JP2005293050A - Process control method, apparatus using the same, sheet-like material manufacturing method, and sheet-like material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately control a control object having a small change by correcting a deviation due to a difference in apparatus accuracy.
In a process of numerically converting a control output value calculated in a calculation process by PID control into a control output value within a predetermined range by a numerical conversion unit, a digital calculation and a D / A converter are performed by a correction calculation unit. The deviation generated due to the difference in device accuracy is corrected to the actual control output value and the output time after the numerical conversion, and the corrected actual control output value is D / A converted and output to the power regulator 14. .
[Selection] Figure 2

Description

  The present invention relates to a process control method used for process control of physical quantities such as temperature, pressure, flow rate, and level, an apparatus using the same, a sheet-like material manufacturing method, and a sheet-like material.

  Conventionally, in industrial / chemical plants, for example, PID control is used for temperature, pressure, flow rate, and level control. This PID control compares the actual measured value of the physical quantity to be controlled with a reference value set in advance in the manufacturing process of the manufacturing object, and calculates an arithmetic control output value for reducing the obtained deviation by a digital arithmetic device, After converting the result into an analog signal, the operation amount of the operation target is adjusted according to the analog signal. In this PID control, the ON / OFF operation timing of the operation target is set in accordance with a continuous proportional system that converts and outputs an analog signal proportional to the calculation control output value of the calculation result of the digital arithmetic device, or according to the calculation control output value of the calculation result. Two types of time proportional adjustment methods have been proposed and implemented (see, for example, Patent Document 1).

  A control device that adjusts the power supplied to the heater using the above-described continuous proportional method and time proportional method will be described as an example.

  In the case of the continuous proportional method, the temperature to be controlled (actually measured value) in the manufacturing process is input to the digital control device using a thermocouple, and the reference value of the actually measured value and the temperature stored in advance in the digital control device is used. The control output value (MV) of 0 to 100% is acquired as a digital value according to the obtained deviation. Further, the control output value is converted into an analog value (AO) of 4 to 20 mA using the following expression (1), and is output to a power regulator that adjusts the power supplied to the heater. The power regulator compares the input analog signal of 4 to 20 mA with the maximum output power (Pmax) of the power regulator itself, and determines the power (PA) to be supplied to the heater from the following equation (2). Yes.

AO = 16/100 × MV + 4 (1)
PA = Pmax (AO-4) / 16 (2)

  In the case of the time proportional method, 0 to 100% of the control output (MV) is acquired as a digital value by the digital control device. Furthermore, a calculation cycle (CP [msec]) for performing calculation processing at a predetermined time interval set in advance in the digital control device, and a time (PON [msec]) for supplying power to the heater from the control output (MV) The non-supply time (POFF [msec]) is determined using the following equations (3) and (4). That is, an ON signal that supplies power and an OFF signal that does not supply power are alternately output at predetermined time intervals.

PON = CP × MV / 100 (3)
POFF = CP × (100−MV) / 100 (4)
JP-A-10-308635

  However, the digital control device using the conventional method has the following problems.

  That is, there is a problem that the resolution is deteriorated due to the accuracy of the apparatus when the control output of the digital value calculated by the digital control device is analog-converted (D / A conversion).

  In general digital control equipment, D / A conversion of 8 to 10 bits is used. For this reason, the control output value calculated by the floating point calculation by the digital control device is calculated with the number of significant digits up to the 12th decimal place. However, when the calculated control output value is D / A converted, the first digit after the decimal point is used as the number of significant digits, so that the resolution after conversion becomes worse. Therefore, even if the calculated control output value, which is a digital value, continuously changes below the second decimal place, the numerical change is not reflected in the analog signal when D / A conversion is performed. As a result, when the control output value is to be controlled to a value that is 4.1 or less after analog signal conversion, the operation target that should operate without the value being reflected in the analog signal does not operate, and the control target has a small amount of change. There is a problem that it is not possible to control the system accurately.

  The present invention has been made in view of such circumstances, and a process control method capable of accurately controlling a control target in process control, an apparatus using the same, a sheet-like material manufacturing method, and a sheet-like material The main purpose is to provide

The first invention uses a deviation obtained from a comparison between a preset reference value of a control target and an actual measurement value, calculates a control output value for control by a digital computing unit, and then calculates a control output value that is a digital value. In a process control method for converting a D / A converter into an analog signal and controlling the control target while operating the operation target according to the analog signal,
A correction calculation process is performed so that a deviation of a control output value generated due to a difference in accuracy between the digital calculator and the D / A converter is compensated by an actual control output value and an output time.

  (Action / Effect) According to this method, the deviation generated by the difference in accuracy between the digital computing unit and the D / A converter is compensated by the actual control output value and the output time, thereby reflecting the deviation that could not be output. It is possible to control the controlled object. In other words, the control object can be controlled in a state in which the variation of the control object with a small change is included in the deviation, so that the control object can be accurately controlled.

In a second aspect based on the first aspect, the correction calculation process includes the following steps:
(A) A process of rounding up and adjusting the number of significant digits below the floating point of the theoretical control output value calculated by the digital computing unit to the number of significant digits of the floating point of the D / A converter;
(B) In the calculation cycle in which the correction calculation processing is performed at predetermined time intervals, the output time of the actual control output value after the round-up adjustment is compared with the actual control output value after adjustment and the theoretical control output value before adjustment. The process of calculating by
(C) a process of inputting the adjusted actual control output value and the start time and end time values of the output time to the D / A converter;
It is provided with.

  (Function / Effect) According to this method, the number of significant digits of the theoretical control output value calculated by the digital arithmetic unit is adjusted to match the number of significant digits of the floating point of the D / A converter. The theoretical control output value is adjusted up to a predetermined floating point. Further, both control output values before and after the adjustment are compared to obtain an output time for outputting the adjusted actual control output value within a predetermined calculation cycle, and the deviation is compensated by the actual control output value and the output time. Therefore, it is possible to control and output a deviation due to a difference in accuracy of devices that could not be output.

  That is, even if a general-purpose D / A converter with low conversion accuracy is used, a value less than the minimum output value of the D / A converter itself can be controlled and output. As a result, highly accurate process control can be constructed at low cost while using a general-purpose D / A converter.

In a third aspect based on the second aspect, the correction calculation process further includes the following steps:
(D) A threshold value of the theoretical control output value is set in advance, and the theoretical control output value calculated by the digital calculator is compared with the threshold value.
(D1) When the theoretical control output value is greater than or equal to a threshold value, a process of inputting the theoretical control output value and the uncorrected output time to the D / A converter;
(D2) When the theoretical control output value is less than the threshold value, a process of performing the correction calculation process from the process (A) to the process (C);
It is provided with.

  (Operation / Effect) According to the present invention, by setting the threshold value of the theoretical control output value in advance, when the theoretical control output value becomes less than the threshold value, the deviation generated when the D / A changes is obtained. Control output is possible. For example, when temperature control is performed with a heater and the temperature control is performed in a state where the temperature is substantially constant and the temperature change is small, the minimum value of the control output value that can supply power to the heater is set as the threshold value. If the threshold value is set in this way, the temperature control can be performed by compensating for the deviation of a value less than the minimum value of the control output value with the actual control output and the output time. That is, the temperature can be accurately controlled in a state where the temperature change is small. Note that the present invention is not limited to temperature, and can be applied in a state where changes in pressure, flow rate, level and various physical quantities are small.

In a fourth aspect based on the first aspect, the correction calculation process includes the following steps:
(A) A process of rounding up and adjusting the number of significant digits below the floating point of the theoretical control output value calculated by the digital computing unit to the number of significant digits of the floating point of the D / A converter;
(B) In the calculation cycle in which the correction calculation processing is performed at predetermined time intervals, the output time of the actual control output value after the round-up adjustment is compared with the actual control output value after adjustment and the theoretical control output value before adjustment. The process of calculating by
(E) inputting the adjusted actual control output value to the D / A converter;
(F) a process of converting the operation target into a switching signal for switching ON / OFF based on the start time and the end time of the output time of the actual control output value after the adjustment, and inputting to the operation target;
It is provided with.

  (Operation / Effect) According to the present invention, an ON / OFF switching signal can be directly input to an operation object without being converted into an analog signal, and the operation object can be easily switched.

According to a fifth aspect of the present invention, in the course of manufacturing a sheet-like material while heating or / and cooling the raw material heated and / or cooled by the heating means or the cooling means, a preset reference for the melting temperature of the raw material is set. After calculating the control output value for controlling the melting temperature using a digital calculator using the temperature deviation obtained from the comparison between the measured value and the measured value, the control output value, which is a digital value, is converted into an analog signal by the D / A converter. In the sheet-like material manufacturing method for manufacturing the sheet-like material while adjusting the amount of electric power supplied to the heating means or / and the supply amount of the cooling medium supplied to the cooling means according to the analog signal,
A correction calculation process is performed so that a deviation of a control output value generated due to a difference in accuracy between the digital calculator and the D / A converter is compensated by an actual control output value and an output time.

  (Operation / Effect) According to the present invention, it is possible to output by compensating the temperature deviation of the melting temperature of the raw material caused by the difference in accuracy between the digital arithmetic unit and the D / A converter by the actual control output value and the output time. The temperature deviation that did not exist can be reflected. That is, it can be realized by adjusting the amount of electric power supplied to the heating means for controlling the melting temperature of the raw material and the supply amount of the cooling medium supplied to the cooling means. That is, since temperature control can be performed in a state in which a small amount of change in temperature change is included in the deviation, the melting temperature can be accurately controlled.

  The “sheet-like material” in the present invention includes a film and a sheet.

  A sixth aspect of the invention is a sheet-like material manufactured using the sheet-like material manufacturing method according to the fifth aspect of the invention.

  (Operation / Effect) According to the present invention, the melting temperature of the raw material in the manufacturing process of the sheet-like material can be accurately controlled by controlling the change amount of the small temperature change in the deviation state. A highly functional sheet-like material having a uniform structure is obtained.

The seventh invention uses a deviation obtained from a comparison between a preset reference value to be controlled and an actual measurement value, converts a control output value calculated by digital arithmetic processing into an analog signal by a D / A converter, In a process control device that controls an operation target according to a signal,
A control calculation unit that calculates a deviation from a comparison between the reference value of the control target and the actual measurement value, and calculates a calculation control output value of the control target by digital calculation from the deviation;
Numerical conversion means for converting into a theoretical control output value to be controlled according to the calculation control output value calculated by the control calculation means;
Correction arithmetic means for correcting a deviation of the control output value caused by the accuracy difference between the digital arithmetic unit comprising the control arithmetic means and the numerical value converting means and the D / A converter, based on the actual control output value and the output time; ,
It is provided with.

  (Operation / Effect) According to the present invention, the control calculation means obtains a deviation from a comparison between the reference value of the control target and the actual measurement value, and calculates the calculation control output value of the control target from the deviation by digital calculation. The numerical value conversion means converts the control output value to be controlled according to the calculation control output value calculated by the control calculation means. The correction calculation means corrects the deviation of the control output value caused by the accuracy difference between the digital calculation unit composed of the control calculation unit and the numerical value conversion unit and the D / A converter by the actual control output value and the output time. . Therefore, according to this invention, the 1st and 2nd invention can be realized suitably.

In an eighth aspect based on the seventh aspect, the process control apparatus further includes the following configuration.
Storage means for preliminarily storing a threshold value of the theoretical control output value;
The threshold value stored in the storage means and the theoretical control output value converted by the numerical value conversion means are compared. If the theoretical control output value is equal to or greater than the threshold value, the theoretical control output value and the uncorrected output time are A comparison / determination unit that inputs to the D / A converter and determines that the theoretical calculation output value is corrected by the actual calculation output value and the output time if the theoretical control output value is less than the threshold;
It is provided with.

 (Operation / Effect) According to the present invention, the storage means stores in advance the threshold value of the theoretical control output value. The comparison determination means compares the threshold value stored in the storage means with the theoretical control output value converted by the numerical value conversion means, and if the theoretical control output value is equal to or greater than the threshold value, the theoretical control output value and the uncorrected output The time is input to the D / A converter, and if the theoretical control output value is less than the threshold value, it is determined by the correction calculation means to be corrected by the actual control output value and the output time. Therefore, according to the present invention, the third invention can be suitably realized.

A ninth invention uses a deviation obtained from a comparison between a preset reference value of a controlled object and an actual measurement value, converts a control output value calculated by digital arithmetic processing into an analog signal by a D / A converter, In a process control device that controls an operation target according to a signal,
A control calculation unit that calculates a deviation from a comparison between the reference value of the control target and the actual measurement value, and calculates a calculation control output value of the control target by digital calculation from the deviation;
Numerical conversion means for converting into a theoretical control output value to be controlled according to the calculation control output value calculated by the control calculation means;
Correction arithmetic means for correcting a deviation of the control output value caused by the accuracy difference between the digital arithmetic unit comprising the control arithmetic means and the numerical value converting means and the D / A converter, based on the actual control output value and the output time; With
In addition, one actual control output value calculated by the correction calculating means is input to the D / A converter, and the output time of the other corrected actual control output value is an operation target based on the output start time and end time. Is converted into a switching signal for ON / OFF switching and input to the operation target.
It is characterized by that.

  (Operation / Effect) According to the present invention, the control calculation means obtains a deviation from the comparison between the reference value of the controlled object and the actual measurement value, and calculates the calculation control output value from this deviation by digital calculation. The numerical value conversion means converts the control output value to be controlled according to the calculation control output value calculated by the control calculation means. The correction calculation means corrects the deviation of the control output value caused by the accuracy difference between the digital calculation unit composed of the control calculation means and the numerical value conversion means and the D / A converter, based on the actual control output value and the output time. Further, one actual control output value calculated by the correction calculation means is input to the D / A converter, and the output time of the other corrected actual control output value is determined based on the output start time and end time. It is configured to be converted into a switching signal for switching ON / OFF and input to the operation target. Therefore, according to the present invention, the fourth invention can be suitably realized.

  The process control method and the apparatus using the same according to the present invention output by compensating the deviation of the control output value caused by the accuracy difference between the digital arithmetic unit and the D / A converter by the actual control output value and the output time. The control object can be controlled by reflecting the deviation that could not be obtained. In other words, the control object can be controlled in a state in which the variation of the control object with a small change is included in the deviation, so that the control object can be accurately controlled.

  Embodiments of the present invention will be described below with reference to the drawings.

  In addition, in the case of a present Example, it demonstrates taking the case where the resin (material) temperature at the time of film manufacture is adjusted by temperature control of a cylinder in the extruder for film manufacture. This film corresponds to the sheet-like material of the present invention.

  FIG. 1 is a side view showing a schematic configuration of an extruder, and FIG. 2 is a block diagram showing a schematic configuration of a cylinder and its surroundings.

  The extruder 1 used in the present embodiment includes a hopper 3 that supplies a material 2 such as a pellet-shaped plastic, a conveying unit 5 that conveys the material 2 while being frictionally and sheared by an internal screw 4, and a material 2 in the conveying unit. And a die 7 that coats the surface of a cooling roll 8 that cools and hardens the material 2 melted in the conveying section.

  In addition, the material 2 coated on the roll from the extruder 1 and formed into a film is a thickness adjusting roll 9, a transport roll group r, and a surface treatment unit for performing a surface treatment (for example, corona treatment) on the filmed material 2. It is conveyed in the order of 10 and is wound and collected by the turret 11 which is a collection unit. Hereinafter, the structure of each part is demonstrated concretely.

  A plurality of cylinders 6 (for example, five in FIG. 1) are attached at substantially equal intervals from the base end to the tip end of the transport unit 5. Each cylinder has a configuration including heaters as heating means and piping (not shown) through which cooling water can be circulated as cooling means. Moreover, as shown in FIG. 2, the controller 12 which transmits the various output signals for adjusting a heating means is provided. The controller 12 will be described later.

  The heating means includes a heater 13 and a power regulator 14 that supplies power to the heater 13. As the power adjuster 14, for example, a thyristor is used, but is not limited thereto.

  Returning to FIG. 1, as the roll 9 for adjusting the thickness of the coating material, for example, a metal or rubber roll is appropriately used. The cooling roll 8 is configured such that cooling water circulates inside the roll. In other words, the molten material 2 is cooled and cured in the process of being uniformly stretched on the roll.

  Next, as a process control method that is a feature of the present embodiment, a case where the temperature of the cylinder 6 is controlled using the above-described extruder 1 will be specifically described with reference to the configuration of the controller 12 shown in FIG. . In this embodiment, the control output value for PID control (0 to 100%) is calculated by digital calculation in the controller using the measured value of the temperature detected by the thermocouple S, and the calculated digital value Is converted to an analog signal of 4 to 20 mA and input to the power adjuster 14 in a timely manner.

  As shown in FIG. 2, the controller 12 includes a control calculation unit 15, a numerical value conversion unit 16, and a D / A converter 17. The control calculation unit 15 corresponds to the control calculation unit of the present invention, and the numerical value conversion unit 16 corresponds to the numerical value conversion unit.

  The control calculation unit 15 receives the temperature (actual measurement value) of the cylinder 6 detected by the thermocouple S, and uses the input actual measurement value and the reference value of the temperature profile in the manufacturing process preset in the control calculation unit 15. A deviation is calculated by comparison, and the electric power supply to the heater 13 is calculated by digital calculation as a calculation control output value (MV0) by PID control using the deviation. The calculation control output value (MV0) calculated in the present embodiment is a value of 0 to 100% including the number of significant digits with 12 decimal places or less.

  The numerical value conversion unit 16 uses an arithmetic control output value (MV0) of 0 to 100%, which is a digital value including the number of significant digits after the decimal point 12 calculated by the control calculation unit 15, using the above-described equation (1), The analog signal is converted to 4 to 20 mA.

  Furthermore, the numerical value conversion unit 16 includes a correction calculation unit 16A that adjusts and corrects so as to compensate for a difference in accuracy generated by digital calculation and analog conversion before converting the digital value into an analog signal. That is, the output time of the actual control output value (MV2) and the actual control output value (MV2) at the previous stage of conversion to an analog signal is calculated. The correction calculation unit 16A corresponds to the correction calculation means of the present invention.

  Specifically, the decimal point 2 is set so that the resolution is effective below the decimal point 1 of the provisional theoretical control output value (MV1) of 4 to 20 including the value below the decimal point 12 calculated using the equation (1). The value is converted into a value in the range of 4.0 to 20.0 as the actual control output value (MV2) rounded up. This round-up adjustment is performed in accordance with the first output value of the D / A converter 17 described later.

  For example, the calculation cycle of calculation processing performed to transmit an analog signal from the controller 12 to the power adjuster 14 is calculated at the previous calculation cycle t0 at intervals of 1 second as shown in FIG. When the value of the calculation control output value (MV0) calculated in the calculation cycle t1 after the value of the calculation control output value (MV0) changes from 38.125 (%) to 38.50 (%), When the theoretical control output value (MV1) numerically converted using (1) is calculated, the theoretical control output value (MV1) in the calculation cycle t0 is 10.1, and the theoretical control output value (MV1) in the control cycle t1 is 10. .16.

  Here, in the case of the conventional apparatus, in order to output an analog signal by performing D / A conversion with an effective resolution of decimal point 1 or less, each calculation cycle t0 per second when rounded down to the second decimal point or less is used. In the calculation cycle t1, as shown by the arrow A in FIG. 3 (b), each value of 10.1 mA is continuously output to the power regulator 14 for one second of the calculation cycle. Although not shown, conversely, when the second decimal place is rounded up, a value of 10.2 mA is continuously output to the power regulator 14 for one second of the calculation cycle.

  However, the correction processing unit 16A of the numerical value conversion unit 16 of the extruder 1 of the present embodiment further performs the following processing.

  That is, an actual control output value (MV2) obtained by rounding up the value of the theoretical control output value (MV1) to the second decimal place is obtained, and further, the deviation between the theoretical control output value (MV1) and the actual control output value (MV2) is calculated. Complement with the output time of the actual control output value (MV2).

  Specifically, the calculation cycle is t seconds, the minimum resolution r (0.1 in this embodiment) of the actual control output value (MV2), MV0 × 16/100 + 4 = x + a (where x is the actual control output value (MV2)) The actual control output value (MV2) obtained by rounding up the value below the predetermined decimal point so that the predetermined resolution is obtained when the real number is valid up to the decimal point y limited by the minimum resolution and 0 <a <r) The first output time value (ON) for outputting and the second output time value (OFF) for not outputting are obtained by the following equations (5) and (6).

First output time value (ON) = (x + a) / (x + r) × t (seconds) (5)
Second output time value (OFF) = (r−a) / (x + r) × t (seconds) (6)

  For example, the calculation cycle t0 and the calculation cycle t1 are as follows. As shown in FIG. 3A, in the calculation cycle t0, the calculation control output value (MV0) is 38.125 (%) as shown in FIG. The actual control output value (MV2) is calculated as 10.1. This actual control output value (MV2) is continuously output within the calculation cycle.

  On the other hand, in the calculation cycle t1 in which the theoretical control output value (MV1) changes from 10.1 to 10.16, the actual control output value (MV2) obtained by numerical conversion is rounded up to the second decimal place to 10.2. It becomes. That is, the first output time value (ON) and the second output time value (OFF) obtained by correcting the actual control output value (MV2) by a deviation amount obtained by rounding up the actual control output value (MV2) from 10.16 to 10.2. Calculate using 5) and (6). Specifically, 10.2 mA is output for 10.16 / 10.2 seconds and 10.1 mA is output for 0.04 / 10.2 seconds in one second from the calculation time t1 to t2. In this embodiment, the actual control output value (MV2) is output during the first output time, and the second output time is not output. In other words, the first output time value (ON) and the second output time value (OFF) determine the ON / OFF timing for switching the output time of the actual control output value (MV2) in one second of the calculation cycle t. ing. The actual control output value (MV2) calculated by the correction calculation unit 16A and the ON / OFF signal obtained by time-correcting the actual control output value are transmitted to the D / A converter 17.

  Next, the D / A converter 17 adjusts the output time output from the correction calculation unit 16A of the numerical value conversion unit 16, and signals and actual control outputs for switching the control output ON / OFF within the calculation cycle. The value (MV2) is converted from a digital signal to an analog signal.

  The analog signal converted by the D / A converter 17 is transmitted to the power adjuster 14. The power regulator 14 determines the power to be supplied to the heater 13 from Equation (2) using the input analog signal of 4 to 20 mA and the maximum output power of the power regulator itself.

  The above processing is performed every predetermined calculation cycle until the manufacture of the film to be manufactured is completed.

  As described above, the arithmetic control output value (MV0) calculated by the control arithmetic unit 15 is simply converted into a predetermined numerical value, and the theoretical control output value (MV1) having the same number of significant digits below the floating point is converted to D / When A conversion is performed, an actual control output value (MV2) obtained by rounding up and adjusting a value below a predetermined floating point to be rounded down is obtained, and a deviation between the theoretical control output value (MV1) and the actual control output value (MV2) is obtained. By correcting the time to the output time of the actual control output value (MV2), the conventional apparatus can output the deviation that could not be reflected as the control output. That is, even if the temperature change that is the control target is small, the temperature control of the cylinder 6 can be performed in response to the detected minute change.

  In addition, it is possible to eliminate a decrease in resolution that has occurred due to D / A conversion. As a result, a control target such as temperature can be accurately controlled even when a generally used D / A converter of about 8 to 10 bits is used.

  In this embodiment, a threshold value for the theoretical control output value (MV1) calculated by the numerical value conversion unit 16 is set in advance, and the theoretical control output value (MV1) calculated for each calculation cycle is equal to or greater than the threshold value. The actual control output value (MV2) obtained by adjusting the number after the decimal point of the theoretical control output value (MV1) to be obtained to a predetermined number of significant digits is continuously output within the calculation cycle. In the same way as 1, the correction calculation unit 16A of the numerical value conversion unit 16 is configured to obtain an actual control output value (MV2) obtained by adjusting the output time within the calculation cycle by calculation processing.

  That is, as shown in FIG. 4, the controller 12A of the present embodiment includes a storage unit 18 corresponding to a storage unit and a comparison determination unit 19 corresponding to a comparison determination unit in a numerical value conversion unit. The comparison determination unit 19 determines whether or not the theoretical control output value (MV1) converted by the numerical value conversion unit 16 is less than a threshold value preset in the storage unit 18. In addition, since it is the same structure as the above-mentioned Example 1 except having the memory | storage part 18 and the comparison determination part 19 in a numerical value conversion part, it attaches | subjects the same code | symbol to the same part, and abbreviate | omits detailed description. Hereinafter, the case where the above-mentioned extruder 1 is used is taken as an example, and the process will be specifically described.

  When the film is produced by the extruder 1, the temperature is raised at an initial stage in order to melt the pellet-shaped plastic charged from the hopper 3, and then the temperature is kept constant from the state where the plastic is melted. . Therefore, in this embodiment, a case where the temperature of the heater built in the cylinder 6 is finely adjusted in the process of keeping the temperature constant is shown.

  Therefore, in the step of keeping the temperature constant, the temperature change of the cylinder 6 is small, so that the control output is also small, and 4.1 is taken into consideration in consideration of the minimum output value (4.1) of the D / A converter 17. A threshold value is set in the storage unit 18 in advance.

  First, the numerical value conversion unit 16 uses a calculation control output value (MV0) for performing PID control of the heater temperature by the control calculation unit 15 based on the input of the actual measurement value of the temperature from the thermocouple S, and the equation (1). The theoretical control output value (MV1) is calculated. The arithmetic control output value (MV0) and the theoretical control output value (MV1) include values having a floating point of 12th or less. At the same time, an actual control output value (MV2) obtained by adjusting the second decimal place of the theoretical control output value (MV1) by the correction calculation unit 16A is also calculated.

  Next, the comparison determination unit 19 reads the threshold value 4.1 stored in the storage unit 18 and compares this threshold value with the theoretical control output value (MV1). As a result of the comparison, when the theoretical control output value (MV1) is equal to or greater than the threshold value 4.1, the actual control output value (MV2) calculated by the correction calculation unit 16A is transmitted to the D / A converter 17.

  As a result of the comparison, when the theoretical control output value (MV1) is less than the threshold value 4.1, the following arithmetic processing is performed. For example, when the calculation control output value (MV0) = 0.3125 (%) obtained by the control calculation unit 15 is calculated using the equation (1) by the numerical value conversion unit 16, the theoretical control output value (MV1) = 4. .05.

  Here, an actual control output value (MV2) = 4.1 obtained by rounding up and adjusting the second decimal place of the theoretical control output value (MV1) by the correction calculation unit 16A is obtained. Further, both output times of the actual control output value (MV2) within the calculation cycle are adjusted. That is, the first output time value (ON) for outputting the actual control output value (MV2) = 4.1 is calculated as 4.05 / 4.1 × t seconds using the equation (5) and is not output. The second output time value (OFF) is calculated as 0.05 / 4.1 × t seconds using Expression (6), and each is transmitted to the D / A converter 17.

  In the extruder 1 of this embodiment, the actual control output value (MV2) = 4.1 is output when converted to an analog signal, but the actual control output value (MV2) is adjusted by rounding up the second decimal place. Thus, the deviation of the rounded up amount is corrected by the output time. Therefore, the second output time value (OFF) is obtained when the output of the actual control output value (MV2) is stopped.

  In the D / A converter 17, the converted actual control output value (MV2), the first output time value (ON), and the second output time value (OFF) are converted into analog signals, and the analog signals are converted into the power adjuster. 14 is transmitted. This completes one round of arithmetic processing in the controller 12A of the present embodiment.

  The power regulator 14 determines the power to be supplied to the heater 13 using Equation (2) based on the input analog signal from the controller 12A and the maximum output power of the power regulator itself.

  The above processing is performed every predetermined calculation cycle until the manufacture of the film to be manufactured is completed.

  As described above, the temperature change of the cylinder 6 to be controlled is small, and the threshold value is set in advance in consideration of the minimum output value of D / A conversion. Even in a state where the change in temperature, which has been unable to reflect the rounded-off deviation as a control output and the temperature cannot be controlled, can be accurately controlled.

  The present invention is not limited to the embodiment described above, and can be modified as follows.

  (1) In each of the above embodiments, the actual control output value (MV2), the first output time value (ON), and the second output time value (OFF) obtained by the correction calculation unit 16A of the numerical value conversion unit 16 are represented by D. Although the digital signal is changed from the digital signal to the analog signal by the / A converter 17 and transmitted to the power adjuster 14, it may be configured as follows.

  For example, as shown in FIG. 5, an actual control output value calculated by the correction calculation unit 16 </ b> A of the numerical value conversion unit 16 with an SSR (Solid State Relay) 20 as a semiconductor relay interposed between the controller 12 </ b> B and the power regulator 14. (MV2) is D / A converted and transmitted to the SSR 19, and the first output time value (ON) and the second output time value (OFF) are directly transmitted from the numerical value changing unit 16 to the SSR 20 as signals for switching the SSR 19 ON / OFF. You may comprise so that it may transmit to. In this case, the actual control output value (MV2) is converted to an analog signal that is continuously output within the calculation cycle and transmitted to the power regulator 14 via the SSR 19, and the output time within the calculation cycle is converted into a numerical value. The SSR 20 adjusts based on the ON / OFF signal transmitted from the unit 16. By configuring in this way, the same effects as in the above-described embodiment can be obtained.

  (2) In each of the above embodiments, the heater 6 is provided in the cylinder 6 to adjust the temperature. However, cooling water is supplied and circulated through the piping of the cooling means for cooling in the cylinder 6 to simultaneously control the temperature. You may comprise as follows. In this case, the amount of cooling water supplied at a substantially constant temperature supplied to the pipe using the same control method as the heater 13 may be performed by valve operation. As described above, the temperature control of the cylinder 6 can be performed with higher accuracy by using the heater 13 and the cooling water supply circulation to the pipe together.

  (3) In each of the above embodiments, the description has been made based on the PID control. However, the present invention can also be applied to the P or PI control. The present invention can also be applied to various control devices using a digital arithmetic unit and a D / A converter. In these cases, the same effects as those of the above-described embodiment can be obtained.

  (4) In each of the above embodiments, the temperature control of the cylinder 6 of the extruder has been described as an example. However, the control target is not limited to the temperature, and the control target is a physical quantity such as pressure, flow rate, and level. The control method can be applied. Further, the present invention can be applied not only to an extruder but also to devices and apparatuses that control physical quantities such as pressure.

  (5) In each of the above embodiments, the case where a film as a sheet-like material is manufactured has been described as an example, but the present invention can also be applied to the case where a sheet other than a film is manufactured.

It is a side view which shows schematic structure of the extruder used for an Example, and its periphery. FIG. 2 is a block diagram illustrating a schematic configuration around a cylinder according to the first embodiment. It is the figure which showed the control output quantitatively. FIG. 5 is a block diagram illustrating a schematic configuration around a cylinder according to a second embodiment. It is a block diagram which shows schematic structure around the cylinder of a modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS S ... Thermocouple 1 ... Extruder 6 ... Cylinder 12 ... Controller 13 ... Heater 14 ... Power controller 15 ... Control calculating part 16 ... Numerical value conversion part 16A ... Correction calculating part 17 ... D / A converter 18 ... Memory | storage part 19 ... Comparison judgment section

Claims (9)

After calculating a control output value for control by a digital computing unit using a deviation obtained from a comparison between a preset reference value of a control target and an actual measurement value, the control output value which is a digital value is converted by a D / A converter. In the process control method of controlling the control object while converting the operation object according to the analog signal, converting to an analog signal,
A process control method, wherein a correction calculation process is performed so that a deviation of a control output value generated by a difference in accuracy between the digital arithmetic unit and the D / A converter is compensated by an actual control output value and an output time. The process control method according to claim 1,
The correction calculation process includes the following steps:
(A) A process of rounding up and adjusting the number of significant digits below the floating point of the theoretical control output value calculated by the digital computing unit to the number of significant digits of the floating point of the D / A converter;
(B) In the calculation cycle in which the correction calculation processing is performed at predetermined time intervals, the output time of the actual control output value after the round-up adjustment is compared with the actual control output value after adjustment and the theoretical control output value before adjustment. The process of calculating by
(C) a process of inputting the adjusted actual control output value and the start time and end time values of the output time to the D / A converter;
A process control method comprising: The process control method according to claim 2, wherein
The correction calculation process further includes the following steps:
(D) A threshold value of the theoretical control output value is set in advance, and the theoretical control output value calculated by the digital calculator is compared with the threshold value.
(D1) When the theoretical control output value is greater than or equal to a threshold value, a process of inputting the theoretical control output value and the uncorrected output time to the D / A converter;
(D2) When the theoretical control output value is less than the threshold value, a process of performing the correction calculation process from the process (A) to the process (C);
A process control method comprising: The process control method according to claim 1,
The correction calculation process includes the following steps:
(A) A process of rounding up and adjusting the number of significant digits below the floating point of the theoretical control output value calculated by the digital computing unit to the number of significant digits of the floating point of the D / A converter;
(B) In the calculation cycle in which the correction calculation processing is performed at predetermined time intervals, the output time of the actual control output value after the round-up adjustment is compared with the actual control output value after adjustment and the theoretical control output value before adjustment. The process of calculating by
(E) inputting the adjusted actual control output value to the D / A converter;
(F) a process of converting the operation target into a switching signal for switching ON / OFF based on the start time and the end time of the output time of the actual control output value after the adjustment, and inputting to the operation target;
A process control method comprising: In the process of manufacturing a sheet by melting the raw material while heating or / and cooling the raw material heated and heated by the heating means and / or cooling means, a preset reference value of the melting temperature of the raw material and After calculating the control output value for controlling the melting temperature using a digital calculator, using the temperature deviation obtained from the comparison of measured values, the control output value, which is a digital value, is converted into an analog signal by the D / A converter. In the sheet-like material manufacturing method for manufacturing the sheet-like material while adjusting the amount of electric power supplied to the heating means and / or the supply amount of the cooling medium supplied to the cooling means according to the analog signal,
A sheet-like material manufacturing method, wherein a correction calculation process is performed so that a deviation of a control output value generated due to a difference in accuracy between the digital calculator and the D / A converter is compensated by an actual control output value and an output time.   A sheet-like material manufactured using the sheet-like material manufacturing method according to claim 5. Using the deviation obtained from the comparison between the preset reference value of the control target and the actual measurement value, the control output value calculated by the digital calculation process is converted into an analog signal by the D / A converter, and the operation target is determined according to the analog signal. In a process control device that controls while operating,
A control calculation unit that calculates a deviation from a comparison between the reference value of the control target and the actual measurement value, and calculates a calculation control output value of the control target by digital calculation from the deviation;
Numerical conversion means for converting into a theoretical control output value to be controlled according to the calculation control output value calculated by the control calculation means;
Correction arithmetic means for correcting a deviation of the control output value caused by the accuracy difference between the digital arithmetic unit comprising the control arithmetic means and the numerical value converting means and the D / A converter, based on the actual control output value and the output time; ,
A process control apparatus comprising: The process control apparatus according to claim 7, wherein
Storage means for preliminarily storing a threshold value of the theoretical control output value;
The threshold value stored in the storage means and the theoretical control output value converted by the numerical value conversion means are compared. If the theoretical control output value is equal to or greater than the threshold value, the theoretical control output value and the uncorrected output time are A comparison / determination unit that inputs to the D / A converter and determines that the theoretical calculation output value is corrected by the actual calculation output value and the output time if the theoretical control output value is less than the threshold;
A process control apparatus comprising: Using a deviation obtained from a comparison between a preset reference value of a control target and an actual measurement value, a control output value calculated by digital arithmetic processing is converted into an analog signal by a D / A converter, and an operation target is determined according to the analog signal. In a process control device that controls while operating,
A control calculation unit that calculates a deviation from a comparison between the reference value of the control target and the actual measurement value, and calculates a calculation control output value of the control target by digital calculation from the deviation;
Numerical conversion means for converting into a theoretical control output value to be controlled according to the calculation control output value calculated by the control calculation means;
Correction arithmetic means for correcting a deviation of the control output value caused by the accuracy difference between the digital arithmetic unit comprising the control arithmetic means and the numerical value converting means and the D / A converter, based on the actual control output value and the output time; With
In addition, one actual control output value calculated by the correction calculating means is input to the D / A converter, and the output time of the other corrected actual control output value is an operation target based on the output start time and end time. Is converted into a switching signal for ON / OFF switching and input to the operation target.
A process control device.

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