KR20180103384A - Fault diagnosis method of motor - Google Patents

Abstract

The present invention relates to a method for diagnosing a fault of a motor, capable of determining a specific degree of demagnetization of the motor, including a first step of measuring a dq axis voltage and a dq axis current of the motor, a second step of calculating a magnetic flux value based on the normal inductance of the motor, the dq axis voltage, and the dq axis current, a third step of calculating virtual inductance based on a characteristic lookup table and the magnetic flux value calculated in the second step, a fourth step of repeating a process of recalculating the magnetic flux value by substituting the virtual inductance instead of the normal inductance of the second step and recalculating the virtual inductance by substituting the recalculated magnetic flux value into the third step until the recalculated magnetic flux value and the virtual inductance value are converged on a specific value, and a fifth step of determining the state of the motor based on a final magnetic flux value converged through the fourth step.

Description

Fault diagnosis method of motor [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of diagnosing a fault in a motor, and more particularly, to a method of determining a degree of a fault in a motor.

A motor is a power machine that generates torque by using electric power. The motor is also called an electric motor.

The motor can consist of a stationary part, a stator, and a rotating part, a rotor. The conductor wire is wound around the stator of the motor to form a coil. The motor has permanent magnets. In this case, permanent magnets may be included in the rotor of the motor.

Motors can be used in many electrical devices. For example, motors can be used in electric appliances such as electric fans or air conditioners, and electric vehicles.

Among these motors, brushless direct current (BLDC) motors or Permanent Magnet Synchronous Motor (PMSM) motors are mainly used in electric vehicles.

Motors of electric vehicles are likely to fail because high voltages can be applied and physical shocks due to various driving environments can be applied.

Particularly, the permanent magnet provided in the motor can be reduced in magnetic force due to heat due to high voltage, physical impact due to the running environment, aging, and the like. The phenomenon in which the magnetic force of the permanent magnet decreases is called a potato. If the magnetic force of the permanent magnet of the motor decreases, the torque output and efficiency of the motor decrease, and if the degree of the potato increases, the motor may not operate normally.

If the motor of the electric vehicle fails, the vehicle can not be driven. Therefore, it is necessary to judge the state of the motor potato fault before the motor is completely demagnetized.

However, conventionally, there is a problem that it is impossible to judge how much the motor has been reduced before the motor is demagnetized and failed.

Accordingly, a method of determining the potato condition of the motor even before the motor failure has been studied.

SUMMARY OF THE INVENTION An object of the present invention is to provide a fault diagnosis method for a motor capable of determining a specific degree of potato of a motor even before a fault occurs in the motor.

The problems of the present invention are not limited to the above-mentioned problems, and other problems not mentioned can be clearly understood by those skilled in the art from the following description.

According to an aspect of the present invention, there is provided a method of diagnosing a motor fault, comprising the steps of: measuring a dq axis voltage and a dq axis current of a motor; measuring a normal inductance of the motor, A third step of calculating a virtual inductance based on the magnetic flux value and the characteristic lookup table calculated in the second step on the basis of the current, the third step of calculating the virtual inductance, And substituting the re-calculated magnetic flux value into the third step to reevaluate the virtual inductance, wherein when the re-calculated magnetic flux value and virtual inductance value are converged to a specific value And a fifth step of determining the state of the motor based on the final magnetic flux value converged through the fourth step.

The details of other embodiments are included in the detailed description and drawings.

According to an embodiment of the present invention, there is one or more of the following effects.

The accuracy of the motor can be determined even before the failure of the motor, so that the failure of the motor can be prevented.

The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by those skilled in the art from the description of the claims.

1 is a flowchart for explaining a fault diagnosis method of a motor according to the present invention.
2 is a flowchart for explaining a step of determining whether a motor is normal or a potato fault between a second step and a third step in the motor fault diagnosis method of the present invention.
3 is a graph showing the relationship between the inductance and the magnetic flux value.
FIGS. 4 to 6 are diagrams for explaining magnetic flux values varying according to the magnitude of the input current. FIG.
FIGS. 7 and 8 are diagrams for explaining the actual magnetizing degree of the motor and the final magnetic flux value calculated according to the failure diagnosis method of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, wherein like reference numerals are used to designate identical or similar elements, and redundant description thereof will be omitted. The suffix "module" and "part" for constituent elements used in the following description are given or mixed in consideration of ease of specification, and do not have their own meaning or role. In the following description of the embodiments of the present invention, a detailed description of related arts will be omitted when it is determined that the gist of the embodiments disclosed herein may be blurred. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. , ≪ / RTI > equivalents, and alternatives.

Electric vehicles can be equipped with electric motors. An electric motor is a power machine that changes the power of rotation. The motor is sometimes called an electric motor. For example, the motor may be a Permanent Magnet Synchronous Motor (PMSM).

The motor can consist of a stationary part, a stator, and a rotating part, a rotor. The conductor wire is wound around the stator of the motor to form a coil. The rotor of the motor may comprise a permanent magnet.

When an electric current is supplied so that a stator having a three-phase coil is formed so as to form a rotor system, the rotor can rotate in synchronization with the rotor system. If the motor is a PMSM, the motor can be controlled via a space vector control technique. Accordingly, direct control of the torque of the motor is possible, and speed control and position control are easy.

In the case of an electric motor provided in an electric vehicle, since a high voltage and a high current are used, a large heat can be applied to the permanent magnet provided in the motor. Due to such a high temperature, the permanent magnet of the motor may be damaged. Further, an electric vehicle runs in various environments, so that a physical shock may be applied to the motor. In this case, the permanent magnet of the motor may be damaged by a physical impact. In addition, when the permanent magnet ages, the magnetic force can be reduced.

For example, Permanent Magnet Synchronous Motor (PMSM) used in an electric vehicle may cause permanent magnet damage.

If the permanent magnet is damaged, a potato phenomenon may occur in which the magnetic force of the permanent magnet is reduced. If a potato phenomenon occurs in the motor, the efficiency and torque of the motor can be reduced. The conventional technique can not accurately determine the degree of the potato of the motor. It is possible to judge whether the motor is broken down by frequency analysis, but it can not judge the specific degree of the potato.

Accordingly, the fault diagnosis method of the motor according to the present invention is a method that can accurately determine the degree of the potato of the motor.

A fault diagnosis method of a motor according to the present invention can be performed by a user. When the motor diagnosis method is performed by the user, the user can perform various calculations included in the motor fault diagnosis method of the present invention by using a computing device such as a computer.

In addition, the fault diagnosis method of the motor according to the present invention may be performed automatically by a separately provided processor. When the fault diagnosis method of the motor according to the present invention is performed by a processor, the processor may operate in connection with an input unit or a measurement unit for receiving various measured values. The processor may output the determination result through a separately connected output unit. The processor is separately provided in an electric vehicle equipped with a motor and is connected to various devices provided in an electric vehicle, and various devices can be controlled in order to perform the fault diagnosis method of the present invention. In the following description, it is assumed that the processor performs the fault diagnosis method of the motor.

Hereinafter, a fault detection method of a motor according to the present invention will be described in detail with reference to the drawings.

1 is a flowchart for explaining a fault diagnosis method of a motor according to the present invention.

A method for diagnosing a fault of a motor according to the present invention comprises a first step (S100) of measuring a dq axis voltage and a dq axis current of a motor, calculating a magnetic flux value based on a normal inductance of the motor, a dq axis voltage and a dq axis current A third step S300 of calculating a virtual inductance based on the magnetic flux value and the characteristic lookup table calculated in the second step S200 and the second step S200, The process of recalculating the magnetic flux value by substituting the inductance and substituting the re-calculated magnetic flux value into the third step (S300) and re-calculating the virtual inductance is performed by calculating the recalculated magnetic flux value and virtual inductance value to converge to a specific value And a fifth step S500 of determining the state of the motor based on the final magnetic flux value converged through the fourth step S400 and the fourth step S400. Each step will be described in detail below.

In the first step, the processor measures the dq axis voltage and the dq axis current of the motor (S100).

For example, the motor may be a Permanent Magnet Synchronous Motor (PMSM). If the motor is a PMSM, it can be controlled by vector control techniques. In order to control the motor by vector control technique, the 3-phase motor should be approached as a vector. Accordingly, in order to easily represent the vector of the three-phase motor system, the motor system represented by the abc coordinate system should be converted into the dq coordinate system.

In the abc coordinate system, the voltage and current on the abc appear, and in the dq coordinate system, the dq axis voltage and current appear. The relation between voltage and current on abc and voltage and current on dq axis is as follows.

,

,

)(

)

,

,

)(

)

The dq-axis voltage may include a d-axis voltage and a q-axis voltage. The dq-axis current may include a d-axis current and a q-axis current.

Unlike the drawing, in the first step, the voltage and current on abc may be measured and converted into dq-axis voltage and current according to the above-mentioned relational expression.

When the motor generates a potato, the dq axis voltage and the dq axis current, which are different from the dq axis voltage and the dq axis current measured in the steady state motor, are measured. Thus, it is possible to judge whether or not the motor is generating a potato based on the dq-axis voltage and the dq-axis current.

In the second step, the processor calculates the magnetic flux value based on the normal inductance of the motor, the dq axis voltage, and the dq axis current (S200).

The inductance of the motor may include the d-axis inductance and the q-axis inductance in the dq coordinate system. In addition, the inductance of the motor may include a-phase inductance, b-phase inductance, and c-phase inductance in the abc coordinate system.

The d-axis inductance and the q-axis inductance can be calculated by a voltage-current relationship in a dq axis coordinate system to be described later.

The normal inductance of the motor represents the inductance when the motor is in a steady state.

The normal inductance is determined based on the input current to the motor, and the characteristic lookup table. The input current of the motor has a magnitude and a phase.

The characteristic lookup table is a lookup table for the change of the inductance of the motor in accordance with the magnetic flux value and the input current of the motor. Specifically, the characteristic lookup table is a look-up table that shows a change in the inductance value according to the magnitude and phase of the input current and the magnetic flux value. The characteristic look-up table is determined according to the performance and characteristics of the motor and is determined by experiments.

The following table is for explaining an example of the characteristic lookup table.

The characteristic lookup table for Ld (mH)

The characteristic lookup table for Lq (mH)

In the above table, A of the current is the magnitude of the input current (A), and P of the current is the phase (angle) of the input current.

In magnetic flux, normal is the magnetic flux value of the permanent magnet of the motor in the steady state. The 1/16 potato is a magnetic flux value reduced by 1/16 based on the normal flux value. The 1/8 potato is a magnetic flux value reduced by 1/8 based on the normal magnetic flux value.

Referring to the table, Lq and Ld may decrease as the magnitude of the input current increases. As the degree of magnetization of magnetic flux increases, Ld decreases and Lq increases.

The normal inductance can be determined by substituting the magnitude and phase of the measured input current into the look-up table, assuming that the flux value is normal.

The processor can determine the normal inductance by applying linear interpolation if the magnitude and phase of the actually measured input current do not match the value shown in the look-up table.

When a potato phenomenon occurs in a motor, the inductance of the motor changes. Thus, the inductance of the motor in which the potato is generated is different from the normal inductance. In this case, the inductance changed by the generation of the potato is a value that can not be directly measured. Accordingly, a process of estimating the changed inductance and flux value using the normal inductance and the measured voltage and current values should be performed.

Since the dq axis voltage and the dq axis current change when a potato occurs in the motor, the processor first calculates the flux value based on the normal inductance, the dq axis voltage and the dq axis current. The calculated magnetic flux value is not accurate, but can be used to determine whether or not the motor is generating a potato.

In the second step, the formula for calculating the magnetic flux value based on the normal inductance, the dq axis voltage and the dq axis current is as follows.

이고,

은, dq축 전압이고,

은, dq축 전류이고,

는,

이고,

는, 상기 모터의 영구자석 극수이고,

및

는, 정상 인덕턴스이고(제4 단계(S400)에서는 가상 인덕턴스),

는 상기 모터의 전기적 각속도이다.In the above equation,

ego,

Is the dq axis voltage,

Is the dq axis current,

Quot;

ego,

Is the number of permanent magnet poles of the motor,

And

Is a normal inductance (virtual inductance in the fourth step (S400)),

Is the electrical angular velocity of the motor.

The above equation is a voltage-current relational expression in the dq axis coordinate system. The d-axis inductance and the q-axis inductance can be calculated from the voltage-current relationship in the dq-axis coordinate system.

In the third step, the processor calculates a virtual inductance based on the magnetic flux value and the characteristic lookup table calculated in the second step (S200) (S300).

The virtual inductance is the re-calculated inductance based on the magnetic flux value calculated based on the normal inductance. When a potentiometer is generated in a motor, the inductance value changes, so that the actual inductance is different from the normal inductance. In this case, since the magnetic flux value calculated based on the normal inductance is inaccurate, the re-computed virtual inductance based on the magnetic flux value is also an inaccurate value but approaches the actual inductance than the normal inductance.

In the third step, the processor can calculate the virtual inductance by applying the linear interpolation method based on the magnetic flux value and the characteristic lookup table calculated in the second step (S200).

For example, when the magnetic flux value calculated in the second step S200 is a specific value between the normal magnetic flux value and the 1/16 magnetic flux value shown in the characteristic lookup table, the virtual inductance also corresponds to the normal magnetic flux value It can be judged that it is a specific value between the inductance and the inductance corresponding to the 1/16 flux value. Referring to FIG. 3, since the d-axis inductance and the magnetic flux value are directly proportional to each other, the processor calculates the inductance corresponding to the inductance corresponding to the normal flux value and the inductance corresponding to the 1/16 flux value in the second step (S200) And the inductance corresponding to the calculated magnetic flux value can be determined by the virtual inductance.

In the fourth step, the processor repeats the steps corresponding to the second step (S200) and the third step (S300) until the magnetic flux value and the virtual inductance value converge to a specific value (S400).

Specifically, the processor re-calculates the magnetic flux value by substituting the virtual inductance calculated in the third step (S300) into the normal inductance of the second step (S200) (S410).

The processor can substitute the virtual inductance into Lq and Ld in the following equation, which is the second step formula, to calculate the persistence value.

Accordingly, the recalculated magnetic flux value is not accurate but is a value close to the actual magnetized magnetic flux value than the magnetic flux value calculated in the second step (S200).

The processor re-calculates the virtual inductance by substituting the re-calculated magnetic flux value into the third step (S300) (S420).

The processor can reassemble the virtual inductance by applying linear interpolation, based on the recalculated flux values and the characteristic lookup table. Accordingly, the re-calculated virtual inductance is closer to the actual inductance than the virtual inductance calculated in the third step (S300).

Since the magnetic flux value and the virtual inductance are re-calculated in the fourth step S400 as the actual flux value and the inductance are close to each other, the processor determines whether the re-calculated magnetic flux value and the virtual inductance value converge to a specific value (S430) And S420 are repeated.

The processor may determine the state of the motor based on the final flux value converged through the fourth step S400 (S500).

The final magnetic flux value is a specific magnetic flux value at which the magnetic flux values converge through the fourth step S400. As the magnetic flux value calculated as the re-calculation of the magnetic flux value is repeated in the fourth step S400, the final magnetic flux value converging on the recalculated magnetic flux value becomes the actual magnetized flux value have.

The processor can determine the specific potato magnitude of the motor based on the final flux value. For example, if the final flux value is 1/16 of the normal flux value, the processor may determine that the motor is 1/16 of the normal state.

2 is a flowchart for explaining a step of determining whether a motor is normal or a potato fault between a second step and a third step in the motor fault diagnosis method of the present invention.

The processor may calculate a magnetic flux value based on the normal inductance in a second step (S200), and then determine whether the calculated magnetic flux value is equal to or higher than a normal reference value (S250).

The steady reference value is a magnetic flux value serving as a reference for judging whether or not a potato has occurred in the motor. The normal reference value may be a value determined by an experiment. For example, the steady reference value may be a flux value at which 1/32 of the potentiometer is generated relative to the flux value of the steady state.

If the magnetic flux value calculated in the second step S200 is equal to or higher than the normal reference value, the processor can determine that the motor is normal (S260).

The processor can determine that an abnormality has occurred in the motor when the magnetic flux value calculated in the second step S200 is less than the normal reference value.

If it is determined that an abnormality has occurred in the motor, the processor proceeds from the third step (S300) to the fifth step (S500) to calculate the final magnetic flux value indicating the degree of the potato of the specific motor.

Therefore, according to the motor fault diagnosis method according to the present invention, even when the motor fails due to the generation of the potato, the degree of the potato of the motor can be grasped, and the complete failure or reduction in efficiency of the motor can be prevented.

3 is a graph showing the relationship between the inductance and the magnetic flux value.

Referring to FIG. 3, the d-axis inductance of the motor and the magnetic flux value may be directly proportional to each other. These graphs are determined by experiments and can vary depending on the characteristics of the motor.

Since the d-axis inductance and the magnetic flux value are directly proportional to each other, when estimating the virtual inductance based on the calculated magnetic flux value, the processor can estimate the virtual inductance by calculating the inductance corresponding to the magnetic flux value calculated on the graph by applying the linear interpolation have.

In the case of q-axis inductance, it may be inversely proportional to the magnetic flux value. In this case, the processor can estimate the virtual inductance value corresponding to the magnetic flux value calculated on the graph indicating the relationship between the q-axis inductance and the magnetic flux value.

FIGS. 4 to 6 are diagrams for explaining magnetic flux values varying according to the magnitude of the input current. FIG.

In the embodiment of FIG. 4, the input current of the motor is 50A in size.

Healthy represents the normal magnetic flux value when the motor is in a normal state. 1/16 Damage represents the magnetic flux value representing 1/16 potato.

Estimation represents a magnetic flux value calculated each time the fourth step is repeated according to the fault diagnosis method of the motor according to the present invention.

The x-axis of the graph represents the number of repetitions of the fourth step of the present invention. The y-axis represents the magnetic flux value of the motor.

It can be confirmed that the magnetic flux value calculated while the fourth step is performed second time than the magnetic flux value calculated by performing the fourth step of the method of diagnosing the fault of the motor is closer to the magnetic flux value representing 1/16 potatoes.

In the embodiment of FIG. 5, the input current of the motor is 250 A in size.

It can be confirmed that the magnetic flux value calculated while the performance of the fourth step is repeated converges to the magnetic flux value representing 1/16 potato.

As shown in FIG. 6, even when the magnitude of the input current is 350 A, it is confirmed that the magnetic flux value calculated while repeating the fourth step converges to the magnetic flux value representing 1/16 potato.

FIGS. 7 and 8 are diagrams for explaining the actual magnetizing degree of the motor and the final magnetic flux value calculated according to the failure diagnosis method of the present invention.

According to the embodiment of Fig. 7, when 1/16 potato is generated in the motor, the magnetic flux value calculated through the third step is smaller than the normal magnetic flux value and larger than the magnetic flux value representing the actual potato.

As the fourth step is repeated, the converging magnetic flux value is close to the magnetic flux value representing 1/16 potato.

The embodiment of Fig. 8 shows a case where 1/32 potato is generated in the motor.

The 1/32 potato indicates that a potato failure of 3.125% has occurred. In this case, the processor can calculate the magnetic flux value closer to the potato failure state than the normal state through the third step.

The processor can reassign the flux value while repeating the fourth step. The magnetic flux value that the processor emits is approaching the magnetic flux value representing 1/32 potentiometer generation.

The converging final flux value is approximately equal to the flux value representing the 1/32 potato.

The present invention described above can be implemented as a computer-readable code on a medium on which a program is recorded. The computer readable medium includes all kinds of recording devices in which data that can be read by a computer system is stored. Examples of the computer readable medium include a hard disk drive (HDD), a solid state disk (SSD), a silicon disk drive (SDD), a ROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, , And may also be implemented in the form of a carrier wave (e.g., transmission over the Internet). In addition, the computer may include a processor or a control unit. Accordingly, the above description should not be construed in a limiting sense in all respects and should be considered illustrative. The scope of the present invention should be determined by rational interpretation of the appended claims, and all changes within the scope of equivalents of the present invention are included in the scope of the present invention.

Claims (9)

A first step of measuring a dq axis voltage and a dq axis current of the motor;
A second step of calculating a magnetic flux value based on the normal inductance of the motor, the dq axis voltage and the dq axis current;
A third step of calculating a virtual inductance based on the magnetic flux value and the characteristic lookup table calculated in the second step;
Calculating a magnetic flux value by re-calculating the magnetic flux value by substituting the virtual inductance of the second step into the normal inductance of the second step, substituting the re-calculated flux value into the third step and reassigning the virtual inductance, Repeating the steps until the virtual inductance value converges to a specific value; And
A fifth step of determining a state of the motor based on a final magnetic flux value converged through the fourth step; And a fault diagnosis method for the motor. The method according to claim 1,
The normal inductance,
The input current in the first step, and the characteristic lookup table. The method according to claim 1,
The second step comprises:

The magnetic flux value (

),
remind

Is the dq-axis voltage,
remind

Is the dq axis current,
remind

Quot;

ego,
remind

Is the number of permanent magnet poles of the motor,
remind

And

Is the normal inductance (virtual inductance in the fourth step), and
remind

A method for diagnosing faults in a motor. The method according to claim 1,
Wherein the characteristic lookup table comprises:
And a change in the inductance of the motor according to the magnetic flux value and the input current of the motor. 5. The method of claim 4,
In the third step,
And calculating the virtual inductance by applying a linear interpolation method based on the magnetic flux value calculated in the second step and the characteristic lookup table. The method according to claim 1,
And judging that the motor is normal when the magnetic flux value calculated in the second step is equal to or higher than a normal reference value. The method according to claim 6,
If the magnetic flux value calculated in the second step is less than the normal reference value,
Wherein the controller determines that an abnormality has occurred in the motor and proceeds to the third to fifth steps. The method according to claim 1,
In the fifth step,
And determining a degree of a potato failure of the motor based on the final magnetic flux value. The method according to claim 1,
Wherein the motor is a PMSM (Permanent Magnet Synchronous Motor).

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