JP2009037377A - Verification simulator for programmable controller with pid process control function and verification system using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the time and cost required to verify the PID computing operation of a programmable controller, while enhancing security. <P>SOLUTION: A verification simulator 3 used 1 in place of the subject of control in order to verify the PID process control function of the programmable controller 1 includes: a buffer part 13 which receives the input of control outputs and gives outputs with delay corresponding to the heat capacity of the subject of control; and a computing part 15 which computes a present value in accordance with control outputs from the buffer part 13 and the heat capacity of the subject of control and inputs the value to the programmable controller 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention performs a PID calculation based on a deviation between a target value and a current value that is a feedback value from a controlled object, and also a programmable with a PID process control function that outputs a control output corresponding to the PID calculation result to the controlled object. The present invention relates to a verification simulator used for a controller (also referred to as a programmable logic controller) in place of the control object in order to verify the PID process control function.

  As disclosed in Patent Document 1, the programmable controller can execute basic instructions for sequence-controlling the controlled object and simple application instructions such as four arithmetic operations and comparisons.

  On the other hand, a programmable controller that has a PID process control command and can be used to perform PID process control has also been developed.

  The programmable controller 1 having a function of executing PID process control with reference to FIG. 3 includes a target value from the target value input unit 5, a current value from the current value input unit 7 (feedback value from the control target 21), and Based on the deviation, the PID calculation unit 9 performs PID calculation and outputs the PID calculation result as a control output from the control output unit 11. The DA conversion unit 17 performs DA conversion and outputs it to the controlled object 21.

  For example, when an electric furnace is given as the control target 21, the electric furnace includes a heater 23 therein, a switch control unit 27 is interposed between the heater 23 and the power source 25, and a temperature sensor 29 is disposed in the electric furnace. is doing.

  When the switch control unit 27 is PID controlled to adjust the power supplied to the heater 23 to control the temperature in the electric furnace to a target value (target temperature) and heat the article 31 to be heated in the electric furnace, The current value (current temperature) in the electric furnace is measured by the sensor 29, and the measured current value is AD-converted by the AD conversion unit 19 in the programmable controller 1 and given to the current value input unit 7.

  Although not shown in the figure, this programmable controller includes, for example, a building block type including a power supply unit, a CPU unit, a DA conversion unit, and an AD conversion unit. The CPU unit includes a CPU, a program memory, and a data memory. Etc., the PID calculation is performed by the CPU, the digital value PID calculation result is DA-converted by the DA conversion unit, and the current value from the controlled object is AD-converted by the AD conversion unit. .

  The above PID process control is a combination of proportional action (P), integral action (I), and differential action (D) to control the process to be controlled. The proportional action performs smooth control without hunting, and the integral action. The offset can be automatically corrected with, and the response to the disturbance can be accelerated by the differential operation.

After designing and manufacturing a programmable controller for electric furnace control with the above configuration, before delivering the programmable controller to the user,
It is necessary to verify whether or not the programmable controller appropriately performs PID process control with the electric furnace as a control target.

  In preparation for the verification, it is necessary to produce an application that assumes an electric furnace that the user may use.

Therefore, the verification takes time. In addition, it takes considerable effort and cost to create an environment for performing verification by operating an application. In addition, in order to operate an application, verification safety may be impaired.
Japanese Patent Laid-Open No. 9-16225

  An object of the present invention is to shorten the time required for verifying the PID calculation operation of the programmable controller, to reduce labor, to reduce costs, and to improve safety in verification.

  As a problem to solve this object, it is possible to create application software capable of having the same operation as the application used by the user, and to control the PID configured by the application used by the user. Even if there are many kinds of products and their movements are different, how to incorporate the movements of the various kinds into the application software becomes a challenge.

  The verification simulator according to the present invention performs PID calculation based on a deviation between a target value and a current value that is a feedback value from a control target, and outputs a control output corresponding to the PID calculation result to the control target. A verification simulator used in place of the control object for verifying the PID process control function for a programmable controller with a function, which inputs the control output and outputs it delayed by a time corresponding to the heat capacity of the control object And a calculation unit that calculates a current value corresponding to the control output output from the buffer unit and the heat capacity to be controlled and supplies the current value to the programmable controller. is there.

  According to the present invention, when a control output that is a PID calculation result corresponding to the deviation between the target value and the current value is input from the programmable controller to the verification simulator, the verification simulator controls the input control output by the buffer unit. Since the calculation unit calculates after a response delay corresponding to the heat capacity of the target, the current value input from the calculation unit to the programmable controller can be changed in the same manner as the verification using the actual control target. Therefore, in the present invention, it becomes possible to verify whether or not the PID calculation function of the programmable controller functions properly for a variety of control objects that the user may use, with a verification simulator, It is no longer necessary to create an application that assumes the electric furnace to be used by the user when performing the verification as in the past, and it is not necessary to create an environment for performing verification by operating the application. Sex can be secured.

  One of the preferred embodiments is that the buffer unit is formed by cascading multiple stages of shift registers, and the control output input to the first stage shift register is sequentially shifted to the next and subsequent shift registers every unit time. In other words, it is configured to output from the last-stage shift register to the arithmetic unit.

One of the preferred embodiments is that the current value calculation unit is PV = Vout × [1-ε when the current value PV is increased, assuming that the current value is PV, the control output is Vout, the time is t, and the heat capacity is CR. ^{(−t / CR)} ], to decrease the current value PV, the current value is calculated by the equation PV = Vout × [ε ^{(−t / CR)} ].

  A verification system according to the present invention performs a PID calculation based on a deviation between a target value and a current value that is a feedback value from a control target, and outputs a control output corresponding to the PID calculation result to the control target. A programmable controller with a control function and the verification simulator of the present invention are provided.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to verify the PID calculation operation of a programmable controller in a short time, with little effort, at low cost, and ensuring safety.

  Hereinafter, a verification simulator according to an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a verification system including a programmable controller and a verification simulator according to the embodiment. The verification system shown in FIG. 1 includes a programmable controller 1 and a verification simulator 3.

  The programmable controller 1 includes a target value input unit 5, a current value input unit 7, a PID calculation unit 9, and a control output unit 11. The target value input unit 5 is set by the user. If the controlled object is an electric furnace, for example, the target value is the target temperature in the electric furnace. The current value input unit 7 is a current temperature in the electric furnace to be controlled. The PID calculation unit 9 performs PID calculation from the deviation between the target value and the current value, and gives the PID calculation result to the control output unit 11. The control output unit 11 outputs a control output corresponding to the PID calculation result to the verification simulator 3. In this case, the current value given from the verification simulator 3 to the current value input unit 7 of the programmable controller 1 is digital data, and the control output given from the programmable controller 1 to the verification simulator 3 is also digital data.

  The verification simulator 3 can be composed of a microcomputer, and outputs a control output input from the programmable controller 1 with a delay corresponding to the actual heat capacity of the control target 21 shown in FIG. 13 and a calculation unit 15 that calculates a current value corresponding to the control output output from the buffer unit 13 and the heat capacity to be controlled and gives the current value to the programmable controller 1 as the current value of the control target.

  As an example, the buffer unit 13 is composed of, for example, n shift registers 131, 132,. Each of the shift registers 131, 132,..., 13n is composed of a storage element. The shift registers 131, 132,..., 13n sequentially shift the control output input to the first-stage shift register 131 to the shift registers 132,. The register 13n is configured to output to the calculation unit 15.

  , 13n are control outputs 1, 2 output from the programmable controller 1 before time n × t, (n−1) × t,..., T before the shift controller 131, 132,. ,..., N are stored and held. Therefore, the control output Vout before time n × t is given from the buffer unit 13 to the calculation unit 15.

When the current value PV is increased, the current value PV is increased, assuming that the current value is PV, the control output is Vout, the time is t, and the heat capacity is CR, PV = Vout × [1-ε ^{(−t / CR)} ] In (1), when the current value PV is decreased, the current value is calculated by the equation (2) of PV = Vout × [ε ^{(−t / CR)} ].

  In the electric furnace to be controlled, for example, even if the control output Vout is given from the programmable controller 1, the current value PV in the electric furnace does not become the target value in response immediately, but the current value PV increases with a delay due to its heat capacity. Or it will decrease. That is, when the control output Vout increases, the current value PV increases, and the increase rate shows a rising curve corresponding to the magnitude of the control output Vout. When the control output Vout decreases, the current value PV decreases, and the decrease rate is A descending curve corresponding to the magnitude of the control output Vout is shown.

  It can be assumed that the up and down curves are determined by the charge / discharge time constant CR in the series charge / discharge circuit, assuming that the heat capacity of the electric furnace to be controlled is a series charge / discharge circuit of a capacitor and a resistor. In this case, when the current value PV is lower than the target value, the control value Vout is increased in order to increase the current value PV. As a result, the current value PV is increased, and the current value PV is higher than the target value. Since the current value PV is decreased, the control output Vout is reduced, and as a result, the current value PV is decreased. The curve changes with a response delay corresponding to the heat capacity.

  The operation will be described with reference to FIG. 2A shows the change in the control output Vout, FIG. 2B shows the change in the current value PV by the PID process control when an actual control target is used, and FIG. 2C shows the verification simulator 3 of the embodiment. In FIG. 2, the current value PV is changed by the PID process control when the control output Vout from the programmable controller 1 is calculated by the calculation unit 15 of the verification simulator 3, and FIG. 2D shows the verification simulator of the embodiment. 3 shows a change in the current value PV by PID process control when the control output Vout is delayed by the buffer unit 13 at the response delay condition equivalent to that of the actual control object and is calculated by the calculation unit 15 of the verification simulator 3. .

  2A and 2D will be mainly described while comparing with the change in the current value PV by the PID process control using the actual control target shown in FIG. FIG. 2 (c) is shown for comparison with FIG. 2 (d) and will not be described in particular.

  First, as shown in FIG. 2A, the control output Vout from the programmable controller 1 changes greatly at time t0. The control output Vout is input to the shift register 13n in the buffer unit 13 of the verification simulator 3.

  The control output Vout is sequentially shifted by the clock for each unit time t in the n shift registers 131, 132,..., 13n in the buffer unit 13, and is input to the arithmetic unit 15. It takes time t × n to be input to.

  That is, the control output Vout given from the programmable controller 1 at time t0 is input to the calculation unit 15 at time t1 after time t × n has elapsed from time t0 and is calculated according to the above equation 1, and the calculation result is currently The value PV is input to the programmable controller 1.

  Next, since this control output Vout does not fall until time tn, the control output Vout from the buffer unit 13 is input every time the unit time t sequentially from the time t1 until the time tn. The calculated current value PV is input to the programmable controller 1. In this case, the current value PV rises from a curve determined by the charge / discharge time constant CR as shown in FIG.

  Next, when the control output Vout falls at time tn as shown in FIG. 2A, the actual current value PV falls after a time t × n response delay as shown in FIG. 2B. . That is, in the embodiment, the control output Vout is calculated by the equation (2) after being input to the operation unit 15 after being delayed by the time t × n by the buffer unit 13 of the verification simulator 3. The value PV falls as shown in FIG.

  From the above, as shown in FIG. 2 (c), if the buffer unit 13 does not delay the response of the control output Vout compared to the shape of the rise and fall curves of the current value PV by the actual control object shown in FIG. 2 (b). It becomes an ascending and descending curve and does not coincide with FIG. On the other hand, when the control output Vout is delayed in response by the buffer unit 13 of the verification simulator 3 of the embodiment, the current value PV is the same as the control output Vout in FIG. As shown, the curve is an ascending / descending curve that coincides with the actual controlled object shown in FIG.

  From the above, in the embodiment, the buffer unit 13 of the verification simulator 3 delays the control output from the programmable controller 1 by the time corresponding to the heat capacity to be controlled and then inputs it to the computing unit 15. When verifying whether the operation is in accordance with the required design, it is not necessary to create an application that assumes a variety of control targets that the user may use, and the application is operated and verified. It is no longer necessary to create an environment for performing verification, and it is possible to secure verification safety.

FIG. 1 is a diagram showing a configuration of a verification system according to an embodiment of the present invention. FIG. 2 is a diagram for explaining the operation of the verification system of FIG. FIG. 3 is a diagram showing the configuration of the PID process control system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Programmable controller 5 Target value input part 7 Present value input part 9 PID calculation part 11 Control output part 3 Verification simulator 13 Buffer part 15 Calculation part

Claims (4)

The PID for a programmable controller with a PID process control function that performs a PID calculation based on a deviation between the target value and a current value that is a feedback value from the control target and outputs a control output corresponding to the PID calculation result to the control target. A verification simulator that is used in place of the control target to verify the process control function,
The verification simulator is
A buffer unit that inputs the control output and outputs a delayed time corresponding to the heat capacity to be controlled;
A calculation unit that calculates a current value corresponding to the control output output from the buffer unit and the heat capacity of the control target and gives the current value to the programmable controller;
A verification simulator characterized by comprising:   The buffer unit is formed by cascading multiple stages of shift registers, and sequentially shifts the control output input to the first stage shift register to the next and subsequent stage shift registers every unit time. The verification simulator according to claim 1, wherein the verification simulator is configured to output from a shift register to the arithmetic unit. When the current value is PV, the control output is Vout, the time is t, and the heat capacity is CR,
When increasing the current value PV, PV = Vout × [1−ε ^{(−t / CR)} ]
PV = Vout × [ε ^{(-t / CR)} ] to decrease the current value PV
3. The verification simulator according to claim 1, wherein the current value is calculated by the following formula.   A programmable controller with a PID process control function, which performs PID calculation based on a deviation between the target value and a current value which is a feedback value from the control target, and outputs a control output corresponding to the PID calculation result to the control target; A verification system comprising the verification simulator according to any one of Items 1 to 3.

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