Speed ​​control device

Abstract

To provide a speed control device which suppresses tension fluctuation generated according to elongation of paper after coating.SOLUTION: A speed control device comprises: torque reference generation means which generates a torque reference so that a speed feedback value of an electric motor follows a preset first speed reference to supply to an inverter driving the electric motor; torque reference setting means which sets a first torque reference, output by the torque reference generation means immediately before a coating command is made active, as a second torque reference at coating; and torque correction value calculation means which calculates a first speed correction value so that the torque reference output by the torque reference generation means follows the second torque reference, and outputs a first correction-speed reference, computed by adding the calculated value to the first speed reference, to the torque reference generation means.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Embodiments of the present invention relate to a speed control device for controlling the tension of coated paper in a paper machine.

Background Art

[0002] In a paper machine, acceleration torque, mechanical loss torque, and tension component torque for maintaining the tension between rolls are required as the drive torque of the rolls. If tension fluctuates and slack occurs, there is a risk that it will lead to reduced product quality and paper breakage.

[0003] In order to convey paper without tension fluctuation, control for suppressing tension fluctuation between rolls is performed using special equipment such as a dancer roll and a tension detector (Patent Document 1). In addition, during winding, since the acceleration torque and the mechanical loss torque can be regarded as constant for constant speed driving, pseudo tension control (hereinafter referred to as torque control) for adjusting the tension component torque by controlling the torque reference may be performed. In these controls, correction is performed by an operator performing feedback control to a preset target value.

[0004] In a paper machine system, between the coating unit that applies a coating material to paper and the subsequent rolls, the paper stretches due to the moisture contained in the coating material. When stretching occurs, it becomes slack, leading to a decrease in the tension component torque. Therefore, based on experience, the operator predicts the amount of paper stretching and speeds up the subsequent rolls in advance at the start of coating to perform control to suppress slack (hereinafter referred to as stretching amount prediction correction control), but there is an appropriate value depending on the paper type, and appropriate parameters need to be set so that slack does not occur.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

[0006] Based on the experience of skilled operators, the elongation during coating is automatically adjusted using elongation prediction and correction control. However, the optimal value differs depending on the product type, and errors can occur in the elongation prediction and correction control, so fine-tuning by manual operation by the operator is ultimately required.

[0007] While tension detectors are not placed on the wet paper in the coating section, a dancer roll may be placed on the paper in the section preceding the coating to automatically suppress tension fluctuations. However, depending on the paper type, differences in the pressure of the coating roll or the paper thickness may cause tension to be cut before and after the coating roll, making it impossible to correct the elongation in the desired area using the dancer roll.

[0008] Embodiments of the present invention have been made to solve the above-mentioned problems and aim to provide a speed control device that suppresses tension fluctuations that occur in accordance with the elongation of paper after coating. [Means for solving the problem]

[0009] Embodiments of the present invention include a torque reference generation means that generates a torque reference such that the speed feedback value of the electric motor follows a preset first speed reference and supplies it to an inverter that drives the electric motor, and a first torque reference output by the torque reference generation means immediately before the coating command is activated during coating. The target torque standard Torque reference setting means for setting a second torque reference, During coating The torque reference generation means calculates a first speed correction value so that the torque reference output by the torque reference follows the second torque reference, and the first speed reference The first speed correction value The system includes a torque correction value calculation means that outputs a first correction speed standard calculated by adding to the torque standard generation means. [Effects of the Invention]

[0010] According to one embodiment, a speed control device is provided that suppresses tension fluctuations that occur in accordance with the elongation of the paper after coating. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic block diagram illustrating a speed control device according to an embodiment. [Figure 2] This is a schematic timing chart for illustrating the operation of the speed control device according to the embodiment. [Modes for carrying out the invention]

[0012] The embodiments will be described below with reference to the drawings. Please note that the drawings are schematic or conceptual, and the relationships between the thickness and width of each part, as well as the ratios of the sizes of the parts, are not necessarily identical to those of reality. Furthermore, even when representing the same part, the dimensions and ratios may differ between drawings. In this specification and in each figure, elements similar to those described above are denoted by the same reference numerals, and detailed explanations are omitted as appropriate.

[0013] Figure 1 is a schematic block diagram illustrating a speed control device according to an embodiment. Figure 1 schematically shows the configuration of the coating section of the paper machine, in addition to the speed control device 10. The speed control device 10 according to this embodiment appropriately controls the tension of the paper before and after coating in the coating section by controlling the speed of the electric motor 4 that transports the paper. First, the configuration of the coating section will be described.

[0014] In the coating section of the paper machine, paint is applied to the surface of the conveyed paper 8. Multiple rolls are arranged in the coating section. The paper 8 is conveyed sandwiched between two applicator rolls 2a and 2b. The applicator rolls 2a and 2b are operated at a constant speed. In this example, the paper 8 is conveyed from left to right, as indicated by the arrows in Figure 1. A metering roll and a fountain roll are arranged correspondingly to each of the applicator rolls 2a and 2b. The two fountain rolls are immersed in paint pans 1a and 1b and are coupled to the applicator rolls 2a and 2b via the metering rolls, thereby initiating the coating process on the conveyed paper 8.

[0015] The paper 8 is transported from the applicator rolls 2a and 2b to the downstream roll 3, and the tension between the applicator rolls 2a and 2b and the downstream roll 3 is appropriately controlled by appropriately controlling the speed of the downstream roll 3.

[0016] Before coating, the paper 8 is transported with appropriate tension, as shown by the dashed line in Figure 1. However, once coating begins, the paper 8 stretches due to the application of the paint, as shown by the solid line in Figure 1. If the subsequent roll 3 is driven at the same speed as before coating, the tension of the paper 8 will decrease as the paper 8 stretches. Therefore, the speed control device 10 controls the speed of the subsequent roll 3 to achieve the desired tension.

[0017] The downstream roll 3 is driven by an electric motor 4 whose speed is controlled by a speed control device 10. More specifically, the electric motor 4 is equipped with a speed sensor 5, and the speed control device 10 performs speed feedback control to follow a speed reference supplied from a line speed reference 20, generates a torque reference τFB and supplies it to the inverter 6. The inverter 6 drives the electric motor 4 to follow the torque reference τFB.

[0018] In the speed control device 10 according to the embodiment, when the coating command is activated, the torque reference τFB immediately before the coating command is activated is set as the torque reference τSET during coating. The speed control device 10 adds a speed correction value VT corresponding to the difference between the set torque reference τSET during coating and the torque reference τFB output by the speed control device 10 to the speed reference V0, thereby performing control to increase the tension in accordance with the elongation of the coated paper 8 and maintain the tension.

[0019] The specific configuration of the speed control device 10 according to the embodiment will be described. As shown in Figure 1, the speed control device 10 includes a speed adjuster 11, a speed controller (torque reference generation unit) 12, a torque memory 13, a torque setter (torque reference setting unit) 15, and a torque correction calculator (torque correction value calculation unit) 16.

[0020] The speed control device 10 according to the embodiment has switches 14 and 17, and the switches 14 and 17 are open during operation before coating. The switches 14 and 17 are closed when the coating command becomes active. The switch 14 is preferably closed at the timing when the coating command becomes active. By closing the switch 14 at this timing, the torque reference τFB acquired and stored immediately before the coating command becomes active can be set as the torque reference τSET during coating. The switch 17 is closed at an arbitrary timing after the timing when the switch 14 is closed. Preferably, it is closed at the timing when the operation by the predictive control unit 18 described later is completed. By closing the switch 17 at such a timing, the tension of the desired paper 8 can be controlled more quickly.

[0021] The speed adjuster 11 acquires the set value of the speed reference from the line speed reference 20, and sets and outputs the speed reference V0 in accordance with a preset acceleration coefficient or deceleration coefficient. The speed reference V0 is subtracted from the speed feedback signal of the electric motor 4 detected by the speed sensor 5, and the resulting difference is output to the speed controller 12.

[0022] The speed controller 12 generates a torque reference τFB for the motor 4 based on the difference between the speed reference V0 and the speed feedback signal, and outputs it to the inverter 6. The inverter 6 drives the motor 4 according to the torque reference τFB.

[0023] The torque memory 13 sequentially receives and stores the torque reference τFB output by the speed controller 12. The storage period is, for example, predetermined.

[0024] The torque setter 15 is connected to the output of the torque memory 13 via a switch 14. The switch 14 is temporarily closed in response to a coating command. For example, the switch 14 is temporarily closed when the coating command becomes active and is opened after a preset period of time has elapsed. Therefore, the torque setter 15 receives the torque command value (first torque reference) τFB immediately before the coating command becomes active and is set as the torque reference (second torque reference) τSET during coating.

[0025] The torque correction calculator 16 receives the difference between the torque reference τSET set in the torque setter 15 during coating and the torque reference τFB output by the speed controller 12. The torque correction calculator 16 consists of, for example, a PI controller, and based on the torque references τFB and τSET, the torque correction calculator 16 generates and outputs a speed correction value (first speed correction value) VT according to the deviation τT of the torque reference. The speed correction value VT is a correction value relative to the speed reference V0.

[0026] The speed correction value VT is added to the speed reference (first speed reference) V0 output by the speed regulator 11 via switch 17. Switch 17 is closed after the coating command is activated, and the corrected speed reference (V0 + VT) is input to the speed controller 12 after coating has started. The speed controller 12 generates a torque reference τFB so that the speed of the motor 4 follows the corrected speed reference (V0 + VT) and outputs it to the inverter 6. As a result, the speed of the downstream roll 3 is controlled to make the deviation τT of the torque reference that occurs in response to the elongation of the paper 8 due to coating zero, so that the tension between the applicator rolls 2a, 2b and the downstream roll 3 is controlled to the desired value before and after coating.

[0027] The speed control device 10 preferably further comprises a predictive control unit 18. The predictive control unit 18 feedforward increases the tension in accordance with the elongation of the paper 8 due to coating. Specifically, the predictive control unit 18 has a predictive controller 18a, and the predictive controller 18a is pre-set with a correction speed (second speed correction value) VPRE corresponding to the elongation of the paper 8 due to coating. The correction speed VPRE is added to the speed reference V0 via a switch 18b.

[0028] In the speed control device 10, if a predictive control unit 18 is provided, preferably, the switch 17 is closed when the time elapsed for the speed of the motor 4 to increase by the correction speed VPRE. The time for the speed of the motor 4 to increase by the correction speed VPRE is calculated in the speed regulator 11 using an acceleration coefficient that is set in advance based on the mechanical constants of the motor 4.

[0029] By providing the predictive control unit 18, it becomes possible to correct the speed reference in a feedforward manner, making it possible to reach the target torque reference more quickly.

[0030] Figure 2 is a schematic timing chart illustrating the operation of the speed control device according to the embodiment. The operation of the speed control device 10 according to this embodiment will be explained with reference to the timing chart in Figure 2. In the example in Figure 2, the operation of the speed control device when a predictive control unit 18 is provided is shown.

[0031] The top row of Figure 2 shows the time evolution of the coating command. The OFF level indicates that the coating command is inactive, and the ON level indicates that the coating command is active. In this example, the coating command is active at time tA. The second row of Figure 2 shows the time variation of the torque reference τFB for the downstream roll 3 output by the speed controller 12 in Figure 1. The bottom diagram in Figure 2 shows the time variation of the speed reference V0 input to the speed controller 12. In the second and bottommost diagrams of Figure 2, the solid lines represent the time changes of the torque reference and speed reference when the prediction control unit 18 is operated and torque correction calculations are performed by the torque correction calculator 16. The dashed lines represent the time changes of the torque reference and speed reference when only the prediction control unit 18 is operated. The dashed lines represent the time changes of the torque reference and speed reference when neither the prediction control unit 18 nor the torque reference correction calculation is performed. In the following, the operation when the prediction control unit 18 is operated will be simply referred to as prediction correction, and the operation when the torque correction calculator 16 is operated will be simply referred to as torque correction.

[0032] First, we will explain the operation of the speed control device 10 in the case of the dashed line in Figure 2, that is, when neither prediction correction nor torque correction is performed. As shown by the dashed line in Figure 2, when the coating command becomes active at time tA, slack occurs in the paper 8 due to coating, as shown by the solid line in Figure 1. Therefore, from time tA onward, the torque reference τFB of the downstream roll 3 decreases, and at time tC, when the leading edge of the paper 8, which has been coated, reaches the downstream roll 3, it asymptotically approaches the torque τ' corresponding to the slack between the applicator rolls 2a and 2b and the downstream roll 3. Torque τ' is a smaller value than the target pre-coating torque reference τSET. Note that the speed reference V0 is not corrected in any way and remains constant throughout the entire time.

[0033] Next, we will explain the operation of the speed control device in the case of the dashed line in Figure 2, that is, when only predictive correction is performed. As shown by the dashed line in Figure 2, when switch 18b is closed at time tA, the correction speed VPRE set in the predictive controller 18a is added to the speed reference V0 supplied from the line speed reference 20. The speed regulator 11 adds the correction speed VPRE to the speed reference V0 according to a preset acceleration coefficient and outputs it to the speed controller 12.

[0034] At time tB, the speed reference output by the speed regulator 11 reaches (V0 + VPRE). During the period between time tA and time tB, the motor 4 is accelerated, so the torque reference τFB output by the speed controller 12 increases in a pulsed manner.

[0035] After time tB has elapsed, the speed controller 12 generates a torque reference τFB and outputs it to the inverter 6 so as to follow the speed reference (V0+VPRE) of the downstream roll 3. After time tB, the speed reference is considered to be constant at (V0+VPRE), so the speed controller 12 outputs a torque that is lower by a deviation τT than the torque reference τSET immediately before coating.

[0036] Next, we will explain the operation of the speed control device in the case of a solid line, that is, when both predictive correction and torque correction are performed. At time (first time) tA, the torque setter 15 sets the torque reference immediately before time tA as the torque reference τSET during coating. The torque setter 15 outputs the set torque reference τSET to the torque correction calculator 16.

[0037] At time (second time) tB, when switch 17 is closed, the torque correction calculator 16 starts calculating the speed correction value VT. The torque correction calculator 16 receives the difference between the torque reference τSET during coating and the torque reference τFB output by the speed controller 12, performs a PI calculation on the difference to generate the speed correction value VT, and adds it to the speed reference. Here, the speed reference is (V0 + VPRE), and (V0 + VPRE + VT) is input to the speed controller 12 as the speed reference.

[0038] Since the speed correction value VT is calculated based on the difference between the torque reference before coating and the torque reference during coating, the control system consisting of the speed control device 10, inverter 6, and electric motor 4 generates the speed correction value VT so that the difference in torque references becomes 0.

[0039] Subsequently, at time tC, the leading edge of the coated paper 8 reaches the downstream roll 3, and at time tD, the torque reference τFB output by the speed controller 12 is approximately equal to the torque reference τSET during coating.

[0040] In this way, the tension of the paper 8 being transported between the applicator rolls 2a and 2b and the subsequent roll 3 is kept constant before and after coating.

[0041] Note that the above description omits the explanation of the case where only torque correction is performed and no predictive correction is performed. Even in such a case, the speed controller 12 generates a torque reference that follows the torque reference before coating, so the torque reference τFB output by the speed controller 12 almost matches the torque reference τSET during coating, similar to the case of the solid line in Figure 2. However, in this case, since the operation due to torque correction is feedback control using PI control or the like, it is necessary to introduce a response delay in the control system. Therefore, in order to more quickly match the torque reference τFB to the torque reference τSET during coating, it is preferable to apply predictive correction.

[0042] Furthermore, as shown by the solid line in Figure 2, when both predictive correction and torque correction are performed, closing the switch 17 at time tB and starting the torque correction calculation can minimize the time until time tD when the desired torque standard is reached.

[0043] The effects of the speed control device 10 according to this embodiment will be described. The speed control device 10 according to this embodiment includes a torque memory 13, a torque setter 15, and a torque correction calculator 16. The torque memory 13 stores the torque reference τFB immediately before the start of coating and sets it in the torque setter 15 as the torque reference τSET during coating. After the start of coating, the torque correction calculator 16 generates a speed correction value VT so that the deviation τT between τSET and τFB becomes 0, and the speed control device 10 adds the generated speed correction value VT to the speed reference to obtain the corrected speed reference. The speed control device 10 calculates the torque reference τFB so that the speed feedback value of the electric motor 4 follows the corrected speed reference and outputs it to the inverter 6. Therefore, even when transporting paper 8 that has been stretched by coating, the speed of the electric motor 4 can be controlled to follow the torque reference before coating. In this way, the tension of the paper 8 transported between the applicator rolls 2a, 2b and the downstream roll 3 can be kept constant before and after coating.

[0044] The speed control device 10 according to this embodiment may include a predictive control unit 18. When the speed control device 10 includes a predictive control unit 18, a correction speed VPRE is pre-set in the predictive control unit 18. The correction speed VPRE is a speed correction value used to compensate for the decrease in tension due to the elongation of the paper 8 during coating at the start of coating. By adding the correction speed VPRE to the speed reference V0 at the start of coating, the speed of the electric motor 4 can be increased to quickly suppress the decrease in tension due to the elongation of the paper 8.

[0045] Subsequently, by adding the speed correction value VT calculated by the torque correction calculator 16 to obtain a corrected speed standard, it becomes possible to quickly suppress the decrease in tension of the paper 8 while accurately driving the electric motor 4 at the pre-coating torque standard, thereby enabling the manufacture of higher quality products.

[0046] As described above, depending on the arrangement of the various parts of the paper machine and the type of paper produced by the paper machine, it may not be possible to install dancer rolls or tension detectors. Even in such cases, the speed control device 10 according to this embodiment can control the speed of the electric motor 4 that drives the downstream rolls so as to maintain a constant tension in the paper 8 before and after coating between the applicator rolls 2a, 2b and the downstream rolls. It is also possible to reduce the overall installation cost of the paper machine by not installing dancer rolls or tension detectors.

[0047] In this way, a speed control device can be realized that suppresses tension fluctuations that occur in accordance with the elongation of the paper after coating.

[0048] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of Symbols]

[0049] 1a, 1b...Paint pan, 2a, 2b...Applicator roll, 3...Reverse roll, 4...Electric motor, 5...Speed ​​sensor, 6...Inverter, 10...Speed ​​control device, 11...Speed ​​regulator, 12...Speed ​​controller, 13...Torque memory, 14, 17, 18b...Switch, 15...Torque setter, 16...Torque correction calculator, 18...Predictive control unit, 18a...Predictive controller, 20...Line speed reference

Claims

1. A torque reference generation means generates a torque reference such that the speed feedback value of the electric motor follows a preset first speed reference, and supplies it to the inverter that drives the electric motor. A torque reference setting means sets the first torque reference output by the torque reference generating means immediately before the coating command is activated to the second torque reference, which is the target torque reference during coating. A torque correction value calculation means calculates a first speed correction value so that the torque reference output by the torque reference generation means during coating follows the second torque reference, and outputs a first corrected speed reference calculated by adding the first speed correction value to the first speed reference to the torque reference generation means, A speed control device equipped with a speed control device.

2. The speed control device according to claim 1, wherein when the coating command is activated, a second corrected speed standard calculated by adding a preset second speed correction value to the first speed standard is output to the torque standard generation means.

3. The first corrected speed standard is calculated by adding the first speed correction value to the second corrected speed standard after calculating the second corrected speed standard. The second correction speed criterion is applied at the first time when the coating command is activated. The speed control device according to claim 2, wherein the first corrected speed standard is applied at a second time after the application of the second corrected speed standard has been completed.

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