Abnormality detection device for brake device

Abstract

This abnormality detection device comprises: a control circuit that applies a first command voltage to a control terminal of a first switching element of a non-excitation operation-type brake device, and applies a second command voltage to a control terminal of a second switching element; a detection circuit that detects a first potential that is the potential of a first terminal of a brake coil, and a second potential that is the potential of a second terminal of the brake coil; and a determination circuit that determines the presence or absence of an abnormality of the first switching element and the second switching element on the basis of a combination pattern of the first command voltage applied to the control terminal of the first switching element by the control circuit, the first potential of the first terminal detected by the detection circuit, the second command voltage applied to the control terminal of the second switching element by the control circuit, and the potential of the second terminal detected by the detection circuit.

Description

Brake system abnormality detection device

[0001] The present disclosure relates to an abnormality detection device for a brake system.

[0002] In motor drive devices, non-excitation actuation mechanical brake devices (hereinafter simply referred to as "brake devices") are widely used to brake rotating motors or to fix stopped motors so that they do not rotate. A switching element is connected between the brake coil of the brake device and the power source. In a non-excitation actuation brake device, when the switching element is closed, current flows from the power source to the brake coil, releasing the brake. When the switching element is opened, the brake is engaged, preventing current from flowing from the power source to the brake coil. Brake devices are safety-related mechanisms and therefore require high reliability. If there is an abnormality in the switching element that controls the current flowing through the brake coil, the brake cannot be engaged or released normally. For this reason, several technologies have been proposed to detect abnormalities in brake devices.

[0003] JP 2022-068140 A JP 2015-211609 A

[0004] There is a demand for technology that can accurately detect abnormalities in non-excitation operating brake devices.

[0005] According to one aspect of the present disclosure, an abnormality detection device includes a control circuit for controlling opening and closing of a first switching element by applying a first command voltage to a control terminal of a first switching element connected between a power source and a first terminal of the brake coil, and controlling opening and closing of a second switching element by applying a second command voltage to a control terminal of a second switching element connected between a second terminal of the brake coil and ground 4, of a non-excitation actuation type brake device that releases the brake when current is flowing through the brake coil and engages the brake when current to the brake coil is interrupted; a detection circuit for detecting a first potential that is the potential of the first terminal of the brake coil and a second potential that is the potential of the second terminal of the brake coil; and a determination circuit for determining the presence or absence of an abnormality in the first switching element and the second switching element based on a combination pattern of the magnitude of the first command voltage applied by the control circuit to the control terminal of the first switching element, the magnitude of the first potential of the first terminal detected by the detection circuit, the magnitude of the second command voltage applied by the control circuit to the control terminal of the second switching element, and the magnitude of the potential of the second terminal detected by the detection circuit.

[0006] FIG. 1 is a diagram illustrating an abnormality detection device according to an embodiment of the present disclosure. FIG. 1 is a cross-sectional view showing the structure of a non-excitation operated brake device that is a target for abnormality detection by the abnormality detection device according to an embodiment of the present disclosure, illustrating a state in which the brake is applied to the motor. FIG. 1 is a cross-sectional view showing the structure of a non-excitation operated brake device that is a target for abnormality detection by the abnormality detection device according to an embodiment of the present disclosure, illustrating a state in which the brake is released from the motor. FIG. 2 is a diagram illustrating an example of noise generation when the brake of the brake device is applied. FIG. 3 is a diagram illustrating a reference pattern when the brake is applied, used for determination processing by a determination circuit in the abnormality detection device according to an embodiment of the present disclosure. FIG. 4 is a diagram illustrating an example of command voltages and detected potentials when each switching element is normal but there is an influence of noise when the brake of the brake device is applied, in an embodiment of the present disclosure. FIG. 5 is a diagram illustrating an example of command voltages and detected potentials when an abnormality exists in a first switching element when the brake of the brake device is applied, in an embodiment of the present disclosure. FIG. 6 is a diagram illustrating a reference pattern when the brake is released, used for determination processing by a determination circuit in the abnormality detection device according to an embodiment of the present disclosure. FIG. 7 is a flowchart showing an operation flow of the determination circuit in the abnormality detection device according to an embodiment of the present disclosure.

[0007] The brake device abnormality detection device will be described below with reference to the drawings. In the following description, components having the same or similar functions will be assigned the same reference numerals. Duplicate descriptions of these components may be omitted. The scale of the drawings has been changed as appropriate to facilitate understanding. In the following description, when the term "brake device" is simply used, it refers to a non-excitation actuated brake device.

[0008] Overall Configuration According to an Embodiment of the Present Disclosure FIG. 1 is a diagram illustrating an abnormality detection device according to an embodiment of the present disclosure.

[0009] An abnormality detection device 1 according to an embodiment of the present disclosure detects the presence or absence of an abnormality in a non-excitation actuation type brake device 2. The non-excitation actuation type brake device 2 releases the brake when excited, that is, when a current flows through the brake coil 25, and applies the brake when not excited, that is, when the current to the brake coil 25 is cut off.

[0010] Prior to describing the abnormality detection device 1 according to an embodiment of the present disclosure, the structure of a brake device 2 controlled by a brake drive device connected to the abnormality detection device 1 will be described with reference to Figures 2 and 3. Figure 2 is a cross-sectional view showing the structure of a non-excitation actuation type brake device that is the target of abnormality detection by the abnormality detection device according to an embodiment of the present disclosure, illustrating a state in which the brake is applied to the motor. Figure 3 is a cross-sectional view showing the structure of a non-excitation actuation type brake device that is the target of abnormality detection by the abnormality detection device according to an embodiment of the present disclosure, illustrating a state in which the brake is released from the motor.

[0011] As shown in FIGS. 2 and 3 , in the brake device 2, a friction plate 21 is disposed between an armature 22 and an end plate 23. A hub 32 is spline-connected to the friction plate 21. The hub 32 and the motor shaft 31 are integrated, for example, by shrink fitting, so that the friction plate 21 rotates in conjunction with the rotation of the motor shaft 31. The end plate 23 and a spacer 27 are connected with bolts 28, and the armature 22 is connected to the spacer 27 so as to be movable toward and away from the friction plate 21. A spring 24 and a brake coil 25 are provided within a core 26. As shown in FIG. 2 , in a non-excited state where no current flows through the brake coil 25, the armature 22 is pressed firmly against the friction plate 21 by the elastic force of the spring 24, and the friction plate 21 is sandwiched between the armature 22 and the end plate 23 and cannot rotate. As a result, the motor shaft 31 connected to the friction plate 21 also cannot rotate, and the motor is braked (brake-engaged state). 3, in an excited state where a brake current flows through the brake coil 25, an electromagnetic force is generated in the core 26 that overcomes the elastic force of the spring 24 that was pressing the armature 22 against the friction plate 21, thereby attracting the armature 22 to the core 26 and releasing the friction plate 21 from contact with the armature 22 and the end plate 23. As a result, the friction plate 21 and therefore the motor shaft 31 can rotate freely, and the brake on the motor is released (brake released state).

[0012] As shown in Fig. 1, a power supply 3 is connected to the brake device 2. The power supply 3 outputs a DC voltage. The power supply 3 is composed of, for example, a rectifier that converts an AC voltage into a DC voltage, a switching regulator, or a battery. As an example, the power supply 3 outputs a DC voltage of 24 V, but it may also be a DC power supply that outputs a DC voltage of another voltage value (for example, 15 V, 12 V, 5 V, etc.).

[0013] The brake device 2 includes a first switching element SW1 , a second switching element SW2 , and a diode 29 to control the current flowing from the power supply 3 to the brake coil 25 .

[0014] The first switching element SW1 and the second switching element SW2 are each connected in series to the brake coil 25 of the brake device 2. The first switching element SW1 is provided to open (disconnect) or close (connect) an electrical path between a first terminal P1, which is the positive terminal of the brake coil 25, and a power supply 3. The second switching element SW2 is provided to open (disconnect) or close (connect) an electrical path between a second terminal P2, which is the negative terminal of the brake coil 25, and ground 4. While one first switching element SW1 and one second switching element SW2 are provided in the example shown in FIG. 1 , two or more of each may be provided. Examples of the first switching element SW1 and the second switching element SW2 include a MOSFET, an IGBT, a thyristor, a GTO, and a transistor. A MOSFET has a gate terminal, a drain terminal, and a source terminal as its terminals. An IGBT has a gate terminal, a collector terminal, and an emitter terminal as its terminals. A transistor has a base terminal, a collector terminal, and an emitter terminal as its terminals. A thyristor and a GTO have a gate terminal, an anode terminal, and a cathode terminal as its terminals. The "current inflow terminals" of the first switching element SW1 and the second switching element SW2 correspond to the "drain terminals" of a MOSFET, the "collector terminals" of an IGBT and a transistor, and the "anode terminals" of a thyristor and a GTO, respectively. The "current outflow terminals" of the first switching element SW1 and the second switching element SW2 correspond to the "source terminals" of a MOSFET, the "emitter terminals" of an IGBT and a transistor, and the "cathode terminals" of a thyristor and a GTO, respectively. The "control terminals" of the first switching element SW1 and the second switching element SW2 correspond to the "gate terminals" of a MOSFET, an IGBT, a thyristor, and a GTO, and the "base terminals" of a transistor, respectively.

[0015] The types of the first switching element SW1 and the second switching element SW2 do not limit this embodiment, and may be switching elements other than those illustrated. In the following description, the first switching element SW1 and the second switching element SW2 are, as an example, normally-off switching elements. If the first switching element SW1 and the second switching element SW2 are normally-on switching elements, in the following description, the close command voltage will be interpreted as L (low) and the open command voltage will be interpreted as H (high).

[0016] The diode 29 is connected between the first terminal P1 and the second terminal P2 of the brake coil 25 so as to be connected in parallel to the brake device 2. The diode 29 removes momentary high voltages such as switching surges and noise of the first switching element SW1 and the second switching element SW2.

[0017] As shown in FIG. 1 , an abnormality detection device 1 according to an embodiment of the present disclosure includes a control circuit 11 , a detection circuit 12 , and a determination circuit 13 .

[0018] The control circuit 11 controls the opening and closing of the first switching element SW1 by applying a first command voltage to the control terminal C1 of the first switching element SW1. The control circuit 11 also controls the opening and closing of the second switching element SW2 by applying a second command voltage to the control terminal C2 of the second switching element SW2. The control circuit 11 functions as a brake drive device for controlling brake engagement and brake release of the brake device 2, and also functions as an abnormality detection device 1 for detecting abnormalities in the brake device 2. That is, the control circuit 11 outputs, as the first command voltage and the second command voltage, a brake engagement command voltage when the brake is engaged, and a brake release command voltage when the brake is released. The control circuit 11 also outputs pulsed test command voltages as the first command voltage and the second command voltage. The first command voltage output from the control circuit 11 is applied to the control terminal C1 of the first switching element SW1. The second command voltage output from the control circuit 11 is applied to the control terminal C2 of the second switching element SW2. Data relating to the first command voltage and the second command voltage output from the control circuit 11 is sent to the determination circuit 13.

[0019] The detection circuit 12 detects a first potential, which is the potential at the first terminal P1 of the brake coil 25, and a second potential, which is the potential at the second terminal P2 of the brake coil 25. Hereinafter, the detected first potential and second potential may be referred to as "detected potentials." Data related to the detection results by the detection circuit 12 is sent to the determination circuit 13.

[0020] The judgment circuit 13 judges whether or not there is an abnormality in the first switching element SW1 and the second switching element SW2 based on a combination pattern of the magnitude of the first command voltage applied by the control circuit 11 to the control terminal C1 of the first switching element SW1, the magnitude of the first potential at the first terminal P1 detected by the detection circuit 12 when the first command voltage is applied to the control terminal C1 of the first switching element SW1, the magnitude of the second command voltage applied by the control circuit 11 to the control terminal C2 of the second switching element SW2, and the magnitude of the potential at the second terminal P2 detected by the detection circuit 12 when the second command voltage is applied to the control terminal C2 of the second switching element SW2.

[0021] If the combination pattern of each command voltage and each detected potential does not match a predetermined reference pattern for a predetermined mismatch determination time, the judgment circuit 13 judges that an abnormality has occurred in at least one of the first switching element SW1 and the second switching element SW2.

[0022] The determination result by the determination circuit 13 may be displayed on, for example, a display device (not shown). Examples of the display device include a standalone display device, a display device attached to a motor drive device connected to the brake device 2, a display device attached to a higher-level control device (for example, a robot controller or a numerical control device), and a display device attached to a personal computer or a mobile terminal.

[0023] When the brake device 2 is engaged, there is a possibility that an erroneous determination may be made due to the influence of noise, so the determination circuit 13 has a configuration for eliminating the influence of noise.

[0024] Here, the generation of noise when the brake is applied will be described. Fig. 4 is a diagram illustrating an example of the generation of noise when the brake of the brake device is applied.

[0025] By setting a threshold value to determine the magnitude of the first potential at the first terminal P1 and the second potential at the second terminal P2 of the brake coil 25, it is possible to distinguish between a potential equal to or greater than the threshold value as a high potential (H) and a potential less than the threshold value as a low potential (L). The threshold value is set, for example, to a value approximately midway between the potential of the power supply 3 and the potential of the ground 4.

[0026] When the brake device 2 is brake-engaged, the control circuit 11 applies a brake engagement open command voltage L (low) to the control terminal C1 of the first switching element SW1 as a first command voltage, and applies a brake engagement open command voltage L (low) to the control terminal C2 of the second switching element SW2 as a second command voltage. If there is no abnormality in the first switching element SW1 or the second switching element SW2, the first switching element SW1 and the second switching element SW2 open. As a result, no DC voltage is applied from the power supply 3 between the first terminal P1 and the second terminal P2 of the brake coil 25, so ideally, the first potential of the first terminal P1 and the second potential of the second terminal P2 should both be low potential (L). If the first potential of the first terminal P1 and / or the second potential of the second terminal P2 becomes H (high) even though the brake device 2 is in the brake applied state, there is a possibility that an abnormality has occurred in the first switching element SW1 and / or the second switching element SW2.

[0027] However, even if no abnormality occurs in the first switching element SW1 and the second switching element SW2, the first potential of the first terminal P1 and / or the second potential of the second terminal P2 may become H (high) due to the influence of noise. The reason for this is as follows.

[0028] Because the first terminal P1 and the second terminal P2 of the brake coil 25 are in a high-impedance state, being disconnected from the ground 4, the first terminal P1 and the second terminal P2 of the brake coil 25 are susceptible to external noise, and the magnitude of the potential between the first terminal P1 and the second terminal P2 of the brake coil 25 fluctuates due to the noise. The example shown in FIG. 4 illustrates how the second potential of the second terminal P2 of the brake coil 25 fluctuates due to the noise. If the first switching element SW1 and the second switching element SW2 are normal, the second potential should be determined to be a low potential (L) when the brake device 2 is engaged. However, due to the influence of noise, a period of time may occur in which the second potential is determined to be a high potential (H), which is inconsistent with the actual determination result. If this "inconsistency period" continues for a certain period of time and exceeds the alarm determination time, the first switching element SW1 and the second switching element SW2 may be erroneously determined to have an abnormality, even though no abnormality has occurred.

[0029] Therefore, in one embodiment of the present disclosure, in order to avoid erroneous determination due to the above-mentioned noise when the brakes of the brake device 2 are applied, the control circuit 11 applies a pulsed test command voltage to the control terminal C1 of the first switching element SW1 and the control terminal C2 of the second switching element SW2 while applying the brake engagement command voltage when the brakes of the brake device 2 are applied. That is, when the brakes of the brake device 2 are applied, the control circuit 11 applies one of a brake engagement open command voltage and a pulsed test close command voltage to the control terminal C1 of the first switching element SW1 as the first command voltage, and applies one of the brake engagement open command voltage and a pulsed test close command voltage to the control terminal C2 of the second switching element SW2 as the second command voltage. Then, the determination circuit 13 determines whether a combination pattern of each command voltage and each detected potential matches a predetermined reference pattern when the brake engagement open command voltage and the pulsed test close command voltage are applied to the control terminals C1 and C2, respectively. The determination circuit 13 determines that an abnormality has occurred in the first switching element SW1 and the second switching element SW2 when the combination pattern of each command voltage and each detected potential does not match the reference pattern (i.e., the mismatch state) for a predetermined mismatch determination time. Furthermore, if the combination pattern of each command voltage and each detected potential does not match the reference pattern (i.e., the mismatch state) for the duration of the mismatch determination time, the determination circuit 13 does not determine that an abnormality has occurred because there is a possibility of noise occurring. Furthermore, if the combination pattern of each command voltage and each detected potential matches the reference pattern, the determination circuit 13 does not naturally determine that an abnormality has occurred.

[0030] <Reference Pattern When Brakes are Engaged> Next, a reference pattern when the brakes are engaged, which is used for the determination process by the determination circuit 13, will be described.

[0031] When the first switching element SW1 and the second switching element SW2 are normal, the magnitude of the first potential at the first terminal P1 of the brake coil 25 and the magnitude of the second potential at the second terminal P2 of the brake coil 25 are determined according to the first command voltage applied to the control terminal C1 of the first switching element SW1 and the second command voltage applied to the control terminal C2 of the second switching element SW2. A combination of the first command voltage, the first potential, the second command voltage, and the second potential when the first switching element SW1 and the second switching element SW2 are normal is defined as a reference pattern.

[0032] Fig. 5 is a diagram showing a reference pattern during brake application used for determination processing by a determination circuit in an abnormality detection device according to an embodiment of the present disclosure. In Fig. 5, the first switching element SW1 and the second switching element SW2 are normally-off switching elements, so the open command voltage is L (low) and the close command voltage is H (high). If the first switching element SW1 and the second switching element SW2 are normally-on switching elements, the reference table in Fig. 5 is applied with the open command voltage being H (high) and the close command voltage being L (low).

[0033] When the brakes of the brake device 2 are applied, the control circuit 11 applies, as a first command voltage, one of a brake engagement open command voltage and a pulsed test close command voltage to the control terminal C1 of the first switching element SW1, and applies, as a second command voltage, one of the brake engagement open command voltage and a pulsed test close command voltage to the control terminal C2 of the second switching element SW2. The reference pattern when the brakes are applied includes a combination of a command voltage and a detected potential for maintaining the brake engagement state of the brake device 2, a combination of a command voltage and a detected potential when the pulsed test command voltage is applied to the control terminal C1 of the first switching element SW1, and a combination of a command voltage and a detected potential when the pulsed test command voltage is applied to the control terminal C2 of the second switching element SW2. More details are as follows.

[0034] In the basic state when the brakes are applied, the reference pattern is a combination in which the first command voltage is L (low), which is the brake application open command voltage, the first potential of the first terminal P1 is L (low), which is a value less than the threshold value, the second command voltage is L (low), which is the brake application open command voltage, and the second potential of the second terminal P2 is L (low), which is a value less than the threshold value.

[0035] When a pulsed test command voltage is applied to the control terminal C1 of the first switching element SW1, the reference pattern is a combination in which the first command voltage is H (high), which is a test close command voltage, the first potential of the first terminal P1 is H (high), which is a value equal to or greater than the threshold value, the second command voltage is L (low), which is a brake engagement open command voltage, and the second potential of the second terminal P2 is H (high), which is a value equal to or greater than the threshold value.

[0036] In a state where a pulsed test command voltage is applied to the control terminal C2 of the second switching element SW2, the reference pattern is a combination in which the first command voltage is L (low), which is an open command voltage for brake engagement, the first potential of the first terminal P1 is L (low), which is a value less than the threshold value, the second command voltage is H (high), which is a close command voltage for test, and the second potential of the second terminal P2 is L (low), which is a value less than the threshold value.

[0037] 6 is a diagram illustrating an example of a command voltage and a detected potential when the switching elements are normal but there is an influence of noise when the brakes of the brake device are applied in an embodiment of the present disclosure. Fig. 6 illustrates a case where noise occurs between the first terminal P1 and the second terminal P2 of the brake coil 25 between time t1 and time t2 and after time t4 when the brakes are applied.

[0038] From the start time to time t1, a first command voltage, a brake engagement open command voltage (L (low)), is applied to the control terminal C1 of the first switching element SW1, and a second command voltage, a brake engagement open command voltage (L (low)), is applied to the control terminal C2 of the second switching element SW2. As a result, both the first switching element SW1 and the second switching element SW2 are in the open state. As a result, the second potential of the second terminal P2 is mainly L (low), but the first potential of the first terminal P1, which should normally be L (low), remains H (high), a value above the threshold, for a relatively long period of time due to the influence of noise. Therefore, from the start time to time t1, the combination pattern of the command voltages and the detected potentials does not match the reference pattern shown in FIG. 5 .

[0039] Between time t1 and time t2, a test close command voltage H (high) is applied as a first command voltage to the control terminal C1 of the first switching element SW1, and a brake engagement open command voltage L (low) is applied as a second command voltage to the control terminal C2 of the second switching element SW2. This causes the first switching element SW1 to be in an open state, and the second switching element SW2 to be in a closed state. As a result, the first potential of the first terminal P1 becomes H (high), which is a value equal to or greater than the threshold, and the second potential of the second terminal P2 becomes H (high), which is a value equal to or greater than the threshold. Therefore, from time t1 to time t2, the combination pattern of the command voltages and the detected potentials matches the reference pattern shown in FIG. 5 , and the mismatch period from the start time to time t1 ends.

[0040] Between time t2 and time t3, a first command voltage, a brake engagement open command voltage (L (low)), is applied to the control terminal C1 of the first switching element SW1, and a second command voltage, a brake engagement open command voltage (L (low)), is applied to the control terminal C2 of the second switching element SW2. As a result, both the first switching element SW1 and the second switching element SW2 are in the open state. The first potential of the first terminal P1 is mainly L (low), but the second potential of the second terminal P2, which should normally be L (low), is H (high), a value above the threshold, for a relatively long period of time due to the influence of noise. Therefore, between time t2 and time t3, the combination pattern of the command voltages and the detected potentials does not match the reference pattern shown in FIG. 5 .

[0041] Between time t3 and time t4, a first command voltage, L (low), which is a brake engagement open command voltage, is applied to the control terminal C1 of the first switching element SW1, and a second command voltage, H (high), which is a test close command voltage, is applied to the control terminal C2 of the second switching element. At this time, the first switching element SW1 is in the open state, and the second switching element SW2 is in the closed state. As a result, the first potential of the first terminal P1 is L (low), which is a value below the threshold, and the second potential of the second terminal P2 is L (low), which is a value below the threshold. Therefore, between time t3 and time t4, the combination pattern of the command voltages and the detected potentials matches the reference pattern shown in FIG. 5 , and the mismatch period from time t2 to time t3 ends.

[0042] 6 , even if the switching elements are normal but affected by noise, a pulsed test command voltage is applied to the control terminal C1 of the first switching element SW1 and the control terminal C2 of the second switching element SW2, causing the combination pattern of the command voltages and the detected potentials to match the reference pattern, so the time during which the patterns do not match due to the influence of noise does not last long. Therefore, when the combination pattern of the command voltages and the detected potentials matches the reference pattern, the mismatch determination time is reset to 0. This eliminates pattern mismatch states caused by noise from the abnormality determination process, preventing erroneous determinations caused by noise.

[0043] 7 is a diagram illustrating an example of a command voltage and a detected potential when an abnormality occurs in the first switching element SW1 during brake application of a brake device in one embodiment of the present disclosure. Fig. 7 illustrates a case where an abnormality occurs in the first switching element SW1 at time t6 during brake application. For simplicity of explanation, Fig. 7 does not illustrate the occurrence of noise.

[0044] From the start time to time t5, a first command voltage, a brake engagement open command voltage L (low), is applied to the control terminal C1 of the first switching element SW1, and a second command voltage, a brake engagement open command voltage L (low), is applied to the control terminal C2 of the second switching element SW2. As a result, the first switching element SW1 and the second switching element SW2 are both in the open state. As a result, the first potential of the first terminal P1 and the second potential of the second terminal P2 are both L (low). Therefore, from the start time to time t5, the combination pattern of each command voltage and each detected potential matches the reference pattern shown in FIG. 5 .

[0045] Between time t5 and time t6, a test close command voltage H (high) is applied as a first command voltage to the control terminal C1 of the first switching element SW1, and a brake engagement open command voltage L (low) is applied as a second command voltage to the control terminal C2 of the second switching element SW2. As a result, the first switching element SW1 is in the open state and the second switching element SW2 is in the closed state. As a result, the first potential of the first terminal P1 becomes H (high), which is a value equal to or greater than the threshold, and the second potential of the second terminal P2 becomes H (high), which is a value equal to or greater than the threshold. Therefore, between time t5 and time t6, the combination pattern of each command voltage and each detected potential matches the reference pattern shown in FIG. 5 .

[0046] After time t6, an abnormality (short circuit failure) occurs in the first switching element SW1.

[0047] Between time t6 and time t7, a brake engagement open command voltage L (low) is applied as the first command voltage to the control terminal C1 of the first switching element SW1, and a brake engagement open command voltage L (low) is applied as the second command voltage to the control terminal C2 of the second switching element SW2. At this time, the second switching element SW2 is in the open state, but the first switching element SW1 remains in the closed state due to a short-circuit fault. As a result, the first potential of the first terminal P1 becomes H (high), and the second potential of the second terminal P2 remains H (high) for a relatively long time. Therefore, between time t6 and time t7, the combination pattern of the command voltages and the detected potentials does not match the reference pattern shown in FIG. 5 .

[0048] Between time t7 and time t8, a brake engagement open command voltage L (low) is applied as the first command voltage to the control terminal C1 of the first switching element SW1, and a test close command voltage H (high) is applied as the second command voltage to the control terminal C2 of the second switching element SW2. At this time, the first switching element SW1 has a short-circuit fault and remains closed, while the second switching element SW2 is closed. As a result, the first potential of the first terminal P1 becomes H (high), and the second potential of the second terminal P2 becomes L (low). Therefore, between time t7 and time t8, the combination pattern of the command voltages and the detected potentials does not match the reference pattern shown in FIG. 5 .

[0049] From time t8 to time t9, a first command voltage, a brake engagement open command voltage L (low), is applied to the control terminal C1 of the first switching element SW1, and a second command voltage, a brake engagement open command voltage L (low), is applied to the control terminal C2 of the second switching element SW2. At this time, the first switching element SW1 has a short-circuit fault and remains closed, while the second switching element SW2 is open. As a result, the first potential of the first terminal P1 becomes high (H), and the second potential of the second terminal P2 becomes high (H). Therefore, from time t7 to time t8, the combination pattern of the command voltages and the detected potentials does not match the reference pattern shown in FIG. 5 .

[0050] 7, once a mismatch between the combination pattern of each command voltage and each detected potential and the reference pattern occurs after time t6 when an abnormality occurs in the first switching element SW1, the pattern mismatch time continues. The same applies if an abnormality occurs in the second switching element SW2.

[0051] As can be seen from FIGS. 6 and 7 described above, if the mismatch determination time is reset to 0 when the combination pattern of each command voltage and each detected potential matches the reference pattern, then even if a determination process is performed that determines that "an abnormality has occurred in the first switching element SW1 and the second switching element SW2 when the state in which the combination pattern of each command voltage and each detected potential does not match the reference pattern continues for the mismatch determination time," an erroneous determination due to noise will not occur.

[0052] Therefore, in an embodiment of the present disclosure, a discrepancy time counter 132 is provided that counts the time period during which a combination pattern of each command voltage and each detected potential does not match a reference pattern, and the discrepancy time counted by the discrepancy time counter 132 is monitored. Once a discrepancy occurs between a combination pattern of each command voltage and each detected potential and the reference pattern, the discrepancy time counter 132 starts counting the discrepancy time, and the count of the discrepancy time counter 132 is reset when the combination pattern of each command voltage and each detected potential matches the reference pattern. If the discrepancy time counted by the discrepancy time counter 132 exceeds a predetermined discrepancy determination time, it is determined that an abnormality has occurred in the first switching element SW1 and / or the second switching element SW2. When the brake device 2 is engaged, a brake engagement open command voltage is mainly applied to the control terminal C1 of the first switching element SW1 and the control terminal C2 of the second switching element SW2, and a pulsed test close command voltage is also periodically applied during this period. The period of application of the pulsed test close command voltage is set shorter than the mismatch determination time, so that the pattern mismatch time caused by noise is not determined to be an abnormality, and erroneous determinations caused by noise can be prevented in the abnormality detection device 1 of the non-excitation operation type brake device 2.

[0053] The abnormality detection device 1 according to an embodiment of the present disclosure can be applied not only when the brake of the brake device 2 is applied but also when the brake is released.

[0054] <Reference Pattern When Brake is Released> Figure 8 is a diagram showing a reference pattern when the brake is released, which is used for the determination process by the determination circuit in the abnormality detection device according to an embodiment of the present disclosure. Note that in Figure 8, the first switching element SW1 and the second switching element SW2 are normally-off switching elements, so the open command voltage is L (low) and the close command voltage is H (high). If the first switching element SW1 and the second switching element SW2 are normally-on switching elements, the reference table in Figure 8 is applied with the open command voltage being H (high) and the close command voltage being L (low).

[0055] When releasing the brakes of the brake device 2, the control circuit 11 applies, as a first command voltage, one of a brake release close command voltage and a pulsed test open command voltage to the control terminal C1 of the first switching element SW1, and applies, as a second command voltage, the brake release close command voltage and the pulsed test open command voltage to the control terminal C2 of the second switching element SW2. The reference pattern when releasing the brakes includes a combination of a command voltage and a detected potential for maintaining the braking mechanism state of the brake device 2, a combination of a command voltage and a detected potential when the pulsed test command voltage is applied to the control terminal C1 of the first switching element SW1, and a combination of a command voltage and a detected potential when the pulsed test command voltage is applied to the control terminal C2 of the second switching element SW2. More details are as follows.

[0056] In the basic state when the brake is released, the reference pattern is a combination in which the first command voltage is H (high), which is the brake release close command voltage, the first potential of the first terminal P1 is H (high), which is a value greater than or equal to the threshold value, the second command voltage is H (high), which is the brake release close command voltage, and the second potential of the second terminal P2 is L (low), which is a value less than the threshold value.

[0057] When a pulsed test command voltage is applied to the control terminal C1 of the first switching element SW1, the reference pattern is a combination in which the first command voltage is L (low), which is a test open command voltage, the first potential of the first terminal P1 is L (low), which is a value less than the threshold value, the second command voltage is H (high), which is a brake release close command voltage, and the second potential of the second terminal P2 is L (low), which is a value less than the threshold value.

[0058] When a pulsed test command voltage is applied to the control terminal C2 of the second switching element SW2, the reference pattern is a combination in which the first command voltage is H (high), which is a brake release close command voltage, the first potential of the first terminal P1 is H (high), which is a value equal to or greater than the threshold value, the second command voltage is L (low), which is a test open command voltage, and the second potential of the second terminal P2 is H (high), which is a value equal to or greater than the threshold value.

[0059] When the brake device 2 is released, both the first switching element SW1 and the second switching element SW2 are in a closed state, so the path from the power supply 3 through the first switching element SW1, the brake coil 25, and the second switching element SW2 to the ground 4 is in a conductive state. Therefore, the area between the first terminal P1 and the second terminal P2 of the brake coil 25 is less susceptible to external noise. Therefore, the discrepancy determination time used in the abnormality determination process by the determination circuit 13 when the brake of the brake device 2 is applied may be set to be shorter than the discrepancy determination time used in the abnormality determination process by the determination circuit 13 when the brake of the brake device 2 is released.

[0060] When the brake of the brake device 2 is released, a brake release close command voltage is mainly applied to the control terminal C1 of the first switching element SW1 and the control terminal C2 of the second switching element SW2, but a pulsed test open command voltage is also applied periodically during this period. The period of application of the pulsed test open command voltage is set shorter than the mismatch determination time. As a result, even if noise occurs, the pattern mismatch time caused by the noise will not be determined to be an abnormality, and erroneous determination caused by noise can be more reliably prevented in the abnormality detection device 1 of the non-excitation operation type brake device 2.

[0061] <Details of the Determination Circuit> In order to realize the determination process by the determination circuit 13 described above, the determination circuit 13 includes a pattern determination unit 131, a mismatch time counter 132, a mismatch time determination unit 133, an alarm output unit 134, a test time counter 135, and a test time determination unit 136.

[0062] The pattern determination unit 131 determines whether or not the combination pattern of each command voltage and each detected potential matches a reference pattern.

[0063] The mismatch time counter 132 stores a mismatch time count value indicating the duration during which the combination pattern of each command voltage and each detected potential does not match the reference pattern.

[0064] The mismatch time determination unit 133 determines whether the mismatch time count value has reached a first specified value, which is set as the mismatch determination time.

[0065] If the mismatch time determination unit 133 determines that the mismatch time count value has reached the first specified value, the alarm output unit 134 outputs an alarm indicating that an abnormality has occurred.

[0066] The test time counter 135 stores a test time count value.

[0067] If the discrepancy time determination unit 133 determines that the discrepancy time count value has not reached the first specified value, the test time determination unit 136 determines whether the test time count value has reached a second specified value. The second specified value is set to the length of one cycle of the application of the pulsed test close command voltage.

[0068] If the pattern determination unit 131 determines that the combination pattern of each command voltage and each detected potential does not match the reference pattern, the mismatch time counter 132 increments the mismatch time count value, and after the mismatch time counter 132 increments the mismatch time count value, the test time determination unit 136 executes a determination process.

[0069] If the pattern determination unit 131 determines that the combination pattern of each command voltage and each detected potential matches the reference pattern, the mismatch time counter 132 resets the mismatch time count value, and after the mismatch time counter 132 resets the mismatch time count value, the test time determination unit 136 executes a determination process.

[0070] If the test time determination unit 136 determines that the test time count value has not reached the second specified value, the test time counter 135 increments the test time count value, and after the test time counter 135 increments the test time count value, the pattern determination unit 131 executes a determination process.

[0071] If the test time determination unit 136 determines that the test time count value has reached the second specified value, the test time counter 135 resets the test time count value, and after the test time counter 135 resets the test time count value, the control circuit 11 applies a pulsed test command voltage to either the control terminal C1 of the first switching element SW1 or the control terminal C2 of the second switching element SW2, and after the pulsed test command voltage has been applied to either the control terminal C1 of the first switching element SW1 or the control terminal C2 of the second switching element SW2, the pattern determination unit 131 executes a determination process.

[0072] 9 is a flowchart showing the operation flow of the determination circuit in the abnormality detection device according to one embodiment of the present disclosure. The flowchart shown in FIG. 9 is applicable to both the brake application and brake release of the brake device 2, but here, the operation of the determination circuit 13 when the brake device 2 is applied will be described.

[0073] When the brake of the brake device 2 is applied, the test time count value of the test time counter 135 is reset in step S101.

[0074] In step S102, the control circuit 11 applies a test close command voltage to the control terminal C1 of the first switching element SW1 as the first command voltage, and applies a brake engagement open command voltage to the control terminal C2 of the second switching element SW2 as the second command voltage.

[0075] In step S103, the pattern determination unit 131 determines whether or not the combination pattern of each command voltage and each detected potential matches a reference pattern.

[0076] If it is determined in step S103 that the combination pattern of each command voltage and each detected potential matches the reference pattern, the mismatch time count value of the mismatch time counter 132 is reset in step S104, and then the process proceeds to step S106.

[0077] If it is determined in step S103 that the combination pattern of each command voltage and each detected potential does not match the reference pattern, the mismatch time count value of the mismatch time counter 132 is incremented in step S105, and then the process proceeds to step S106.

[0078] In step S106, the mismatch time determination unit 133 determines whether the mismatch time count value has reached a first specified value, which is set to the mismatch determination time.

[0079] If it is determined in step S106 that the mismatch time count value has reached the first specified value, the alarm output unit 134 outputs an alarm in step S107.

[0080] If it is determined in step S107 that the mismatch time count value has not reached the first specified value, the test time determination unit 136 determines in step S108 whether the test time count value has reached a second specified value, which is set to the length of one cycle of the application of the pulsed test close command voltage.

[0081] If it is determined in step S108 that the test time count value has not reached the second specified value, the test time count value of the test time counter 135 is incremented in step S109, and then the process returns to step S103.

[0082] If it is determined in step S108 that the test time count value has reached the second specified value, the process proceeds to step S110.

[0083] In step S110, the test time count value of the test time counter 135 is reset.

[0084] In step S111, the control circuit 11 applies a brake engagement open command voltage to the control terminal C1 of the first switching element SW1 as the first command voltage, and applies a test close command voltage to the control terminal C2 of the second switching element SW2 as the second command voltage.

[0085] In step S112, the pattern determination unit 131 determines whether or not the combination pattern of each command voltage and each detected potential matches a reference pattern.

[0086] If it is determined in step S112 that the combination pattern of each command voltage and each detected potential matches the reference pattern, the mismatch time count value of the mismatch time counter 132 is reset in step S113, and then the process proceeds to step S115.

[0087] If it is determined in step S112 that the combination pattern of each command voltage and each detected potential does not match the reference pattern, the mismatch time count value of the mismatch time counter 132 is incremented in step S114, and then the process proceeds to step S115.

[0088] In step S115, the mismatch time determination unit 133 determines whether the mismatch time count value has reached a first specified value.

[0089] If it is determined in step S115 that the mismatch time count value has reached the first specified value, the alarm output unit 134 outputs an alarm in step S116.

[0090] If it is not determined in step S115 that the mismatch time count value has reached the first specified value, in step S117, the test time determination unit 136 determines whether the test time count value has reached a second specified value.

[0091] If it is determined in step S117 that the test time count value has not reached the second specified value, the test time count value of the test time counter 135 is incremented in step S118, and then the process returns to step S112.

[0092] If it is determined in step S117 that the test time count value has reached the second specified value, the process returns to step S101.

[0093] <Processor and Memory> The abnormality detection device 1 includes at least one processor, which is an arithmetic processing device. Examples of the arithmetic processing device include an IC, an LSI, a CPU, an MPU, and a DSP. The arithmetic processing device may be provided in a motor drive device to which the brake device 2 is connected. The arithmetic processing device includes a control circuit 11, a detection circuit 12, a determination circuit 13, and other processing units. Each of these units included in the arithmetic processing device is a functional module implemented by a program executed on the processor. For example, if the control circuit 11, the detection circuit 12, the determination circuit 13, and other processing units are implemented in a program format, the functions of each unit can be realized by operating the arithmetic processing device in accordance with the program. The programs for executing the processes in the control circuit 11, the detection circuit 12, the determination circuit 13, and other processing units may be provided in a form recorded on a computer-readable recording medium such as a semiconductor memory, a magnetic recording medium, or an optical recording medium. Alternatively, the control circuit 11, the detection circuit 12, the determination circuit 13, and other processing units may be implemented as semiconductor integrated circuits on which programs implementing the functions of each unit are written.

[0094] The abnormality detection device 1 also includes at least one memory serving as a storage device. The memory may be provided in a motor drive device to which the brake device 2 is connected. Examples of the memory include electrically erasable and recordable nonvolatile memories such as EEPROM (registered trademark), or high-speed read / write random access memories such as DRAM and SRAM. The storage device may also include a hard disk drive (HDD) or solid state drive (SSD). The memory stores programs for operating the control circuit 11, the detection circuit 12, the determination circuit 13, and other processing units. The memory also stores a discrepancy time count value of the discrepancy time counter 132. The memory also stores a test time count value of the test time counter 135. The memory also stores thresholds for distinguishing whether the first potential detected by the detection circuit 12 and the second battery are H (high) or L (low). The memory also stores various programs and data related to the abnormality detection device 1.

[0095] <Operation of Abnormality Detection Device> According to the abnormality detection device 1 according to an embodiment of the present disclosure, it is possible to accurately detect an abnormality in the brake device 2 when the brake of the non-excitation operation type brake device 2 is applied or released.

[0096] As described above, in one embodiment of the present disclosure, if a state in which the combination pattern of each command voltage and each detected potential does not match the reference pattern continues for a mismatch determination time, it is determined that an abnormality has occurred. When the brake device 2 is brake-applied, the first terminal P1 and the second terminal P2 of the brake coil 25 are in a high-impedance state, disconnected from the ground 4, making the first terminal P1 and the second terminal P2 of the brake coil 25 more susceptible to external noise. If the combination pattern of each command voltage and each detected potential matches the reference pattern when a pulsed test command voltage is applied to the control terminal C1 of the first switching element SW1 and the control terminal C2 of the second switching element SW2, the mismatch time counter value that counts the mismatch determination time is reset. This eliminates pattern mismatch states caused by noise, thereby preventing erroneous determinations caused by noise.

[0097] Although the present disclosure has been described in detail above, the present disclosure is not limited to the individual embodiments described above. Various additions, substitutions, modifications, partial deletions, etc. are possible in these embodiments without departing from the gist of the present disclosure or the spirit of the present disclosure derived from the content of the claims and their equivalents. These embodiments can also be implemented in combination. For example, in the above-described embodiments, the order of each operation and the order of each process are shown as examples and are not limited to these. The same applies when numerical values ​​or mathematical expressions are used in the description of the above-described embodiments.

[0098] <Supplementary Notes> The following supplementary notes are further disclosed regarding the above embodiment.

[0099] (Note 1) A non-excitation actuation type brake device 2 that releases the brake when current flows through a brake coil 25 and applies the brake when the current to the brake coil 25 is interrupted comprises a control circuit 11 that controls opening and closing of a first switching element SW1 by applying a first command voltage to a control terminal C1 of the first switching element SW1 connected between a power source 3 and a first terminal P1 of the brake coil 25, and controls opening and closing of a second switching element SW2 by applying a second command voltage to a control terminal C2 of a second switching element connected between a second terminal P2 of the brake coil 25 and ground 4; a detection circuit 12 that detects a first potential that is the potential of the first terminal P1 of the brake coil 25 and a second potential that is the potential of the second terminal P2 of the brake coil 25; and a determination circuit 13 that determines whether or not an abnormality exists in the first switching element SW1 and the second switching element SW2, based on a combination pattern of the magnitude of a first command voltage applied to the control terminal C1 of the first switching element SW1 by the control circuit 11, the magnitude of the first potential at the first terminal P1 detected by the detection circuit 12, the magnitude of a second command voltage applied to the control terminal C2 of the second switching element SW2 by the control circuit 11, and the magnitude of the potential at the second terminal P2 detected by the detection circuit 12. (Supplementary Note 2) The abnormality detection device 1 according to Supplementary Note 1, wherein the determination circuit 13 determines that an abnormality has occurred in the first switching element SW1 and the second switching element SW2 when a state in which the combination pattern does not match a predetermined reference pattern continues for a predetermined mismatch determination time. (Supplementary Note 3) The abnormality detection device 1 according to Supplementary Note 2, wherein the control circuit 11 applies one of a brake engagement open command voltage and a pulsed test close command voltage to the control terminal C1 of the first switching element SW1 as the first command voltage when the brake device 2 is brake engaged, and applies one of a brake engagement open command voltage and a pulsed test close command voltage to the control terminal C2 of the second switching element SW2 as the second command voltage. (Supplementary Note 4) The reference pattern isThe abnormality detection device 1 described in Appendix 3 includes a combination in which the first command voltage is a brake engagement open command voltage, and the first potential is a value less than the threshold, and the second command voltage is a brake engagement open command voltage, and the second potential is a value less than the threshold; a combination in which the first command voltage is a test close command voltage, and the first potential is a value equal to or greater than the threshold, and the second command voltage is a brake engagement open command voltage, and the second potential is a value equal to or greater than the threshold; and a combination in which the first command voltage is a brake engagement open command voltage, and the first potential is a value less than the threshold, and the second command voltage is a test close command voltage, and the second potential is a value less than the threshold. (Appendix 5) When the brake of the brake device 2 is released, the abnormality detection device 1 described in Appendix 2 applies, as a first command voltage, one of a brake release close command voltage and a pulsed test open command voltage to the control terminal C1 of the first switching element SW1, and applies, as a second command voltage, a brake release close command voltage and a pulsed test open command voltage to the control terminal C2 of the second switching element SW2. (Supplementary Note 6) The abnormality detection device 1 according to Supplementary Note 5, wherein the reference patterns include: a combination where the first command voltage is a brake release close command voltage, and the first potential is a value equal to or greater than a threshold, and the second command voltage is a brake release close command voltage, and the second potential is a value less than the threshold, a combination where the first command voltage is a test open command voltage, and the first potential is a value less than the threshold, and the second command voltage is a brake release close command voltage, and the second potential is a value less than the threshold, and a combination where the first command voltage is a brake release close command voltage, and the first potential is a value equal to or greater than a threshold, and the second command voltage is a test open command voltage, and the second potential is a value equal to or greater than a threshold. (Supplementary Note 7) The abnormality detection device 1 according to Supplementary Note 2, wherein the discrepancy determination time used in the abnormality determination process by the determination circuit 13 when the brakes of the brake device 2 are applied is shorter than the discrepancy determination time used in the abnormality determination process by the determination circuit 13 when the brakes of the brake device 2 are released. (Note 8) The determination circuit 13 includes a pattern determination unit 131 that determines whether a combination pattern matches a reference pattern;the combination pattern determining unit 131 determines that the combination pattern does not match the reference pattern, ... If the pattern determination unit 131 determines that the combination pattern matches the reference pattern, the mismatch time counter 132 resets the mismatch time count value, and after the mismatch time counter 132 resets the mismatch time count value, the test time determination unit 136 executes a determination process; if the test time determination unit 136 determines that the test time count value has not reached the second specified value, the test time counter 135 increments the test time count value, and after the test time counter 135 increments the test time count value, the pattern determination unit 131 executes a determination process;The abnormality detection device 1 described in any one of Appendices 2 to 7, wherein, when it is determined as a result of the determination by the test time determination unit 136 that the test time count value has reached a second specified value, the test time counter 135 resets the test time count value, and after the test time count value has been reset by the test time counter 135, the control circuit 11 applies a pulsed test command voltage to either the control terminal C1 of the first switching element SW1 or the control terminal C2 of the second switching element SW2, and after the pulsed test command voltage has been applied to either the control terminal C1 of the first switching element SW1 or the control terminal C2 of the second switching element SW2, a determination process is executed by the pattern determination unit 131.

[0100] REFERENCE SIGNS LIST 1 Abnormality detection device 2 Brake device 3 Power supply 4 Ground 11 Control circuit 12 Detection circuit 13 Determination circuit 21 Friction plate 22 Armature 23 End plate 24 Spring 25 Brake coil 26 Core 27 Spacer 28 Bolt 29 Diode 31 Shaft 32 Hub 131 Pattern determination unit 132 Discrepancy time counter 133 Discrepancy time determination unit 134 Alarm output unit 135 Test time counter 136 Test time determination unit C1, C2 Control terminal P1 First terminal P2 Second terminal SW1 First switching element SW2 Second switching element

Claims

1. A non-excitation actuated brake device which releases the brake when current flows through a brake coil and engages the brake when current to the brake coil is cut off, the brake device comprising: a control circuit which controls opening and closing of a first switching element by applying a first command voltage to a control terminal of the first switching element connected between a power source and a first terminal of the brake coil, and controls opening and closing of the second switching element by applying a second command voltage to a control terminal of a second switching element connected between a second terminal of the brake coil and ground; a detection circuit which detects a first potential which is the potential of the first terminal of the brake coil, and a second potential which is the potential of the second terminal of the brake coil; and a determination circuit which determines the presence or absence of an abnormality in the first switching element and the second switching element based on a combination pattern of the magnitude of the first command voltage applied by the control circuit to the control terminal of the first switching element, the magnitude of the first potential of the first terminal detected by the detection circuit, the magnitude of the second command voltage applied by the control circuit to the control terminal of the second switching element, and the magnitude of the potential of the second terminal detected by the detection circuit. An abnormality detection device comprising:

2. The abnormality detection device of claim 1, wherein the judgment circuit judges that an abnormality has occurred in the first switching element and the second switching element if the state in which the combination pattern does not match a predefined reference pattern continues for a predetermined mismatch judgment time.

3. The abnormality detection device as described in claim 2, wherein the control circuit applies, as the first command voltage, one of a brake engagement open command voltage and a pulsed test close command voltage to the control terminal of the first switching element when the brakes of the brake device are engaged, and applies, as the second command voltage, one of a brake engagement open command voltage and a pulsed test close command voltage to the control terminal of the second switching element.

4. The abnormality detection device according to claim 3, wherein the reference patterns include: a combination in which the first command voltage is the brake fastening open command voltage, and the first potential is a value less than a threshold value, and the second command voltage is the brake fastening open command voltage, and the second potential is a value less than the threshold value; a combination in which the first command voltage is the test close command voltage, and the first potential is a value equal to or greater than the threshold value, and the second command voltage is the brake fastening open command voltage, and the second potential is a value equal to or greater than the threshold value; and a combination in which the first command voltage is the brake fastening open command voltage, and the first potential is a value less than the threshold value, and the second command voltage is the test close command voltage, and the second potential is a value less than the threshold value.

5. The abnormality detection device as described in claim 2, wherein the control circuit applies, as the first command voltage, one of a brake release close command voltage and a pulsed test open command voltage to the control terminal of the first switching element when the brake of the braking device is released, and applies, as the second command voltage, one of a brake release close command voltage and a pulsed test open command voltage to the control terminal of the second switching element.

6. The abnormality detection device according to claim 5, wherein the reference patterns include: a combination in which the first command voltage is the brake release close command voltage, and the first potential is a value equal to or greater than a threshold value, and the second command voltage is the brake release close command voltage, and the second potential is a value less than the threshold value; a combination in which the first command voltage is the test open command voltage, and the first potential is a value less than the threshold value, and the second command voltage is the brake release close command voltage, and the second potential is a value less than the threshold value; and a combination in which the first command voltage is the brake release close command voltage, and the first potential is a value equal to or greater than the threshold value, and the second command voltage is the test open command voltage, and the second potential is a value equal to or greater than the threshold value.

7. An abnormality detection device as described in claim 2, wherein the inconsistency judgment time used in the abnormality judgment processing by the judgment circuit when the brake of the brake device is applied is shorter than the inconsistency judgment time used in the abnormality judgment processing by the judgment circuit when the brake of the brake device is released.

8. The judgment circuit comprises: a pattern judgment unit which judges whether or not the combination pattern matches the reference pattern; a mismatch time counter which stores a mismatch time count value; a mismatch time judgment unit which judges whether or not the mismatch time count value has reached a first specified value; an alarm output unit which outputs an alarm indicating that an abnormality has occurred when the mismatch time judgment unit judges that the mismatch time count value has reached the first specified value; a test time counter which stores a test time count value; and a test time judgment unit which judges whether or not the test time count value has reached a second specified value when the mismatch time judgment unit judges that the mismatch time count value has not reached the first specified value; and when the pattern judgment unit judges that the combination pattern does not match the reference pattern, the mismatch time counter increments the mismatch time count value, and after the mismatch time counter increments the mismatch time count value, a judgment process is performed by the test time judgment unit, when it is determined as a result of the determination by the pattern determination unit that the combination pattern matches the reference pattern, the mismatch time counter resets the mismatch time count value, and a determination process is performed by the test time determination unit after the mismatch time count value is reset by the mismatch time counter; when it is determined as a result of the determination by the test time determination unit that the test time count value has not reached the second specified value, the test time counter increments the test time count value, and a determination process is performed by the pattern determination unit after the test time counter increments the test time count value;8. The abnormality detection device according to claim 2, wherein when it is determined as a result of the determination by the test time determination unit that the test time count value has reached the second specified value, the test time counter resets the test time count value, and after the test time count value has been reset by the test time counter, the control circuit applies a pulsed test command voltage to either the control terminal of the first switching element or the control terminal of the second switching element, and after the pulsed test command voltage has been applied to either the control terminal of the first switching element or the control terminal of the second switching element, a determination process is executed by the pattern determination unit.

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