JP5890206B2 - Potentiometer degradation diagnosis method - Google Patents

Description

  The present invention relates to a potentiometer degradation diagnosis method for diagnosing degradation of performance of a potentiometer.

  Conventionally, a potentiometer has been used to detect a rotation angle of an electric valve actuator or the like. Due to the structure of this potentiometer, the resistor is liable to be damaged or worn powder due to wear by the slider, which is particularly severe in the frequently used sliding range. As a result, even if the slider is slightly displaced, a phenomenon in which the resistance value accidentally changes greatly occurs. Along with this, the output signal of the potentiometer also changes suddenly and appears as a beard-like signal S as shown in FIG. In FIG. 11, the horizontal axis indicates the potentiometer displacement (slider displacement) or angle, and the vertical axis indicates the magnitude of the output signal of the potentiometer.

  When such a beard-like signal appears in the output signal of the potentiometer, a control device or the like that is operating with the output signal may accidentally perform an abnormal control operation. Therefore, in Patent Document 1, a beard-like signal appearing in the output signal of the potentiometer is detected, and when the beard-like signal is larger than a predetermined upper limit value or smaller than a lower limit value, the beard-like signal is also detected. When the rate of change of the value is larger than a predetermined value, a failure is diagnosed. When the potentiometer is diagnosed as malfunctioning, the control device or the like which is operating with the output signal supplied immediately shifts to control when a predetermined signal is abnormal.

Japanese Patent Publication No. 7-95081

  However, the above-mentioned beard-like signal (noise) is generated at the initial stage of the aging of the potentiometer, and if such noise generation does not cause a problem, it can be used later and diagnosed as a failure. There is a problem of being done. That is, since Patent Document 1 captures the occurrence of noise that occurs at the initial stage of the aging of the potentiometer, it is diagnosed as a failure at an early stage, resulting in a decrease in system operation rate and troublesome parts replacement. There was a problem of cost.

  The present invention has been made to solve such a problem, and its purpose is to diagnose deterioration of a potentiometer that is not diagnosed as a failure at an early stage such as generation of noise. It is to provide a method.

In order to achieve such an object, the present invention measures the output resistance value R in the operating state of the potentiometer, compares the measured output resistance value R with the predicted value R ′, and based on the comparison result, the potentiometer. As one of the performance degradations up to the failure, linearity between input and output (hereinafter simply referred to as linearity) is diagnosed.

For this reason, the present invention sets the maximum and minimum output resistance values in the movable range of the potentiometer as Ro, max and Ro, min, and sets the operation time after passing a predetermined guarantee point as t, The operation time from the maximum value Ro, max to the minimum value Ro, min is tmax, the output resistance value at the guaranteed point is Ro, x%, and the predicted value is R ′ = [(Ro, max−Ro, min) / tmax ] T + Ro, x%, and when | R−R ′ | exceeds a predetermined threshold value, it is determined that the linearity is lost.

  It is known that the performance of a potentiometer deteriorates in the order of noise generation, linearity deterioration, resistance value change, and rotational torque increase. In the present invention, attention is paid to the deterioration of linearity that is slower than the occurrence of noise in this order, and this linearity deterioration is diagnosed.

  According to the present invention, since the deterioration of linearity between the input and output is diagnosed as one of the performance deterioration until the potentiometer failure, the failure is detected at an early stage such as noise generation. You will never be diagnosed.

It is a block diagram which shows the principal part of the system containing the degradation diagnostic apparatus of the potentiometer used for implementation of this invention. It is a flowchart for demonstrating the function which the potentiometer degradation diagnostic apparatus in this system has. It is a flowchart following FIG. It is a figure explaining the definition of the resistance value between each electrode of a potentiometer. It is a figure for _{demonstrating} the measurement of total resistance value _RAB . It is a figure explaining voltage V1 used at the time of measurement of contact resistance value r and terminal resistance value _RAC , _RBC . It is a figure explaining the voltage V2 used at the time of the measurement of contact resistance value r and terminal resistance value _RAC , _RBC . It is a figure which specifies the predicted value R 'calculated | required as a linearly interpolated value. It is a figure which illustrates the change speed and acceleration of the resistance value calculated | required by the difference method. It is a figure which illustrates dωp, o / dt and dωp / dt in a transient state. It is a figure which shows the beard-like signal which appears in the output signal of a potentiometer.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram showing a main part of a system including a potentiometer deterioration diagnosis apparatus used for implementing the present invention. In the figure, 1 is a potentiometer, 1-1 is a slider, 2 is a potentiometer deterioration diagnosis device (hereinafter referred to as a potentiometer deterioration diagnosis device), and 3 is a deterioration diagnosis result display device.

  In this system, the output signal of the potentiometer 1 taken out from the slider 1-1 is sent to the potentiometer deterioration diagnosis device 2. 1, A and B are fixed electrodes of the potentiometer 1, C is a movable electrode of the potentiometer 1, 1-2 is a resistor of the potentiometer 1, and 1-3 is a resistor 1-2 of the movable electrode C. Contact resistance.

  The potentiometer 1 is attached to a device in which the angular speed of the entire rotating system is a constant speed in a steady state in conjunction with the power supply frequency. For example, the degree of opening of a valve body mounted on an electric valve actuator and driven by a motor is detected.

  In this system, the potentiometer deterioration diagnosis device 2 is realized by hardware including a processor and a storage device, and a program that realizes various functions in cooperation with these hardware.

  It is known that the performance of a potentiometer deteriorates in the order of noise generation, linearity (linearity between input and output), resistance value change, and rotational torque increase. In this embodiment, paying attention to the order of the performance deterioration, the performance deterioration of the potentiometer 1 is diagnosed in the order of noise generation, linearity deterioration, resistance value change, and rotational torque increase. To do.

  That is, as the diagnosis items of performance deterioration until the failure of the potentiometer 1, "noise generation", "linearity deterioration", "resistance value change", "rotational torque increase" are determined as diagnosis items, Diagnosis is made in stages in the order of “generation of noise”, “deterioration of linearity”, “change in resistance value”, and “increase in rotational torque”. This diagnosis is performed without removing the potentiometer 1 from the apparatus, that is, while the potentiometer 1 is incorporated in the apparatus.

  Hereinafter, with reference to flowcharts shown in FIG. 2 and FIG. 3, functions unique to the present embodiment of the potentiometer deterioration diagnosis device 2 will be described.

[Diagnosis of noise generation]
The potentiometer degradation diagnosis device 2 first diagnoses the occurrence of noise in the potentiometer 1 (step S101: FIG. 2).

  The diagnosis of the occurrence of noise is performed by detecting a beard-like signal included in the output signal of the potentiometer 1 taken out from the slider 1-1. When this beard-like signal is larger than a predetermined upper limit value or smaller than a lower limit value, and when the rate of change of the beard-like signal is larger than a predetermined value, it is determined that noise has occurred.

  When the potentiometer deterioration diagnosis device 2 determines that noise has occurred (YES in step S102), the potentiometer deterioration diagnosis device 2 sends the diagnosis result to the deterioration diagnosis result display device 3, and the current deterioration stage of the potentiometer 1 is the noise generation stage (first stage). (Initial stage)) is displayed (step S103).

[Diagnosis of linearity degradation]
Next, the potentiometer deterioration diagnosis device 2 diagnoses the deterioration of linearity (step S104: FIG. 3). The diagnosis of the deterioration of linearity is performed as follows.

The output resistance value R in the operating state of the potentiometer 1 is measured, and the predicted value R ′ at that time is obtained by the following equation.
R ′ = [(Ro, max−Ro, min) / tmax] · t + Ro, x% (1)

  In the equation (1), Ro, max and Ro, min are the maximum and minimum values of the output resistance value in the movable range of the potentiometer 1, and t is the operation time after passing a predetermined guarantee point ( Tmax is the operating time from the maximum value Ro, max to the minimum value Ro, min, Ro, x% is the output resistance value at the guaranteed point, and Ro, max and Ro, min are measured initially. Keep it.

  The predicted value R ′ obtained by the equation (1) is a predicted value of the output resistance value for each fixed section and is linearly interpolated. The guarantee point and the method of measuring the output resistance value R will be described later.

  Then, the potentiometer deterioration diagnosis apparatus 2 obtains | R−R ′ | from the measured output resistance value R and the predicted value R ′ at that time, and determines | R−R ′ | and a predetermined threshold value ΔRth. In comparison, if | R−R ′ |> ΔRth, it is determined that the linearity is lost. That is, it is determined that the linearity has deteriorated.

  When the potentiometer deterioration diagnosis device 2 determines that the linearity has been lost (YES in step S105), it sends the diagnosis result to the deterioration diagnosis result display device 3, and the current deterioration stage of the potentiometer 1 is the linearity deterioration stage (second step). Stage) is displayed (step S106).

[Diagnosis of changes in resistance value]
Next, the potentiometer deterioration diagnosis device 2 diagnoses a change in resistance value (step S107). In the diagnosis of the change in resistance value, the total resistance value R _AB of the potentiometer 1 is measured on a regular basis, and when a certain threshold value is exceeded, it is determined that the resistance value has deteriorated. The measurement of the total resistance value R _AB of the potentiometer 1 will be described later.

  When the potentiometer deterioration diagnosis device 2 determines that the resistance value has changed (YES in step S108), it sends the diagnosis result to the deterioration diagnosis result display device 3, and the current deterioration stage of the potentiometer 1 is the resistance value change stage (first step). 3 stages) is displayed (step S109).

[Diagnosis of increase in rotational torque]
Next, the potentiometer deterioration diagnosis device 2 diagnoses an increase in rotational torque (step S110). The diagnosis of the increase in rotational torque is performed as follows.

  The load torque Tp in the operating state of the potentiometer 1 is measured, the measured load torque Tp is compared with a predetermined threshold value Tpth, and if Tp> Tpth, it is determined that the rotational torque has increased.

The load torque Tp in the operating state of the potentiometer 1 can be obtained by the following equation.
Tp = Ip (dωp, o / dt−dωp / dt) (2)

  In this equation (2), dωp, o / dt is the angular acceleration in the transient state when the potentiometer 1 is removed from the device and the motor is driven, and dωp / dt is the value when the potentiometer 1 is assembled in the device and the motor is driven. The angular acceleration, Ip, in the transient state is the inertia of the potentiometer 1, and dωp, o / dt is measured in the initial stage. dωp / dt is converted from the output resistance value R. Ip is obtained from the manufacturer (a constant value). The initial measurement of dωp, o / dt and the conversion from the output resistance value R of dωp / dt will be described later.

  When potentiometer deterioration diagnosis device 2 determines that the rotational torque has increased (YES in step S111), it sends the diagnosis result to deterioration diagnosis result display device 3, and the current deterioration stage of potentiometer 1 is the rotational torque deterioration stage (first step). 4 stages (final stage)) is displayed (step S112).

  In this way, in this embodiment, it is possible to know the progress of the performance deterioration of the potentiometer 1 in a stepwise manner. As a result, it is possible to eliminate the diagnosis of a failure at an early stage, improve the operating rate of the system, and allow parts to be replaced at an appropriate time according to the usage situation.

[Method of measuring resistance value]
The measurement method of the resistance value used for each deterioration diagnosis is shown below. Here, as shown in FIG. 4, the resistance value between the fixed electrodes A and C of the potentiometer 1 is R _AC , the resistance value between B and C is R _BC , and the resistance value between A and B is R _AB (total resistance Value). Further, the resistance value (contact resistance value) of the contact resistance 1-3 between the movable electrode C and the resistor 1-2 is set to r.

(1) Measurement of total resistance value R _{AB As} shown in FIG. 5, a constant current i is passed between terminals A and B, and a voltage V at that time is measured. The resistance value R _AB is obtained by the following equation according to Ohm's law.
R _AB = V / i (3)

(2) Measurement of Contact Resistance Value r As shown in FIG. 6, a constant current i is passed between terminals A and C, and the voltage V1 at that time is measured. Next, as shown in FIG. 7, a constant current i is passed between the terminals C-B, and the voltage V2 at that time is measured. These values can be expressed by the following formula.
V1 = (R _AC + r) · i (4)
V2 = (R _BC + r) · i (5)

Therefore, the contact resistance value r is
r = {[(V1 + V2) / i] + R _AB } / 2 (6)
It can ask for.

(3) inter-terminal resistance value R _AC, measured inter-terminal resistance value R _AC of R _BC, R _BC is
R _AC = V1 / ir (7)
R _BC = V2 / ir (8)
Can be obtained.

[Details of diagnosis of degradation of linearity]
The maximum value Ro, max and the minimum value Ro, min of the output resistance value in the movable range of the potentiometer 1 are measured in advance.

  Next, the prediction resistance at every certain opening (for example, in the case of opening in an electric valve actuator, 20, 40, 60, 80%, etc., these intervals are considered to pass at any point at the time of diagnosis) Calculate the value.

The calculation is performed by linear interpolation of the maximum and minimum output resistance values, and these values are Ro, ₂₀ %, Ro, ₄₀ %,. Separately, the device has a module that can guarantee the absolute position accuracy at the above-mentioned fixed opening (for example, a disk with radial slits is completely fixed to the rotation angle measurement target, and light transmission is confirmed with a photocoupler) And each point is defined as a guarantee point.

  Diagnosis starts when one of the guarantee points is passed, and the output resistance value R in the operating state is measured, and the predicted value R ′ at that time is obtained by the equation (1) (see FIG. 8).

Then, | R−R ′ | is obtained from the measured output resistance value R and the predicted value R ′ at that time, and | R−R ′ | is compared with a predetermined threshold value ΔRth. If “|> ΔRth”, it is determined that the linearity is lost. The output resistance value R is calculated by the above-mentioned “(2) Measurement of contact resistance value r” and “(3) Measurement of inter-terminal resistance values R _AC and R _BC ”.

[Details of diagnosis of resistance change]
The total resistance value R _AB is measured on a regular basis, and when a certain threshold value is exceeded, it is determined that the resistance value is deteriorated. The method of measuring the total resistance value R _AB is based on the above-mentioned “(1) Measurement of the total resistance value R _AB ”.

[Details of diagnosis of increase in rotational torque]
First, the potentiometer 1 is removed from the apparatus, the motor is driven, and the angular acceleration dωo / dt in a transient state is measured using a tachometer or the like. If the gear ratio is i, the angular acceleration converted to the potentiometer axis is
dωp, o / dt = (1 / i) · dωo / dt (9)
It becomes.

The potentiometer 1 is incorporated in the apparatus. The angular acceleration dωa / dt in the transient state of the potentiometer 1 after incorporation of the device is obtained as follows. For example, when the potentiometer with a total resistance value of 1 kΩ and a rotation angle of 320 ° changes from 21 to 21, 22, 24 Ω every 0.1 s from a certain time, the change rate and acceleration of the resistance value are calculated by the differential method as shown in FIG. Can be sought. Therefore, the acceleration of the potentiometer at this time is
dωa / dt = 50 × (320 × π / 180) /10000=2.79 e-003 [rad / s]
It becomes.

Here, the angular motion equation when there is no load torque of the potentiometer 1 is
Ip · (dωp, o / dt) = T (10)
Here, T is a torque for driving the potentiometer 1, and Ip is inertia of the potentiometer alone (obtained from the manufacturer, fixed value).

On the other hand, when there is a load torque of the potentiometer 1, the angular motion equation is
Ip · (dωa / dt) = T−Tp (11)
From the equations (10) and (11), the load torque Tp of the potentiometer 1 can be obtained as the following equation.
Tp = Ip. (Dωp, o / dt−dωp / dt) (12)

Here, in the transient state, as shown in FIG. 10, dωp, o / dt> dωo / dt, dωp, o / dt ≠ 0, dωo / dt ≠ 0.
Therefore, Tp can be calculated even in an apparatus in which the angular velocity of the entire rotating system is constant in a steady state in conjunction with the power supply frequency.
These Tp are measured and calculated from moment to moment, and it is determined that the rotational torque has increased when a certain threshold value Tpth is exceeded.

  In the above-described embodiment, the diagnosis is made in stages in the order of “generation of noise”, “deterioration of linearity”, “change in resistance value”, and “increase in rotational torque”. Only “deterioration of linearity” may be diagnosed.

[Extension of the embodiment]
The present invention has been described above with reference to the embodiment. However, the present invention is not limited to the above embodiment. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the technical idea of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Potentiometer, 1-1 ... Slider, 1-2 ... Resistor, 1-3 ... Contact resistance, 2 ... Potentiometer deterioration diagnostic apparatus, 3 ... Diagnosis result display apparatus.

Claims (1)

The output resistance value R in the operating state of the potentiometer is measured, and the measured output resistance value R and the predicted value R ′ are compared. Based on the comparison result, one of the performance deteriorations until the potentiometer fails. A potentiometer degradation diagnosis method for diagnosing degradation of linearity between input and output,
The maximum and minimum output resistance values in the movable range of the potentiometer are Ro, max and Ro, min,
Let t be the operating time after passing a predetermined guarantee point,
The operating time from the maximum value Ro, max to the minimum value Ro, min is tmax,
Assuming that the output resistance value at the guaranteed point is Ro, x%,
The predicted value is determined as R ′ = [(Ro, max−Ro, min) / tmax] · t + Ro, x%,
When | R−R ′ | exceeds a predetermined threshold value, it is determined that the linearity is lost.
A method for diagnosing deterioration of a potentiometer.

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