JPH11231902A - Valve positioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a valve positioner capable of dealing with the abnormality of a microprocessor even in various control valves having respectively different parameters. SOLUTION: The valve positioner having a microprocessor 1 for sending a deviation between an input signal and an output from a position detector 7 as a drive signal corresponding to the input signal, an actualtor 5 for outputting a signal corresponding to an output from the microprocessor 1 to a control valve 6 and the position detector 7 for detecting the driven state of the control valve and converting the detected state into an electric signal is also provided with an abnormal time set point storing means 10 for storing a value capable of driving the control valve 6 so as not to generate an accident in a process as an output from the actuator 5, an operation means 11 for calculating the set value stored in the means 10 and the deviation between the output of the detector 7 and the input signal, a means 12 for switching an output signal from the means 11 to an output signal from the microprocessor 1 when abnormality occurs in the microprocessor 1 and supplying the switched signal to the actuator 5 and a means for setting up a control parameter for the valve 6 in the means 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve positioner suitable for use in a valve positioner or the like equipped with a microprocessor so that valve control can be performed safely even when an abnormality occurs in the microprocessor. It relates to an improved circuit.

[0002]

2. Description of the Related Art A valve positioner is disclosed, for example, in Japanese Patent Application Laid-Open No. 8-129401 proposed by the present applicant. FIG. 5 is a configuration diagram of a conventional valve positioner. In the figure, a microprocessor 1 is provided with an interface 2 for transmitting and receiving signals from the outside, and a memory 3 for storing a program such as an operation order. D
The / A converter 4 converts a digital signal sent from the microprocessor 1 into an analog signal. The actuator 5 outputs an air signal corresponding to the output of the D / A converter 4. The driving device 6 operates in response to an air signal from the actuator 5, and corresponds to, for example, a control valve.

The position detector 7 detects the position of a valve stem (not shown) of the control valve 6 and outputs an electric signal corresponding to the position. The A / D converter 8 converts an analog signal from the position detector 7 into a digital signal and sends the digital signal to the microprocessor 1. The watchdog timer 9 monitors the operation state of the microprocessor 1 and sends a signal to the changeover switch 12 when an abnormality occurs. The abnormal-time set value storage unit 10 is, for example, an electronic volume whose voltage or resistance value changes according to an electric signal.
The set value of the control valve 6 at the time of abnormality is stored. The abnormal setting value is selected such that the control valve 6 is operated to such an extent that the process is not excessively affected. Arithmetic means 11
Is a signal from the position detector 7 and an abnormal setting value storage unit 10
And outputs the deviation of the signal. For example, an analog operation circuit using an OP amplifier is used. The changeover switch 12 is located on the A side as shown in the figure when the microprocessor 1 is operating normally, and switches to the B side when an abnormality occurs.

In the device configured as described above, the set value in the abnormal set value storage unit 10 is set by the microprocessor 1 during normal operation. Then, a control signal for the control valve 6 is transmitted from an external control device (not shown) or the like. This control signal is taken into the microprocessor 1 via the interface 2 and signal processing is performed in accordance with the driving order stored in the memory 3, and its output is D /
The signal is converted into a predetermined electric signal by the A converter 4. This electric signal is output to the actuator 5, converted into an air signal corresponding to the electric signal, and sent to the control valve 6.

As a result, the valve of the control valve 6 opens and closes, and the position of the stem interlocked with the valve is displaced, so that the position detector 7 outputs an electric signal corresponding to this position. A / D
The converter 8 converts the electric signal into a digital signal,
It is sent to the microprocessor 1 as a feedback signal. Then, the microprocessor 1 calculates a deviation between the feedback signal and the input signal input through the interface 2, and outputs a signal that makes the difference zero.

The watchdog timer 9 monitors whether the microprocessor 1 is operating according to a predetermined procedure, and issues a predetermined electric signal when an abnormality of the microprocessor 1 is detected. Then, the changeover switch 12 is switched to the B side, and the control valve 6
1, the output from the microprocessor 1 is transmitted, and even if an abnormality occurs in the microprocessor 1, it is possible to prevent the possibility that the process will run away and cause a major accident.

[0007]

However, when the present invention is applied to an actual control valve, only the set value can be set in advance in case of a microprocessor abnormality, so that the polarity in the valve driving direction, the valve stroke amount, There was a problem that it was not possible to cope with various control valves having different parameters such as the air capacity of the valve actuator and the friction of the valve stem. SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to provide a valve positioner which can cope with a variety of control valves having different parameters when a microprocessor malfunctions.

[0008]

According to a first aspect of the present invention, there is provided a valve positioner comprising: a microprocessor for transmitting a drive signal corresponding to an input signal;
An actuator 5 for outputting a signal corresponding to the output of the microprocessor to the control valve 6, a position detector 7 for detecting an operation state of the control valve and converting it into an electric signal,
In a valve positioner having the microprocessor for transmitting a deviation between the output of the position detector and the input signal as a drive signal, a value for operating the control valve is stored as an output of the actuator to such an extent that an accident does not occur in a process. An abnormal set value storage means 10; a means 11 for calculating a deviation between a set value stored in the abnormal set value storage means, an output of the position detector, and the input signal; and an abnormality occurring in the microprocessor. In this case, a means 12 for switching the output signal of the arithmetic means to an output signal of the microprocessor and supplying the signal to the actuator, and a means for setting the control parameter of the control valve in the arithmetic means are provided. .

With this configuration, the value which can be set in advance in case of a microprocessor abnormality can be set in the arithmetic means in addition to the abnormality set value. Stroke amount,
Various control valves having different parameters such as the air capacity of the valve actuator and the friction of the valve stem can be supported.

Here, it is preferable that the control parameter is at least one of the gain 13 of the control loop, the polarity 14 of the control direction, or the integration time or the differentiation time 15. If the configuration is such that the gain of the control loop can be set,
Can handle valves with different strokes and actuator capacities. If the configuration is such that the polarity of the control direction can be set, it is possible to cope with valves having different drive directions. If the configuration is such that PID control parameters such as the integration time and the differentiation time can be set, it is possible to achieve high response and high precision control.

More specifically, if the gain of the control loop is set by means for setting the gain of the inverting amplifier of the arithmetic means, the analog arithmetic device has a principle of operation similar to that of a microprocessor. Since they are different, the reliability is improved as a provision for when the microprocessor is abnormal. If the gain setting means is a combination of an electronic volume, an analog switch capable of holding a connection state and a resistor, or a D / A converter with an EEPROM, the gain setting means is compatible with the inverting amplifier.

Here, the polarity of the control direction is determined by the output of the first inverting amplifier 15 of the arithmetic means,
If the switch 17 is configured to select the output of the second inverting amplifier 16 for inverting the output of the first inverting amplifier, it is possible to cope with both the positive direction and the negative direction.
Further, the integration time and the differentiation time are determined by the resistance values (R1, R1) connected to the inverting amplifier of the arithmetic means.
The configuration set in 2) is compatible with the inverting amplifier.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing one embodiment of the present invention.
In FIG. 1, components having the same functions as those in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted. In the figure, a gain storage unit 13 is provided with an abnormal setting value storage unit 10 → actuator 5
The control valve 6 stores the gain of the backup control loop in the event of an abnormality in the microprocessor. The second electronic volume is used, for example. The polarity storage unit 14 stores the polarity of the backup control loop, and uses, for example, a third electronic volume.

FIG. 2 is a main part circuit diagram showing a specific first embodiment of the present invention. The arithmetic circuit 11 performs proportional control, and has a second electronic volume 13 for gain storage, a third electronic volume 14 for polarity storage, a changeover switch 17, and inverting amplifiers 15 and 16 connected in series. ing. The inverting amplifier 15 has a plus terminal to which a signal from the electronic volume 10 for storing a set value at the time of abnormality is applied, and a minus terminal to which the valve stem from the position detector 7 passes via the second electronic volume 13 for gain storage. A position signal is input. The inverting amplifier 16 is an inverter having a gain of -1. The output signal of the inverting amplifier 15 is input to the minus terminal, and the plus terminal is grounded. As the changeover switch 17, for example, a CMOS analog switch is used.

In the device configured as described above, the second electronic regulator 13 sets the gain of the inverting amplifier 15 to set the gain of the backup control loop. The third electronic volume 14 is provided with a changeover switch 17
And the output of the arithmetic circuit 11 is set to the output of the inverting amplifier 15 or the output of the inverting amplifier 16 to determine the polarity of the control direction of the backup control loop.

FIG. 3 is a main part circuit diagram showing a second specific embodiment of the present invention. The arithmetic circuit 11 has a PID
In order to perform control, a fourth electronic regulator 19 (R1) for storing integration time and a fifth electronic regulator 18 (R2) for storing differential time are provided. The inverting amplifier 15 has a plus terminal connected to an electronic volume 10 for storing a set value at the time of abnormality, a minus terminal connected in series with a capacitor C2 and a fifth electronic volume 18 for storing integration time, and a fifth terminal for storing gain. A circuit in which two electronic regulators 13 (R4) are connected in parallel is connected. In a feedback loop connecting the output terminal and the minus terminal, a parallel circuit of a resistor R3, a capacitor C1, and a fifth electronic regulator 19 for storing a differential time is connected in series.

In the device configured as described above, the transfer function of the inverting amplifier 15 is given by the following equation.

(Equation 1)

FIG. 4 shows the frequency characteristics. In the low frequency region where the frequency ω is equal to or less than (1 / C ₁ R ₁ ), the gain is (R ₃ / R ₄ ) · {(R ₂ + R ₄ ) / R ₂ )}. When the frequency ω is (1 / C ₁ R ₁ ) from {1+ (R ₁ + R ₃ ) / C ₁ R ₁ }
In the frequency range of, the gain decreases with the frequency. When the frequency ω changes from {1+ (R ₁ + R ₃ ) / C ₁ R ₁ } to {1 / C ₂ (R ₂ +
R ₄ )}, the gain is (R ₃ / R ₄ ). The frequency ω changes from {1 / C ₂ (R ₂ + R ₄ )} to (1 /
In the frequency domain of C ₂ R ₂ ), the gain increases with frequency. In the high frequency region where the frequency ω is equal to or more than (1 / C ₂ R ₂ ), the gain is (R ₃ / R ₄ ) · {1+ (R ₁ / R ₃ )}.

That is, the integration time can be set by the resistor R1, the differentiation time can be set by the resistor R2, and the proportional gain can be set by the resistor R4. When the frequency characteristics are discussed, the integration time and the low frequency gain interfere with each other. Also, the proportional gain and the derivative time interfere.

In the above embodiment, various control parameters are set by the electronic regulators 10, 13, 14, 18, and 19. However, the present invention is not limited to this, and the connection state can be maintained. A combination of an analog switch and a resistor or a D / A converter with an EEPROM may be used. Further, it goes without saying that the present invention can be implemented with various changes within a range not departing from the gist.

[0021]

As described above, according to the valve positioner of the first aspect, the value which can be set in advance in case of the microprocessor abnormality is not only the abnormality setting value but also other control of the control valve by the arithmetic means. Since parameters can also be set, it is possible to cope with various control valves having different parameters such as the polarity in the valve driving direction, the valve stroke amount, the air capacity of the valve actuator, and the friction of the valve stem.

Here, it is preferable that the control parameter is at least one of the gain 13 of the control loop, the polarity 14 of the control direction, or the integration time or the differentiation time 15, as set forth in claim 2. If the configuration is such that the gain of the control loop can be set,
Can handle valves with different strokes and actuator capacities. If the configuration is such that the polarity of the control direction can be set, it is possible to cope with valves having different drive directions. If the configuration is such that PID control parameters such as the integration time and the differentiation time can be set, it is possible to achieve high response and high precision control.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention.

FIG. 2 is a main part circuit diagram showing a first specific example of the present invention.

FIG. 3 is a main part circuit diagram showing a second specific example of the present invention.

FIG. 4 is a frequency characteristic diagram of the inverting amplifier 15;

FIG. 5 is a configuration diagram of a conventional valve positioner.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Microprocessor 5 Actuator 6 Control valve 7 Position detector 10 Abnormal set value storage means 11 Calculation means 12 Changeover switch 13 Gain storage part 14 Polarity storage part

Claims (6)

[Claims] 1. A microprocessor (1) for transmitting a drive signal corresponding to an input signal, an actuator (5) for outputting a signal corresponding to an output of the microprocessor to a control valve (6), A valve positioner comprising: a position detector (7) for detecting an operation state and converting it into an electric signal; and a microprocessor for transmitting a deviation between an output of the position detector and the input signal as a drive signal. An abnormal setting value storing means (10) for storing a value at which the control valve is operated to such an extent that an accident does not occur in the process; and a setting value stored in the abnormal setting value storing means and an output of the position detector. Means (1) for calculating a deviation from the input signal
1) When an abnormality occurs in the microprocessor, means (12) for switching the output signal of the arithmetic means to the output signal of the microprocessor and supplying the output signal to the actuator.
And a means for setting a control parameter of the control valve in the arithmetic means. 2. The control parameter according to claim 1, wherein the control parameter is at least one of a gain (13) of a control loop, a polarity (14) of a control direction, and an integration time or a differentiation time (15). Valve positioner. 3. The valve positioner according to claim 2, wherein the gain of said control loop is set by means for setting a gain of an inverting amplifier of said arithmetic means. 4. The gain setting means includes a combination of an electronic volume, an analog switch capable of holding a connection state and a resistor,
4. The valve positioner according to claim 3, wherein the D / A converter includes an EEPROM. 5. The polarity of the control direction is determined by the output of a first inverting amplifier (15) of the arithmetic means and the output of a second inverting amplifier (16) for inverting the output of the first inverting amplifier. 3. The valve positioner according to claim 2, wherein the switch is set by a switch (17). 6. The valve positioner according to claim 2, wherein said integration time and differentiation time are set by resistance values (R1, R2) connected to an inverting amplifier of said arithmetic means.