阅读说明：本技术 永磁同步电机的减速控制方法、装置和系统 (Speed reduction control method, device and system for permanent magnet synchronous motor ) 是由 程云峰 于 2019-03-19 设计创作，主要内容包括：本发明公开了一种永磁同步电机的减速控制方法、装置和系统,所述减速控制方法,包括以下步骤：获取永磁同步电机的直流母线电压；计算预设电压与直流母线电压之间的差值；确认接收到减速指令,根据差值对永磁同步电机的q轴电流进行控制。根据本发明的减速控制方法,能够实现快速减速,有效避免器件过压而损坏的现象。(The invention discloses a speed reduction control method, a speed reduction control device and a speed reduction control system of a permanent magnet synchronous motor, wherein the speed reduction control method comprises the following steps: acquiring direct-current bus voltage of the permanent magnet synchronous motor; calculating a difference value between a preset voltage and a direct current bus voltage; and confirming that the deceleration command is received, and controlling the q-axis current of the permanent magnet synchronous motor according to the difference value. According to the speed reduction control method, rapid speed reduction can be realized, and the phenomenon that the device is damaged due to overvoltage is effectively avoided.)

1. A speed reduction control method of a permanent magnet synchronous motor is characterized by comprising the following steps:

acquiring the direct-current bus voltage of the permanent magnet synchronous motor;

calculating a difference value between a preset voltage and the direct current bus voltage;

and confirming that a deceleration command is received, and controlling the q-axis current of the permanent magnet synchronous motor according to the difference value.

2. The deceleration control method of a permanent magnet synchronous motor according to claim 1, characterized by further comprising:

and confirming that the deceleration instruction is received, and controlling the d-axis current of the permanent magnet synchronous motor according to a preset current threshold value.

3. The deceleration control method of a permanent magnet synchronous motor according to claim 1, wherein the preset voltage is greater than a rated dc bus voltage of the permanent magnet synchronous motor and less than a safe dc bus voltage of the permanent magnet synchronous motor.

4. The deceleration control method of a permanent magnet synchronous motor according to claim 1, wherein said controlling the q-axis current of the permanent magnet synchronous motor according to the difference value comprises:

and controlling the q-axis current to be opposite to the rotation direction of the permanent magnet synchronous motor and less than or equal to the product of the difference value and a preset coefficient, wherein the preset coefficient is greater than 0.

5. The deceleration control method of a permanent magnet synchronous motor according to claim 2, wherein the preset current threshold is a negative value of a maximum allowable d-axis current of the permanent magnet synchronous motor, wherein the maximum allowable d-axis current is less than or equal to a demagnetization current of the permanent magnet synchronous motor.

6. A speed reduction control device of a permanent magnet synchronous motor is characterized by comprising:

the acquisition unit is used for acquiring the direct-current bus voltage of the permanent magnet synchronous motor;

the calculating unit is used for calculating the difference value between the preset voltage and the direct current bus voltage;

and the control unit is used for confirming that a deceleration instruction is received and controlling the q-axis current of the permanent magnet synchronous motor according to the difference value.

7. The deceleration control method of a permanent magnet synchronous motor according to claim 6, characterized in that the control unit is further configured to:

and confirming that the deceleration instruction is received, and controlling the d-axis current of the permanent magnet synchronous motor according to a preset current threshold value.

8. A deceleration control apparatus of a permanent magnet synchronous motor comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that the processor implements the deceleration control method of the permanent magnet synchronous motor according to any one of claims 1 to 5 when executing the program.

9. A deceleration control system of a permanent magnet synchronous motor, comprising: deceleration control apparatus of a permanent magnet synchronous machine according to any of claims 6-7.

10. A deceleration control system of a permanent magnet synchronous motor, comprising:

a permanent magnet synchronous motor;

a power supply for supplying an alternating current;

the rectifying circuit is used for rectifying the alternating current so as to output direct current to a direct current bus of the permanent magnet synchronous motor;

the IPM module is used for controlling the permanent magnet synchronous motor;

a controller for performing the deceleration control method of a permanent magnet synchronous machine according to any one of claims 1 to 5, and outputting a control command to the IPM module to control the permanent magnet synchronous machine through the IPM module.

Technical Field

The invention relates to the technical field of motors, in particular to a speed reduction control method, a speed reduction control device and a speed reduction control system for a permanent magnet synchronous motor.

Background

When the permanent magnet synchronous motor operates, acceleration and deceleration operation is a common working condition. During deceleration operation, if the purpose of rapid deceleration is to be achieved, braking torque needs to be generated through braking control. However, in the permanent magnet synchronous motor control system, the braking control means that the permanent magnet synchronous motor enters a power generation state, that is, the device is charged directly through the dc bus, and the voltage of the dc bus may rise rapidly, causing the device to be damaged by overvoltage.

Therefore, how to control the permanent magnet synchronous motor to rapidly decelerate without causing overvoltage and damage of devices becomes a problem to be solved urgently at present.

Disclosure of Invention

The present invention is directed to solving, at least to some extent, one of the technical problems in the related art.

Therefore, a first object of the present invention is to provide a deceleration control method for a permanent magnet synchronous motor, which can realize rapid deceleration and effectively avoid the phenomenon of damage caused by overvoltage of devices.

The second purpose of the invention is to provide a speed reduction control device of a permanent magnet synchronous motor.

A third object of the present invention is to provide another deceleration control apparatus for a permanent magnet synchronous motor.

The fourth purpose of the invention is to provide a speed reduction control system of a permanent magnet synchronous motor.

A fifth object of the present invention is to provide another deceleration control system of a permanent magnet synchronous motor.

In order to achieve the above object, an embodiment of a first aspect of the present invention provides a deceleration control method for a permanent magnet synchronous motor, including the following steps: acquiring the direct-current bus voltage of the permanent magnet synchronous motor; calculating a difference value between a preset voltage and the direct current bus voltage; and confirming that a deceleration command is received, and controlling the q-axis current of the permanent magnet synchronous motor according to the difference value.

According to the speed reduction control method of the permanent magnet synchronous motor, the direct current bus voltage of the permanent magnet synchronous motor is obtained, and then the difference value between the preset voltage and the direct current bus voltage is calculated, so that when the speed reduction instruction is confirmed to be received, the q-axis current of the permanent magnet synchronous motor is controlled according to the difference value. The method can realize rapid deceleration and effectively avoid the phenomenon that the device is damaged due to overvoltage.

In addition, the deceleration control method for the permanent magnet synchronous motor according to the above embodiment of the present invention may further have the following additional technical features:

according to an embodiment of the present invention, the speed reduction control method of the permanent magnet synchronous motor further includes: and confirming that the deceleration instruction is received, and controlling the d-axis current of the permanent magnet synchronous motor according to a preset current threshold value.

According to an embodiment of the present invention, the preset voltage is greater than a rated dc bus voltage of the permanent magnet synchronous motor and less than a safe dc bus voltage of the permanent magnet synchronous motor.

According to an embodiment of the present invention, the controlling the q-axis current of the permanent magnet synchronous motor according to the difference value includes: and controlling the q-axis current to be opposite to the rotation direction of the permanent magnet synchronous motor and less than or equal to the product of the difference value and a preset coefficient, wherein the preset coefficient is greater than 0.

According to an embodiment of the invention, the preset current threshold is a negative value of a maximum allowable d-axis current of the permanent magnet synchronous motor, wherein the maximum allowable d-axis current is less than or equal to a demagnetization current of the permanent magnet synchronous motor.

In order to achieve the above object, a second aspect of the present invention provides a deceleration control apparatus for a permanent magnet synchronous motor, including: the acquisition unit is used for acquiring the direct-current bus voltage of the permanent magnet synchronous motor; the calculating unit is used for calculating the difference value between the preset voltage and the direct current bus voltage; and the control unit is used for confirming that a deceleration instruction is received and controlling the q-axis current of the permanent magnet synchronous motor according to the difference value.

According to the speed reduction control device of the permanent magnet synchronous motor, the acquisition unit is used for acquiring the direct current bus voltage of the permanent magnet synchronous motor, and the calculation unit is used for calculating the difference value between the preset voltage and the direct current bus voltage, so that when the speed reduction command is confirmed to be received, the control unit controls the q-axis current of the permanent magnet synchronous motor according to the difference value. The device can realize rapid deceleration, and effectively avoids the phenomenon that the device is damaged due to overvoltage.

In addition, the deceleration control device of the permanent magnet synchronous motor according to the above embodiment of the present invention may further have the following additional technical features:

according to an embodiment of the present invention, the control unit is further configured to: and confirming that the deceleration instruction is received, and controlling the d-axis current of the permanent magnet synchronous motor according to a preset current threshold value.

In order to achieve the above object, a deceleration control device for a permanent magnet synchronous motor according to a third aspect of the present invention includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the deceleration control method for the permanent magnet synchronous motor when executing the computer program.

The speed reduction control device of the permanent magnet synchronous motor can realize rapid speed reduction and effectively avoid the phenomenon that devices are damaged due to overvoltage.

In order to achieve the above object, a fourth aspect of the present invention provides a deceleration control system for a permanent magnet synchronous motor, including the deceleration control device for a permanent magnet synchronous motor according to the third aspect of the present invention.

According to the speed reduction control system of the permanent magnet synchronous motor, the speed reduction can be rapidly realized through the speed reduction control device of the permanent magnet synchronous motor, and the phenomenon that devices are damaged due to overvoltage is effectively avoided.

In order to achieve the above object, a fifth embodiment of the present invention provides a deceleration control system for a permanent magnet synchronous motor, including: a permanent magnet synchronous motor; a power supply for supplying an alternating current; the rectifying circuit is used for rectifying the alternating current so as to output direct current to a direct current bus of the permanent magnet synchronous motor; an IPM Module (Intelligent Power Module) for controlling the permanent magnet synchronous motor; the controller is configured to execute the speed reduction control method for the permanent magnet synchronous motor according to the embodiment of the first aspect, and output a control command to the IPM module to control the permanent magnet synchronous motor through the IPM module.

According to the speed reduction control system of the permanent magnet synchronous motor, alternating current is provided through the power supply, the alternating current is rectified through the arrangement module to output direct current to the direct current bus of the permanent magnet synchronous motor, the direct current bus provides direct current for the IPM module, the controller executes the speed reduction control method of the permanent magnet synchronous motor and outputs a control instruction to the IPM module to control the permanent magnet synchronous motor through the IPM module, so that rapid speed reduction can be achieved, and the phenomenon that devices are damaged due to overvoltage is effectively avoided.

Drawings

Fig. 1 is a flowchart of a deceleration control method of a permanent magnet synchronous motor according to an embodiment of the present invention;

fig. 2 is a block schematic diagram of a deceleration control apparatus of a permanent magnet synchronous motor according to an embodiment of the present invention; and

fig. 3 is a schematic diagram of a deceleration control system of a permanent magnet synchronous motor according to an embodiment of the present invention.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.

The following describes a deceleration control method, apparatus, and system of a permanent magnet synchronous motor according to an embodiment of the present invention with reference to the drawings.

Fig. 1 is a flowchart of a deceleration control method of a permanent magnet synchronous motor according to an embodiment of the present invention. As shown in fig. 1, the speed reduction control method for a permanent magnet synchronous motor according to an embodiment of the present invention includes the following steps:

and S1, acquiring the direct current bus voltage of the permanent magnet synchronous motor.

And S2, calculating the difference between the preset voltage and the direct current bus voltage.

According to an embodiment of the invention, the predetermined voltage U_refRated direct current bus voltage U larger than permanent magnet synchronous motor_{Rated value}And is less than the safe DC bus voltage U of the permanent magnet synchronous motor_SecurityI.e. U_{Rated value}＜U_ref＜U_Security. Wherein, the rated DC bus voltage U_{Rated value}And the safe DC bus voltage U of the permanent magnet synchronous motor_SecurityAll can be made of permanent magnetThe performance of the stepper motor.

And S3, confirming that the speed reduction command is received, and controlling the q-axis current of the permanent magnet synchronous motor according to the difference value.

According to one embodiment of the present invention, controlling q-axis current of a permanent magnet synchronous motor according to a difference value includes: and controlling the q-axis current to be opposite to the rotation direction of the permanent magnet synchronous motor and less than or equal to the product of the difference and a preset coefficient, namely k & ltDELTA & gt, wherein the preset coefficient k is more than 0.

It is understood that when the q-axis current is the same as the rotation direction of the permanent magnet synchronous motor, a driving torque is generated; when the q-axis current is opposite to the rotation direction of the permanent magnet synchronous motor, a braking torque is generated.

Specifically, in the working process of the permanent magnet synchronous motor, the direct current bus voltage U of the permanent magnet synchronous motor is obtained in real time_dcAnd calculating a preset voltage U_ref(U_{Rated value}＜U_ref＜U_Security) And DC bus voltage U_dcThe difference between △ U, i.e., △ U ═ U_ref-U_dcWhether a deceleration instruction is received or not is judged in real time, and when the deceleration instruction is confirmed to be received, the q-axis current is controlled to be opposite to the rotation direction of the permanent magnet synchronous motor (namely, braking torque is generated) and not to exceed k × △ U, so that rapid deceleration is realized, the voltage formed on a direct current bus in the deceleration process is lower than the voltage of a safe direct current bus, and the situation that the counter electromotive force generated by the permanent magnet synchronous motor forms higher voltage on the direct current bus due to braking power generation of the permanent magnet synchronous motor, and the device is damaged is avoided.

Further, according to an embodiment of the present invention, the deceleration control method of the permanent magnet synchronous motor further includes: and confirming that the deceleration instruction is received, and controlling the d-axis current of the permanent magnet synchronous motor according to a preset current threshold value.

According to an embodiment of the invention, the current threshold I is preset_{Preset of}Negative value-I of maximum allowable d-axis current of permanent magnet synchronous motor_dmaxWherein the maximum allowable d-axis current I_dmaxLess than or equal to the demagnetization current I of the permanent magnet synchronous motor_{Demagnetization}Should ever be good atDemagnetization current I of a synchronous magnet machine_{Demagnetization}May be determined by the performance of the permanent magnet synchronous machine.

Specifically, in the working process of the permanent magnet synchronous motor, the direct current bus voltage U of the permanent magnet synchronous motor is obtained in real time_dcAnd calculating a preset voltage U_ref(U_{Rated value}＜U_ref＜U_Security) And DC bus voltage U_dcThe difference between △ U, i.e., △ U ═ U_ref-U_dcJudging whether a deceleration instruction is received or not in real time, controlling the q-axis current to be opposite to the rotation direction of the permanent magnet synchronous motor (namely, generating braking torque) when the deceleration instruction is confirmed to be received, and controlling the d-axis current of the permanent magnet synchronous motor to be a negative value-I of the maximum allowable d-axis current of the permanent magnet synchronous motor at the same time, wherein k is not more than △ U_dmax(the maximum allowable d-axis current I_dmaxNo more than the demagnetization current I of the permanent magnet synchronous motor_{Demagnetization}) Therefore, the speed is quickly reduced, the voltage formed on the direct current bus in the speed reduction process is lower than the voltage of the safe direct current bus, and the situation that the counter electromotive force generated by the permanent magnet synchronous motor forms higher voltage on the direct current bus due to braking power generation of the permanent magnet synchronous motor, so that the device is damaged is avoided.

In summary, according to the speed reduction control method of the permanent magnet synchronous motor in the embodiment of the present invention, the dc bus voltage of the permanent magnet synchronous motor is obtained, and then the difference between the preset voltage and the dc bus voltage is calculated, so that when it is determined that the speed reduction command is received, the q-axis current of the permanent magnet synchronous motor is controlled according to the difference. The method can realize rapid deceleration and effectively avoid the phenomenon that the device is damaged due to overvoltage.

Based on the above embodiment, the present invention further provides a deceleration control apparatus for a permanent magnet synchronous motor, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the deceleration control method for the permanent magnet synchronous motor is implemented.

The speed reduction control device of the permanent magnet synchronous motor can realize rapid speed reduction and effectively avoid the phenomenon that devices are damaged due to overvoltage.

Fig. 2 is a block schematic diagram of a deceleration control apparatus of a permanent magnet synchronous motor according to an embodiment of the present invention. As shown in fig. 2, a speed reduction control apparatus 200 of a permanent magnet synchronous motor according to an embodiment of the present invention includes: an acquisition unit 210, a calculation unit 220 and a control unit 230.

The obtaining unit 210 is configured to obtain a dc bus voltage of the permanent magnet synchronous motor, the calculating unit 220 is configured to calculate a difference between a preset voltage and the dc bus voltage, and the control unit 230 is configured to confirm that a deceleration instruction is received, and control a q-axis current of the permanent magnet synchronous motor according to the difference.

According to an embodiment of the invention, the predetermined voltage U_refRated direct current bus voltage U larger than permanent magnet synchronous motor_{Rated value}And is less than the safe DC bus voltage U of the permanent magnet synchronous motor_SecurityI.e. U_{Rated value}＜U_ref＜U_Security. Wherein, the rated DC bus voltage U_{Rated value}And the safe DC bus voltage U of the permanent magnet synchronous motor_SecurityAll can be determined by the performance of the permanent magnet synchronous motor.

According to an embodiment of the present invention, the control unit 230 is specifically configured to: and controlling the q-axis current to be opposite to the rotation direction of the permanent magnet synchronous motor and less than or equal to the product of the difference and a preset coefficient, namely k & ltDELTA & gt, wherein the preset coefficient k is more than 0.

It is understood that when the q-axis current is the same as the rotation direction of the permanent magnet synchronous motor, a driving torque is generated; when the q-axis current is opposite to the rotation direction of the permanent magnet synchronous motor, a braking torque is generated.

Specifically, during the operation of the permanent magnet synchronous motor, the direct current bus voltage U of the permanent magnet synchronous motor is obtained in real time through the obtaining unit 210_dcAnd calculates the preset voltage U in real time by the calculating unit 220_ref(U_{Rated value}＜U_ref＜U_Security) And DC bus voltage U_dcThe difference between △ U, i.e., △ U ═ U_ref-U_dcThe control unit 230 determines whether a deceleration command is received in real time, and controls the q-axis current to be the same as the permanent magnet when it is determined that the deceleration command is receivedThe rotation directions of the step motors are opposite (namely, braking torque is generated), and the rotation directions are not more than k × △ U, so that rapid speed reduction is realized, the voltage formed on the direct current bus in the speed reduction process is lower than the voltage of the safe direct current bus, and the situation that the counter electromotive force generated by the permanent magnet synchronous motor forms higher voltage on the direct current bus due to braking power generation of the permanent magnet synchronous motor, and the device is damaged is avoided.

Further, the control unit 230 is further configured to: and confirming that the deceleration instruction is received, and controlling the d-axis current of the permanent magnet synchronous motor according to a preset current threshold value.

According to an embodiment of the invention, the current threshold I is preset_{Preset of}Negative value-I of maximum allowable d-axis current of permanent magnet synchronous motor_dmaxWherein the maximum allowable d-axis current I_dmaxLess than or equal to the demagnetization current I of the permanent magnet synchronous motor_{Demagnetization}Demagnetization current I of the permanent magnet synchronous motor_{Demagnetization}May be determined by the performance of the permanent magnet synchronous machine.

Specifically, during the operation of the permanent magnet synchronous motor, the direct current bus voltage U of the permanent magnet synchronous motor is obtained in real time through the obtaining unit 210_dcAnd calculates the preset voltage U in real time by the calculating unit 220_ref(U_{Rated value}＜U_ref＜U_Security) And DC bus voltage U_dcThe difference between △ U, i.e., △ U ═ U_ref-U_dcThe control unit 230 determines whether a deceleration command is received in real time, and controls the q-axis current to be opposite to the rotation direction of the permanent magnet synchronous motor (i.e., to generate a braking torque) and not to exceed k × △ U when it is determined that the deceleration command is received, and controls the d-axis current of the permanent magnet synchronous motor to be a negative value-I of the maximum allowable d-axis current of the permanent magnet synchronous motor_dmax(the maximum allowable d-axis current I_dmaxNo more than the demagnetization current I of the permanent magnet synchronous motor_{Demagnetization}) Therefore, the speed is quickly reduced, the voltage formed on the direct current bus in the speed reduction process is lower than the voltage of the safe direct current bus, and the situation that the counter electromotive force generated by the permanent magnet synchronous motor forms higher voltage on the direct current bus due to braking power generation of the permanent magnet synchronous motor, so that the device is damaged is avoided.

According to the speed reduction control device of the permanent magnet synchronous motor, the acquisition unit is used for acquiring the direct current bus voltage of the permanent magnet synchronous motor, and the calculation unit is used for calculating the difference value between the preset voltage and the direct current bus voltage, so that when the speed reduction command is confirmed to be received, the control unit controls the q-axis current of the permanent magnet synchronous motor according to the difference value. The device can realize rapid deceleration, and effectively avoids the phenomenon that the device is damaged due to overvoltage.

Based on the above embodiment, the present invention further provides a speed reduction control system for a permanent magnet synchronous motor, including: the speed reduction control device of the permanent magnet synchronous motor.

According to the speed reduction control system of the permanent magnet synchronous motor, the speed reduction can be rapidly realized through the speed reduction control device of the permanent magnet synchronous motor, and the phenomenon that devices are damaged due to overvoltage is effectively avoided.

Fig. 3 is a schematic diagram of a deceleration control system of a permanent magnet synchronous motor according to an embodiment of the present invention. As shown in fig. 3, a deceleration control system of a permanent magnet synchronous motor according to an embodiment of the present invention includes: the permanent magnet synchronous motor 310, the power supply 320, the rectification circuit 330, the IPM module 340 and the controller 350.

The power source 320 is configured to provide ac power, the rectifier circuit 330 is configured to rectify the ac power to output dc power to a dc bus of the permanent magnet synchronous motor 310, the IPM module 340 is configured to control the permanent magnet synchronous motor 310, and the controller 350 is configured to execute the above-mentioned speed reduction control method for the permanent magnet synchronous motor and output a control instruction to the IPM module 340 to control the permanent magnet synchronous motor 310 through the IPM module 340.

According to the speed reduction control system of the permanent magnet synchronous motor, alternating current is provided through the power supply, the alternating current is rectified through the arrangement module to output direct current to the direct current bus of the permanent magnet synchronous motor, the direct current bus provides direct current for the IPM module, the controller executes the speed reduction control method of the permanent magnet synchronous motor and outputs a control instruction to the IPM module to control the permanent magnet synchronous motor through the IPM module, so that rapid speed reduction can be achieved, and the phenomenon that devices are damaged due to overvoltage is effectively avoided.

In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting of the invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.