Electric motor control device and method for detecting anomaly of electric motor

Abstract

The present invention provides technology for making it possible to accurately detect an anomaly such as non-wiring and disconnection without complicating a configuration in an electric motor control device and a method for detecting an anomaly of an electric motor. An electric motor control device 10 for an electric motor 1 in which a plurality of multi-phase windings having the same electrical characteristics are connected in parallel comprises: a current control unit 11 that sums up and controls current values of a plurality of multi-phase windings 31 and 32; and an anomaly detection unit 12 that detects non-wiring and disconnection of the electric motor 1 on the basis of electrical information which has been acquired by the current control unit 11.

Description

Motor control device and motor abnormality detection method

[0001] The present disclosure relates to a motor control device and a motor abnormality detection method.

[0002] Conventionally, in a motor control device that controls a motor in which a plurality of windings are connected in parallel, a technique for detecting an abnormality of the motor based on a current value is known. For example, Patent Documents 1 to 3 describe this type of technology.

[0003] International Publication WO2015 / 136918, Japanese Unexamined Patent Publication No. 2000-078883, Japanese Unexamined Patent Publication No. 2024-090134

[0004] Incidentally, in some motors, a configuration in which a plurality of windings are connected in parallel to one servo amplifier is adopted. Since the servo amplifier is shared, there are advantages that the number of controlled objects (axes) can be reduced, and the device configuration such as the number of amplifiers, encoders, and magnetic pole detectors can be reduced.

[0005] However, in a configuration where a plurality of windings are connected in parallel to one servo amplifier, current protection (overcurrent alarm) is controlled by summing the currents of the plurality of windings for each axis. Therefore, when unwiring or disconnection occurs in one of the parallel-connected windings, the current load for two windings is concentrated on one winding, which may cause motor burnout or demagnetization.

[0006] Further, in a configuration where a plurality of windings are connected in parallel to a common servo amplifier, if unwiring or disconnection occurs in one winding, a current equivalent to that of two windings flows through one winding, so it is impossible to detect an abnormality using the magnitude or current phase of the motor current with respect to the current command. It is also conceivable to make a determination based on the rotational position (direction) or rotational speed with respect to the speed command, but since the operation of the motor itself can operate to a certain extent with the normal winding, it may be determined as normal depending on the determination threshold.

[0007] There is also a method of detecting unwiring or disconnection by measuring a winding resistance value or the like and comparing it with a value obtained during normal wiring, but this requires a separate measuring device in addition to the motor control device.

[0008] This disclosure has been made in view of the above-mentioned problems, and aims to provide a technology for an electric motor control device and an electric motor abnormality detection method that can accurately detect abnormalities such as unwired or broken wires without complicating the configuration.

[0009] This disclosure relates to a motor control device for controlling an electric motor in which a plurality of multiphase windings having the same electrical characteristics are connected in parallel, comprising: a current control unit that controls by summing the current values ​​of the plurality of multiphase windings; and an abnormality detection unit that detects unwired or broken wires in the electric motor based on electrical information acquired by the current control unit.

[0010] Furthermore, this disclosure relates to a motor abnormality detection method for detecting an abnormality in a motor in which a plurality of multiphase windings having the same electrical characteristics are connected in parallel, and includes a current control step of summing and controlling the current values ​​of the plurality of multiphase windings, and an abnormality detection step of detecting unwired or broken wires in the motor based on the electrical information acquired in the current control step.

[0011] This is a functional block diagram of the motor control device according to the first embodiment. This is a graph showing the time change of current when wiring abnormality is determined based on the time it takes for the current to reach the command current value. This is a graph showing the time change of current when wiring abnormality is determined based on the instantaneous current value until it reaches the command current value. This is a flowchart showing an example of abnormality determination processing. This is a functional block diagram of the motor control device according to the second embodiment.

[0012] The embodiments of this disclosure will be described in detail below with reference to the drawings. In the description of the second and subsequent embodiments, components common to the first embodiment will be denoted by the same reference numerals, and their descriptions will be omitted as appropriate.

[0013] [First Embodiment] Figure 1 is a functional block diagram of the motor control device 10 according to the first embodiment. The motor control device 10 shown in Figure 1 controls the operation of a motor 1 used in industrial machinery, for example.

[0014] First, let's describe the configuration of the electric motor 1. The electric motor 1 consists of multiple multiphase windings 31 and 32 connected in parallel. In this embodiment, multiple multiphase windings 31 and 32 are housed in a single terminal box 35.

[0015] Both the multiphase winding 31 and the multiphase winding 32 are three-phase AC (U-phase, V-phase, and W-phase), and have the same electrical characteristics such as resistance. The multiphase winding 31 and the multiphase winding 32 are connected to a common motor control device 10.

[0016] Next, the motor control device 10 will be described. The motor control device 10 is, for example, a servo amplifier, and controls the motor 1 based on instruction signals such as position commands that are input to it. The instruction signals input to the motor control device 10 are input from a higher-level computer (not shown) such as a numerical control device, a programmable controller, or an industrial PC such as an IPC (Industrial Personal Computer). The motor control device 10 may be configured integrally with the numerical control device, programmable controller, or industrial PC.

[0017] The motor control device 10 of this embodiment includes a current control unit 11 and an abnormality detection unit 12 as functional units.

[0018] The current control unit 11 controls the motor 1 by summing the current values ​​of multiple multiphase windings 31 and 32 based on instruction signals such as position commands. For example, speed commands, torque commands, etc. are sequentially generated based on the position command included in the instruction signal, and a current value command is generated based on the torque command. The motor 1 operates based on the current value command summed by the current control unit 11.

[0019] The abnormality detection unit 12 detects unwired or broken wires in the motor 1 based on the current value obtained by the current control unit 11. In this embodiment, the abnormality detection unit 12 can select either the first abnormality detection method or the second abnormality detection method.

[0020] Referring to Figure 2, the first abnormality detection method will be explained. Figure 2 is a graph showing the time change of current when abnormality in wiring is determined based on the time it takes for the current to reach the commanded current value.

[0021] The graph in Figure 2 shows, with a solid line, the time change of the current up to the command current value in the normal state of the motor 1, in which the multiphase windings 31 and 32 are connected in parallel. The time change of the current up to the command current value in the normal state is data obtained by actually measuring the current of the motor 1 when the wiring is not unconnected and there are no breaks in the wires.

[0022] On the other hand, the time change of the current up to the command current value in the unwired state is shown by the dashed line. When jumper wires, etc., are unwired or broken, the combined inductance as seen from the drive side increases. In this case, compared to the normal wiring state, the current response (rise time) from the stopped state to reaching the command current value becomes slower. As shown in the graph in Figure 2, in the unwired state, the time to reach the command current value is delayed and deviates from the normal state. This behavior is the same even in the case of a broken wire.

[0023] Therefore, in the first abnormality detection method, the abnormality detection unit 12 detects wiring abnormalities based on the time it takes for the current value acquired by the current control unit 11 to reach the command current value. The abnormality detection unit 12 uses the time it took to reach the command current value under normal conditions as the reference time, and determines that an abnormality of unwired or broken wire has occurred if the determination time T exceeds this reference time. The method for setting the determination time T is not particularly limited, as long as it is within a range in which abnormalities such as unwired or broken wire can be detected. The determination time T may be set based on actual measurements of the actual machine, may be set according to the specifications through multiple trials by the manufacturer, or may be calculated theoretically.

[0024] The abnormality detection unit 12 monitors changes in the current flowing through the motor 1, and determines that an abnormality such as unwired or broken wire has occurred if the time until the commanded current value is reached exceeds the judgment time T from the reference time.

[0025] Next, the second abnormality detection method will be explained with reference to Figure 3. Figure 3 is a graph showing the time change of current when abnormality in wiring is determined based on the instantaneous current value until the command current value is reached.

[0026] In the graph of Figure 3, as in the graph of Figure 2, the time change of the current up to the command current value in the normal state of the motor 1, in which the multiphase windings 31 and 32 are connected in parallel, is shown by a solid line. In addition, the time change of the current up to the command current value in the unwired state is shown by a dashed line.

[0027] In the unwired state, it can be observed that the time taken to reach the commanded current value is lower than under normal conditions, indicating a deviation. This behavior is the same even in the case of a broken wire.

[0028] Therefore, in the second abnormality detection method, the abnormality detection unit 12 detects abnormalities in the wiring based on the instantaneous current value before it reaches the command current value. The abnormality detection unit 12 uses the instantaneous current value at a certain time as the reference current value, and determines that an abnormality has occurred if the difference between this reference current value and the instantaneous current value at a certain time exceeds the judgment value D. The method for setting the judgment value D is not particularly limited, as long as it is within a range in which abnormalities such as unwired or broken wires can be detected. The judgment value D may be set based on actual measurements of the actual machine, may be set according to the specifications through multiple trials by the manufacturer, or may be calculated theoretically.

[0029] The abnormality detection unit 12 monitors changes in the current flowing through the motor 1 and determines that an abnormality such as unwired or broken wire has occurred if the difference between the reference current value and the instantaneous current value during a certain period of time until the command current value is reached exceeds the determination value D. The certain period of time for comparing the instantaneous current values ​​may be one or more. Furthermore, the abnormality detection unit 12 is not limited to the difference between the reference current value and the instantaneous current value; it may also determine that an abnormality has occurred if the area between the curve of the reference current value and the curve of the instantaneous current value on the graph exceeds a predetermined value.

[0030] The first and second anomaly detection methods have been described above. The anomaly detection method of the anomaly detection unit 12 may be the first anomaly detection method or the second anomaly detection method. Furthermore, the system may be configured so that the user can select either the first or second anomaly detection method.

[0031] Alternatively, the abnormality detection unit 12 may perform abnormality detection by combining the first abnormality detection method and the second abnormality detection method. For example, the abnormality detection unit 12 may determine that an abnormality has occurred if the time to reach the command current value exceeds the determination time T, or if the difference between the reference current value and the instantaneous current value exceeds the determination value D. The abnormality detection unit 12 may also determine that an abnormality has occurred if the time to reach the command current value exceeds the determination time T AND the difference between the reference current value and the instantaneous current value exceeds the determination value D.

[0032] Next, with reference to Figure 4, the flow of the abnormality detection process by the abnormality detection unit 12 will be explained. Figure 4 is a flowchart showing an example of the abnormality detection process.

[0033] In step S1, the abnormality detection unit 12 starts monitoring the current value acquired by the current control unit 11.

[0034] In step S2, the abnormality detection unit 12 determines whether or not an abnormality such as unwired or broken wire has occurred based on the monitored current. As described above, the abnormality detection unit 12 determines that an abnormality has occurred if the time until the command current value is reached exceeds the determination time T, or if the difference between the reference current value and the instantaneous current value at a certain time exceeds the determination value D.

[0035] If an abnormality occurs, the abnormality detection unit 12 proceeds to step S3 (step S2; Yes). If no abnormality occurs, the abnormality detection unit 12 continues to monitor the current value (step S2; No).

[0036] In step S3, the abnormality detection unit 12 performs notification processing to inform the user that an abnormality has occurred. The abnormality detection unit 12 outputs information to the motor control device 10 or an external computer to notify them that an abnormality has occurred. The format of the notification processing is not particularly limited. For example, the motor control device 10 or an external computer may notify the user that an abnormality has occurred through images, sounds, the illumination of indicator lights, etc.

[0037] The motor control device 10 described above provides the following effects. The motor control device 10 of this embodiment controls a motor 1 in which multiple multiphase windings 31 and 32 having the same electrical characteristics are connected in parallel. This device includes a current control unit 11 that controls the motor by summing the current values ​​of the multiple multiphase windings 31 and 32, and an abnormality detection unit 12 that detects unwired or broken wires in the motor 1 based on the electrical information acquired by the current control unit 11.

[0038] Furthermore, the method for detecting abnormalities in the motor 1 of this embodiment includes a current control step of summing and controlling the current values ​​of a plurality of multiphase windings 31 and 32, and an abnormality detection step of detecting unwired or broken wires in the motor 1 based on the electrical information acquired in the current control step.

[0039] In this way, with the motor control device 10 and the motor 1 abnormality detection method configured, abnormalities such as unwired or broken wires can be accurately detected even in a motor 1 configuration where multiple multiphase windings 31 and 32 are connected in parallel to a single servo amplifier. Furthermore, no additional equipment such as resistance measuring devices is required, and abnormalities such as unwired or broken wires can be easily and accurately detected on the motor control device 10 side.

[0040] Furthermore, in this embodiment, the abnormality detection unit 12 detects wiring abnormalities by comparing the time it takes for the current value, which is electrical information acquired by the current control unit 11, to reach a commanded current value.

[0041] As described above, in an electric motor 1 in which multiphase windings 31 and 32 are connected in parallel, when there are unwired or broken wires, the time it takes to reach the commanded current value in the rise time of the current response tends to be longer. By using this tendency to compare and diagnose with the rise time under normal conditions, unwired or broken wires can be easily and accurately measured with a simple process.

[0042] In this embodiment, the abnormality detection unit 12 detects wiring abnormalities by comparing the current value, which is electrical information acquired by the current control unit 11, with the instantaneous current value before the command current value is reached.

[0043] As described above, in the electric motor 1 in which the multiphase windings 31 and 32 are connected in parallel, in a state where unwiring, disconnection, or the like has occurred, the instantaneous current value at a certain time during the rise time of the current response tends to decrease. By utilizing this tendency to perform comparative diagnosis with a reference current value at a certain time in a normal state, unwiring and disconnection can be easily and accurately detected with simple processing.

[0044] [Second Embodiment] Next, a motor control device 10a according to a second embodiment will be described with reference to FIG. 5. FIG. 5 is a functional block diagram of the motor control device 10a according to the second embodiment.

[0045] The motor control device 10a of the second embodiment differs from the first embodiment in the configuration of the motor 1a to be controlled. The motor 1a of the second embodiment includes a first motor 21 having a multiphase winding 31, and a second motor 22 having a multiphase winding 32.

[0046] The first motor 21 and the second motor 22 are motors of the same specifications. The multiphase winding 31 of the first motor 21 and the multiphase winding 32 of the second motor 22 have the same electrical characteristics. Further, magnets (not shown) of the first motor 21 and the second motor 22 also have the same characteristics.

[0047] A machine 41 to which the first motor 21 is connected and a machine 42 to which the second motor 22 is connected are coupled by a high-rigidity mechanical element 43. The first motor 21 and the second motor 22 are controlled by a common motor control device 10a, and the machine 41 and the machine 42 operate synchronously.

[0048] A magnetic pole detector 51 is disposed on the first motor 21, and a detection signal of the magnetic pole detector 51 is output to a position detector 53. An encoder 52 is disposed on the machine 41, and a detection signal of the encoder 52 is output to the position detector 53. The position detector 53 outputs position feedback based on the detection signal of the magnetic pole detector 51 and the detection signal of the encoder 52 to the motor control device 10a.

[0049] Even when the multiphase winding 31 and the multiphase winding 32 are not housed in a common casing, as in the second embodiment, the multiphase winding 31 and the multiphase winding 32 are connected in parallel as viewed from the motor control device 10a, and are essentially the same as the configuration of the motor 1 in the first embodiment. Therefore, as explained with reference to Figures 2 and 3, in the case of unwired or disconnected states, the time it takes to reach the commanded current value in the rise time of the current tends to be delayed, and the instantaneous current value until the commanded current value is reached tends to decrease.

[0050] In the second embodiment as well, the abnormality detection unit 12 detects abnormalities such as unwired or broken wires using the same method as the first or second abnormality determination method described in the first embodiment. The motor control device 10a of the second embodiment also provides the same effects as the motor control device 10 of the first embodiment.

[0051] In the first and second embodiments, examples were described in which two multiphase windings, 31 and 32, are connected in parallel. However, the configuration is not limited to this. The abnormality detection unit 12 of this embodiment can also be applied to motors in which three or more multiphase windings are connected in parallel, such as motors with three motors.

[0052] Furthermore, while the above embodiment uses current values ​​as electrical information, it is also possible to perform abnormality detection using electrical information other than current values.

[0053] [Other Variations] The series of processes described above can be executed by hardware or by software. In other words, the functional configuration described above is merely an example and is not particularly limited. That is, it is sufficient that a computer or electrical circuit is equipped with a function that can execute the series of processes described above as a whole, and the type of functional block used to realize this function is not particularly limited to the example above. Furthermore, the location of the functional block is not particularly limited and can be arbitrary. For example, a single functional block may be composed of hardware alone, software alone, or a combination of both. When the series of processes are executed by software, the program that constitutes that software is installed on a computer or the like from a network or recording medium. The computer may be a computer built into dedicated hardware. Alternatively, the computer may be a computer capable of executing various functions by installing various programs, such as a server, a general-purpose smartphone, or a personal computer.

[0054] While this disclosure has been described in detail, it is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, partially deleted, etc., in any way that does not depart from the gist of this disclosure or from the spirit of this disclosure derived from the claims and their equivalents. Furthermore, these embodiments can be implemented in combination. For example, the order of operations and processes in the embodiments described above are shown as examples only and are not limited thereto. The same applies when numerical values ​​or mathematical formulas are used in the description of the embodiments described above.

[0055] With respect to the above embodiments and modifications, the following additional notes are disclosed. (Addendum 1) A motor control device (10, 10a) for controlling a motor (1, 1a) in which a plurality of multiphase windings having the same electrical characteristics are connected in parallel, comprising: a current control unit (11) that controls by summing the current values ​​of the plurality of multiphase windings (31, 32); and an abnormality detection unit (12) that detects unwired or broken wires in the motor (1, 1a) based on electrical information acquired by the current control unit (11).

[0056] (Note 2) In the motor control device (10, 10a) described in Note 1, the abnormality detection unit (12) detects a wiring abnormality by comparing the time it takes for the current value, which is the electrical information acquired by the current control unit (11), to reach the commanded current value.

[0057] (Note 3) In the motor control device (10, 10a) described in Note 1, the abnormality detection unit (12) detects an abnormality in the wiring by comparing the current value as electrical information acquired by the current control unit (11) with the instantaneous current value before the command current value is reached.

[0058] (Note 4) An abnormality detection method for an electric motor (1, 1a) in which a plurality of multiphase windings having the same electrical characteristics are connected in parallel, comprising: a current control step of summing and controlling the current values ​​of the plurality of multiphase windings (31, 32); and an abnormality detection step of detecting unwired or broken wires in the electric motor (1, 1a) based on the electrical information acquired in the current control step.

[0059] 1, 1a Electric motor 10, 10a Electric motor control device 11 Current control unit 12 Anomaly detection unit 31 Multiphase winding 32 Multiphase winding

Claims

1. A motor control device for controlling an electric motor in which multiple multiphase windings having the same electrical characteristics are connected in parallel, comprising: a current control unit that controls by summing the current values ​​of the multiple multiphase windings; and an abnormality detection unit that detects unwired or broken wires in the electric motor based on electrical information acquired by the current control unit.

2. The motor control device according to claim 1, wherein the abnormality detection unit detects an abnormality in the wiring by comparing the time it takes for the current value, which is electrical information acquired by the current control unit, to reach a commanded current value.

3. The motor control device according to claim 1, wherein the abnormality detection unit detects an abnormality in the wiring by comparing the current value as electrical information acquired by the current control unit with the instantaneous current value before the command current value is reached.

4. A method for detecting an abnormality in an electric motor in which multiple multiphase windings having the same electrical characteristics are connected in parallel, comprising: a current control step of summing and controlling the current values ​​of the multiple multiphase windings; and an abnormality detection step of detecting unwired or broken wires in the electric motor based on the electrical information obtained in the current control step.

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