Stepping motor abnormality detecting device

Abstract

The present disclosure provides a stepping motor abnormality detection device capable of detecting an abnormality of a stepping motor. The stepping motor abnormality detection device (100) includes a power supply unit (1), a stepping motor (4), a stepping motor drive unit (3), a determination unit (5), and a control unit (6). The stepping motor drive unit (3) causes the stepping motor (4) to operate by the control unit (6). A current level detection unit (2) acquires a current level during driving of the stepping motor (4) and compares the acquired current level with a threshold value determined in advance by the determination unit (5) to detect an abnormality of the stepping motor (4).

Description

Technical Field

[0001] This disclosure relates to an apparatus for detecting anomalies occurring during the operation of a stepper motor. More particularly, this disclosure relates to an apparatus for detecting anomalies in a stepper motor used in a two-way valve for opening and closing gas flow in a gas meter. Background Technology

[0002] Patent document 1 discloses a shut-off valve device for determining whether a stepper motor is in a stall or step loss state.

[0003] The shut-off valve device includes: a drive control circuit section that drives and controls the stepper motor; and a valve movement abnormality circuit section that determines whether the stepper motor is in a stalled or stepless state. Therefore, as... Figure 4 As shown, the shut-off valve device can compare the maximum value or the wave height of the drive voltage waveform detected by the stepper motor with a predetermined threshold to determine the stall state or the step loss state. Figure 4 This is a graph showing the changes in current level during stepper motor driving.

[0004] Patent Document 2 discloses a method for detecting step loss in a stepper motor. In this method, the current waveform of the motor in the stepper motor driver that drives the stepper motor is converted into a rectangular wave signal, and then the rectangular wave signal is converted into a voltage signal. Then, by comparing the voltage value obtained from the voltage signal with a reference voltage, it is possible to determine whether a step loss state has occurred.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2006-118642

[0008] Patent Document 2: Japanese Patent Application Publication No. 1999-187697 Summary of the Invention

[0009] Patent documents 1 and 2 both disclose techniques that focus on the differences in current and voltage waveforms between normal operation and step loss states. In these techniques, the difference in waveforms can be detected in a stable step loss state. However, in actual operating environments, stepper motors often perform unstable actions such as repeated slight rotations or backward movements. In such cases, the differences in the aforementioned waveforms become unclear, making it difficult to distinguish between normal operation and step loss states.

[0010] This disclosure provides a stepper motor anomaly detection device capable of correcting waveforms detected under unstable conditions to stably detect stepper motor anomalies.

[0011] The stepper motor anomaly detection device disclosed herein includes an instantaneous current level detection unit, an integrator, and a determination unit. The instantaneous current level detection unit acquires a reference current of the stepper motor. The integrator generates an average drive current. Based on the reference current, the determination unit compares the average drive current with a predetermined threshold to determine whether the stepper motor is abnormal.

[0012] This disclosure provides a stepper motor anomaly detection device that can detect stepper motor anomalies even in unstable operating environments. Attached Figure Description

[0013] Figure 1 This is a block diagram illustrating an example of the structure of the stepper motor anomaly detection device in Embodiment 1.

[0014] Figure 2 This is a block diagram showing an example of the structure of the current level detection unit in Embodiment 1.

[0015] Figure 3 This is a flowchart used to explain the operation of the determination unit in Embodiment 1.

[0016] Figure 4 It is a graph showing the change in current level during the driving of a stepper motor.

[0017] Figure 5 This is a graph showing the current level after the current level during the driving of the stepper motor is corrected by the correction unit in Embodiment 1.

[0018] Figure 6 It is a graph showing the current level during normal operation and the current level during abnormal operation of the stepper motor. Detailed Implementation

[0019] The embodiments will now be described in detail with reference to the accompanying drawings. However, sometimes unnecessary detailed descriptions are omitted. For example, detailed descriptions of well-known matters or repeated descriptions of substantially the same structures are sometimes omitted. This is to avoid the following description becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art.

[0020] Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this disclosure and are not intended to limit the subject matter described in the claims.

[0021] (Implementation Method 1)

[0022] Next, use Figures 1-6 To illustrate implementation method 1.

[0023] [1-1. Structure]

[0024] [1-1-1. Structure of the Anomaly Detection Device]

[0025] Figure 1 This is a block diagram illustrating an example of the structure of the stepper motor anomaly detection device 100 in Embodiment 1. Figure 1 As shown, stepper motor 4 is connected to stepper motor drive unit 3. Stepper motor drive unit 3 is connected to power supply unit 1 via current level detection unit 2. In addition, current level detection unit 2 is also connected to determination unit 5. Determination unit 5 and stepper motor drive unit 3 are connected to control unit 6 and controlled by control unit 6.

[0026] The power supply unit 1 is constructed by connecting multiple primary lithium batteries (not shown) in parallel. The power supply unit 1 has a battery capacity equivalent to the current consumed by the electrical system during the certification period. The certification period is, for example, 15 years.

[0027] The current level detection unit 2 includes an instantaneous current level detection unit 21 that detects the instantaneous current flowing through the stepper motor drive unit 3. The current level detection unit 2 also includes an integration unit 22 that integrates the detected current level and a power supply impedance estimation unit 23 that estimates the impedance of the power supply unit 1 (hereinafter referred to as the power supply impedance).

[0028] The stepper motor drive unit 3 is controlled by the control unit 6, which outputs drive pulses to drive the stepper motor 4.

[0029] When the stepper motor 4 is used in a gas meter, it functions as a valve to control the gas flow rate. In this case, the stepper motor 4 performs two actions: a shut-off action to cut off the gas flow and a restore action to release the gas flow.

[0030] The determination unit 5 includes a correction unit 55. The correction unit 55 corrects the current level detected by the instantaneous current level detection unit 21 and integrated by the integration unit 22 based on the power supply impedance obtained by the power supply impedance estimation unit 23. Furthermore, the determination unit 5 includes a first comparator 53 and a second comparator 54. The first comparator 53 and the second comparator 54 compare the current level corrected by the correction unit 55 with a predetermined determination threshold, respectively. Moreover, the determination threshold used in the first comparator 53 is set by a first determination threshold setting unit 51, and the determination threshold used in the second comparator 54 is set by a second determination threshold setting unit 52.

[0031] The control unit 6 controls the stepper motor drive unit 3. The control unit 6 drives the stepper motor 4 via the stepper motor drive unit 3, thereby performing the cutoff and recovery actions in the gas meter. Additionally, the control unit 6 maintains timing information for determining when the current level is detected by the current level detection unit 2. Furthermore, the control unit 6 stores the determination result obtained by the determination unit 5.

[0032] [1-1-2. Structure of the Current Level Detection Unit]

[0033] Figure 2 This is a block diagram showing an example of the structure of the current level detection unit 2 in Embodiment 1.

[0034] The instantaneous current level detection unit 21 has a resistor 20.

[0035] The integrator 22 integrates the current flowing from the resistor 20 to the stepper motor drive unit 3 via the resistor 30 and the capacitor 31. The capacitor 31 is connected to GND.

[0036] The analog-to-digital converter 40 has the function of converting the current level of the input current from an analog value to a digital value. Specifically, using the output voltage of the power supply unit 1 as a reference voltage, the voltage obtained by integrating the current flowing through the resistor 20 through the integrator 22 is converted into a digital value. Therefore, the smaller the digital value, the larger the current. In this embodiment, this digital value is set as the current level. The digital value obtained by this conversion is output to the determination unit 5, where the determination unit 5 uses the digital value to make a determination. In addition, the analog-to-digital converter 40 also serves as the power supply impedance estimation unit 23.

[0037] [1-2. Actions]

[0038] The operation of the stepper motor malfunction detection device 100 configured as described above will now be explained. The stepper motor malfunction detection device 100 acquires the current level when the stepper motor 4 is driven via the instantaneous current level detection unit 21. Then, the correction unit 55 corrects the current level based on the power supply impedance estimated by the power supply impedance estimation unit 23. Then, the first comparator 53 and the second comparator 54 compare a preset judgment threshold with the corrected current level, thereby the judgment unit 5 determines whether the stepper motor is malfunctioning. Each operation will now be described in detail.

[0039] [1-2-1. Obtaining the Current Level]

[0040] The current level detection unit 2 maintains timing information for determining when to detect the current level. Based on this timing information, the current level detection unit 2 acquires the current level at a predetermined time when the stepper motor 4 is driven. Specifically, as shown below. The stepper motor drive unit 3 drives the stepper motor 4 according to control from the control unit 6. The analog-to-digital converter 40 converts the current level acquired by the instantaneous current level detection unit 21 during the driving of the stepper motor 4 into a digital value. The timing at which the analog-to-digital converter 40 acquires the digital value can be arbitrarily set. However, this timing is limited to the driving of the stepper motor 4. The number of times the analog-to-digital converter 40 acquires the digital value is not limited to once. For example, by acquiring the digital value multiple times and calculating its average value, misjudgments due to noise or other factors can be prevented.

[0041] [1-2-1. Correction]

[0042] Figure 4 This graph illustrates the change in current level during the driving of stepper motor 4 when it is used to drive a shut-off valve, using the difference in power supply impedance. Figure 4 The diagram shows the change in current level from when the stepper motor drive unit 3 is turned on (ON) at time A, causing the shut-off valve to be cut off from the fully open state and become fully closed, until the stepper motor drive unit 3 becomes turned off (OFF) at time B after the stepper motor 4 stops rotating. Furthermore, in Figure 4 In this context, the current level is the numerical value mentioned above.

[0043] exist Figure 4 In the diagram, the change in current level immediately preceding timing B indicates the increase in load due to the stopping of stepper motor 4. Additionally, in... Figure 4 The diagram shows that the current level becomes higher than usual when the power supply section 1 has high impedance. This confirms that the lithium battery constituting the power supply section 1 experiences increased internal impedance due to temperature changes and a decrease in battery capacity, resulting in a greater current flow.

[0044] Furthermore, the current level is obtained by converting the instantaneous current flowing through the stepper motor drive unit 3 into voltage using resistor 20. The detected current level is divided by the voltage value of the power supply unit 1, and the resulting value is multiplied by 1024 to calculate the numerical value. In other words, when the stepper motor 4 is not operating, since the detected current level and the voltage value of the power supply unit 1 are equal, the calculated current level is 1024. Figure 4 The change in current level from timing B to timing C shows that after the current consumption of stepper motor 4 becomes 0 at timing B, the current level gradually reaches 1024 due to the action of integrator 22.

[0045] At the instants of operation initiation and deitiation, the stepper motor anomaly detection device 100 obtains the power supply impedance through the power supply impedance estimation unit 23. Specifically, the power supply impedance is calculated by determining the difference between the upper limit of the current level (1024) and the current level detected at each of the operation initiation (timing A) and operation deitiation (timing B). Figure 4 As shown, when the power supply impedance is high, the aforementioned difference becomes smaller when the operation is on, and the aforementioned difference becomes larger when the operation is off. The correction unit 55 corrects the current level based on the power supply impedance obtained by the power supply impedance estimation unit 23.

[0046] As described above, the current level detection unit 2 converts the current flowing at a predetermined time when the stepper motor is driven into a current level expressed as a digital value using the analog-to-digital converter 40. Furthermore, the correction unit 55 uses the power supply impedance calculated by the power supply impedance estimation unit 23 to correct the current level calculated by the integrator 22 to a current level used for anomaly detection.

[0047] Figure 5 This shows the alignment of the calibration section 55. Figure 4 The graph shows the current level after correction. Figure 4 It can be confirmed that when the power supply impedance is high, the absolute value of the current level increases during the start-up and operation of the stepper motor, and decreases when the operation is stopped. The variation in current level caused by this power supply impedance can be corrected by performing the aforementioned adjustment. Figure 5 As shown, the variation in current level is converted to a constant level. This significantly reduces false judgments caused by variations in power supply impedance in the determination unit 5 described later, enabling high-precision anomaly detection.

[0048] [1-2-1. Thresholds and Comparisons]

[0049] Figure 3 This is a flowchart illustrating the anomaly determination method in the determination unit 5 of Embodiment 1.

[0050] Figure 6 It is a diagram showing the current level of the stepper motor 4 under normal operation, the current level of the stepper motor 4 under abnormal operation (circuit break), the current level of the stepper motor 4 under step loss and jamming, the first threshold (first determination threshold), and the second threshold (second determination threshold).

[0051] like Figure 3 As shown, firstly, the stepper motor anomaly detection device 100 detects the corrected current level Z1 at a predetermined timing during stepper motor operation (step S1). In this embodiment, the predetermined timing is set at... Figure 6During the period from point D to point E, when the current level is stable. Next, in the first comparator 53, the current level Z1 is compared with a first threshold (step S2). If it is determined in step S2 that the current level Z1 is greater than the first threshold (yes in step S2), the determination unit 5 determines that the stepper motor 4 is in an open circuit state (R1). On the other hand, if it is determined in step S2 that the current level Z1 is below the first threshold (no in step S2), the current level Z1 is compared with a second threshold in the second comparator 54 (step S3). If it is determined in step S3 that the current level Z1 is less than the second threshold (yes in step S3), the determination unit 5 determines that the stepper motor 4 is in a step-out or jammed state (R2). If no abnormality is determined in the comparison of the current level Z1 with the first threshold and the second threshold (no in step S3), the determination unit 5 determines that the stepper motor 4 is operating normally (R3). Furthermore, in Figure 3 In the flowchart shown, the order of processing steps S2 and S3 can also be reversed.

[0052] [1-3. Effects, etc.]

[0053] As described above, in this embodiment, the stepper motor anomaly detection device 100 includes a power supply unit 1, a current level detection unit 2, a stepper motor drive unit 3, and a determination unit 5. The current level detection unit 2 detects and integrates the instantaneous current flowing from the power supply unit 1 to the stepper motor drive unit 3 to estimate the power supply impedance. The determination unit 5 uses the power supply impedance value to correct the integrated value and compares the corrected integrated value with a predetermined threshold.

[0054] Therefore, even during unstable operation, the stepper motor abnormality detection device 100 corrects the current level according to the power supply impedance, so it is not affected by the unstable operation of the stepper motor and can detect stepper motor operation abnormalities such as open circuit and jamming with high precision.

[0055] Furthermore, in this embodiment, an example of detecting the current level during a period of stable current level has been described. However, the timing of current level detection is not limited to a period of stable current level. Even during periods of current level variation, the stepper motor anomaly detection device 100 can detect anomalies in the stepper motor by setting the first threshold and the second threshold to values ​​that allow for anomaly determination.

[0056] Alternatively, in this embodiment, the stepper motor abnormality detection device 100 may not use the instantaneous current level detection unit 21 and the integrator 22, but instead input the current level of the current flowing through the stepper motor drive unit 3 to the analog-to-digital converter 40.

[0057] Furthermore, the above-described embodiments are for illustrating the technology in this disclosure, and therefore various changes, substitutions, additions, omissions, etc., can be made within the scope of the claims or their equivalents.

[0058] Industrial availability

[0059] This disclosure can be applied to battery-powered devices that use stepper motors. Specifically, this disclosure can be applied to water meters, etc.

[0060] Explanation of reference numerals in the attached figures

[0061] 1: Power supply unit; 2: Current level detection unit; 3: Stepper motor drive unit; 4: Stepper motor; 5: Judgment unit; 6: Control unit; 20: Resistor; 30: Resistor; 31: Capacitor; 40: Analog-to-digital converter; 100: Stepper motor abnormality detection device.

Claims

1. A stepping motor abnormality detection device, comprising: a stepping motor drive section that outputs a drive pulse for driving a stepping motor; a power supply section that supplies a power supply to the stepping motor drive section; a current level detection section that detects a current level of a current flowing through the stepping motor drive section; a determination section that determines whether the stepping motor is in a normal operation state by comparing the current level detected by the current level detection section with a determination threshold value that is determined in advance based on a current level in a case where the stepping motor is normally operating, wherein the current level detection section has a power supply impedance estimation section that estimates a power supply impedance of the power supply section, and corrects the determination threshold value or the current level based on the estimated power supply impedance.

2. The stepping motor abnormality detection device according to claim 1, wherein the determination section has a first determination threshold value as the determination threshold value for determining that the stepping motor is in an open circuit state.

3. The stepping motor abnormality detection device according to claim 1, wherein the determination section has a second determination threshold value as the determination threshold value for determining that the stepping motor is in a stuck state.

4. The stepping motor abnormality detection device according to any one of claims 1 to 3, wherein the current level detection section is configured to include an integration section that integrates a current level of a transient current.

5. The stepping motor abnormality detection device according to claim 4, wherein the current level detection section is configured to insert a resistor between the power supply section and the stepping motor drive section, and the integration section is configured to integrate a signal at a connection point of the resistor and the stepping motor drive section via a capacitor. wherein 6. The stepping motor abnormality detection device according to claim 1, wherein the current level detection section has an analog-digital conversion section that converts the current level into a digital signal corresponding to the current level.

7. The stepping motor abnormality detection device according to claim 1, wherein the larger the difference in output voltage of the power supply section between when the stepping motor drive section is operating and when the stepping motor drive section is not operating, the larger the power supply impedance estimation section estimates the power supply impedance to be.

8. The stepping motor abnormality detection device according to claim 7, wherein as the difference in output voltage of the power supply section between when the stepping motor drive section is operating and when the stepping motor drive section is not operating, a ratio of an output voltage of the power supply section after the stepping motor drive section changes from operating to not operating to an output of the integration section is used. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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