Motor drive control device, fan unit, and diagnosis method

Abstract

To make it possible to appropriately determine a state of a motor regardless of disturbance.SOLUTION: A motor drive control device 10 includes: a drive control signal generation unit 11 that generates a drive control signal Sd; a motor drive circuit 19 that drives a motor 50 based on the drive control signal Sd; a storage unit 25; a measurement value acquisition unit 23 that sets a physical quantity related to an operation of the motor 50 as a monitoring parameter, acquires a measurement value of the monitoring parameter, and stores it in the storage unit 25; and a monitoring unit 24 that monitors a state of the motor 50 based on the measurement value of the monitoring parameter. The monitoring unit 24 includes: a first calculation unit 241 that calculates a first coefficient of variation CV that is a coefficient of variation of the measurement value based on the measurement value stored in the storage unit 25; a second calculation unit 242 that calculates a second coefficient of variation CVCV that is a coefficient of variation of the first coefficient of variation CV; and a diagnosis unit 243 that diagnoses a state of the motor 50 based on the second coefficient of variation CVCV.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a motor drive control device, a fan unit, and a diagnostic method, and more particularly to a motor drive control device capable of diagnosing the state of a motor to be driven, for example. [Background technology]

[0002] In recent years, there has been a demand for a diagnostic function to detect motor abnormalities as a function to be equipped in motor drive control devices for controlling the drive of motors. For example, in fans widely used as devices for cooling the inside of office automation equipment, machine tools, etc., it is necessary to prevent a decline in fan cooling performance and the shutdown of machine tools, etc., due to deterioration of the bearings of the motor that constitutes the fan. Therefore, it is desirable for a motor drive control device to determine the presence or absence of an abnormality in the motor (fan) to be driven and the degree of deterioration, and to prompt the user to perform maintenance on the fan at an appropriate time.

[0003] For example, Patent Document 1 discloses a technology in which control parameters (e.g., power supply voltage, rotation speed, load voltage, etc.) to be monitored are set for each type of motor abnormality, and the presence or absence of a motor abnormality is determined by monitoring those control parameters. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-19398 Summary of the Invention [Problem to be solved by the invention]

[0005] When the current flowing through the motor coil, the load voltage, and the rotation speed are used as parameters to monitor to determine whether the motor is in an abnormal state, the above parameters may fluctuate due to disturbances caused by the motor's operating environment, even if the motor is in a normal state. For example, in the case of an internal motor of an office automation equipment, The above parameters of a fan installed in a motor vary depending on the ambient temperature, the influence of wind from other fans, etc. Therefore, with the conventional technique disclosed in Patent Document 1, if the above parameters vary due to the influence of disturbances, even though the motor is in a normal state, there is a risk that the technique may erroneously determine that the motor is in an abnormal state.

[0006] The present invention is intended to solve the above-mentioned problems, and has an object to make it possible to appropriately diagnose the state of a motor regardless of disturbances. [Means for solving the problem]

[0007] A motor drive control device according to a representative embodiment of the present invention comprises a drive control signal generation unit that generates a drive control signal for controlling the drive of a motor, a motor drive circuit that drives the motor based on the drive control signal, a memory unit, a measurement value acquisition unit that uses physical quantities related to the operation of the motor as monitoring parameters, acquires measured values ​​of the monitoring parameters and stores them in the memory unit, and a monitoring unit that monitors the state of the motor based on the measured values ​​of the monitoring parameters, wherein the monitoring unit includes a first calculation unit that calculates a first coefficient of variation, which is the coefficient of variation of the measured values, based on the measured values ​​stored in the memory unit, a second calculation unit that calculates a second coefficient of variation, which is the coefficient of variation of the first coefficient of variation, and a diagnosis unit that diagnoses the state of the motor based on the second coefficient of variation. [Effects of the Invention]

[0008] According to one aspect of the present invention, it is possible to appropriately diagnose the state of a motor regardless of disturbances. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram illustrating an example of the configuration of a fan system including a motor drive control device according to an embodiment; [Figure 2] 4 is a flowchart showing a flow of processing related to a monitoring function performed by the motor drive control device according to the embodiment. [Figure 3] 10 is a flowchart showing an example of the flow of a statistical quantity calculation process (step S1). [Figure 4] 10 is a flowchart showing an example of the flow of diagnostic processing (step S2). [Figure 5A] FIG. 10 is a diagram showing an example of a change over time in a first coefficient of variation CV. [Figure 5B] FIG. 10 is a diagram showing an example of a change over time in a first coefficient of variation CV. [Figure 5C] FIG. 10 is a diagram showing an example of a change over time in a first coefficient of variation CV. [Figure 6A] FIG. 10 is a diagram showing an example of a change over time in a second coefficient of variation CVCV. [Figure 6B] FIG. 10 is a diagram showing an example of a change over time in a second coefficient of variation CVCV. [Figure 6C] FIG. 10 is a diagram showing an example of a change over time in a second coefficient of variation CVCV. DETAILED DESCRIPTION OF THE INVENTION

[0010] 1. Overview of the embodiment First, an outline of a typical embodiment of the invention disclosed in this application will be given. In the following description, for example, reference numerals in the drawings corresponding to components of the invention will be written in parentheses.

[0011] [1] A motor drive control device (10) according to a representative embodiment of the present invention includes a drive control signal generation unit (11) that generates a drive control signal (Sd) for controlling the drive of a motor (50), a motor drive circuit (19) that drives the motor based on the drive control signal, a memory unit (25), a measurement value acquisition unit (23) that sets physical quantities related to the operation of the motor as monitoring parameters, acquires measurement values ​​of the monitoring parameters and stores them in the memory unit, and a monitoring unit (24) that monitors the state of the motor based on the measurement values ​​of the monitoring parameters, wherein the monitoring unit includes a first calculation unit (241) that calculates a first coefficient of variation (CV) that is a coefficient of variation of the measurement values ​​based on the measurement values ​​stored in the memory unit, a second calculation unit (242) that calculates a second coefficient of variation (CVCV) that is a coefficient of variation of the first coefficient of variation, and a diagnosis unit (243) that diagnoses the state of the motor based on the second coefficient of variation.

[0012] [2] In the motor drive control device described in [1] above, the diagnosing unit may diagnose the state of the motor based on a value obtained by smoothing the second coefficient of variation.

[0013] [3] In the motor drive control device described in [2] above, the diagnostic unit may calculate a smoothed value (CVCVs) of the second coefficient of variation by calculating an exponential moving average of the second coefficient of variation.

[0014] [4] In the motor drive control device described in [1] above, the monitoring parameters may include a current flowing through a coil of the motor.

[0015] [5] In the motor drive control device described in [1] above, the diagnostic unit may multiply a value (CVCV, CVCVs) based on the second coefficient of variation by a predetermined coefficient (k) to calculate an index value (abnormality score Scab) indicating the degree of deterioration of the motor.

[0016] [6] In the motor drive control device described in [5] above, the memory unit may further store a reference value of the monitoring parameter, and the diagnosis unit may compare the index value with the reference value and determine whether or not there is an abnormality in the motor based on the comparison result.

[0017] [7] The motor drive control device described in [1] above may further include a communication unit (42) that communicates with an external device, and the communication unit may transmit a diagnosis result by the diagnosis unit to the external device.

[0018] [8] A fan unit (2) according to a representative embodiment of the present invention is characterized by comprising a motor drive control device (10) described in any one of [1] to [7] above, a motor (50) driven by the motor drive control device, and a fan (5) including an impeller (51) configured to be rotatable by the rotational force of the motor.

[0019] [9] A diagnostic method according to a representative embodiment of the present invention includes a first step (S11) of acquiring measured values ​​of monitoring parameters, each of which is a physical quantity related to the operation of a motor; a second step (S12-S14) of calculating a first coefficient of variation (CV) based on the measured values, which is the coefficient of variation of the measured values; a third step (S15-S17) of calculating a second coefficient of variation based on the first coefficient of variation, which is the coefficient of variation of the first coefficient of variation; and a fourth step (S18, S21-S24) of diagnosing the state of the motor based on the second coefficient of variation.

[0020] 2. Specific examples of embodiments Specific examples of embodiments of the present invention will be described below with reference to the drawings.

[0021] <Embodiment> FIG. 1 is a diagram showing an example of the configuration of a fan system 1 including a motor drive control device 10 according to an embodiment.

[0022] The fan system 1 shown in Figure 1 is a system that includes a higher-level device 4 as a control device and a motor drive control device 10, and the higher-level device 4 controls the motor drive control device 10 to drive a fan 5 (motor 50) connected to the motor drive control device 10.

[0023] The fan system 1 constitutes a cooling system in which the operation of one or more fans 5 arranged in a closed space inside, for example, an electrical device or a machine tool is controlled by a host device 4 to send air to an object to be cooled. For example, the fan system 1 is arranged in a closed space inside a server to constitute a cooling system in which the fans 5 cool various electronic components that make up the server.

[0024] The fan system 1 includes a host device 4, at least one fan 5, and a motor drive control device 10 for driving a motor 50 of the fan 5.

[0025] In this embodiment, as an example, the fan system 1 is described as having one fan 5 and one motor drive control device 10 that controls the fan 5, but the fan system 1 may have multiple combinations of fans 5 and motor drive control devices 10.

[0026] The host device 4 is a control device that controls the driving of the motor drive control device 10. For example, if the fan system 1 constitutes a cooling system for a server, the host device 4 is a program processing device that realizes the main functions of the server.

[0027] For example, the upper device 4 includes a program processing device (e.g., a microcontroller) having a configuration in which a processor such as a CPU, various storage devices such as RAM and ROM, and peripheral circuits such as a counter (timer), an A / D conversion circuit, a D / A conversion circuit, a clock generation circuit, and an input / output I / F circuit are connected to one another via a bus or dedicated lines. For example, the fan system 1 is realized by accommodating the program processing device, the motor drive control device 10, and the fan 5 in a single housing.

[0028] The host device 4 controls the fan 5 via the motor drive control device 10 so that the airflow of the fan 5 is appropriate in response to environmental changes in the fan system 1 (such as changes in the processing load of the server or changes in the temperature inside the server).

[0029] The fan 5 includes, for example, a motor 50 and an impeller 51. The fan 5 and a motor drive control device 10 that controls the driving of the motor 50 in response to a command from the higher-level device 4 constitute one fan unit 2.

[0030] The motor 50 is, for example, a three-phase brushless motor. The type of the motor 50 is not particularly limited, and the number of phases is not limited to three.

[0031] The impeller (impeller wheel) 51 is a component that generates wind, and is configured to be rotatable by the torque of the motor 50. For example, the rotation shaft of the impeller 51 is coaxially connected to the output shaft of the motor 50. In this embodiment, for example, the impeller 51 and the motor 50 constitute one fan (fan motor) 5.

[0032] The motor drive control device 10 is a device for controlling the drive of the motor 50. The motor drive control device 10 controls the drive of the motor 50 in response to commands from the higher-level device 4, for example, and transmits the state of the motor 50 to the higher-level device 4.

[0033] First, the specific configuration of the higher-level device 4 will be described. As shown in FIG. 1, the higher-level device 4 includes, for example, a data processing control unit 41 for realizing the main functions of a server, and a communication unit 42 for communicating with the fan unit 2.

[0034] The communication between the higher-level device 4 (communication unit 42) and the fan unit 2 (motor drive control device 10) is realized by, for example, serial communication.

[0035] The data processing control unit 41 and the communication unit 42 are realized, for example, in a program processing device constituting the above-mentioned upper device 4, by a processor executing various arithmetic processing in accordance with a program stored in a memory and controlling peripheral circuits such as a counter and an A / D conversion circuit.

[0036] The data processing control unit 41 transmits a speed command signal Sc specifying the target rotation speed (target rotation speed) of the motor 50 of the fan unit 2 to the fan unit 2 via the communication unit 42, for example, to adjust the air volume supplied from the fan unit 2 arranged within the server.

[0037] The transmission and reception of the speed command signal Sc may be realized not by the above-described serial communication but by using, for example, a dedicated line connecting the higher-level device 4 and the fan unit 2. In this case, the speed command signal Sc may be, for example, a PWM signal having a duty ratio according to the target rotation speed.

[0038] The data processing control unit 41 monitors the rotation state of the motor 50 of the fan unit 2 by receiving, via the communication unit 42, a rotation speed signal So (e.g., an FG (Frequency Generator) signal) that indicates the actual rotation speed (number of rotations) of the motor 50 output from the fan unit 2. The transmission and reception of the rotation speed signal So may be achieved, for example, by using a dedicated line that connects the higher-level device 4 and the fan unit 2, or by the above-mentioned serial communication.

[0039] Next, the motor drive control device 10 will be described. The motor drive control device 10 has, as its main functions, a motor drive control function for controlling the rotation of the motor 50, a communication function for communicating with the higher-level device 4, and a monitoring function for monitoring the state of the motor 50.

[0040] Specifically, as a motor drive control function, the motor drive control device 10 generates a drive control signal Sd in response to a command (speed command signal Sc) from the higher-level device 4, and rotates the motor 50 by periodically passing a sinusoidal drive current through the coils of each phase (e.g., three phases) of the motor 50.

[0041] As a communication function, the motor drive control device 10 receives various commands from the higher-level device 4 by transmitting and receiving data to the higher-level device 4, and transmits responses to the received commands to the higher-level device 4. For example, the motor drive control device 10 receives the above-mentioned speed command signal Sc from the higher-level device 4, and notifies the higher-level device 4 of the state of the motor 50 by transmitting abnormality determination information 254 and a rotational speed signal So, which will be described later, to the higher-level device 4.

[0042] As a monitoring function, the motor drive control device 10 monitors the state of the motor 50 by measuring physical quantities related to the operation of the motor 50 to be driven, and diagnoses the state of the motor 50 to be driven based on the measurement results.

[0043] As shown in FIG. 1, the motor drive control device 10 has functional units for realizing the above-mentioned functions, such as a drive control signal generation unit 11, a communication unit 15, a motor drive circuit 19, a sensor unit 20, a rotational speed measurement unit 21, an FG signal generation unit 22, a measurement value acquisition unit 23, a monitoring unit 24, and a memory unit 25.

[0044] Of these functional units, the drive control signal generating unit 11, the communication unit 15, the rotational speed measuring unit 21, the measurement value acquiring unit 23, the monitoring unit 24, and the storage unit 25 are realized, for example, by a program processing device. For example, in a program processing device (for example, a microcontroller) having a configuration in which a processor such as a CPU, various storage devices such as RAM and ROM, and peripheral circuits such as a counter (timer), an A / D conversion circuit, a D / A conversion circuit, a clock generating circuit, an input / output I / F circuit, and a communication circuit are connected to one another via a bus or a dedicated line, the CPU executes various arithmetic processes in accordance with programs stored in the memory, and controls the peripheral circuits such as the A / D conversion circuit and the input / output interface circuit based on the processing results, thereby realizing the above-mentioned functional blocks.

[0045] The motor drive control device 10 may be configured such that the motor drive circuit 19 and at least some of the other functional units are packaged as a single integrated circuit device (IC), or such that the motor drive circuit 19 and the other functional units are each packaged as individual integrated circuit devices.

[0046] The drive control signal generator 11 is a functional unit for generating a drive control signal Sd for controlling the drive of the motor 50. For example, when the drive control signal generator 11 receives a speed command signal Sc output from the higher-level device 4, the drive control signal generator 11 generates a drive control signal Sd so that the rotation speed of the motor 50 coincides with a target rotation speed specified by the speed command signal Sc. The drive control signal Sd is, for example, a PWM (Pulse Width Modulation) signal.

[0047] As shown in FIG. 1, the drive control signal generating unit 11 includes, for example, a speed command analyzing unit 12, a duty ratio determining unit 13, and an energization control unit .

[0048] The speed command analysis unit 12 receives the speed command signal Sc output from the higher-level device 4, and analyzes the target rotation speed specified by the speed command signal Sc. For example, when the speed command signal Sc is a PWM signal having a duty ratio corresponding to the target rotation speed, the speed command analysis unit 12 analyzes the duty ratio of the speed command signal Sc, and outputs information on the rotation speed corresponding to the duty ratio as the target rotation speed.

[0049] Duty ratio determiner 13 determines the duty ratio of the PWM signal serving as drive control signal Sd based on the target rotation speed output from speed command analyzer 12 and the measurement value of the rotation speed of motor 50 measured by rotation speed measurement unit 21, which will be described later. Specifically, duty ratio determiner 13 calculates a control amount for motor 50 so as to reduce the difference between the target rotation speed and the measurement value of the rotation speed of motor 50, and determines the duty ratio of the PWM signal according to the control amount. Energization control unit 14 generates a PWM signal having the duty ratio determined by duty ratio determiner 13, and outputs it as drive control signal Sd.

[0050] The motor drive circuit 19 drives the motor 50 based on the drive control signal Sd generated by the drive control signal generation unit 11. The motor drive circuit 19 includes, for example, an inverter circuit and a pre-drive circuit (not shown).

[0051] The inverter circuit outputs a drive signal to the motor 50 based on the output signal from the pre-drive circuit, and energizes the coils of the motor 50. The inverter circuit is configured, for example, by disposing a pair of series circuits of two switch elements provided at both ends of a DC power supply, one for each phase of the coil. In each pair of two switch elements, a terminal of each phase of the motor 50 is connected to the connection point between the switch elements.

[0052] The pre-drive circuit generates an output signal for driving the inverter circuit based on the drive control signal Sd and outputs it to the inverter circuit. The pre-drive circuit generates and outputs a drive signal for driving each switch element of the inverter circuit based on the drive control signal Sd, for example. The drive signal turns on / off each switch element constituting the inverter circuit, thereby supplying power to each phase of the motor 50 and rotating the rotor of the motor 50.

[0053] The sensor unit 20 is a functional unit that detects physical quantities related to the state of the motor 50. The sensor unit 20 includes various sensors, such as a position detector (e.g., a Hall element) that detects the rotational position of the motor 50, a current sensor (e.g., a shunt resistor) that detects the current flowing through the coils of the motor 50, a voltage sensor (e.g., a resistive voltage divider circuit) that detects the voltage of the coils of the motor 50, and a temperature sensor (e.g., a thermistor) that detects the temperature of the windings of the motor 50 and the temperatures of the windings and internal circuits of the motor 50. Each sensor that constitutes the sensor unit 20 outputs an electrical signal corresponding to the detected physical quantity. Note that, in this embodiment, an example is shown in which the various sensors that constitute the sensor unit 20 are provided within the motor drive control device 10, but all or some of the various sensors that constitute the sensor unit 20 may be provided external to the motor drive control device 10.

[0054] The rotation speed measurement unit 21 is a functional unit that measures the rotation speed of the motor 50. The rotation speed measurement unit 21 measures the rotation speed of the motor 50 based on, for example, a detection signal (Hall signal) of a Hall element serving as a position detector in the sensor unit 20, and outputs the measurement result.

[0055] The FG signal generating unit 22 generates an FG signal as a rotation speed signal So that indicates the rotation speed of the motor 50. The FG signal generating unit 22 generates the FG signal, which is a signal having a period (frequency) proportional to the rotation speed of the motor 50, based on, for example, a detection signal (Hall signal) output from a Hall element that serves as a position detector in the sensor unit 20. The FG signal output from the FG signal generating unit 22 is input to the higher-level device 4 as the rotation speed signal So.

[0056] The FG signal generating unit 22 may be realized by an FG pattern formed on a board (printed board) on which the motor 50 is mounted, for example.

[0057] The communication unit 15 is a functional unit for communicating with the outside. Specifically, the communication unit 15 transmits and receives data to and from the higher-level device 4 as a control device. The communication unit 15 transmits the diagnosis result by the diagnosis unit 243 (described later) to the outside.

[0058] The communication unit 15 has, for example, a transmitting unit 16, a receiving unit 17, and a communication control unit 18. The transmitting unit 16 transmits a signal to the outside (for example, the higher-level device 4). The receiving unit 17 receives a signal from the outside. The transmitting unit 16 and the receiving unit 17 are, for example, serial communication interface circuits that are controlled by the communication control unit 18 to generate a predetermined serial signal, transmit it to a communication line, and receive the serial signal from the communication line.

[0059] The communication control unit 18 transmits encoded data to the transmitting unit 16 and decodes data received by the receiving unit 17, thereby transmitting and receiving data between the higher-level device 4 and other motor drive control devices 10. The communication control unit 18 is realized, for example, by program processing by a processor constituting the motor drive control device 10 described above.

[0060] The measurement value acquisition unit 23 is a functional unit that acquires measurement values ​​of physical quantities related to the operation of the motor 50. The measurement value acquisition unit 23 sets the physical quantities related to the operation of the motor 50 as monitoring parameters, acquires the measurement values ​​of the monitoring parameters, and stores them in the storage unit 25. Specifically, the measurement value acquisition unit 23 acquires the detection results of the physical quantities related to the state of the motor 50 detected by the sensor unit 20 as the measurement values ​​of the monitoring parameters.

[0061] The measurement value acquiring unit 23 includes, for example, an A / D conversion circuit. The measurement value acquiring unit 23 converts electrical signals output from the various sensors constituting the sensor unit 20 into digital values ​​by sampling them at a predetermined sampling period (every unit time), and stores the digital values ​​in the storage unit 25 as measurement values ​​of physical quantities related to the state of the motor 50 (measurement values ​​of monitoring parameters). Here, examples of physical quantities related to the state of motor 50 that can serve as monitoring parameters include the current flowing through the coil of motor 50 (hereinafter also referred to as the "drive current of motor 50"), the rotational speed (number of rotations) of motor 50, the power supply voltage of the inverter circuit that drives motor 50 (hereinafter also referred to as the "drive voltage of motor 50"), the power of motor 50 (for example, the drive current of motor 50 x the drive voltage of motor 50), the duty ratio determined by duty ratio determination unit 13, the temperature of the windings of motor 50, and the temperature of the windings and internal circuits of motor 50.

[0062] The measurement value acquiring unit 23 acquires at least one of the detected values ​​of the physical quantities related to the state of the motor 50 as the measurement value of the monitoring parameter. For example, the measurement value acquiring unit 23 samples the detection value of the drive current of the motor 50 by the current sensor of the sensor unit 20 at every unit time, and stores the result in the storage unit 25 as the measurement value 251 of the monitoring parameter. The measurement value acquiring unit 23 may also sample the temperature detection result by the temperature sensor of the sensor unit 20 at every unit time, and store the result in the storage unit 25 as the measurement value 251 of the monitoring parameter. The measurement value acquiring unit 23 may also sample the rotation speed per unit time of the motor 50 measured by the rotation speed measuring unit 21 at every unit time, and store the result in the storage unit 25 as the measurement value 251 of the monitoring parameter. Furthermore, the measurement value acquiring unit 23 may also sample the detection value of the drive voltage (power supply voltage) of the motor 50 by the voltage sensor at every unit time, and store the result in the storage unit 25 as the measurement value 251 of the monitoring parameter. The measurement value acquiring unit 23 may sample the detection value of the drive voltage of the motor 50 by the voltage sensor and the detection value of the drive current of the motor 50 by the current sensor of the sensor unit 20 every unit time, multiply the detection value of the drive voltage and the detection value of the drive current together to calculate the power of the motor 50, and store the calculated power in the storage unit 25 as the measurement value 251 of the monitoring parameter. The measurement value acquiring unit 23 may acquire the duty ratio determined by the duty ratio determining unit 13 every unit time, and store the calculated power in the storage unit 25 as the measurement value 251 of the monitoring parameter.

[0063] The measurement value acquiring unit 23 may acquire the measurement value 251 of the monitoring parameter in response to a request from the higher-level device 4.

[0064] The monitoring unit 24 is a functional unit for monitoring the state of the motor 50 to be driven. The monitoring unit 24 monitors the state of the motor 50 based on the measurement values ​​251 of the monitoring parameters. Specifically, the monitoring unit 24 calculates statistics of the monitoring parameters based on the measurement values ​​251 of the monitoring parameters, and diagnoses the state of the motor 50 based on the statistics. In this embodiment, the statistics include, for example, an average value, a standard deviation, and a coefficient of variation, and preferably includes a "coefficient of variation of the coefficient of variation" calculated based on the average value of the coefficients of variation and the standard deviation of the coefficients of variation.

[0065] As shown in FIG. 1, the monitoring unit 24 includes, for example, a first calculation unit 241, a second calculation unit 242, and a diagnosis unit 243.

[0066] The first calculation unit 241 is a functional unit that calculates the coefficient of variation of the measured value of the monitoring parameter (hereinafter also referred to as the "first coefficient of variation"). The second calculation unit 242 is a functional unit that calculates the coefficient of variation of the first coefficient of variation (hereinafter also referred to as the "second coefficient of variation"). The diagnosis unit 243 is a functional unit that diagnoses the state of the motor 50 based on the second coefficient of variation. The diagnosis unit 243 may diagnose the state of the motor 50 based on, for example, a value obtained by smoothing the second coefficient of variation.

[0067] Here, a description will be given of an example of a method for calculating statistics of the monitoring parameters by the monitoring unit 24. In the following description, an example will be given in which the drive current of the motor 50 is used as the monitoring parameter.

[0068] In the monitoring unit 24, the first calculation unit 241 calculates an average value Xa of the measurement values ​​of the monitoring parameters based on the measurement values ​​251 of the plurality of monitoring parameters acquired by the measurement value acquisition unit 23 at a predetermined sampling period. For example, the average value Xa(n) of the measurement value of the nth monitoring parameter can be calculated by the following formula (1): In formula (1), N is an integer equal to or greater than 2 (for example, an integer between 100 and 1000), x(n) is the measurement value of the nth monitoring parameter, and Xa(n-1) is the average value of the measurement value of the (n-1)th monitoring parameter.

[0069]

number

[0070] First, the first calculation unit 241 calculates and updates the average value Xa(n) of the measurement values ​​of the n-th monitoring parameter at a predetermined period (hereinafter also referred to as the "calculation period") based on the formula (1). Here, the calculation period may be the same as or different from the sampling period by the measurement value acquisition unit 23 described above.

[0071] Next, the first calculation unit 241 calculates the root mean square value Xsa(n) of the measurement value of the n-th monitoring parameter based on the following formula (2): In formula (2), Xsa(n-1) is the root mean square value of the measurement value of the (n-1)-th monitoring parameter.

[0072]

number

[0073] Here, as shown in the following formula (3), the root mean square value Xsa(n) corresponds to the average value of the squares of the measurement values ​​x of the monitoring parameters.

[0074]

number

[0075] Next, the first calculation unit 241 calculates the standard deviation σ(n) of the measurement values ​​of the nth monitoring parameter using the following equation (4) based on the average value Xa(n) of the measurement values ​​of the nth monitoring parameter calculated based on the above equation (1) and the root mean square value Xsa(n) of the measurement values ​​of the nth monitoring parameter calculated based on the above equations (2) and (3).

[0076]

number

[0077] For example, in general, when a method is adopted in which the variance of a plurality of data is calculated and the standard deviation is calculated using the variance, the amount of data that needs to be temporarily stored becomes large, and the memory capacity for storing the data needs to be large. In contrast, by using the recurrence formula (exponential moving average) shown in the above formula (1) and formula (2), the standard deviation can be calculated by sequential calculation, thereby reducing the required memory capacity.

[0078] Next, the first calculation unit 241 calculates the coefficient of variation CV(n) of the measurement value of the nth monitoring parameter using the following formula (5) based on the nth average value Xa(n) calculated based on the above formula (1) and the nth standard deviation σ(n) calculated based on the above formula (4). Hereinafter, the coefficient of variation of the measurement value of the monitoring parameter will also be referred to as the "first coefficient of variation CV".

[0079]

number

[0080] The second calculation unit 242 calculates statistics of the first coefficients of variation CV. Specifically, first, the second calculation unit 242 calculates an average value CVa(n) of the nth first coefficients of variation CV using the following formula (6) based on the nth first coefficients of variation CV(n) calculated by the first calculation unit 241. In formula (6), CV(n) is the nth first coefficient of variation CV, and CVa(n-1) is the average value of the (n-1)th first coefficients of variation CV.

[0081]

number

[0082] Next, the second calculation unit 242 calculates the root mean square value CVsa(n) of the n-th first coefficient of variation based on the following formula (7): In formula (7), CVsa(n-1) is the root mean square value of the (n-1)-th first coefficient of variation CV.

[0083]

number

[0084] Next, the second calculation unit 242 calculates the standard deviation σCV(n) of the nth first coefficient of variation CV using the following equation (8) based on the average value CVa(n) of the nth first coefficient of variation CV calculated based on the above equation (6) and the root mean square value CVsa(n) of the nth first coefficient of variation CV calculated based on the above equation (7).

[0085]

number

[0086] Next, the second calculation unit 242 calculates the coefficient of variation CVCV(n) of the nth first coefficient of variation CV using the following equation (9) based on the average value CVa(n) of the first coefficients of variation CV calculated based on the above equation (6) and the standard deviation σCV(n) of the nth first coefficient of variation CV calculated based on the above equation (8). Hereinafter, the coefficient of variation of the first coefficient of variation CV will also be referred to as the "second coefficient of variation CVCV."

[0087]

number

[0088] Furthermore, the second calculation unit 242 may calculate a smoothed value of the second coefficient of variation CVCV(n). For example, the second calculation unit 242 calculates an exponential moving average of the second coefficient of variation CVCV(n) to calculate the smoothed value of the second coefficient of variation CVCV(n). More specifically, the second calculation unit 242 calculates a smoothed coefficient of variation CVCVs(n), which is a value obtained by smoothing the second coefficient of variation CVCV(n), by the following equation (10). In equation (10), Ns is a smoothing coefficient.

[0089]

number

[0090] The smoothing coefficient Ns is preferably set to a value equivalent to 24 hours or more. For example, if the sampling period is 50 ms, the smoothing coefficient Ns is preferably set to 172800 (=24×3600×2) or more. Also, if the sampling period is 1 s, the smoothing coefficient Ns is preferably set to 86400 (=24×3600×1) or more.

[0091] The coefficient of variation CVCVs(n) after smoothing is not limited to a value calculated based on the recurrence formula of the exponential moving average (Equation (10)) described above, but may be a value calculated by other known methods for smoothing calculations.

[0092] The calculation results of the various statistics by the first calculation unit 241 and the second calculation unit 242 are stored in the storage unit 25 as statistics information 252 for each calculation period (sampling period) described above, and are updated.

[0093] Next, an example of a method for diagnosing the motor 50 by the diagnosing unit 243 will be described.

[0094] The diagnosis unit 243 uses a value based on the second coefficient of variation CVCV to calculate an index value (hereinafter also referred to as "abnormality score") Scab that indicates the degree of deterioration of the motor 50. For example, the diagnosis unit 243 calculates the abnormality score Scab by multiplying the value based on the second coefficient of variation by a predetermined coefficient. For example, the diagnosis unit 243 calculates the abnormality score Scab by multiplying the second coefficient of variation CVCV or the smoothed coefficient of variation CVCVs by a predetermined coefficient k. In the present embodiment, as an example, the diagnosis unit 243 calculates the abnormality score Scab (=CVCVs×k) by multiplying the smoothed coefficient of variation CVCVs by a coefficient k (>0).

[0095] The diagnosis unit 243, for example, compares the abnormality score Scab with a reference value Sth and determines whether or not there is an abnormality in the motor based on the comparison result. Here, the reference value Sth is a value (threshold value) that serves as a reference for determining whether or not there is an abnormality in the motor 50, and is stored in the storage unit 25 as reference value information 253, for example.

[0096] For example, if the abnormality score Scab is lower than the reference value Sth, the diagnosis unit 243 determines that the motor 50 is not abnormal. For example, if the abnormality score Scab is equal to or greater than the reference value Sth, the diagnosis unit 243 determines that the motor 50 is abnormal. The diagnosis unit 243 stores the diagnosis result including the above-mentioned determination result in the storage unit 25 as abnormality determination information 254. Here, the abnormality determination information 254 may include the abnormality score Scab in addition to the above-mentioned diagnosis result. Alternatively, the abnormality determination information 254 may include only the abnormality score Scab.

[0097] When the diagnosing unit 243 determines that the motor 50 is abnormal, the monitoring unit 24 may transmit data indicating that an abnormality in the motor 50 has been detected to the outside (host device 4) via the communication unit 15. For example, the monitoring unit 24 may transmit abnormality determination information 254 to the host device 4 via the communication unit 15. Furthermore, when the monitoring unit 24 receives a request from the host device 4 via the communication unit 15 to instruct the execution of a diagnosis of the motor 50, the monitoring unit 24 may execute the diagnosis by the diagnosing unit 243 and transmit abnormality determination information 254 including the diagnosis result to the host device 4 via the communication unit 15 as a response to the request.

[0098] Next, the flow of processing related to the monitoring function performed by the motor drive control device 10 will be described.

[0099] FIG. 2 is a flowchart showing the flow of processing related to the monitoring function performed by the motor drive control device 10 according to the embodiment.

[0100] For example, when rotating the fan 5, the higher-level device 4 transmits a speed command signal Sc to the motor drive control device 10. The drive control signal generator 11 of the motor drive control device 10 generates a drive control signal Sd so that the rotation speed of the motor 50 matches the target rotation speed specified by the speed command signal Sc. This causes the fan 5 to start rotating.

[0101] After the fan 5 starts rotating, the motor drive control device 10 measures physical quantities (monitoring parameters) related to the operation of the motor 50 to be driven, and monitors the state of the motor 50 based on the measurement results.

[0102] Specifically, first, the motor drive control device 10 performs a statistical quantity calculation process to calculate statistical quantities of the monitoring parameters (step S1). Next, the motor drive control device 10 performs a diagnostic process to diagnose the state of the motor using the statistical quantities of the monitoring parameters calculated in step S1 (step S2). Steps S1 and S2 will be described in detail below.

[0103] FIG. 3 is a flowchart showing an example of the flow of the statistics calculation process (step S1).

[0104] In the statistical quantity calculation process of step S1, first, motor drive control device 10 acquires the measurement value of the monitoring parameter (step S11). For example, as described above, measurement value acquisition unit 23 acquires the detection value of the drive current of motor 50 detected by sensor unit 20 at a predetermined sampling period, and stores it in memory unit 25 as measurement value 251 of the monitoring parameter.

[0105] Next, the motor drive control device 10 calculates the average value Xa of the measurement values ​​of the monitoring parameters (step S12). Specifically, in the monitoring unit 24, the first calculation unit 241 calculates the average value Xa(n) of the measurement values ​​of the n-th monitoring parameter using the method described above.

[0106] Next, the motor drive control device 10 calculates the standard deviation σ of the measurement values ​​of the monitoring parameters (step S13). Specifically, in the monitoring unit 24, the first calculation unit 241 calculates the root mean square value Xsa(n) of the measurement values ​​of the n-th monitoring parameter using the method described above, and calculates the standard deviation σ(n) of the measurement values ​​of the n-th monitoring parameter based on the root mean square value Xsa(n) and the mean value Xa(n).

[0107] Next, the motor drive control device 10 calculates a first coefficient of variation CV, which is the coefficient of variation of the measured value of the monitoring parameter (step S14). Specifically, in the monitoring unit 24, the first calculation unit 241 calculates the first coefficient of variation CV(n), which is the coefficient of variation of the measured value of the n-th monitoring parameter, based on the average value Xa(n) calculated in step S12 and the standard deviation σ(n) calculated in step S13, using the method described above.

[0108] Next, the motor drive control device 10 calculates the average value CVa of the first coefficients of variation CV (step S15). Specifically, in the monitoring unit 24, the second calculation unit 242 calculates the average value CVa(n) of the n-th first coefficients of variation CV using the method described above.

[0109] Next, the motor drive control device 10 calculates the standard deviation σCV of the first coefficients of variation CV (step S16). Specifically, in the monitoring unit 24, the second calculation unit 242 calculates the root mean square value CVsa(n) of the n-th first coefficients of variation CV using the method described above, and calculates the standard deviation σCV(n) of the n-th first coefficients of variation CV based on the root mean square value CVsa(n) and the mean value CVa(n).

[0110] Next, the motor drive control device 10 calculates a second coefficient of variation CVCV, which is the coefficient of variation of the first coefficient of variation CV (step S17). Specifically, in the monitoring unit 24, the second calculation unit 242 calculates the second coefficient of variation CVCV(n), which is the n-th coefficient of variation of the first coefficient of variation CV, based on the average value CVa(n) calculated in step S15 and the standard deviation σCV(n) calculated in step S16, using the method described above.

[0111] Next, the motor drive control device 10 calculates the abnormality score Scab (step S18). For example, the diagnosis unit 243 calculates the abnormality score Scab by multiplying the second coefficient of variation CVCV(n) calculated in step S17 by a predetermined coefficient k (for example, 1.00), and stores the calculated abnormality score Scab in the storage unit 25. The statistical calculation process (step S1) is performed according to the above processing procedure.

[0112] Next, the flow of the diagnostic process (step S2) will be described.

[0113] FIG. 4 is a flowchart showing an example of the flow of the diagnosis process (step S2).

[0114] In the diagnosis process of step S2, first, the motor drive control device 10 acquires the abnormality score Scab (step S21). For example, in the monitoring unit 24, the diagnosis unit 243 reads out the abnormality score Scab from the storage unit 25.

[0115] Next, the motor drive control device 10 compares the abnormality score Scab acquired in step S21 with the reference value Sth (step S22). For example, in the monitoring unit 24, the diagnosis unit 243 determines whether the abnormality score Scab is equal to or greater than the reference value Sth.

[0116] If the abnormality score Scab is smaller than the reference value Sth (step S22: NO), the diagnosis unit 243 determines that the motor 50 is not abnormal (step S23). On the other hand, if the abnormality score Scab is equal to or greater than the reference value Sth (step S22: YES), the diagnosis unit 243 determines that the motor 50 is abnormal (step S24).

[0117] After steps S23 and S24, motor drive control device 10 generates abnormality determination information 254 (step S25). Specifically, diagnosis unit 243 generates abnormality determination information 254 based on the diagnosis results of step S23 or step S24 using the method described above, and stores the information in storage unit 25. If motor 50 is determined to be abnormal in step S24, motor drive control device 10 may notify higher-level device 4 that motor 50 is abnormal by transmitting abnormality determination information 254 to higher-level device 4.

[0118] The diagnostic process (step S2) is performed according to the above procedure.

[0119] The above-described statistical quantity calculation process (step S1) is repeatedly executed for each calculation period while the fan 5 is operating. The calculation period in which the statistical quantity calculation process (step S1) is executed and the period in which the diagnostic process (step S2) is executed may be the same or different. For example, the period in which the diagnostic process (step S2) is executed may be longer than the calculation period in which the statistical quantity calculation process (step S1) is executed. For example, the motor drive control device 10 may periodically execute the statistical quantity calculation process (step S1), and when a command to execute a diagnosis is input to the motor drive control device 10 from an external device such as the higher-level device 4, the motor drive control device 10 may execute the diagnostic process (step S2).

[0120] Next, the effects of the motor drive control device 10 according to the embodiment will be described.

[0121] 5A to 5C are diagrams showing an example of the change over time of the first coefficient of variation CV. 6A to 6C are diagrams showing an example of the change over time of the second coefficient of variation CV.

[0122] 5A to 5C, the horizontal axis represents time (s), and the vertical axis represents the first coefficient of variation CV, which is the coefficient of variation of the monitored parameter when the drive current of the motor 50 is used as the monitored parameter. Fig. 5A shows characteristic 501 of the change over time of the first coefficient of variation CV when the motor 50 is normal and the influence of disturbances is small. Fig. 5B shows characteristic 502 of the change over time of the first coefficient of variation CV when the motor 50 is normal and the influence of disturbances is large. Fig. 5C shows characteristic 503 of the change over time of the first coefficient of variation CV when the motor 50 is abnormal and the influence of disturbances is small.

[0123] 6A to 6C, the horizontal axis represents time (s), and the vertical axis represents the second coefficient of variation CVCV, which is the coefficient of variation of the first coefficient of variation CV of the monitoring parameter when the drive current of the motor 50 is used as the monitoring parameter. Fig. 6A shows a characteristic 601 of the change over time of the second coefficient of variation CVCV when the motor 50 is normal and the influence of disturbances is small. Fig. 6B shows a characteristic 602 of the change over time of the second coefficient of variation CVCV when the motor 50 is normal and the influence of disturbances is large. Fig. 6C shows a characteristic 603 of the change over time of the second coefficient of variation CVCV when the motor 50 is abnormal and the influence of disturbances is small.

[0124] 5A to 5C, the first coefficient of variation CV is easily affected by disturbances. That is, as can be seen from characteristic 501 shown in FIG. 5A and characteristic 502 shown in FIG. 5B, even if the motor 50 is normal, the first coefficient of variation CV fluctuates significantly when the influence of disturbances is large. Furthermore, as can be seen from characteristic 503 shown in FIG. 5C, the first coefficient of variation CV also fluctuates significantly when the motor 50 is abnormal. Therefore, for example, if a method is employed in which an abnormality score is calculated using the first coefficient of variation CV and the abnormality score is compared with a reference value to diagnose whether or not the motor 50 is abnormal, there is a high possibility that the motor 50 will be erroneously determined to be abnormal in a situation in which the influence of disturbances is large, even if the motor 50 is normal.

[0125] 6A to 6C, the second coefficient of variation CVCV is less susceptible to the influence of disturbances than the first coefficient of variation CV. That is, as can be seen from characteristic 601 shown in FIG. 6A and characteristic 602 shown in FIG. 6B, even when the influence of disturbances is large, fluctuations in the second coefficient of variation CVCV are suppressed when the motor 50 is normal. Furthermore, as can be seen from characteristic 603 shown in FIG. 6C, when the motor 50 is abnormal, the second coefficient of variation CVCV fluctuates significantly, similar to the first coefficient of variation CV. Therefore, even if a method is adopted in which the abnormality score is calculated using the second coefficient of variation CV and the abnormality score is compared with a reference value to diagnose whether or not there is an abnormality in the motor 50, it is possible to accurately determine whether or not there is an abnormality in the motor 50, regardless of the influence of external disturbances.

[0126] As described above, the motor drive control device 10 according to the embodiment uses physical quantities related to the operation of the motor as monitoring parameters, calculates a first coefficient of variation CV that is the coefficient of variation of the measured value of the monitoring parameter, calculates a second coefficient of variation CVCV that is the coefficient of variation of the first coefficient of variation CV, and diagnoses the state of the motor 50 to be driven based on the second coefficient of variation CVCV. This makes it possible to appropriately determine the state of the motor, as described above, regardless of external disturbances.

[0127] Furthermore, the motor drive control device 10 according to the embodiment may diagnose the state of the motor 50 based on a value (CVCVs) obtained by smoothing the second coefficient of variation CVCV. This makes it possible to further suppress fluctuations in the second coefficient of variation CVCV caused by the influence of disturbances, thereby further improving the accuracy of diagnosing the state of the motor 50.

[0128] Furthermore, the motor drive control device 10 according to the embodiment may calculate an exponential moving average of the second coefficient of variation CVCV(n) to calculate a smoothed value (CVCVs) of the second coefficient of variation CVCV. This makes it easy to calculate a statistical quantity that is less susceptible to the influence of disturbances.

[0129] Furthermore, in the motor drive control device 10 according to the embodiment, the monitoring parameters may include the current flowing through the coil of the motor 50 (the drive current of the motor 50). As described above, when the motor 50 is in an abnormal state, the second coefficient of variation CVCV related to the drive current of the motor 50 fluctuates significantly. Therefore, by using the drive current of the motor 50 as a monitoring parameter, it is possible to more accurately diagnose the state of the motor 50 to be driven.

[0130] Furthermore, the motor drive control device 10 according to the embodiment compares an index value (abnormality score Scab) indicating the degree of deterioration of the motor 50 with a reference value Sth, and determines whether or not there is an abnormality in the motor 50 based on the comparison result. This makes it possible to easily determine whether or not there is an abnormality in the motor 50.

[0131] <<Extension of Embodiment>> The invention made by the inventor has been specifically described above based on an embodiment, but it goes without saying that the invention is not limited thereto and can be modified in various ways without departing from the spirit of the invention.

[0132] For example, in the above embodiment, a case has been described in which one physical quantity related to the operation of the motor 50 (the drive current of the motor 50) is used as a monitoring parameter, but this is not limiting. For example, two or more physical quantities may be used as monitoring parameters from among the drive current of the motor 50, the rotation speed of the motor 50, the drive voltage of the motor 50, the power of the motor 50, the duty ratio determined by the duty ratio determination unit 13, the temperature of the windings of the motor 50, and the temperatures of the windings and internal circuits of the motor 50. When multiple physical quantities are used as monitoring parameters, for example, the above-mentioned statistical quantity and anomaly score Scab may be calculated for each monitoring parameter.

[0133] Furthermore, in the above embodiment, the motor drive control device 10 diagnoses the condition of the motor 50 based on the abnormality score Scab, but this is not limiting. For example, the motor drive control device 10 may calculate the statistics (first coefficient of variation CV and second coefficient of variation CVCV) and transmit the calculated statistics to the host device 4, and the host device 4 may diagnose the condition of the motor 50 based on the received statistics. That is, in the flowchart shown in FIG. 2, the motor drive control device 10 may perform the statistics calculation process (step S1), and the host device 4 may perform the diagnosis process (step S2). In other words, the monitoring unit 24 in the motor drive control device 10 may include the first calculation unit 241 and the second calculation unit 242, and the data processing control unit 41 of the host device 4 may include the diagnosis unit 243. In this case, the calculation of the abnormality score Scab may be performed by the diagnosis unit 243 or the second calculation unit 242.

[0134] Furthermore, the number of phases of the motor 50 driven by the motor drive control device 10 according to the above embodiment is not limited to three. The number of Hall elements serving as the sensor unit 20 is not limited to three. The method for detecting the rotational speed of the motor is not particularly limited. For example, the rotational speed may be detected by a position sensorless method that detects the rotational speed using the back electromotive force induced in the motor coil, without using a position detector such as a Hall element.

[0135] The above-described flowcharts are specific examples, and are not limited to the processing procedures shown in Figures 2 to 4. For example, other processes may be inserted between the steps shown in Figures 2 to 4, or some of the processes may be parallelized. [Explanation of symbols]

[0136] 1...fan system, 2...fan unit, 4...higher-level device (an example of an external device), 5...fan (fan motor), 10...motor drive control device, 11...drive control signal generation unit, 12...speed command analysis unit, 13...duty ratio determination unit, 14...power control unit, 15...communication unit, 16...transmission unit, 17...reception unit, 18...communication control unit, 19...motor drive circuit, 20...sensor unit, 21...rotational speed measurement unit, 22...FG signal generation unit, 23...measurement value acquisition unit, 24...monitoring unit, 25...memory unit, 41...data processing control unit, 42...communication unit, 50...motor, 51...impeller (impeller), 241...first calculation unit, 242...second calculation unit, 243...diagnosis unit, 251...measurement value, 252...statistical information, 253...reference value information, 254...abnormality determination information, Sc...speed command signal, Sd...drive control signal, So...rotational speed signal.

Claims

1. a drive control signal generation unit that generates a drive control signal for controlling the driving of the motor; a motor drive circuit that drives the motor based on the drive control signal; A memory unit; a measurement value acquisition unit that sets physical quantities related to the operation of the motor as monitoring parameters, acquires measurement values ​​of the monitoring parameters, and stores the measurement values ​​in the storage unit; a monitoring unit that monitors the state of the motor based on the measurement value of the monitoring parameter, The monitoring unit a first calculation unit that calculates a first coefficient of variation, which is a coefficient of variation of the measurement value, based on the measurement value stored in the storage unit; a second calculation unit that calculates a second coefficient of variation that is a coefficient of variation of the first coefficient of variation; a diagnosis unit that diagnoses a state of the motor based on the second coefficient of variation. Motor drive control device.

2. 2. The motor drive control device according to claim 1, The diagnosing unit diagnoses the state of the motor based on a value obtained by smoothing the second coefficient of variation. Motor drive control device.

3. 3. The motor drive control device according to claim 2, The diagnostic unit calculates an exponential moving average of the second coefficient of variation to calculate a smoothed value of the second coefficient of variation. Motor drive control device.

4. 2. The motor drive control device according to claim 1, The monitored parameters include a current flowing through a coil of the motor. Motor drive control device.

5. 2. The motor drive control device according to claim 1, The diagnostic unit multiplies a value based on the second coefficient of variation by a predetermined coefficient to calculate an index value indicating a degree of deterioration of the motor. Motor drive control device.

6. 6. The motor drive control device according to claim 5, the storage unit further stores a reference value of the monitoring parameter; The diagnostic unit compares the index value with the reference value and determines whether or not there is an abnormality in the motor based on the comparison result. Motor drive control device.

7. 2. The motor drive control device according to claim 1, Further comprising a communication unit for communicating with the outside, The communication unit transmits a diagnosis result by the diagnosis unit to the outside. Motor drive control device.

8. The motor drive control device according to any one of claims 1 to 7; the motor driven by the motor drive control device and a fan including an impeller configured to be rotatable by the rotational force of the motor. Fan unit.

9. a first step of acquiring measured values ​​of monitoring parameters that are physical quantities related to the operation of the motor; a second step of calculating a first coefficient of variation, which is a coefficient of variation of the measurement value, based on the measurement value; a third step of calculating a second coefficient of variation, which is a coefficient of variation of the first coefficient of variation, based on the first coefficient of variation; a fourth step of diagnosing the state of the motor based on the second coefficient of variation. Diagnostic methods.

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