Locked rotor detection method, locked rotor detection device and control system of permanent magnet synchronous motor
阅读说明：本技术 永磁同步电机的堵转检测方法、堵转检测装置和控制系统 (Locked rotor detection method, locked rotor detection device and control system of permanent magnet synchronous motor ) 是由 程云峰 于 2018-08-31 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堵转检测方法、堵转检测装置和控制系统,所述堵转检测方法包括以下步骤：获取永磁同步电机的相电压和相电流；根据相电压和相电流,判断永磁同步电机是否发生堵转。本发明实施例的堵转检测方法,弥补了相关技术的不足,且可以实现转矩电流控制模式或者速度控制模式下的堵转检测,实用性强,并且安全可靠性高。(The invention discloses a locked rotor detection method, a locked rotor detection device and a control system of a permanent magnet synchronous motor, wherein the locked rotor detection method comprises the following steps: acquiring phase voltage and phase current of the permanent magnet synchronous motor; and judging whether the permanent magnet synchronous motor is locked according to the phase voltage and the phase current. The locked rotor detection method disclosed by the embodiment of the invention makes up the defects of the related technology, can realize locked rotor detection in a torque current control mode or a speed control mode, and has strong practicability and high safety and reliability.)
1. A locked rotor detection method of a permanent magnet synchronous motor is characterized by comprising the following steps:
obtaining phase voltage and phase current of the permanent magnet synchronous motor;
and judging whether the PMSM is locked-rotor or not according to the phase voltage and the phase current.
2. The locked rotor detection method according to claim 1, wherein the determining whether the PMSM is locked rotor according to the phase voltage and the phase current comprises:
calculating to obtain a back electromotive force according to the phase voltage and the phase current;
calculating to obtain a phase current amplitude according to the phase current;
and judging whether the permanent magnet synchronous motor is locked according to the counter potential and the phase current amplitude.
3. The locked rotor detection method according to claim 2, wherein the determining whether the PMSM is locked rotor according to the back electromotive force and the phase current amplitude comprises:
and if the back electromotive force is continuously smaller than a preset back electromotive force threshold value within a preset time and the phase current amplitude value is continuously larger than a preset amplitude value threshold value, judging that the permanent magnet synchronous motor is locked.
4. The locked rotor detection method according to claim 3, wherein if the back electromotive force is continuously smaller than a preset back electromotive force threshold value and the phase current amplitude value is continuously larger than a preset amplitude threshold value within a preset time, determining that the locked rotor of the permanent magnet synchronous motor occurs comprises:
when the counter electromotive force is smaller than the counter electromotive force threshold value and the phase current amplitude is larger than the amplitude threshold value, timing is started, and timing data are generated;
if the counter electromotive force is equal to or larger than the counter electromotive force threshold value, or the phase current amplitude is equal to or smaller than the amplitude threshold value, clearing the timing data;
and when the timing data is equal to the preset time, judging that the permanent magnet synchronous motor is locked.
5. The utility model provides a locked rotor detection device of PMSM which characterized in that includes:
the acquisition module is used for acquiring phase voltage and phase current of the permanent magnet synchronous motor;
and the judging module is used for judging whether the permanent magnet synchronous motor is locked according to the phase voltage and the phase current.
6. The locked-rotor detection device according to claim 5, wherein the determination module comprises:
the first calculating unit is used for calculating and obtaining a back electromotive force according to the phase voltage and the phase current;
the second calculation unit is used for calculating phase current amplitude according to the phase current;
and the judging unit is used for judging whether the permanent magnet synchronous motor is locked according to the counter potential and the phase current amplitude.
7. The locked rotor detection device according to claim 6, wherein the determination unit is configured to:
and if the back electromotive force is continuously smaller than a preset back electromotive force threshold value within a preset time and the phase current amplitude value is continuously larger than a preset amplitude value threshold value, judging that the permanent magnet synchronous motor is locked.
8. The locked-rotor detection device according to claim 7, wherein the determination unit is specifically configured to:
when the counter electromotive force is smaller than the counter electromotive force threshold value and the phase current amplitude is larger than the amplitude threshold value, timing is started, and timing data are generated;
if the counter electromotive force is equal to or larger than the counter electromotive force threshold value, or the phase current amplitude is equal to or smaller than the amplitude threshold value, clearing the timing data;
and when the timing data is equal to the preset time, judging that the permanent magnet synchronous motor is locked.
9. A control system of a permanent magnet synchronous motor, comprising: a locked rotor detection device for a permanent magnet synchronous machine and a permanent magnet synchronous machine according to any one of claims 5 to 8;
and after the locked rotor detection device judges that the permanent magnet synchronous motor is locked, the permanent magnet synchronous motor is controlled to stop.
10. An electronic device, comprising: memory, processor and computer program stored on the memory and executable on the processor, which when executed by the processor implements the method of stall detection for a permanent magnet synchronous machine according to any of claims 1-4.
11. A non-transitory computer-readable storage medium, on which a computer program is stored, which, when executed by a processor, implements a method of detecting stalling of a permanent magnet synchronous motor according to any one of claims 1-4.
Technical Field
The invention relates to the technical field of permanent magnet synchronous motors, in particular to a locked rotor detection method of a permanent magnet synchronous motor, a locked rotor detection device of the permanent magnet synchronous motor, a control system of the permanent magnet synchronous motor, an electronic device and a non-transitory computer readable storage medium.
Background
When the rotating speed of the motor is zero, the motor still outputs torque, namely, locked rotor occurs. The motor stalling is caused by a plurality of reasons, including mechanical or artificial reasons, for example, the rotor is stuck in contact with the stator, a driven device is stuck, the motor cannot be driven due to too large load of the device, and the like.
Disclosure of Invention
The present invention is directed to solving, at least to some extent, one of the technical problems in the art described above.
Therefore, a first objective of the present invention is to provide a stalling detection method for a permanent magnet synchronous motor, which overcomes the disadvantages of the related art, can implement stalling detection in a torque current control mode or a speed control mode, and has strong practicability and high safety and reliability.
The second purpose of the invention is to provide a locked rotor detection device of a permanent magnet synchronous motor.
A third object of the present invention is to provide a control system of a permanent magnet synchronous motor.
A fourth object of the invention is to propose an electronic device.
A fifth object of the invention is to propose a non-transitory computer-readable storage medium.
In order to achieve the above object, an embodiment of a first aspect of the present invention provides a locked rotor detection method for a permanent magnet synchronous motor, including the following steps: obtaining phase voltage and phase current of the permanent magnet synchronous motor; and judging whether the PMSM is locked-rotor or not according to the phase voltage and the phase current.
According to the locked rotor detection method of the permanent magnet synchronous motor, the phase voltage and the phase current of the permanent magnet synchronous motor are firstly obtained, and then whether locked rotor occurs in the permanent magnet synchronous motor is judged according to the phase voltage and the phase current. Therefore, the locked rotor detection method makes up the defects of the related technology, can realize locked rotor detection in a torque current control mode or a speed control mode, and has strong practicability and high safety and reliability.
In addition, the locked rotor detection method for the permanent magnet synchronous motor provided by the above embodiment of the present invention may further have the following additional technical features:
in an embodiment of the present invention, the determining whether the pm synchronous motor is locked according to the phase voltage and the phase current includes: calculating to obtain a back electromotive force according to the phase voltage and the phase current; calculating to obtain a phase current amplitude according to the phase current; and judging whether the permanent magnet synchronous motor is locked according to the counter potential and the phase current amplitude.
In an embodiment of the present invention, the determining whether the pm synchronous motor is locked according to the back electromotive force and the phase current amplitude includes: and if the back electromotive force is continuously smaller than a preset back electromotive force threshold value within a preset time and the phase current amplitude value is continuously larger than a preset amplitude value threshold value, judging that the permanent magnet synchronous motor is locked.
In an embodiment of the present invention, if the back electromotive force is continuously smaller than a preset back electromotive force threshold value and the phase current amplitude is continuously larger than a preset amplitude threshold value within a preset time, determining that the rotation blockage of the permanent magnet synchronous motor occurs includes: when the counter electromotive force is smaller than the counter electromotive force threshold value and the phase current amplitude is larger than the amplitude threshold value, timing is started, and timing data are generated; if the counter electromotive force is equal to or larger than the counter electromotive force threshold value, or the phase current amplitude is equal to or smaller than the amplitude threshold value, clearing the timing data; and when the timing data is equal to the preset time, judging that the permanent magnet synchronous motor is locked.
In order to achieve the above object, a second embodiment of the present invention provides a stalling detection device for a permanent magnet synchronous motor, including: the acquisition module is used for acquiring phase voltage and phase current of the permanent magnet synchronous motor; and the judging module is used for judging whether the permanent magnet synchronous motor is locked according to the phase voltage and the phase current.
According to the device for detecting the locked rotor of the permanent magnet synchronous motor, the phase voltage and the phase current of the permanent magnet synchronous motor are obtained through the obtaining module, so that the judging module judges whether the locked rotor of the permanent magnet synchronous motor occurs or not according to the phase voltage and the phase current. Therefore, the locked rotor detection device makes up the defects of the related technology, can realize locked rotor detection in a torque current control mode or a speed control mode, and is high in practicability, safety and reliability.
In addition, the stalling detection device of the permanent magnet synchronous motor provided by the embodiment of the invention can also have the following additional technical characteristics:
in an embodiment of the present invention, the determining module includes: the first calculating unit is used for calculating and obtaining a back electromotive force according to the phase voltage and the phase current; the second calculation unit is used for calculating phase current amplitude according to the phase current; and the judging unit is used for judging whether the permanent magnet synchronous motor is locked according to the counter potential and the phase current amplitude.
In an embodiment of the present invention, the determining unit is configured to: and if the back electromotive force is continuously smaller than a preset back electromotive force threshold value within a preset time and the phase current amplitude value is continuously larger than a preset amplitude value threshold value, judging that the permanent magnet synchronous motor is locked.
In an embodiment of the present invention, the determining unit is specifically configured to: when the counter electromotive force is smaller than the counter electromotive force threshold value and the phase current amplitude is larger than the amplitude threshold value, timing is started, and timing data are generated; if the counter electromotive force is equal to or larger than the counter electromotive force threshold value, or the phase current amplitude is equal to or smaller than the amplitude threshold value, clearing the timing data; and when the timing data is equal to the preset time, judging that the permanent magnet synchronous motor is locked.
In order to achieve the above object, a third embodiment of the present invention provides a control system for a permanent magnet synchronous motor, including: a permanent magnet synchronous motor and a locked rotor detection device of the permanent magnet synchronous motor according to the embodiment of the second aspect of the invention; and after the locked rotor detection device judges that the permanent magnet synchronous motor is locked, the permanent magnet synchronous motor is controlled to stop.
According to the control system of the permanent magnet synchronous motor, the defect of the related technology is overcome through the locked rotor detection device of the permanent magnet synchronous motor, locked rotor detection in a torque current control mode or a speed control mode can be achieved, and the control system is high in practicability and safety and reliability.
To achieve the above object, a fourth aspect of the present invention provides an electronic device, including: the invention further provides a device for detecting stalling of a permanent magnet synchronous motor, which comprises a memory, a processor and a computer program stored on the memory and capable of running on the processor, wherein when the processor executes the program, the method for detecting stalling of a permanent magnet synchronous motor is realized.
According to the electronic equipment provided by the embodiment of the invention, the processor executes the computer program stored on the memory, so that the defects of the related technology are overcome, the locked rotor detection in a torque current control mode or a speed control mode can be realized, the practicability is high, and the safety and the reliability are high.
To achieve the above object, a fifth embodiment of the present invention provides a non-transitory computer-readable storage medium, on which a computer program is stored, where the computer program, when executed by a processor, implements the locked rotor detection method for a permanent magnet synchronous motor according to the first embodiment of the present invention.
The non-transitory computer-readable storage medium according to the embodiment of the present invention, by executing the stored computer program, makes up for the deficiencies of the related art, and can implement locked rotor detection in the torque current control mode or the speed control mode, and has high practicability, safety and reliability.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The foregoing and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
fig. 1 is a flowchart of a locked rotor detection method of a permanent magnet synchronous motor according to an embodiment of the present invention;
fig. 2 is a flowchart of a locked rotor detection method of a permanent magnet synchronous motor according to another embodiment of the present invention;
fig. 3 is a block schematic diagram of a stalling detection device of a permanent magnet synchronous machine according to an embodiment of the invention;
fig. 4 is a block schematic diagram of a stalling detection device of a permanent magnet synchronous machine according to another embodiment of the invention; and
fig. 5 is a block schematic diagram of a control system of a permanent magnet synchronous machine according to one embodiment of the 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.
A locked rotor detection method of a permanent magnet synchronous motor, a locked rotor detection device of a permanent magnet synchronous motor, a control system of a permanent magnet synchronous motor, an electronic apparatus, and a non-transitory computer-readable storage medium according to embodiments of the present invention are described below with reference to the accompanying drawings.
Fig. 1 is a flowchart of a locked rotor detection method of a permanent magnet synchronous motor according to an embodiment of the present invention. In an embodiment of the present invention, the permanent magnet synchronous motor may be an alternating current motor.
As shown in fig. 1, the locked rotor detection method of the permanent magnet synchronous motor according to the embodiment of the present invention includes the following steps:
and S1, obtaining phase voltage and phase current of the permanent magnet synchronous motor. The phase voltage of the permanent magnet synchronous motor can be acquired in real time through the voltage sensor, and the phase current of the permanent magnet synchronous motor can be acquired in real time through the current sensor.
Further, in the embodiment of the present invention, the phase voltage u of the motor in the αβ stationary coordinate system can be obtainedα、uβSum phase current iα、iβTo facilitate subsequent computing operations.
And S2, judging whether the PMSM is locked rotor or not according to the phase voltage and the phase current.
In an embodiment of the present invention, as shown in fig. 2, the determining whether the pm synchronous motor is locked according to the phase voltage and the phase current may include the following steps:
and S21, calculating to obtain the counter electromotive force according to the phase voltage and the phase current.
In the embodiment of the invention, the back electromotive force of the permanent magnet synchronous motor can be calculated according to the phase current, the phase voltage and the stator resistance of the permanent magnet synchronous motor.
Specifically, the back electromotive force of the permanent magnet synchronous motor can be calculated by the following formula (1):
wherein e may be the back electromotive force of the PMSM, uαAnd uβMay be the phase voltage i of the permanent magnet synchronous motor on αβ static coordinate systemαAnd iβPhase current in αβ stationary coordinate system, R, for a permanent magnet synchronous machinesMay be the resistance of the stator resistor of the permanent magnet synchronous motor.
And S22, calculating to obtain the phase current amplitude according to the phase current.
Specifically, the phase current amplitude of the permanent magnet synchronous motor can be calculated by the following formula (2):
wherein, I can be phase current amplitude of the permanent magnet synchronous motor, IαAnd iβWhich may be the phase current of the permanent magnet synchronous machine at αβ stationary frame.
And S23, judging whether the permanent magnet synchronous motor is locked according to the counter potential and the phase current amplitude.
Considering the influence of the use environment and other factors, in an embodiment of the present invention, determining whether the pm synchronous motor is locked up according to the back electromotive force and the phase current amplitude may include determining that the pm synchronous motor is locked up if the back electromotive force is continuously smaller than a preset back electromotive force threshold and the phase current amplitude is continuously larger than a preset amplitude threshold within a preset time. The preset time, the preset back electromotive force threshold value and the preset amplitude threshold value can be calibrated according to actual conditions.
That is to say, whether the permanent magnet synchronous motor is locked or not is judged, and the judgment cannot be carried out according to the instantaneous detection result, that is, the motor locked or not cannot be judged according to the condition that the counter electromotive force or the phase current amplitude at a certain moment is larger than the corresponding set threshold value.
Specifically, if the back electromotive force is continuously smaller than the preset back electromotive force threshold value within the preset time, and the phase current amplitude value is continuously larger than the preset amplitude threshold value, determining that the rotation blockage of the permanent magnet synchronous motor occurs may include: and when the counter electromotive force is smaller than the counter electromotive force threshold value and the phase current amplitude is larger than the amplitude threshold value, timing is started, timing data is generated, if the counter electromotive force is equal to or larger than the counter electromotive force threshold value or the phase current amplitude is equal to or smaller than the amplitude threshold value, the timing data is cleared, and when the timing data is equal to preset time, the permanent magnet synchronous motor is judged to be locked.
That is to say, after acquiring the counter electromotive force and the phase current amplitude, the permanent magnet synchronous motor may determine whether the counter electromotive force is smaller than a counter electromotive force threshold, and whether the phase current amplitude is larger than an amplitude threshold, and if it is determined that the counter electromotive force is smaller than the counter electromotive force threshold and the phase current amplitude is larger than the amplitude threshold, start timing, and generate corresponding timing data, where the timing data includes timing time. Then, the permanent magnet synchronous motor can compare the back electromotive force and the phase current amplitude obtained in real time with the preset back electromotive force threshold value and the preset amplitude threshold value respectively within the period from the timing time to the preset time, if the back electromotive force obtained in real time is smaller than the back electromotive force threshold value and the phase current amplitude obtained in real time is larger than the amplitude threshold value within the period from the timing time to the preset time, the permanent magnet synchronous motor can be judged to be locked, otherwise, the timing data can be cleared, and the step of obtaining the phase voltage and the phase current of the permanent magnet synchronous motor can be returned.
It should be noted that, in this embodiment, after the permanent magnet synchronous motor acquires the counter electromotive force and the phase current amplitude, it may be determined whether the counter electromotive force is smaller than a counter electromotive force threshold, and the phase current amplitude is larger than an amplitude threshold, if it is determined that the counter electromotive force is smaller than the counter electromotive force threshold, and the phase current amplitude is larger than the amplitude threshold, timing is started, and corresponding timing data is generated, otherwise, the step of acquiring the phase voltage and the phase current of the permanent magnet synchronous motor may be returned.
In the embodiment of the invention, after the permanent magnet synchronous motor is judged to be locked, the permanent magnet synchronous motor can be controlled to stop so as to prevent the permanent magnet synchronous motor from being damaged.
In summary, according to the method for detecting locked rotor of a permanent magnet synchronous motor in the embodiment of the present invention, the phase voltage and the phase current of the permanent magnet synchronous motor are first obtained, and then whether locked rotor occurs in the permanent magnet synchronous motor is determined according to the phase voltage and the phase current. Therefore, the locked rotor detection method makes up the defects of the related technology, can realize locked rotor detection in a torque current control mode or a speed control mode, and has strong practicability and high safety and reliability.
Fig. 3 is a block schematic diagram of a stalling detection device of a permanent magnet synchronous machine according to one embodiment of the invention.
As shown in fig. 3, the stalling
The obtaining module 100 is configured to obtain a phase voltage and a phase current of the permanent magnet synchronous motor.
The judging module 200 is configured to judge whether the PMSM has locked rotor according to the phase voltage and the phase current.
In one embodiment of the present invention, as shown in fig. 4, the determining module 200 may include a first calculating unit 210, a second calculating unit 220, and a determining unit 230.
The first calculating unit 210 is configured to calculate a back electromotive force according to the phase voltage and the phase current, the second calculating unit 220 is configured to calculate a phase current amplitude according to the phase current, and the determining unit 230 is configured to determine whether the permanent magnet synchronous motor is locked according to the back electromotive force and the phase current amplitude.
In an embodiment of the present invention, the determining unit 230 is configured to determine that the pm synchronous motor is locked if the back electromotive force is continuously smaller than the preset back electromotive force threshold and the phase current amplitude is continuously larger than the preset amplitude threshold within the preset time.
In an embodiment of the present invention, the determining unit 230 is specifically configured to start timing and generate timing data when the counter potential is smaller than the counter potential threshold and the phase current amplitude is greater than the amplitude threshold; if the counter potential is equal to or greater than the counter potential threshold value or the phase current amplitude is equal to or less than the amplitude threshold value, clearing the timing data; and when the timing data is equal to the preset time, judging that the permanent magnet synchronous motor is locked.
It should be noted that details not disclosed in the device for detecting a locked rotor of a permanent magnet synchronous motor according to the embodiment of the present invention refer to details disclosed in the method for detecting a locked rotor of a permanent magnet synchronous motor according to the embodiment of the present invention, and are not described herein again in detail.
To sum up, the device for detecting a locked rotor of a permanent magnet synchronous motor according to the embodiment of the present invention obtains the phase voltage and the phase current of the permanent magnet synchronous motor through the obtaining module, so that the determining module determines whether the locked rotor of the permanent magnet synchronous motor occurs according to the phase voltage and the phase current. Therefore, the locked rotor detection device makes up the defects of the related technology, can realize locked rotor detection in a torque current control mode or a speed control mode, and is high in practicability, safety and reliability.
Fig. 5 is a block schematic diagram of a control system of a permanent magnet synchronous machine according to one embodiment of the invention.
As shown in fig. 5, the
After the locked
It should be noted that details not disclosed in the control system of the permanent magnet synchronous motor according to the embodiment of the present invention refer to details disclosed in the stalling detection method of the permanent magnet synchronous motor according to the embodiment of the present invention, and details are not repeated herein.
In summary, the control system of the permanent magnet synchronous motor according to the embodiment of the present invention makes up for the deficiencies of the related art by the above-mentioned stalling detection device of the permanent magnet synchronous motor, and can realize stalling detection in the torque current control mode or the speed control mode, and has strong practicability and high safety and reliability.
In order to implement the foregoing embodiments, the present invention further provides an electronic device, which includes a memory, a processor, and a computer program stored in the memory and running on the processor, and when the processor executes the computer program, the method for detecting a locked rotor of a permanent magnet synchronous motor according to the foregoing embodiments is implemented.
According to the electronic equipment provided by the embodiment of the invention, the processor executes the computer program stored on the memory, so that the defects of the related technology are overcome, the locked rotor detection in a torque current control mode or a speed control mode can be realized, the practicability is high, and the safety and the reliability are high.
In order to implement the above embodiments, the present invention also proposes a non-transitory computer-readable storage medium on which a computer program is stored, which, when executed by a processor, implements the stalling detection method of the permanent magnet synchronous motor of the foregoing embodiments.
The non-transitory computer-readable storage medium according to the embodiment of the present invention, by executing the stored computer program, makes up for the deficiencies of the related art, and can implement locked rotor detection in the torque current control mode or the speed control mode, and has high practicability, safety and reliability.
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 device or element must have a particular orientation, be constructed and operated in a particular orientation, and are 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 one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined 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; either directly or indirectly through intervening media, either internally or in any other relationship. 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.