JP2003140734A - Method and device for diagnosing equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a practical method and device for accurately diagnosing equipment even when an input to be diagnosed is operating at much higher speed than the arithmetic cycle of an arithmetic function or function block to be used for diagnosis. SOLUTION: In this method for diagnosing the equipment by diagnosing the operation of the equipment, the instantaneous value or statistics of a signal associated with the equipment to be diagnosed is compared with a reference signal associated with the equipment so that the operation of the equipment can be diagnosed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for diagnosing field devices in the field of process control.

The present invention relates to a diagnostic method and apparatus that can be effectively applied to field devices that perform digital communication with a host system. The digital communication mentioned here is, for example, a general-purpose communication protocol for process industry, that is, Foundation Fieldbus, PROFIBUS, HART, BRAIN.
Etc. is a protocol.

The field devices are, for example, sensor and actuator devices for the process industry, that is, transmitters, flow meters, valve positioners and the like. The higher-level system is an interface device (I / O) to which field devices are connected, a higher-level computer, or the like.

[0004]

2. Description of the Related Art FIG. 4 is a functional block diagram showing a configuration of a diagnostic device for equipment proposed by the applicant in Japanese Patent Application No. 2000-225553. Reference numeral 1 denotes a calculation unit, which calculates a signal proportional to velocity or acceleration from the input displacement signal X-1 of the valve positioner or the like and outputs it as a signal Y-1.

These calculations are usually performed by digital signal processing. In the case of digital signal processing, the calculation of the signal proportional to the speed calculates the difference between the previous displacement signal and the current displacement signal, and the signal proportional to the acceleration calculates the difference between the previous velocity signal and the current speed signal. Can be obtained.

Reference numeral 2 is a comparison operation unit, which is an output signal Y-1 of the operation unit 1 and a reference signal X-2 such as a set point signal to the valve.
Is input, these comparison operations are executed and the result is signaled as Y-
Output as 2. The signal Y-2 is output as an alarm signal, a discrete signal, a numerical signal, or a combination of these signals by a device that receives the signal.

An example of the operation of the comparison calculation unit 2 will be described with reference to FIG. In FIG. 5A, X-2 is a reference signal such as a valve set point signal. In (B), X-
1 is the valve opening signal, set point X at time t1
-When 2 rises, the valve opening signal X-
1 begins to change. In (C), Y-1 is a speed signal of the valve opening, which is a non-zero value while the valve opening is changing.

In (C), Yth is a threshold value for diagnosis. The comparison calculation unit 2 compares the valve opening speed signal Y-1 with the threshold value Yth for a predetermined period T.
That is, the rising timing t1 of the reference signal X-2 is used as the starting point of the diagnosis period T. Valve opening speed signal
Since Y-1 is below the level of the threshold value Yth when the value is not zero during the diagnosis period T, it is diagnosed that it is operating normally.

FIG. 5D shows an example in which stick-slip occurs in the valve, as an example of occurrence of abnormality. X-1 '
Is a valve opening signal when stick-slip occurs, and sharply rises significantly at timing t3, which is delayed from t2, and shows irregular movement.

Y-1 'shown in (E) is a speed signal of the valve opening obtained by differentiating X-1'. The comparison calculation unit 2 compares the valve opening speed signal Y-1 'with the threshold value Yth' during the diagnosis period T. At time t3, since the speed signal Y-1 'exceeds the threshold value Yth', it is diagnosed that stick-slip has occurred.

As described above, by using the valve opening degree as the operated input signal and the valve set point signal as the reference input signal, the phenomenon that the response of the valve becomes abnormally slow by a simple comparison operation and It is possible to diagnose an abnormal phenomenon that responds rapidly by stick-slip.

Furthermore, when the arithmetic function is implemented as a function block conforming to the Foundation Fieldbus standard, the output value of the function block of another device on the fieldbus was measured in-house. It is possible to combine the process values such as the valve opening and the output pressure signal and select them as the input signal to be operated.

[0013]

In the applicant's earlier application, the "arithmetic function" or "function block" used for diagnosis is shown in a highly versatile form, but the problem is that
Arithmetic functions and function blocks used for diagnosis generally have an arithmetic cycle (for example, 200 mse) necessary for process control.
Since it is executed in a cycle of c to 1 sec), if the speed or acceleration of a signal that changes rapidly such as valve output pressure or valve opening signal is calculated, the sampling interval is too long for the valve displacement speed. Therefore, an accurate value may not be obtained.

An object of the present invention is to diagnose a practical device that enables accurate diagnosis even when an input to be diagnosed operates faster than a calculation cycle of a calculation function or a function block used for diagnosis. The method and apparatus are to be realized. Practical means to show a configuration for executing highly accurate diagnostics in less computation time in field devices with limited power consumption and limited microprocessor performance.

[0015]

The present invention which achieves the above objects is as follows. (1) In a device diagnostic method for diagnosing device operation,
A method of diagnosing a device, wherein an instantaneous value or a statistical value of a signal related to a device to be diagnosed and a reference signal related to the device are compared and operated to diagnose the operation of the device. (2) In a device diagnostic device for diagnosing whether or not a device is operating normally, a comparison operation unit is provided to which an instantaneous value or statistical value of a signal related to the device and a reference signal related to the device are input. An apparatus diagnostic apparatus is characterized in that whether or not the apparatus is operating normally is diagnosed by the comparison calculation unit. (3) The method and apparatus for diagnosing a device according to (1) or (2), wherein the statistical value targets a signal proportional to a velocity or an acceleration of the device. (4) The statistical value includes a maximum value, a minimum value, an average value, a variance, a standard deviation, etc. of a signal proportional to the speed or acceleration of the device, according to (1) or (2). Equipment diagnostic method and apparatus. (5) Data relating to the input / output in a device diagnostic device formed in a field device that has a function block that communicates with a host system through digital communication means and that inputs process data and outputs a calculation result (1) through (1) to collect the data and calculate the instantaneous value or statistical value thereof, and a diagnostic means for executing and outputting a process for diagnosis using the statistical value calculated by the computing means. The method and apparatus for diagnosing a device according to any one of (4). (6) A diagnostic device for a device formed in a field device having a function block which communicates with a host system through digital communication means and which inputs a process data and outputs a calculation result at a predetermined calculation cycle. Calculating the instantaneous values or statistical values of the data relating to the input and output, and executing and outputting a process for diagnosis using the statistical values calculated by the calculating means The diagnostic method and apparatus for the device according to any one of (1) to (4), comprising: a diagnostic unit that operates at a slower calculation cycle than the calculation cycle of the unit. (7) A calculation unit for inputting a valve opening signal or an output pressure signal to the valve to calculate an instantaneous value or statistical value of the speed or acceleration of the signal, and an output of the calculation unit and a setting signal of the valve. A comparison calculation unit to which a related signal is input, and the comparison calculation unit performs a comparison calculation on the statistical value and a signal related to the setting signal to diagnose whether an abnormality has occurred in the valve. The method and apparatus for diagnosing equipment according to any one of (1) to (6) are characterized in that

[0016]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a functional block diagram showing an embodiment in which the present invention is applied to a system including a fieldbus. Reference numeral 3 is a field bus, and 4 is a field device connected to the field bus 3 for digital communication with a host system or an input / output device. The field device 4 measures, for example, a process value such as a valve opening degree and outputs a control signal.

Reference numeral 5 is a calculation block configured as a function block in the field device 4. The calculation block 5 executes a predetermined calculation by collecting measured valve opening and signals from other function blocks connected to the fieldbus 3 via the fieldbus 3 or inside itself. And output a signal. The arithmetic block 5 diagnoses the equipment based on these collected process value input / output signals and outputs the diagnosis result.

With such a configuration, by providing the function block having open input / output, it is possible to perform optimum process diagnosis and valve diagnosis by combining the devices with multiple vendors.

FIG. 2 is a functional block diagram showing a concrete configuration example of the diagnostic device 5. In this example, the field device to be diagnosed is assumed to be a valve positioner. Reference numeral 6 is a transducer operation block, and 7 is a process value input / output signal to this block. The valve positioner has a function of detecting a valve position signal by a displacement sensor and outputting a drive signal to an actuator. In this transducer calculation block 6, the calculation cycle is normally 10 msec to 20 in order to smoothly perform valve control.
It is set to a relatively high speed of about msec.

Reference numeral 8 is a diagnostic calculation block, which uses the collected process value input / output signals to perform self-diagnosis of the field device itself, diagnosis of devices such as valves and piping, and diagnosis of process control loops. Normally, the operation cycle of this diagnostic operation block is the transducer operation block 6 described above.
It is set later than the cycle of, for example, about 100 msec to 1 sec.

Reference numeral 9 is a data transfer means for exchanging data between the transducer operation block 6 and the diagnostic operation block 8. If 6 and 8 operate on the same CPU, 9 is realized by a memory (RAM). If 6 and 8 operate on different CPUs or hardware, 9 is realized by data transfer means such as serial communication means or dual port memory. 1
Reference numeral 0 is a diagnostic result output signal output by the diagnostic operation block, and is, for example, an alarm signal or an On / Off data status.

The process value input / output signal 7 is data input / output by the transducer operation block 6, and includes, for example, a displacement sensor signal, a drive pressure sensor signal to a valve actuator, and a drive current to an electropneumatic conversion element (IP module). Signals, etc. are targets.

The transducer calculation block 6 calculates the following values for diagnosis and transfers them to the diagnosis calculation block 8 via the data transfer means 9. (1) Instantaneous value and statistical value of the process value input / output signal shown in 7. (2) Instantaneous value and statistical value of a value proportional to the speed of the process value input / output signal shown in 7. (3) Instantaneous value and statistical value of a value proportional to the acceleration of the process value input / output signal shown in 7.

The statistical values mentioned here are maximum value, minimum value,
Mean value, variance, standard deviation, etc. The time for statistics is 6
The time period during which the transducer operation block can be executed a plurality of times is set to, for example, the cycle in which the 8 diagnosis operation blocks operate.

An example of diagnosis according to the present invention for the stick-slip phenomenon of the valve will be described with reference to the waveform diagram of FIG. It is assumed that the periods τ1 to τ4 divided by the dotted line are the calculation cycle of the diagnosis calculation block 9. (A) is the calculation cycle τ1
Is a reference waveform generated in step S, step input to the process, and T is a diagnostic period calculated from this step input.

(B) is a response waveform to the step input (A) by the transducer operation block 6 faster than the operation cycle of the diagnostic operation block 9, and the time delay d
After that, it rises in the calculation cycle τ2. (C) is a velocity waveform obtained by differentiating this response waveform.

In (D), at the end of each calculation cycle, the maximum and minimum values of the velocity waveform in the previous calculation cycle are calculated. The maximum value (MAX) is the symbol ◯ and the minimum value (MIN) is Symbol □
The waveform is plotted in. This plot level is held until the end of the next calculation cycle (for one calculation cycle), and this held value is passed to the diagnostic calculation block 8.

Yth is a threshold value for abnormality diagnosis. In this example, since the maximum value holding level in the calculation cycle τ2 exceeds Yth, the maximum value holding data and the holding level are in the calculation cycle τ3. Yth is compared and the diagnostic result of the abnormality is output.

In FIG. 3, an extremely simple example is given in which the maximum value exceeds the threshold value Yth, which is abnormal.
When a more complicated diagnostic calculation is performed, the diagnostic calculation is simplified by executing the diagnosis based on the statistical value in this way, and the calculation load of the diagnostic calculation block, that is, the CPU.
The load can be significantly reduced.

The present invention can be applied not only to the valve positioner shown in the embodiments but also to diagnosis of sensors such as transmitters and flow meters, and higher level systems such as distributed control systems (DCS).

For example, in the case of a sensor, the process value input / output signal 7 in FIG. 2 is a process signal such as a pressure value, a flow rate value, a temperature value, a level (liquid level), or an environmental signal value such as vibration or sound. It is possible. With DCS, all data input / output in I / O can be given as process value input / output signals.

When the present invention is applied to a device conforming to the Foundation Fieldbus standard, the operation function of the diagnostic block 8 can be implemented as a standard function block.

In this case, since the diagnostic result output signal 8 is an alarm signal or a data status signal corresponding to the standard, it can be used by other manufacturer's equipment to change the process control operation or the operation method. It becomes easy to do.

[0034]

As is apparent from the above description,
According to the present invention, the control calculation process of the process value input / output signal and the statistical values thereof are calculated by the transducer calculation block that operates at high speed, and the statistics prepared in the diagnostic calculation block that operates at lower speed than this transducer calculation block. By passing the value and executing the diagnostic calculation, the calculation load on the CPU is reduced, low power consumption is achieved without degrading the performance of the control calculation, the response of the valve becomes abnormally slow, It becomes possible to detect and alarm with high accuracy an abnormal phenomenon such as a sudden response due to stick-slip.

[Brief description of drawings]

FIG. 1 is a functional block diagram of a diagnostic device in which the present invention is applied to a system including a fieldbus.

FIG. 2 is a functional block diagram showing a specific configuration example of a calculation block 5 in FIG.

FIG. 3 is a waveform diagram illustrating a diagnostic operation according to the present invention for a stick-slip phenomenon of a valve.

FIG. 4 is a functional block diagram showing a configuration of a conventional device diagnosis apparatus.

FIG. 5 is a waveform diagram illustrating a diagnostic operation of a conventional device for a valve stick-slip phenomenon.

[Explanation of symbols]

3 fieldbus 4 field devices 5 operation blocks 6 Transducer calculation block 7 Process value input / output signal 8 Diagnostic operation block 9 Data transfer means 10 Diagnostic result output signal

Claims (7)

[Claims] 1. A method for diagnosing an operation of a device, wherein the operation of the device is evaluated by comparing and calculating an instantaneous value or a statistical value of a signal related to the device to be diagnosed and a reference signal related to the device. A method for diagnosing a device, characterized in that diagnosis is performed. 2. A diagnostic device for a device for diagnosing whether or not the device is operating normally, wherein a comparison operation unit receives an instantaneous value or a statistical value of a signal related to the device and a reference signal related to the device. A diagnostic device for a device, comprising: a comparison operation unit for diagnosing whether the device is normally operating. 3. The device diagnostic method and apparatus according to claim 1, wherein the statistical value targets a signal proportional to a speed or an acceleration of the device. 4. The statistical value includes a maximum value, a minimum value, an average value, a variance, a standard deviation, etc. of a signal proportional to the speed or acceleration of the device, according to claim 1 or 2. Equipment diagnostic method and apparatus. 5. A diagnostic device for a device formed in a field device having a function block for inputting process data and outputting a calculation result while communicating with a host system through digital communication means. It is provided with a calculating means for collecting related data and obtaining an instantaneous value or a statistical value thereof, and a diagnostic means for executing and outputting processing for diagnosis using the statistical value obtained by the calculating means. 5. A device diagnosis method and apparatus according to any one of 1 to 4. 6. Diagnosis of a device formed in a field device having a function block which communicates with a host system via digital communication means and which operates at a predetermined calculation cycle for inputting process data and outputting a calculation result. In the device, the data relating to the input and output is collected, a calculation unit for obtaining an instantaneous value or a statistical value thereof, and a process for diagnosis is executed and output using the statistical value obtained by the calculation unit, and output. The diagnostic method and apparatus for equipment according to any one of claims 1 to 4, further comprising: a diagnosis unit that operates at a calculation cycle lower than a calculation cycle of the calculation unit. 7. An arithmetic unit for inputting a valve opening signal or an output pressure signal to the valve to calculate an instantaneous value or a statistical value of the speed or acceleration of the signal, and an output of the arithmetic unit and setting of the valve. A comparison calculation unit to which a signal related to the signal is input, and the comparison calculation unit compares and calculates the statistical value and the signal related to the setting signal to determine whether an abnormality has occurred in the valve. The method and apparatus for diagnosing equipment according to any one of claims 1 to 6, wherein: