KR101756447B1

KR101756447B1 - Method for controlling motor of vehicle

Info

Publication number: KR101756447B1
Application number: KR1020150142868A
Authority: KR
Inventors: 황현두; 변진호; 임동휘
Original assignee: 현대오트론 주식회사
Priority date: 2015-10-13
Filing date: 2015-10-13
Publication date: 2017-07-11
Also published as: KR20170043291A

Abstract

A control device for a vehicle motor is disclosed. The control device for a vehicle motor according to an embodiment of the present invention includes a driving speed measuring unit for measuring a driving speed of a motor, a temperature measuring unit for measuring a temperature of a switching element of the motor when the driving speed of the motor is a predetermined threshold value or more, A harmonic distortion factor calculator for calculating a harmonic distortion factor (HDF) when the temperature of the motor switching element is less than or equal to a preset first threshold value, and a harmonic distortion factor calculator for calculating a modified discontinuous pulse width And outputs a first control signal for controlling the motor by a DPWM (Discrete Pulse Width Modulation) method. If the harmonic distortion factor is less than a predetermined threshold value, the motor is driven by a space vector pulse width modulation (SVPWM) And outputs the second control signal.

Description

METHOD FOR CONTROLLING MOTOR OF VEHICLE [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention [0002] The present invention relates to a control method of a vehicle motor, and more particularly, to a control method of a vehicle motor capable of selecting an optimum control method according to a driving characteristic of the motor.

The in-wheel drive system uses electric motors such as hybrid vehicles, fuel cell automobiles and electric automobiles. Instead of using a single large motor, each wheel is equipped with a small individual motor, It is a system that generates power.

In this in-wheel driving system, since each wheel is equipped with an individual motor (hereinafter referred to as an in-wheel motor), the driving system is simple compared to a vehicle having a large driving motor, Therefore, it is possible to omit a complex power device such as a differential device.

These in-wheel motors are generally controlled by a pulse width modulation (PWM) method that changes the current applied to the motor by an inverter circuit.

The pulse width modulation method includes an optimal voltage modulation method, a sinusoidal pulse width modulation (SPWM) method, a space vector pulse width modulation (SVPWM) method, a discontinuous pulse width modulation (DPWM) : discrete pulse width modulation) method.

However, in the past, one of the above-described pulse width modulation methods was selected without considering the operation characteristics of the motor to control the in-wheel motor. As a result, the in-wheel motor was overheated, Vibration and noise due to harmonics generated in the inverter are generated.

Accordingly, there is a need for a control method of a vehicle motor capable of selecting an optimum pulse width modulation method in accordance with the operation characteristics of the motor.

Korean Unexamined Patent Publication No. 2001-0133306 Japanese Patent Application Laid-Open No. 2008-0241212

SUMMARY OF THE INVENTION It is an object of the present invention to provide a control method of a vehicle motor capable of selecting an optimum control method according to the operating characteristics of the motor.

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

According to another aspect of the present invention, there is provided a method of controlling a vehicle motor, the method comprising: measuring a driving speed of the motor; and if the driving speed of the motor is equal to or greater than a predetermined threshold value, Calculating a harmonic distortion factor (HDF) if the temperature of the motor switching element is less than or equal to a predetermined first threshold value, and if the harmonic distortion factor is equal to or greater than a predetermined threshold value, And outputs a first control signal for controlling the motor by a DPWM (Discrete Pulse Width Modulation) method. If the harmonic distortion factor is less than a predetermined threshold value, a space vector pulse width modulation (SVPWM) And outputting a second control signal for controlling the motor.

According to an embodiment of the present invention, the step of measuring the driving speed of the motor may include outputting a second control signal for controlling the motor by a space vector pulse width modulation method if the driving speed of the motor is less than a predetermined threshold value .

According to an embodiment of the present invention, the step of measuring the temperature of the switching element of the motor includes the steps of: when the temperature of the switching element exceeds a predetermined first threshold value and a second threshold value higher than the first threshold value, And outputting a third control signal for controlling the motor by a pulse width modulation method.

According to an embodiment of the present invention, when the temperature of the motor switching element is lower than a predetermined first threshold value, the step of calculating the harmonic distortion factor (HDF) And calculating the harmonic distortion factor if it is maintained to be equal to or less than the first threshold value for a predetermined period of time.

According to an embodiment of the present invention, the modified discontinuous pulse width modulation scheme may generate a PWM control signal for controlling the motor by amplifying the carrier frequency by a predetermined multiple.

A control device for a vehicle motor according to another embodiment of the present invention includes a driving speed measuring unit for measuring a driving speed of a motor and a temperature measuring unit for measuring a temperature of the switching device of the motor when the driving speed of the motor is not less than a predetermined threshold A harmonic distortion factor calculator for calculating a harmonic distortion factor (HDF) when the temperature of the motor switching element is less than or equal to a preset first threshold value, and a harmonic distortion factor calculator for calculating a harmonic distortion factor And outputs a first control signal for controlling the motor by a modified discrete pulse width modulation (DPWM) method. If the harmonic distortion factor is less than a predetermined threshold value, a space vector pulse width modulation (SVPWM) And a controller for outputting a second control signal for controlling the motor by a Plume Width Modulation (PWM) method.

According to an embodiment of the present invention, the controller may output a second control signal for controlling the motor by a space vector pulse width modulation method when the driving speed of the motor is less than a preset threshold value.

According to an embodiment of the present invention, when the temperature of the switching element exceeds a predetermined first threshold value and a second threshold value higher than the first threshold value, the control unit controls the motor by a discontinuous pulse width modulation method The third control signal can be output.

According to an embodiment of the present invention, the harmonic distortion factor calculator may calculate the harmonic distortion factor when the temperature of the motor switching element is maintained to be longer than a predetermined time in a state where the temperature is lower than a predetermined first threshold value.

According to an embodiment of the present invention, the modified discontinuous pulse width modulation method may be a pulse width modulation method for generating a PWM control signal for controlling the motor by amplifying the carrier frequency by a predetermined multiple.

According to the control method of the vehicle motor according to the above-described embodiments of the present invention, it is possible to select the optimum control method according to the harmonic distortion factor, which is an index indicating the driving speed of the motor, the temperature of the switching element, Effect can be achieved.

1 is a functional block diagram illustrating a control apparatus for a vehicle motor according to an embodiment of the present invention.
2 is a flowchart illustrating a method of controlling a vehicle motor according to an embodiment of the present invention.
3 is a diagram for explaining a switching pattern of the SVPWM control scheme.
4 is a diagram for explaining the switching pattern of the DPWM control method.
FIG. 5 is a diagram comparing HDFs in each control method.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. To fully disclose the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

Unless defined otherwise, all terms (including technical and scientific terms) used herein may be used in a sense commonly understood by one of ordinary skill in the art to which this invention belongs. Also, commonly used predefined terms are not ideally or excessively interpreted unless explicitly defined otherwise.

Also, the singular forms herein may include plural forms unless specifically stated in the text. It is noted that the terms "comprises" and / or "comprising" used in the specification are intended to be inclusive in a manner similar to the components, steps, operations, and / Or additions.

1 is a functional block diagram illustrating a control apparatus for a vehicle motor according to an embodiment of the present invention.

The controller 100 of the vehicle motor according to an embodiment of the present invention includes a driving speed measuring unit 110, a temperature measuring unit 120, a harmonic distortion calculating unit 130, and a controller 140.

FIG. 1 shows only components that are related to embodiments of the present invention. Therefore, it will be understood by those skilled in the art that other general-purpose components other than the components shown in FIG. 1 may be further included.

The driving speed measuring unit 110 measures the driving speed of the motor. The motor according to an embodiment of the present invention is an in-wheel motor attached to a wheel. The driving speed measuring unit 110 is implemented by an encoder, a hall sensor, or the like, and can measure a driving speed of the motor. Also, the measured driving speed of the motor may be transmitted to the control unit 140 so that the optimal PWM control scheme may be selected.

The temperature measuring unit 120 measures the temperature of the switching element of the motor when the driving speed of the motor is not less than a predetermined threshold value. Specifically, when the driving speed of the motor is greater than or equal to a preset threshold value, the controller 140 receives the control signal, measures the temperature of the switching element of the motor, and transmits the measured result to the controller 140.

An inverter (not shown) for controlling the motor by the PWM signal includes a switching element, and a signal corresponding thereto is outputted in accordance with the on / off state of each switching element. At this time, if the number of on / off times of the switching elements increases according to the driving speed of the motor, the temperature of the switching elements also increases. The temperature measuring unit 120 measures the temperature of the switching elements. The temperature information of the switching elements measured by the temperature measuring unit 120 is transmitted to the controller 140.

The harmonic distortion calculator 130 calculates a harmonic distortion factor (HDF) when the temperature of the motor switching element is lower than a predetermined first threshold value.

Specifically, the modulation index (MI) is calculated and the harmonic distortion factor is calculated using the calculated modulation index. Generally, as the harmonic distortion ratio increases, the noise generated by the inverter increases. Therefore, the harmonic distortion factor can be calculated as an index for indirectly measuring the driving noise of the motor.

The control unit 140 outputs a first control signal for controlling the motor by a modified discontinuous pulse width modulation (DPWM) method if the harmonic distortion factor is equal to or greater than a predetermined threshold value, and the harmonic distortion factor And outputs a second control signal for controlling the motor by a space vector pulse width modulation (SVPWM) method if the threshold value is less than the set threshold value.

Since the harmonic distortion factor is greater than a predetermined threshold value, it means that the driving noise of the motor is large. Therefore, the control unit 140 generates a first control signal for controlling the motor by the modified discontinuous pulse width modulation method to reduce the driving noise of the motor Output.

Here, the modified discontinuous pulse width modulation method means a method of outputting a PWM control signal by amplifying the carrier frequency of the inverter by a predetermined multiple, unlike a general discontinuous pulse width modulation method. That is, it is possible to amplify the carrier frequency to a frequency exceeding the human audible frequency, and to enjoy the same effect as the drive noise of the inverter is reduced.

On the other hand, when the harmonic distortion factor is less than the predetermined threshold value, it means that the driving noise of the inverter is not large. Therefore, a second control signal for controlling the motor by the space vector pulse width modulation (SVPWM) Output.

As described above, when the motor control method is selected according to the harmonic distortion factor, which is an index indicating the driving speed of the motor, the temperature of the switching element, and the drive noise of the inverter, the motor can be controlled by the optimal control method according to the motor driving characteristics Can be achieved.

2 is a flowchart illustrating a method of controlling a vehicle motor according to an embodiment of the present invention.

In the present embodiment, the vehicle motor is an in-wheel motor attached to a wheel to provide power, but the present invention is not limited thereto and the same control method may be applied to other motors.

The driving speed measuring unit 110 measures the driving speed of the motor (S210). Then, the controller 140 determines whether the measured driving speed of the motor is less than a predetermined threshold value (S220). If the driving speed is less than the predetermined threshold value, the controller 140 performs a space vector pulse width modulation (SVPWM) , SVPWM) to the motor (S230).

On the other hand, when the driving speed is equal to or greater than the predetermined threshold value, a procedure for selecting the optimal control method proceeds. For example, in the case of the SVPWM control method, the switching frequency is higher than the other control methods when the carrier frequency is the same, so that the switching element may be deteriorated due to the heat generated by the switching. Accordingly, when the temperature of the switching element is high, a control method having a small number of switching times should be selected.

When the driving speed of the motor is equal to or greater than a predetermined threshold value, the temperature measuring unit 120 measures the temperature of the switching device (S240).

If it is determined that the temperature of the switching element of the motor is lower than the first threshold value, it is determined whether the temperature is lower than the first threshold value for a predetermined period of time (S260). Even if the switching element of the motor temporarily exceeds the first threshold value, if the control method is changed, the control method may be frequently changed and an unnecessary load may be generated in the controller 140.

If the temperature of the motor switching element is maintained to exceed the first threshold value for a predetermined time (S270), the harmonic distortion calculator 130 calculates the harmonic distortion factor (MI) using the modulation index (MI) (HDF: Harmonic Distortion Factor) (S280).

The more the load is applied to the motor, the larger the noise and vibration of the motor. That is, the harmonic distortion ratio increases as the noise and vibration of the motor increases.

When the harmonic distortion factor is calculated (S290), the harmonic distortion factor is calculated, and if the harmonic distortion factor is equal to or greater than a preset threshold value, a corrected discrete pulse width modulation (DPWM) The modified DPWM method is selected (S300). On the other hand, if the harmonic distortion factor is less than a predetermined threshold value because the load applied to the motor is not large, the motor is controlled by the SVPWM control method (S310).

The modified DPWM control method is a method of outputting a PWM control signal by amplifying the carrier frequency of the inverter by a predetermined multiple as described with reference to FIG. Therefore, since the carrier frequency is amplified to exceed the human audible frequency, it is possible to achieve the same effect that the driving noise of the inverter is reduced. In addition, since the number of switching times is smaller than that of the SVPWM control method, it is possible to prevent an effect that the switching element is frequently turned on / off and the switching element is deteriorated due to heat generation.

If the temperature of the switching device exceeds the first threshold value and the second threshold value in step S250 (S320), the motor is controlled according to a DPWM (Discrete Pulse Width Modulation) method ).

As described above, by selecting the control method of the motor in consideration of not only the driving speed of the motor, noise and vibration but also the temperature of the switching element, it is possible to control the motor with an optimal control method that can solve the above- can do.

Hereinafter, the process of selecting the optimal control method according to the driving characteristics of the motor will be described by comparing the SVPWM control method, the DPWM control method, and the modified DPWM control method.

3 is a diagram for explaining a switching pattern of the SVPWM control scheme.

The basic principle of the SVPWM control method is that the setpoint of the output voltage within one period of the carrier frequency is made to be the same on average by vectoring the effective vectors corresponding to the sides of the triangle.

3 shows a switching pattern of the U + switch 310, the V + switch 320, and the W + switch 330. As shown in FIG. The U-switch (not shown), the V-switch (not shown), and the W-switch (not shown) are connected to the U + switch 310 ), The V + switch 320, and the W + switch 330, the operation of the entire switch can be understood by the contents shown in FIG.

When the U + switch 310, the V + switch 320, and the W + switch 330 are in the same state, for example, both are turned on or turned off, no current is applied to the motor. In FIG. 3, a region where no current is applied to the motor is shown as a zero vector. Specifically, the current is not applied to the motor because the switch is turned off in the period from 0 to t1 (340) and after t6 (300).

On the other hand, when the switching state of one of the U + switch 310, the V + switch 320, and the W + switch 330 is different, current is supplied to the motor. In Fig. 3, this region is shown as an effective vector.

In the SVPWM control method, six switching cycles are performed within one cycle of the carrier frequency. Specifically, the U + switch 310 is changed from the turn-off state to the turn-on state at t1 340 and from the turn-on state to the turn-off state at t6 390. Similarly, it can be seen that the V + switch 320 changes its switching state at t2 350 and t5 380, and the W + switch 330 changes at t3 360 and t4 370. That is, in the case of the SVPWM control method, a total of six switching changes are made within one cycle of the carrier frequency.

4 is a diagram for explaining the switching pattern of the DPWM control method.

As described with reference to FIG. 3, the process of supplying the current to the motor according to the switching state of each switch is the same, so that a duplicate description will be omitted.

In the case of the DPWM control method, it can be seen that the switching frequency in one period of the carrier frequency is smaller than that of the SVPWM control method.

Specifically, since the U + switch 410 changes its switching state at t7 440 and t11 480 and the V + switch 420 changes its switching state at t8 450 and t10 470, It can be seen that the switching frequency is four times in one cycle.

That is, in the SVPWM control method, it is possible to efficiently arrange the zero vector section, thereby suppressing the switching noise of the current. On the other hand, since the switching frequency is higher than that of the DPWM method, the switching element may be deteriorated due to heat generation There is a problem.

In the method of controlling a vehicle motor according to an embodiment of the present invention, the temperature of the switching device is measured in step S240 of FIG. 2, and the measured temperature is compared with a first threshold value and a second threshold value higher than the first threshold value And outputs a third control signal for controlling the motor by the DPWM control method with a small number of switching times.

The difference between the DPWM control method and the modified DPWM control method will be described below.

Fig. 5 is a diagram comparing HDFs in each control method.

The general DPWM control method has an advantage that the heat generation is not high because the number of switching times in one cycle of the carrier frequency is smaller than that of the SVPWM control method. However, there is a problem that noise is larger than SVPWM.

In FIG. 5, the x-axis denotes a modulation index (MI) and the y-axis denotes a harmonic distortion factor (HDF). The modulation index on the x-axis is a measure of the load applied to the motor.

Harmonic Distortion Factor (HDF) is the degree to which the harmonic component contributes to the distortion of the waveform. The higher the harmonic component, the greater the value. If the harmonic component is within the audible frequency, noise is generated in the surroundings. Thus, the higher the HDF, the greater the noise generated in the surroundings.

Referring to FIG. 5, the HDF 530 of the DPWM control method and the HDF 520 of the SVPWM control method are shown in FIG. 5, and the HDF 530 of the DPWM control method always has a large value regardless of the load applied to the motor. .

That is, it can be seen that the DPWM control method generates more noise than the SVPWM control method.

For this purpose, the method of controlling a vehicle motor according to an embodiment of the present invention includes calculating a harmonic distortion factor in step S290 of FIG. 2, and if the calculated harmonic distortion factor is equal to or greater than a preset threshold value, And outputs a second control signal for controlling.

The modified DPWM control method means a control method in which the carrier frequency of the inverter is amplified by a predetermined multiple as described above. In this embodiment, the case where the carrier frequency in the modified DPWM control scheme is amplified 1.5 times the carrier frequency in the general DPWM control scheme is shown as an example.

It can be confirmed that the modified HDP of the DPWM control method is smaller than the HDP of the SVPWM control method based on t10 (510) in which the motor is loaded with a certain size or more. That is, noise can be reduced by reducing the switching frequency and reducing the heat generation while amplifying the carrier frequency.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the disclosed methods should be considered from an illustrative point of view, not from a restrictive point of view. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

Claims

A method of selecting a pulse width modulation scheme for controlling an in-wheel motor provided in a vehicle,
Measuring a driving speed of the in-wheel motor;
Measuring a temperature of a switching element of the in-wheel motor when the driving speed of the in-wheel motor is equal to or greater than a preset threshold value;
Calculating a modulation index, which is a measure indicating a load applied to the motor, when the temperature of the in-wheel motor switching element is lower than a predetermined first threshold value;
Calculating a harmonic distortion factor (HDF) using the modulation index; And
And outputs a first control signal for controlling the in-wheel motor by a modified discrete pulse width modulation (DPWM) method when the harmonic distortion factor is equal to or greater than a preset threshold value, And outputting a second control signal for controlling the in-wheel motor by a space vector pulse width modulation (SVPWM) method if the in-wheel motor is less than the first control signal.

The method according to claim 1,
Wherein the step of measuring the driving speed of the in-
And outputting a second control signal for controlling the in-wheel motor by a space vector pulse width modulation method if the driving speed of the in-wheel motor is less than a preset threshold value.

The method according to claim 1,
Wherein the step of measuring the temperature of the switching element of the in-
And outputting a third control signal for controlling the in-wheel motor by a discontinuous pulse width modulation method when the temperature of the switching element exceeds a predetermined first threshold value and a second threshold value higher than the first threshold value A method of controlling a vehicle motor.

The method according to claim 1,
Wherein the step of calculating a harmonic distortion factor (HDF) when the temperature of the in-wheel motor switching element is less than or equal to a predetermined first threshold value,
And calculating the harmonic distortion factor if the temperature of the in-wheel motor switching element is maintained to exceed a predetermined time with the temperature being equal to or lower than a predetermined first threshold value.

The method according to claim 1,
The modified discontinuous pulse width modulation scheme includes:
And a PWM control signal for controlling the in-wheel motor by amplifying the carrier frequency by a predetermined multiple.

A driving speed measuring unit for measuring a driving speed of the in-wheel motor;
A temperature measuring unit for measuring a temperature of a switching element of the in-wheel motor when the driving speed of the in-wheel motor is a predetermined threshold or more;
A modulation index calculating unit for calculating a modulation index which is a scale indicating a load applied to the motor when the temperature of the in-wheel motor switching element is lower than a predetermined first threshold value;
A harmonic distortion factor calculator for calculating a harmonic distortion factor (HDF) using the modulation index; And
And outputs a first control signal for controlling the in-wheel motor by a modified discrete pulse width modulation (DPWM) method when the harmonic distortion factor is equal to or greater than a preset threshold value, A second control signal for controlling the in-wheel motor by a space vector pulse width modulation (SVPWM) method.

The method according to claim 6,
Wherein,
And outputs a second control signal for controlling the in-wheel motor by a space vector pulse width modulation method when the driving speed of the in-wheel motor is less than a preset threshold value.

The method according to claim 6,
Wherein,
And a third control signal for controlling the in-wheel motor by a discontinuous pulse width modulation method when the temperature of the switching element exceeds a predetermined first threshold value and a second threshold value higher than the first threshold value Device.

The method according to claim 6,
Wherein the harmonic distortion factor calculator comprises:
Wherein the harmonic distortion factor is calculated when the temperature of the in-wheel motor switching element is maintained to be equal to or less than a predetermined first threshold value for a predetermined time.

The method according to claim 6,
The modified discontinuous pulse width modulation scheme includes:
And a PWM control signal for controlling the in-wheel motor by amplifying the carrier frequency by a predetermined multiple.