JP2009199219A - Pid control device, and method for protecting nonvolatile memory - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a probability that a non volatile memory such as an EEPROM reaches the end of the life. <P>SOLUTION: A PID control device includes a RAM 3 for storing a latest parameter value, an EEPROM 4 for storing a definite parameter value, and a writing/reading unit 5 for writing/reading the RAM 3 or the EEPROM 4. The writing/reading unit 5 includes an operation detecting unit 50 for detecting operations other than a setting change operation of the PID parameter, and a writing processing unit 51 for writing the latest PID parameter value stored in the RAM 3 in the EEPROM 4 as the definite value when the operation detecting unit 50 detects operations other than the setting change operation of the PID parameter. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a PID control device such as a temperature controller, and more particularly to a PID control device and nonvolatile memory protection capable of reducing the probability that a nonvolatile memory such as an EEPROM mounted on the PID control device reaches the end of its life. It is about the method.

  A loop level PID control device such as a temperature controller has parameters that need to be set and stored in advance, and an EEPROM (Electronically Erasable and Programmable Read Only Memory) is used as a storage device. . For example, in the control device disclosed in Patent Document 1 and Patent Document 2, the PID parameter value is automatically corrected during the online operation of control such as during step response or when hunting occurs. In a compact loop level control device, these parameter values are stored in EEPROM. Thus, in the control device, writing to the EEPROM is normally performed during online operation.

  However, the EEPROM has a life as a characteristic of the hardware, and when the number of times of writing increases, it reaches the life and does not operate normally. In the PID control device, it is inevitable that the writing / updating is necessary in practice as the property of the parameter written in the EEPROM. On the other hand, since it is incorporated into the apparatus as a PID control device and used continuously, it is not easy to replace the EEPROM, and at the same time, it is not preferable that the EEPROM reaches its life and does not operate normally.

JP-A-9-160604 JP-A-10-105201

  As described above, in the conventional control device, writing to the EEPROM is normally performed during online operation. However, Patent Document 1 and Patent Document 2 do not consider the life of the EEPROM, and do not disclose a clear improvement method for the method of using the control device in consideration of the life of the EEPROM. Note that the above-mentioned problems occur not only in the EEPROM but also in a non-volatile memory with a limited number of writings.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a PID control device and a nonvolatile memory protection method capable of suppressing the probability that a nonvolatile memory such as an EEPROM will reach the end of its life. And

The PID control device of the present invention includes a volatile memory that stores the latest value of the PID parameter, a non-volatile memory that stores the determined value of the PID parameter, and whether or not the PID parameter stored in the volatile memory has been determined. When the parameter determination determining unit determines that the PID parameter has been determined, the latest value of the PID parameter stored in the volatile memory is written to the nonvolatile memory as a determined value. And a writing processing means.
Further, in one configuration example of the PID control device according to the present invention, the parameter confirmation determining unit determines that the PID parameter is confirmed when an operation other than a setting change operation of the latest value of the PID parameter is detected. It is.
Further, in one configuration example of the PID control device of the present invention, the parameter confirmation determining unit determines that the PID parameter has been confirmed when the settling state of the control is detected.
Further, in one configuration example of the PID control device according to the present invention, the parameter determination determining unit determines that the PID parameter is fixed when the attenuation of the vibration state of the control is detected.
In addition, one configuration example of the PID control device of the present invention further includes setting change means for changing the latest value of the PID parameter in accordance with an input from an operator.
In addition, one configuration example of the PID control device of the present invention further includes setting change means for changing the latest value of the PID parameter in accordance with an input from a PID parameter adjustment device that adjusts the PID parameter by an auto-tuning function. It is.

  The present invention also relates to a parameter determination method for determining whether or not the latest value of a PID parameter stored in a volatile memory is fixed in a nonvolatile memory protection method for protecting a nonvolatile memory that stores a fixed value of a PID parameter. A determination procedure, and a write processing procedure for writing the latest value of the PID parameter stored in the volatile memory into the nonvolatile memory as a determined value when the parameter determination determination procedure determines that the PID parameter has been determined. It is to be prepared.

  According to the present invention, it is determined whether or not the PID parameter stored in the volatile memory is fixed, and when it is determined that the PID parameter is fixed, the latest value of the PID parameter stored in the volatile memory is determined. Since the fixed value is written in the non-volatile memory, the number of times of writing to the non-volatile memory such as the EEPROM can be reduced, and the probability that the non-volatile memory reaches the end of its life can be kept low.

[Principle of Invention 1]
Needless to say, there is a PID parameter as a parameter written to the EEPROM in the PID control device. When it is necessary to readjust and change the PID parameter frequently, the numerical value writing of the PID parameter greatly affects the life of the EEPROM. That is, it is important for the life of the EEPROM to reduce the number of times of writing the PID parameter. There is no need to write the PID parameter directly to the EEPROM, and the PID to be stored in the EEPROM in the process of changing the PID parameter. The inventors have noted that the parameters are limited. Then, the inventor believes that it is effective for solving the problem if the PID parameters P, I, and D are individually changed and written in the RAM area, and after the change of the PID parameters is confirmed and written in the EEPROM. I came up with it. The time when the PID parameter is determined is “when an operation other than the PID parameter setting change operation is detected” as disclosed in the PID parameter previous value restoration method of Japanese Patent Laid-Open No. 2005-215730.

[Principle of Invention 2]
Further, the inventor noted that only PID parameters that can be normally controlled are necessary PID parameters that should be stored, and that PID parameters that are recognized as being confirmed are PID parameters that can be normally controlled. . Then, the inventor has conceived that it is effective for solving the problem if the PID parameter is changed and written in the RAM area and the PID parameter is written in the EEPROM after detecting the settling state of the control. The PID parameter that can be normally controlled is a PID parameter that can stabilize the control and obtain a settling state in many cases.

[Principle 3 of the invention]
Furthermore, when a PID parameter that can be controlled normally is used as a criterion for determining the PID parameter, a damping state that oscillates from a transient state is detected without waiting for the detection of the control stabilization state. The inventor has conceived that, if possible, the settling state may be regarded as being confirmed. In this case, since writing to the EEPROM can be performed earlier than detecting the settling state, the probability that the set numerical value is lost when an unexpected trouble such as a power failure occurs can be reduced.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a PID control device according to the first embodiment of the present invention. This embodiment corresponds to Principle 1 of the invention described above. The PID control device includes a PID control unit 1 that controls the control target, an input unit 2 such as an operation panel for an operator (user) of the PID control device to input and change parameters, RAM (Random Access Memory) 3 that is a volatile memory that stores the latest value, EEPROM 4 that is a nonvolatile memory that stores a fixed value of a parameter, and writing that performs writing / reading to / from RAM 3 or EEPROM 4 as necessary / Reading unit 5.

  The writing / reading unit 5 is stored in the RAM 3 when the operation detection unit 50 detects an operation other than the PID parameter setting change operation and the operation detection unit 50 detects an operation other than the PID parameter setting change operation. A write processing unit 51 that writes the latest value of the PID parameter to the EEPROM 4 as a definite value, and a read processing unit 52 that reads the parameter from the RAM 3 or the EEPROM 4. The operation detection unit 50 constitutes parameter confirmation determination means for determining whether or not the PID parameter is confirmed. Further, the writing processing unit 51 constitutes a setting changing unit that changes the latest value of the PID parameter in accordance with an input from an operator or an input from a PID parameter adjusting device (not shown) that adjusts the PID parameter by an auto tuning function. ing.

  FIG. 2 is a diagram illustrating an example of a temperature control system to which the PID control device of the present embodiment is applied. In the example of FIG. 2, a heater 112 and a temperature sensor 113 are installed inside the heat treatment furnace 111. The temperature sensor 113 measures the temperature PV of the air heated by the heater 112. The temperature controller 100 calculates the manipulated variable MV so that the temperature PV matches the target value SP. The power adjuster 114 determines power according to the operation amount MV, and supplies the determined power to the heater 112 through the power supply circuit 115. Thus, the temperature controller 100 controls the temperature in the heat treatment furnace 111. The PID control device is provided inside the temperature controller 100.

Hereinafter, the operation of the PID control device will be described. In the EEPROM 4, parameters such as a target value SP and PID parameters (proportional band P, integration time I, differential time D) are set and stored in advance.
The reading processing unit 52 of the writing / reading unit 5 reads the target value SP and the PID parameter from the EEPROM 4 when the PID control device is activated, and develops them on the RAM 3 as the latest parameter values.

  The PID control unit 1 is known based on the latest value of the target value SP and the PID parameter read from the RAM 3 through the writing / reading unit 5 and the control amount PV (temperature in the example of FIG. 2) input from the sensor. The manipulated variable MV is calculated by the PID control calculation algorithm so that the target value SP and the controlled variable PV coincide. In the example of FIG. 2, the manipulated variable MV is output to the power regulator 14.

  The writing / reading unit 5 writes data to the RAM 3 or the EEPROM 4 in accordance with an input from the input unit 2 or an external device such as a PID parameter adjusting device. Further, the writing / reading unit 5 reads data from the RAM 3 or the EEPROM 4 as necessary. FIG. 3 is a flowchart showing operations related to the writing process of the writing / reading unit 5. Hereinafter, the writing process of the writing / reading unit 5 will be described with reference to FIG.

  First, the writing processing unit 51 of the writing / reading unit 5 is input from the input unit 2 when the operator operates the input unit 2 and performs a PID parameter setting change operation (YES in step S100 in FIG. 3). The PID parameter thus written is written in the RAM 3 (step S101). As a result, the latest value of the parameter stored in the RAM 3 is changed. Note that it is not necessary to change all of the proportional band P, the integration time I, and the differential time D, and this setting change operation was performed when a setting change operation was performed for at least one of these parameters. Change the parameter to the latest value. Further, the PID parameter setting change operation may be performed not only from the input unit 2 but also from an external device such as a PID parameter adjustment device.

  Next, the operation detection unit 50 of the writing / reading unit 5 performs a determination process for detecting an operation other than the PID parameter setting change operation by the operator (step S102). Operations other than the PID parameter setting change operation include, for example, an operation for changing the target value SP, and an operation for switching from the PID parameter setting change operation screen to the control state monitoring screen.

  When the operation detection unit 50 detects an operation other than the PID parameter setting change operation (YES in step S102), the writing processing unit 51 stores the latest value of the PID parameter stored in the RAM 3 and the EEPROM 4. The determined PID parameter value is compared (step S103). If the latest value and the final value of at least one parameter of the proportional band P, the integration time I, and the differential time D are different from each other (YES in step S103), the writing processing unit 51 determines the different parameters. Only, the fixed value of the parameter stored in the EEPROM 4 is updated to the latest value of the parameter stored in the RAM 3 (step S104).

  The processes in steps S100 to S104 as described above are repeatedly executed at regular operation cycles until, for example, the operator instructs the end of PID control. This operation cycle may normally be the same as the control cycle of the PID control unit 1.

  As described above, in the present embodiment, once the PID parameter is written to the RAM 3 and an operation other than the PID parameter setting change operation is performed, the operator assumes that the PID parameter has been determined and changed. Since the latest value of the PID parameter is written to the EEPROM 4 as a definite value, the number of times of writing to the EEPROM 4 can be reduced, and the probability that the EEPROM 4 reaches the end of its life can be kept low.

  In the present embodiment, for the target value SP, the changed latest value is immediately written as a confirmed value in the EEPROM 4, but the principle 1 of the invention may be applied to the target value SP as in the case of the PID parameter.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. FIG. 4 is a block diagram showing a configuration of a PID control device according to the second embodiment of the present invention. This embodiment corresponds to Principle 2 of the invention described above. The PID control device according to the present embodiment includes a PID control unit 1, an input unit 2, a RAM 3, an EEPROM 4, and a writing / reading unit 5a.

  The writing / reading unit 5a includes a writing processing unit 51a that writes the latest value of the PID parameter stored in the RAM 3 to the EEPROM 4 as a definite value when a settling detection unit described later detects a control settling state, A processing unit 52 and a settling detection unit 53 that detects the settling state of the control are provided. The settling detection unit 53 constitutes a parameter confirmation determination unit, and the write processing unit 51a constitutes a setting change unit.

FIG. 5 is a flowchart showing operations related to the writing process of the writing / reading unit 5a. Hereinafter, the writing process of the writing / reading unit 5a will be described with reference to FIG.
The processes in steps S200 and S201 are the same as steps S100 and S101 in FIG.

  Next, the settling detection unit 53 of the writing / reading unit 5a determines whether or not the control is set after the control by the PID control unit 1 is started (step S202). FIG. 6 is a waveform diagram for explaining the operation of the settling detection unit 53. FIG. 6 shows a control response waveform when the PID parameter auto-tuning (AT) is started by the PID parameter adjusting device and the latest value of the PID parameter is set. That is, when the AT is finished, the processes of steps S200 and S201 are performed, and the latest value of the PID parameter is updated. As a typical AT method, there is a limit cycle method in which an upper limit value and a lower limit value are set in advance for the operation amount MV to be output to the control target, a limit cycle having a constant operation amount amplitude is generated, and a PID parameter is adjusted. is there. The limit cycle type AT is disclosed in, for example, Japanese Patent Application Laid-Open No. 2003-330504.

  The settling detection unit 53 compares the absolute value | SP-PV | of the deviation between the target value SP and the control amount PV with a predetermined reference deviation Erx, and the absolute value | SP-PV | of the deviation is based on the reference deviation Erx. Is smaller than the predetermined reference duration time Tx, it is determined that the control is settled. The settling detection unit 53 determines whether or not such control has been settled at regular operation cycles. Note that the measurement of the duration is a precondition that the control is continuously executed in a state where the PID parameter is not changed. Therefore, when the PID parameter is changed, the settling detection unit 53 resets the duration to 0, and starts measuring the duration again after the absolute value | SP-PV | of the deviation becomes smaller than the reference deviation Erx. Then, it is determined whether or not this duration has reached the reference duration Tx.

  Write processing unit 51a determines the latest value of the PID parameter stored in RAM 3 and the PID parameter stored in EEPROM 4 when settling detection unit 53 detects the settling state of control (YES in step S202). The values are compared (step S203). When the latest value and the final value of at least one parameter of the proportional band P, the integration time I, and the differential time D are different (YES in step S203), the writing processing unit 51a determines the different parameters. Only, the final value of the parameter stored in the EEPROM 4 is updated to the latest value of the parameter stored in the RAM 3 (step S204).

  The processes in steps S200 to S204 as described above are repeatedly executed at regular operation cycles until, for example, the operator instructs the end of PID control. This operation cycle may normally be the same as the control cycle of the PID control unit 1.

  In this embodiment, it is considered that the PID parameter is fixed when the control is settled, and the latest value of the PID parameter is written in the EEPROM 4 as a fixed value, so that the number of times of writing to the EEPROM 4 can be reduced, The probability that the EEPROM 4 reaches the end of its life can be kept low. This embodiment is particularly effective when the PID parameter is changed by the AT function of the PID parameter adjusting device as described with reference to FIG.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. FIG. 7 is a block diagram showing a configuration of a PID control device according to the third embodiment of the present invention. This embodiment corresponds to Principle 3 of the invention described above. The PID control device according to the present embodiment includes a PID control unit 1, an input unit 2, a RAM 3, an EEPROM 4, and a writing / reading unit 5b.

  The writing / reading unit 5b includes a writing processing unit 51b that writes the latest value of the PID parameter stored in the RAM 3 to the EEPROM 4 as a definite value when a later-described damping detecting unit detects damping of the vibration state of control. , A read processing unit 52, a swing width calculation unit 54 that calculates a swing width when the control amount PV moves up and down, and attenuation of the vibration state of the control is detected based on the swing width calculated by the swing width calculation unit 54. An attenuation detection unit 55. The swing width calculation unit 54 and the attenuation detection unit 55 constitute a parameter determination determination unit, and the write processing unit 51b constitutes a setting change unit.

FIG. 8 is a flowchart showing operations related to the writing process of the writing / reading unit 5b. Hereinafter, the writing process of the writing / reading unit 5b will be described with reference to FIG.
The processes in steps S300 and S301 are the same as those in steps S100 and S101 in FIG.

  Next, the swing width calculation unit 54 of the writing / reading unit 5b calculates the swing width of the control amount PV (step S302). FIG. 9 is a waveform diagram for explaining the operations of the swing width calculator 54 and the attenuation detector 55. FIG. 9 shows a control response waveform when the PID parameter AT is started by the PID parameter adjusting device and the latest value of the PID parameter is set. That is, when the AT is finished, the processes of steps S300 and S301 are performed, and the latest value of the PID parameter is updated.

The swing width calculation unit 54 detects the maximum deviation absolute value when the deviation (SP−PV) between the target value SP and the control amount PV becomes a positive value (when the control amount PV is smaller than the target value SP). Er1 = | SP−PV | which is the maximum deviation absolute value detected when the deviation (SP−PV) becomes a negative value (when the control amount PV is larger than the target value SP). Er2 = | SP-PV | is detected. Then, the swing width calculation unit 54 calculates the swing width A of the control amount PV by the following equation.
A = Er1 + Er2 (1)

  Note that the calculation of the swing width A is a precondition that the control is continuously executed in a state where there is no change in the PID parameter. Therefore, when the PID parameter is changed, the swing width calculation unit 54 redoes the detection of the maximum deviation absolute values Er1 and Er2. Further, the swing width calculation unit 54 operates at a constant operation cycle, but the calculation of the swing width A is not limited to each operation cycle. As shown in FIG. 9, the swing width A is calculated when the maximum deviation absolute value Er1 is detected after the maximum deviation absolute value Er2 is detected, or after the maximum deviation absolute value Er1 is detected. This is either when the absolute value Er2 is detected.

The attenuation detector 55 compares the latest amplitude A1 calculated by the amplitude calculator 54 with the previous amplitude A2, and determines whether or not the vibration state of control has been attenuated by the following equation (step S303).
A1 / A2 <α (2)

  α is a threshold value having a value smaller than 1, for example, 0.7. In this case, when the ratio A1 / A2 of the latest amplitude A1 to the previous amplitude A2 is smaller than α = 0.7, the attenuation detection unit 55 determines that the vibration state of the control is attenuated. Although the attenuation detection unit 55 operates every fixed operation cycle, the determination of Expression (2) is not always performed every operation cycle. The determination of Expression (2) is performed when the swing width A1 is calculated after the swing width A2 is calculated.

  When the attenuation detection unit 55 detects the attenuation of the vibration state of the control (YES in step S303), the writing processing unit 51b and the latest value of the PID parameter stored in the RAM 3 and the PID parameter stored in the EEPROM 4 Is compared with the determined value (step S304). If the latest value and the final value of at least one parameter of the proportional band P, integration time I, and differentiation time D are different (YES in step S304), the writing processing unit 51b determines the different parameters. Only, the final value of the parameter stored in the EEPROM 4 is updated to the latest value of the parameter stored in the RAM 3 (step S305).

  The processes in steps S300 to S305 as described above are repeatedly executed at regular operation cycles until the operator instructs the end of PID control. This operation cycle may normally be the same as the control cycle of the PID control unit 1.

  In the present embodiment, it is assumed that the PID parameter is determined when the vibration of the control response is attenuated, and the latest value of the PID parameter is written in the EEPROM 4 as the determined value. The probability that the EEPROM 4 reaches the end of its life can be kept low. This embodiment is particularly effective when the PID parameter is changed by the AT function of the PID parameter adjusting device as described with reference to FIG.

  The PID control device described in the first to third embodiments can be realized by a computer including a CPU, a storage device, and an interface, and a program that controls these hardware resources. The CPU executes the processes described in the first to third embodiments in accordance with a program stored in the storage device.

  In this embodiment, the EEPROM is described as an example. However, the present invention is not limited to the EEPROM, and the present invention is effective as long as the memory element has a limited number of times of writing.

  The present invention can be applied to a PID control device equipped with a storage element that has a limited number of times of writing such as an EEPROM.

It is a block diagram which shows the structure of the PID control apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows one example of the temperature control system to which the PID control apparatus which concerns on the 1st Embodiment of this invention is applied. It is a flowchart which shows operation | movement of the writing / reading part of the PID control apparatus which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the structure of the PID control apparatus which concerns on the 2nd Embodiment of this invention. It is a flowchart which shows operation | movement of the writing / reading part of the PID control apparatus which concerns on the 2nd Embodiment of this invention. It is a wave form diagram for demonstrating operation | movement of the settling detection part of the writing / reading part which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the PID control apparatus which concerns on the 3rd Embodiment of this invention. It is a flowchart which shows operation | movement of the writing / reading part of the PID control apparatus which concerns on the 3rd Embodiment of this invention. It is a wave form diagram for demonstrating operation | movement of the amplitude calculation part and attenuation | damping detection part of the writing / reading part which concerns on the 3rd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... PID control part, 2 ... Input part, 3 ... RAM, 4 ... EEPROM, 5, 5a, 5b ... Write / read part, 50 ... Operation detection part, 51, 51a, 51b ... Write processing part, 52 ... Read processing unit, 53... Settling detection unit, 54... Swing amount calculation unit, 55.

Claims (7)

A volatile memory for storing the latest value of the PID parameter;
A non-volatile memory for storing a definite value of the PID parameter;
Parameter confirmation determination means for determining whether or not the PID parameter stored in the volatile memory is confirmed;
A write processing means for writing the latest value of the PID parameter stored in the volatile memory as a confirmed value into the nonvolatile memory when the parameter confirmation determining means determines that the PID parameter is confirmed. A featured PID control device. The PID control device according to claim 1,
The PID control device, wherein the parameter confirmation determining unit determines that the PID parameter is confirmed when an operation other than a setting change operation of the latest value of the PID parameter is detected. The PID control device according to claim 1,
The PID control device, wherein the parameter confirmation determining unit determines that the PID parameter is confirmed when a settling state of control is detected. The PID control device according to claim 1,
The parameter confirmation determining means determines that the PID parameter has been confirmed when the attenuation of the vibration state of the control is detected. In the PID control device according to any one of claims 2 to 4,
The PID control device further comprises setting change means for changing the latest value of the PID parameter in response to an input from an operator. The PID control device according to claim 3 or 4,
The PID control device further comprises setting changing means for changing the latest value of the PID parameter in accordance with an input from a PID parameter adjusting device for adjusting the PID parameter by an auto tuning function. In a nonvolatile memory protection method for protecting a nonvolatile memory that stores a definite value of a PID parameter,
A parameter confirmation determination procedure for determining whether or not the latest value of the PID parameter stored in the volatile memory is confirmed;
A write processing procedure for writing the latest value of the PID parameter stored in the volatile memory into the nonvolatile memory as a determined value when it is determined in the parameter determination determining procedure that the PID parameter has been determined. A nonvolatile memory protection method.

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