JP7694062B2 - Abnormality determination device - Google Patents

Description

This disclosure relates to an abnormality determination device that determines whether a heater is abnormal.

Patent document 1 discloses an electric heater that determines whether the heater is abnormal based on the magnitude of the change in the rate of increase in electrical resistance when electricity is applied.

Japanese Patent Application Publication No. 8-124653

The electrical resistance of the heater wire of an electric heater has temperature characteristics. The electric heater of Patent Document 1 does not have a sensor for detecting the temperature of the heater wire, so it may not be possible to accurately determine the magnitude of the change in the rate of increase in electrical resistance when electricity is applied.

The objective of this disclosure is to solve the above problem by providing an abnormality determination device that can determine whether a heater is abnormal without using heater temperature information.

In order to achieve the above object, an abnormality determination device according to one aspect of the present disclosure includes:
a first calculation unit that calculates a resistance value and a power value of the electric heating body from a voltage detected by a voltage sensor that detects a voltage across both ends of the electric heating body of the heater and a current detected by a current sensor that detects a current flowing through the electric heating body;
a second calculation unit that calculates a reference resistance value based on the resistance value and the power value;
and an abnormality determination unit that determines that the heater is abnormal when the resistance value is greater than the reference resistance value.

According to the above aspect of the present disclosure, it is possible to determine a heater abnormality without using heater temperature information.

1 is a block diagram illustrating a configuration of an abnormality determination device according to an embodiment of the present disclosure. FIG. 4 is a diagram showing an example of an estimated temperature characteristic related to a resistance value of a heating wire. 4 is a flowchart for explaining an abnormality determination process executed by the abnormality determination device of FIG. 1 . 4 is a flowchart for explaining a filter time constant adjustment process executed by the abnormality determination device of FIG. 1 .

The following describes in detail the embodiments of the present disclosure with reference to the drawings.

(Embodiment)
1, an abnormality determination device 200 according to an embodiment of the present disclosure is connected to a heating wire 20 (an example of a heating element) of an electric resistance heater 2 (hereinafter simply referred to as a "heater"). As an example, a temperature regulator 100 and a solid-state relay (SSR) 110, which is an example of a switching element, are connected to the heating wire 20. A power source 120 is connected to the solid-state relay 110. The solid-state relay 110 is controlled to be turned on and off by the temperature regulator 100, and the heating wire 20 is energized by the power source 120 during an on-period of the solid-state relay 110.

The abnormality determination device 200 includes a voltage sensor 210, a current sensor 220, a calculation unit 240, and an abnormality determination unit 270. In this embodiment, the abnormality determination device 200 includes an AD (analog-to-digital) converter 230, a display unit 250, and an operation unit 260.

The voltage sensor 210 detects the voltage across both ends of the heating wire 20. Analog data corresponding to the detected voltage is output to the AD converter 230.

The current sensor 220 detects the current flowing through the heating wire 20. Analog data corresponding to the current detected by the current sensor 220 is output to the AD converter 230.

The AD converter 230 converts analog data corresponding to the voltage output from the voltage sensor 210 into digital data, a voltage value V. The AD converter 230 converts analog data corresponding to the current output from the current sensor 220 into digital data, a current value I. The voltage value V and the current value I are output to the calculation unit 240.

The calculation unit 240 has a CPU that performs calculations and a memory unit 246 that stores programs and data necessary for determining an abnormality in the heating wire 20. The calculation unit 240 has a first calculation unit 242 and a second calculation unit 244. The first calculation unit 242 and the second calculation unit 244 are functions that are realized, for example, by the CPU executing a predetermined program.

The first calculation unit 242 calculates the power value W and resistance value R of the heating wire 20 from the voltage detected by the voltage sensor 210 and the current detected by the current sensor 220. The calculated resistance value R is output to the second calculation unit 244, the display unit 250, and the abnormality determination unit 270. In addition, the power value W calculated by the first calculation unit 242 is output to the second calculation unit 244 and the display unit 250.

The second calculation unit 244 calculates the reference resistance value Rr based on the resistance value R and the power value W. In this embodiment, the second calculation unit 244 calculates the reference resistance value Rr based on the resistance value R and the LPF output value (hereinafter referred to as the LPF output value Wf) of the power value obtained by subjecting the power value W to first-order lag filtering (hereinafter referred to as the LPF). When the LPF is f1, the Laplace operator is s, and the time constant is T1, the LPF can be expressed by the formula f1 = 1/(1 + T1 s).

Specifically, the second calculation unit 244 acquires time series data of the voltage and current (hereinafter referred to as the voltage and current in the temperature rising state) detected by the voltage sensor 210 and the current sensor 220 when the heater 2 is in the temperature rising state, and calculates the resistance value R and the LPF output value Wf from the acquired time series data of the voltage and current in the temperature rising state. For example, if a first-order lag filter process equivalent to the delay time from power to temperature is performed on the power value W, the horizontal axis X can be converted into the LPF output value Wf proportional to the temperature of the heating wire 20 (see FIG. 2). It can be estimated that the LPF output value Wf obtained from the power and current in the temperature rising state and the LPF output value Wf obtained from the voltage and current (hereinafter referred to as the power and current in the stable state) detected by the voltage sensor 210 and the current sensor 220 when the heater 2 is in the stable state are on the same straight line or curve. In FIG. 2, the vertical axis Y indicates the resistance value R, and the horizontal axis X indicates the LPF output value Wf.

The heated state refers to a state in which the temperature of the heating wire 20 is not maintained at the target value, and the stable state refers to a state in which the temperature of the heating wire 20 is maintained at the target value.

The second calculation unit 244 evaluates the variation of the resistance value R from the time series data of the calculated resistance value R and the LPF output value Wf. For example, the second calculation unit 244 evaluates the sum of square errors from the approximation line L in the vertical axis Y direction in the time series data of all the resistance values R and the LPF output value Wf as the variation of the resistance value R. The approximation line L is obtained, for example, by using the least squares method from the time series data of the resistance value R and the LPF output value Wf. The approximation line L may be a broken line consisting of multiple straight lines by dividing the horizontal axis X into multiple sections. If it is evaluated that the variation of the resistance value R is minimum, the second calculation unit 244 calculates the approximation line L as the estimated temperature characteristic, and calculates the reference resistance value Rr from the calculated estimated temperature characteristic and the LPF output value Wf.

If it is determined that the variation in the resistance value R is not minimum, the second calculation unit 244 resets the time constant T1 of the LPF and evaluates the variation in the resistance value R from the time series data of the recalculated resistance value R and the LPF output value Wf.

The adjustment unit 248 adjusts the time constant T1 of the LPF. The adjustment of the time constant T1 of the LPF can be performed using, for example, simulated annealing or a genetic algorithm. The adjustment of the time constant T1 of the LPF is performed until the second calculation unit 244 determines that the variation in the resistance value R is minimal.

In this embodiment, the time constant T1 of the LPF is adjusted by setting predetermined parameters and searching for the time constant T1. The predetermined parameters include, for example, the number of searches, the time constant, the number of search points, the convergence condition, the upper limit of the time constant, the lower limit of the time constant, and the time constant width. As an example, the initial values of the parameters are set as follows:
Number of searches It=0
Time constant T1=0
Number of search points J=1
Convergence condition De=0.01 (Ω ² )
Time constant upper limit Tma = 1000 (S)
Time constant lower limit Tmi=0(S)
Time constant width Wid=Tma-Tmi

The memory unit 246 is composed of, for example, a RAM (Random Access Memory), a ROM (Read Only Memory), and an SSD (Solid State Drive). The memory unit 246 stores the time series data of the power and voltage detected by the voltage sensor 210 and the current sensor 220, the power value and resistance value calculated by the first calculation unit 242, the time constant T1 of the LPF, and the LPF output value Wf and reference resistance value Rr calculated by the second calculation unit 244.

When the LPF output value Wf of the power value W is X and the resistance value R is Y, if the curve representing the estimated temperature characteristics is approximated by the formula Y = aX + b, the memory unit 246 stores the reference resistance value Rr in a format that stores two coefficients a and b.

The display unit 250 is, for example, a liquid crystal display device. The display unit 250 displays the results calculated by the calculation unit 240 (for example, the graph shown in FIG. 2). The GUI (graphic user interface) displayed on the display unit 250 is realized, for example, by software stored in the storage unit 246 or an external device.

The operation unit 260 is configured, for example, as a key input switch or a slide switch, and inputs instructions from the user (operator) and sets the input contents. In this embodiment, the operation unit 260 is configured to be able to input, for example, the time constant T1 of the LPF.

The abnormality determination unit 270 determines that the heater 2 is abnormal if the resistance value R calculated by the first calculation unit 242 is greater than the reference resistance value Rr calculated by the second calculation unit 244, for example, if the resistance value R is 1.1 times or more the reference resistance value Rr. An abnormality in the heater 2 includes, for example, a state in which the heating wire 20 cannot be controlled to the target temperature due to deterioration of the heating wire 20. When it is determined that the heater 2 is abnormal, the abnormality determination unit 270 outputs a signal to an alarm device to notify the abnormality, for example, via a wireless communication device.

In this embodiment, the abnormality determination unit 270 performs abnormality determination processing when the heater 2 is in a stable state. In this case, for example, the abnormality determination unit 270 sets an upper limit value and a lower limit value (hereinafter referred to as a stable range) of the LPF output value Wf that is to be in a stable state. When the LPF output value Wf is in the stable range and a preset waiting time (for example, twice the time constant T1 of the LPF) has elapsed since the LPF output value Wf entered the stable range, the abnormality determination unit 270 determines that the heater 2 is in a stable state. The abnormality determination is performed using the LPF output value Wr after it is determined that the heater 2 is in a stable state. If the LPF output value Wf goes out of the stable range before the predetermined time has elapsed, the measured time is reset.

Next, the abnormality determination process of the abnormality determination device 200 will be described.

As shown in FIG. 3, the voltage sensor 210 detects the voltage across both ends of the heating wire 20, and the current sensor 220 detects the current flowing through the heating wire 20 (step S11). The detected voltage and current flowing through the heating wire 20 are converted into digital data by the AD converter 230 and output to the calculation unit 240.

When the detected voltage and current are output to the calculation unit 240, the first calculation unit 242 calculates the power value W and the resistance value R from the output voltage and current (step S12).

Once the power value W and resistance value R are calculated, the second calculation unit 244 calculates the reference resistance value Rr based on the power value W (step S13).

Once the reference resistance value Rr is calculated, the abnormality determination unit 270 determines whether the heater 2 is in a stable state (step S14). Step S14 is repeated until it is determined that the heater 2 is in a stable state.

When it is determined that the heater 2 is in a stable state, the abnormality determination unit 270 determines whether the resistance value R is greater than the reference resistance value Rr (step S15).

If it is determined that the resistance value R is greater than the reference resistance value Rr, the abnormality determination unit 270 determines that the heater 2 is abnormal and outputs an abnormality signal indicating that the heater 2 is abnormal (step S16).

When it is determined in step S15 that the resistance value R is equal to or less than the reference resistance value Rr, or when an abnormality signal is output in step S16, the calculation unit 240 determines whether or not to end the abnormality determination process (step S17). For example, when the power supply to the heater 2 is turned off, the calculation unit 240 ends the abnormality determination process. Steps S11 to S17 are repeated until it is determined that the abnormality determination process has ended.

Next, we will explain the LPF time constant adjustment process in the second calculation unit 244.

As shown in FIG. 4, the first calculator 242 acquires time series data of voltage and current in a temperature rise state (step S21).

When the time series data of the voltage and current in the heating state is acquired, the first calculation unit 242 calculates the resistance value in the heating state (hereinafter referred to as the heating resistance value Ru) and the LPF output value in the heating state Wru (hereinafter referred to as the heating LPF output value Wru) from the acquired voltage and current (step S22).

Once the temperature rise resistance value Ru and the temperature rise LPF output value Wru are calculated, the second calculation unit 244 performs initial setting of parameters for adjusting the time constant T1 of the LPF (step S23).

When the parameters are initially set, the second calculation unit 244 calculates squared errors from the time series data of the heating resistance value Ru and the heating LPF output value Wru based on multiple time constants T1 with different values, and stores the smallest squared error (hereinafter referred to as the minimum error) among the calculated squared errors in the memory unit 246 (step S24).

When the minimum error is stored in the memory unit 246, the second calculation unit 244 determines whether the termination condition is satisfied (step S25). For example, the termination condition is satisfied when the number of adjustments It is 2 or more and the difference between the minimum error calculated in the previous adjustment and the minimum error calculated in the current adjustment satisfies the convergence condition De.

If it is determined that the termination condition is met, the second calculation unit 244 sets the time constant T1 when the minimum error calculated in the current adjustment was calculated as the time constant T1 of the LPF (step S27), and the LPF time constant adjustment process ends. The set time constant T1 is stored in the storage unit 246. If it is determined that the termination condition is not met, the second calculation unit 244 changes the parameters, that is, the time constant width, the upper limit of the time constant, and the lower limit of the time constant, from the set values (step S26). When the parameters are changed, the number of adjustments is incremented by 1, and the minimum error is calculated again in step S24.

According to the abnormality determination device 200, the abnormality determination unit 270 determines that the heater 2 is abnormal when the resistance value of the heating wire 20 is greater than the reference resistance value Rr calculated based on the LPF output value Wr of the resistance value of the heating wire 20 and the power value of the heating wire 20. With this configuration, it is possible to determine an abnormality in the heater 2 without using temperature information of the heating wire 20 of the heater 2.

The second calculation unit 244 calculates the reference resistance value Rr based on the estimated temperature characteristics calculated based on the LPF output value Wf and the resistance value R, and on the LPF output value Wf. With this configuration, an abnormality in the heater 2 can be determined more reliably without using temperature information on the heating wire 20 of the heater 2.

The filtering process is a first-order lag filtering process. This simple configuration makes it possible to determine an abnormality in the heater 2 without using temperature information on the heating wire 20 of the heater 2.

The abnormality determination device 200 includes an operation unit 260 and a display unit 250. With this configuration, for example, the user can manually input the time constant T1 of the LPF.

The abnormality determination device 200 includes a memory unit 246 that stores the reference resistance value Rr. This configuration eliminates the need to calculate the reference resistance value Rr each time an abnormality is determined, reducing the processing load on the calculation unit 240.

When the power value is X and the resistance value is Y, and the equation representing the estimated temperature characteristics is approximated by the equation Y = aX + b, the memory unit 246 stores the reference resistance value Rr in a format that stores the coefficients a and b of the equation. With this configuration, it is no longer necessary to comprehensively store combinations of the LPF output value Wf and the reference resistance value Rr, so the amount of data stored in the memory unit 246 can be reduced.

The abnormality determination unit 270 determines whether or not the heater 2 is abnormal when the LPF output value is within the stable range and after a preset waiting time has elapsed since the LPF output value entered the stable range. With this configuration, an abnormality in the heater 2 can be determined more accurately.

In this embodiment, the filter processing in the second calculation unit 244 is a first-order lag filter processing, but the filter processing is not limited to this. The filter processing may be, for example, a second-order lag filter processing. When the second-order lag filter is f2, the Laplace operator is s, and the time constants are T1 and T2, the second-order lag filter can be expressed by the calculation formula f2 = 1 / {(1 + T1 · s) · (1 + T2 · s)}. At this time, when the LPF output value of the power value W is X and the resistance value R is Y, the curve representing the estimated temperature characteristic is approximated by the calculation formula Y = aX ² + bX + c. In this case, the storage unit 246 can store the reference resistance value Rr in a format that stores three coefficients a, b, and c. Even when the second-order lag filter processing is performed, it is possible to determine an abnormality of the heater 2 with a simple configuration without using temperature information of the heating wire 20 of the heater 2. In addition, the capacity of the data stored in the storage unit 246 can be reduced.

In this embodiment, the operation unit 260 may be configured to input other parameters or control contents in addition to the time constant.

In this embodiment, the operation unit 260 is configured with a key input switch or a slide switch, but the means by which the user (operator) sets the input contents for the second calculation unit 244 is not limited to this. The means by which the user (operator) sets the input contents for the second calculation unit 244 may be recorded as software (computer program) on a recording medium capable of storing data non-transiently, such as a CD (compact disc), a DVD (digital all-purpose disc), or a flash memory. By installing the software recorded on such a recording medium on a substantial computer device such as a personal computer, a PDA (personal digital assistant), a smartphone, or a PLC (programmable logic controller), the computer device can be made to execute the above-mentioned means by which the user (operator) sets the input contents for the second calculation unit 244.

In this embodiment, the case where the second calculation unit 244 automatically adjusts the time constant T1 of the LPF has been described, but the means for adjusting the time constant T1 of the LPF is not limited to this. After the second calculation unit 244 exploratory adjusts the time constant T1 of the LPF, the user (operator) may input the value of the time constant T1 by operating the operation unit 260 while watching the display unit 250. In this way, the value of the time constant T1 of the LPF can be fine-tuned.

In this embodiment, the abnormality determination unit 270 may be configured to perform abnormality determination not only when the heater 2 is in a stable state, but also when the heater 2 is in a temperature rise state. In this case, step S14 is omitted in the flowchart of FIG. 3.

In this embodiment, the abnormality determination device 200 includes a voltage sensor 210, a current sensor 220, a calculation unit 240, and an abnormality determination unit 270, but the configuration of the abnormality determination device 200 is not limited to this. The voltage sensor 210 and the current sensor 220 can be omitted. For example, the abnormality determination device 200 may be configured integrally with the voltage sensor 210 and the current sensor 220, or may be configured separately from the voltage sensor 210 and the current sensor 220. When configured separately from the voltage sensor 210 and the current sensor 220, the abnormality determination unit 270 may be provided in an external device such as a server, and various data may be input and output between them via a wireless communication device.

The above embodiments are merely examples, and various modifications are possible without departing from the scope of the invention.

Various embodiments of the present disclosure have been described above in detail with reference to the drawings. Finally, various aspects of the present disclosure will be described. In the following description, reference symbols will also be used as examples.

The abnormality determination device 200 according to the first aspect of the present disclosure includes:
a first calculation unit 242 that calculates a resistance value R and a power value W of the electric heating body from a voltage detected by a voltage sensor 210 that detects a voltage across both ends of the electric heating body of the heater 2 and a current detected by a current sensor 220 that detects a current flowing through the electric heating body;
a second calculation unit 244 that calculates a reference resistance value Rr based on the resistance value R and the power value W;
and an abnormality determination unit 270 that determines that the heater 2 is abnormal when the resistance value R is greater than a reference resistance value Rr.

The abnormality determination device 200 according to the second aspect of the present disclosure includes:
The second calculation unit 244 calculates a reference resistance value Rr based on the filtered power value W and the resistance value R, and on the estimated temperature characteristic calculated based on the filtered power value W and the resistance value R.

The abnormality determination device 200 according to the third aspect of the present disclosure includes:
The filtering process is a first-order lag filtering process.

The abnormality determination device 200 according to the fourth aspect of the present disclosure includes:
The filtering process is a second-order lag filtering process.

The abnormality determination device 200 according to the fifth aspect of the present disclosure includes:
The second calculation unit 244 sets the time constant of the filtering process so that the variation in the resistance value R in the estimated temperature characteristic is minimized.

The abnormality determination device 200 according to the sixth aspect of the present disclosure includes:
A voltage sensor 210;
A current sensor 220;
an operation unit 260 capable of inputting the time constant;
and a display unit 250 for displaying the resistance value R and the filtered power value Wf.

The abnormality determination device 200 according to the seventh aspect of the present disclosure includes:
The device includes a storage unit 246 that stores the reference resistance value Rr calculated by the second calculation unit 244 .

The abnormality determination device 200 according to the eighth aspect of the present disclosure includes:
The storage unit 246 is
When the filtered power value Wf is X and the resistance value R is Y,
Y = aX + b
When the curve representing the estimated temperature characteristic is approximated by the following formula, the reference resistance value Rr is stored in a format in which two coefficients a and b are stored.

The abnormality determination device 200 according to the ninth aspect of the present disclosure includes:
The storage unit 246 is
When the filtered power value Wf is X and the resistance value R is Y,
Y=aX ² +bX+c
When the curve representing the estimated temperature characteristic is approximated by the following formula, the reference resistance value Rr is stored in a format in which three coefficients a, b, and c are stored.

The abnormality determination device 200 according to the tenth aspect of the present disclosure includes:
The abnormality determination unit 270
A stable range of the filtered power value Wf is set,
When the filtered power value Wf is within the stable range and a preset waiting time has elapsed since the filtered power value Wf entered the stable range, it is determined whether or not the heater 2 is abnormal.

The abnormality determination device according to the above aspect of the present invention can be applied to determine abnormalities in electric heaters, as well as in electric heating elements that generate heat by resistance heating, such as fuses, conductors, or power lines.

2 heater 20 heating wire 100 temperature regulator 110 solid state relay 120 power supply 200 abnormality determination device 210 voltage sensor 220 current sensor 230 AD converter 240 calculation section 242 first calculation section 244 second calculation section 246 storage section 248 adjustment section 250 display section 260 operation section 270 abnormality determination section

Claims (7)

a first calculation unit that calculates a resistance value and a power value of the electric heating body from a voltage detected by a voltage sensor that detects a voltage across both ends of the electric heating body of the heater and a current detected by a current sensor that detects a current flowing through the electric heating body;
a second calculation unit that calculates a reference resistance value based on the resistance value and the power value;
an abnormality determination unit that determines that the heater is abnormal when the resistance value is greater than the reference resistance value ;
the second calculation unit calculates the reference resistance value based on an estimated temperature characteristic calculated based on the power value and the resistance value after filtering and based on the power value after filtering;
The abnormality determination device, wherein the filtering process is a first-order lag filtering process . a first calculation unit that calculates a resistance value and a power value of the electric heating body from a voltage detected by a voltage sensor that detects a voltage across both ends of the electric heating body of the heater and a current detected by a current sensor that detects a current flowing through the electric heating body;
a second calculation unit that calculates a reference resistance value based on the resistance value and the power value;
an abnormality determination unit that determines that the heater is abnormal when the resistance value is greater than the reference resistance value;
Equipped with
the second calculation unit calculates the reference resistance value based on an estimated temperature characteristic calculated based on the power value and the resistance value after filtering and based on the power value after filtering;
The abnormality determination device, wherein the filtering process is a second-order lag filtering process. The abnormality determination device according to claim 1 , wherein the second calculation unit sets a time constant for the filtering process so that a variation in the resistance value in the estimated temperature characteristic is minimized. The voltage sensor;
The current sensor;
An operation unit capable of inputting the time constant;
The abnormality determination device according to claim 3 , further comprising a display unit that displays the resistance value and the power value after the filtering process. The abnormality determination device according to claim 1 , further comprising a storage unit that stores the reference resistance value calculated by the second calculation unit. The storage unit is
Let X be the power value after the filtering process and Y be the resistance value.
Y = aX + b
6. The abnormality determination device according to claim 5 , wherein the reference resistance value is stored in a format in which two coefficients a and b are stored when the curve representing the estimated temperature characteristic is approximated by a formula: The storage unit is
Let X be the power value after the filtering process and Y be the resistance value.
Y=aX2+bX+c
6. The abnormality determination device according to claim 5 , wherein the reference resistance value is stored in a format in which three coefficients a, b, and c are stored when the curve representing the estimated temperature characteristic is approximated by a formula:

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