 of the winding tension roller determined by the winding PID controller.

[0030] As Figure 2 shown, by using the actual speed of the upper traction roller as a reference for the set speed of the lower traction roller, and the actual speed of the lower traction roller as a reference for the speed of the winding roller, a basis for speed synchronization can be established among the three. Therefore, the tension control of the lower traction roller and the winding roller forms a cascade relationship based on the basis of speed synchronization. When adjusting the traction speed or tension arbitrarily, the influence among the three can be reduced, and the stability of the system tension control can be enhanced.

[0031] Figure 3 The figure shows a schematic diagram of a schematic embodiment of a cascade control method for a blown film machine. Figure 3Steps for explaining the actual speed Vlow_act of the lower draw roll. As Figure 3 shown, the cascade control method for a blown film machine includes:

[0032] After step S20, S31 is carried out: Assign the actual speed Vup_act of the upper draw roll to the set reference speed Vlow_set_ref of the lower draw roll;

[0033] S32: Set the first set tension Tlow_set_1;

[0034] S33: Determine the first PID speed Vt1_pid of the lower draw tension roll according to the first set tension Tlow_set_1, where the first PID speed is a function of the first set tension, that is:

[0035] Vt1_pid = f(Tlow_set_1);

[0036] S34: Determine the actual speed Vlow_act of the lower draw roll according to the set reference speed Vlow_set_ref of the lower draw roll and the first PID speed Vt1_pid, that is: Vlow_act = Vlow_set_ref + Vt1_pid.

[0037] Proceed to step S40.

[0038] Steps S10, S20 and S40 are as Figure 2 shown and will not be elaborated here.

[0039] Figure 4 shown is a schematic diagram of a schematic implementation manner of the cascade control method for a blown film machine. Figure 4 Steps for explaining the determination of the actual speed Vwind_act of the winding roll. As Figure 4 shown, the cascade control method for a blown film machine includes:

[0040] After step S30, S41 is carried out: Assign the actual speed Vlow_act of the lower draw roll to the set reference speed Vwind_set_ref of the winding roll;

[0041] S42: Set the second set tension Twind_set_2;

[0042] S43: Determine the second PID speed Vt2_pid of the winding PID controller according to the second set tension Twind_set_2, where the second PID speed is a function of the second set tension, that is: Vt2_pid = f(Tlow_set_2);

[0043] S44: Determine the set reference speed Vwind_set_ref of the winding roller and the second PID speed Vt2_pid as the actual speed Vwind_act of the winding roller, i.e., Vwind_act = Vwind_set_ref + Vt2_pid.

[0044] Steps S10, S20, and S40 are as Figure 2 shown and will not be elaborated here.

[0045] By Figure 2-4 the steps shown, the cascade control method for the blown film machine can minimize the situation where the tension adjustment between the traction and winding completely depends on the output of their respective tension PID controls when adjusting the traction speed or tension. When the traction and winding speeds are basically synchronized to form a cascade, the PID fine-tuning ensures the stable control of their respective tensions, and at the same time, the purpose of synchronous speed regulation of the traction and winding is satisfied.

[0046] Figure 5 Shown is a schematic diagram of another schematic embodiment of the blown film machine. As Figure 5 shown, the blown film machine in this embodiment is different from the Figure 1 blown film machine shown in that: the blown film machine further includes a pair of intermediate traction rollers 40, and the intermediate traction rollers 40 are located between the upper traction roller 10 and the lower traction tension roller 22.

[0047] It should be understood that although this specification is described according to each embodiment, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0048] The series of detailed descriptions listed above are only specific descriptions of the feasible embodiments of the present invention, and they are not intended to limit the protection scope of the present invention. Any equivalent implementation or change made without departing from the technical spirit of the present invention, such as the combination, division, or repetition of features, shall be included in the protection scope of the present invention.

Claims

1. A cascade control method for a blown film machine, the blown film machine comprising an upper traction roller (10), a lower traction roller (20), a lower traction tension roller (22), a lower traction PID controller (24), a winding roller (30), a winding tension roller (32) and a winding PID controller (34), characterized in that The described cascade control method includes: Setting the set speed Vup_set of the upper traction roller; Determining the actual speed Vup_act of the upper traction roller; Calculating the actual speed Vlow_act of the lower traction roller according to the actual speed Vup_act of the upper traction roller and the first set tension Tlow_set_1 of the lower traction tension roller determined by the lower traction PID controller; and Calculating the actual speed Vwind_act of the winding roller according to the actual speed Vlow_act of the lower traction roller and the second set tension Twind_set_2 of the winding tension roller determined by the winding PID controller; where The actual speed Vup_act of the upper traction roller is determined by the following steps: The actual speed Vup_act of the upper traction roller is determined by increasing or decreasing based on the set speed Vup_set of the upper traction roller with a ramp function, that is: Vup_act = kf(Vset); The actual speed Vlow_act of the lower traction roller is calculated by the following steps: Assigning the actual speed Vup_act of the upper traction roller to the set reference speed Vlow_set_ref of the lower traction roller; Setting the first set tension Tlow_set_1; Determining the first PID speed Vt1_pid of the lower traction tension roller according to the first set tension Tlow_set_1; and Determining the actual speed Vlow_act of the lower traction roller according to the set reference speed Vlow_set_ref and the first PID speed Vt1_pid of the lower traction roller, that is: Vlow_act = Vlow_set_ref + Vt1_pid; The actual speed Vwind_act of the winding roller is calculated by the following steps: Assigning the actual speed Vlow_act of the lower traction roller to the set reference speed Vwind_set_ref of the winding roller; Setting the second set tension Twind_set_2; Determining the second PID speed Vt2_pid of the winding PID controller according to the second set tension Twind_set_2; and Determining the set reference speed Vwind_set_ref and the second PID speed Vt2_pid of the winding roller as the actual speed Vwind_act of the winding roller, that is Vwind_act = Vwind_set_ref + Vt2_pid.

2. The cascade control method according to claim 1, wherein k is a constant within 0.01 - 5.

3. The cascade control method according to claim 1, characterized in that, The The first PID speed is a function of the first set tension, that is: Vt1_pid = f(Tlow_set_1).

4. The cascade control method according to claim 1, characterized in that, The second PID speed is a function of the second set tension, that is: Vt2_pid = f(Tlow_set_2).

5. A blown film machine using the cascade control method according to any one of claims 1 to 4, including: A pair of upper traction rollers (10); A pair of lower traction rollers (20); A pair of winding rollers (30); The lower drawing tension roller (22) located between the upper drawing roller (10) and the lower drawing roller (20); The lower drawing PID controller (24) for controlling the lower drawing tension roller; The winding tension roller (32) located between the winding roller (30) of the lower drawing roller (20); and The winding PID controller (34) for controlling the winding tension roller.

6. The blown film machine according to claim 5, characterized in that The blown film machine further includes a pair of intermediate drawing rollers (40), and the intermediate drawing rollers (40) are located between the upper drawing roller (10) and the lower drawing tension roller (22).

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