阅读说明：本技术 针对无人机探测定位的北斗相参系统及设备 (Beidou coherent system and equipment for unmanned aerial vehicle detection and positioning ) 是由 李超 罗翔 孟令为 叶露 姚伟华 罗鹏 姜水 于 2021-08-31 设计创作，主要内容包括：本发明提供了一种针对无人机探测定位的北斗相参系统及设备,包括：卫星接收模块,用于解调和解析北斗卫星信号,并生成原始北斗秒脉冲信号和北斗时长信号；运算建模模块,用于优化北斗卫星星座模型,生成北斗秒脉冲信号；铷原子钟模块,用于提供原始频率信号；功分倍频输出模块,用于输出主振频率源信号；相参锁相模块,用于将原始频率信号的相位与北斗秒脉冲信号的相位锁定；分频脉冲输出模块,用于输出与主振频率信号的相位相参的定时脉冲信号；中央控制模块,用于对各模块进行状态监控以及协调控制。本发明可以生成与北斗秒信号同步的定时脉冲信号及相参主振频率源信号,缩短了无人机的探测定位时长并提高了无人机的探测定位精度。(The invention provides a Beidou coherent system and equipment for unmanned aerial vehicle detection and positioning, which comprise: the satellite receiving module is used for demodulating and analyzing the Beidou satellite signals and generating original Beidou second pulse signals and Beidou duration signals; the operation modeling module is used for optimizing a Beidou satellite constellation model and generating a Beidou second pulse signal; the rubidium atomic clock module is used for providing an original frequency signal; the power division and frequency multiplication output module is used for outputting a master vibration frequency source signal; the phase-coherent phase-locked module is used for locking the phase of the original frequency signal with the phase of the Beidou second pulse signal; the frequency division pulse output module is used for outputting a timing pulse signal which is coherent with the phase of the master vibration frequency signal; and the central control module is used for monitoring the state of each module and performing coordination control. The invention can generate the timing pulse signal and the coherent main vibration frequency source signal which are synchronous with the Beidou second signal, shortens the detection and positioning time of the unmanned aerial vehicle and improves the detection and positioning precision of the unmanned aerial vehicle.)

1. The utility model provides a big dipper coherent system to unmanned aerial vehicle surveys location which characterized in that includes: the satellite receiving module is used for demodulating and analyzing the Beidou satellite signals and generating original Beidou second pulse signals and Beidou duration signals; the operation modeling module is used for optimizing a Beidou satellite constellation model and generating a Beidou second pulse signal; the rubidium atomic clock module is used for providing an original frequency signal; the power division and frequency multiplication output module is used for outputting a master vibration frequency source signal; the phase-coherent phase-locked module is used for locking the phase of the original frequency signal with the phase of the Beidou second pulse signal; the frequency division pulse output module is used for outputting a timing pulse signal which is coherent with the phase of the master vibration frequency signal; and the central control module is used for monitoring the state of each module and performing coordination control.

2. The Beidou coherent system for unmanned aerial vehicle detection and positioning according to claim 1, further comprising: and the key display module is used for carrying out state display and key control on the device under the control of the central control module.

3. The Beidou coherent system for unmanned aerial vehicle detection and positioning according to claim 2, further comprising: and the unmanned aerial vehicle detection positioning system is used for carrying out state monitoring on the Beidou coherent system for unmanned aerial vehicle detection positioning through the central control module.

4. The Beidou coherent system for unmanned aerial vehicle detection and positioning according to claim 3, wherein the outputting of the master oscillator frequency source signal comprises: and performing power distribution and frequency multiplication on the original frequency signal output by the rubidium atomic clock module, and outputting a main vibration frequency source signal related to the phase of the original frequency signal.

5. The Beidou coherent system for unmanned aerial vehicle detection and positioning according to claim 4, wherein the locking the phase of the original frequency signal with the phase of the Beidou second pulse signal comprises: the phase detection is carried out on the Beidou second pulse signal output by the operation modeling module and the main vibration frequency source signal output by the power division frequency multiplication output module, a frequency adjusting code is output to the rubidium atomic clock module, and the phase of the original frequency signal output by the rubidium atomic clock module and the phase of the Beidou second pulse signal output by the operation modeling module are locked.

6. The Beidou coherent system for unmanned aerial vehicle detection and positioning according to claim 5, wherein the outputting of the timing pulse signal coherent with the phase of the master oscillator frequency signal comprises: and directly dividing the frequency of the main vibration frequency signal output by the power division and frequency multiplication output module, and outputting a timing pulse signal which is coherent with the phase of the main vibration frequency signal.

7. The Beidou coherent system for unmanned aerial vehicle detection and positioning according to claim 6, further comprising a timing pulse output module for receiving the frequency division pulse output module and a coherent master vibration frequency output module for receiving the power division frequency multiplication frequency output module.

8. The Beidou coherent system for unmanned aerial vehicle detection and positioning according to claim 7, further comprising: and the satellite antenna module is used for receiving the Beidou satellite signals.

9. An electronic device, comprising:

at least one processor, at least one memory, a communication interface, and a bus; wherein the content of the first and second substances,

the processor, the memory and the communication interface complete mutual communication through the bus;

the memory stores program instructions executable by the processor, which are invoked by the processor to implement the system of any one of claims 1 to 8.

10. A non-transitory computer-readable storage medium storing computer instructions that cause a computer to implement the system of any one of claims 1 to 8.

Technical Field

The embodiment of the invention relates to the technical field of unmanned aerial vehicle detection and positioning, in particular to a Beidou coherent system and Beidou coherent equipment for unmanned aerial vehicle detection and positioning.

Background

In recent years, unmanned technologies and platforms have been extended to a plurality of fields such as sea, land, air, sky and the like, wherein unmanned planes are undoubtedly the most rapidly developed among a plurality of unmanned platforms, and with the wide application of unmanned planes and the gradual opening of national policies to low airspace, unmanned planes fly black and abuse cause potential harm to personal safety of social public. Currently, unmanned aerial vehicle detection and positioning are mainly realized by means of radar and a time difference of arrival (TDOA) method, and the TDOA needs a stable master vibration frequency source and time timing pulses. With the great application of the Beidou navigation system, the traditional mode that the Beidou signal disciplines the atomic clock to provide a main vibration frequency source and the Beidou synchronous second is used as time timing pulse is used as a main method of TDOA, and because the phase of the main vibration frequency source and the phase of the timing pulse are considered independently, the requirements on the detection locking time length and the detection precision can not be met under the conditions that the size of the unmanned aerial vehicle is smaller and the navigational speed is faster and faster. Therefore, developing a big dipper coherent system and equipment to unmanned aerial vehicle surveys location can effectively overcome the defect in the above-mentioned correlation technique, just becomes the technological problem that the industry is urgent to solve.

Disclosure of Invention

Aiming at the problems in the prior art, the embodiment of the invention provides a Beidou coherent system and equipment for unmanned aerial vehicle detection and positioning.

In a first aspect, an embodiment of the present invention provides a Beidou coherent system for unmanned aerial vehicle detection and positioning, including: the satellite receiving module is used for demodulating and analyzing the Beidou satellite signals and generating original Beidou second pulse signals and Beidou duration signals; the operation modeling module is used for optimizing a Beidou satellite constellation model and generating a Beidou second pulse signal; the rubidium atomic clock module is used for providing an original frequency signal; the power division and frequency multiplication output module is used for outputting a master vibration frequency source signal; the phase-coherent phase-locked module is used for locking the phase of the original frequency signal with the phase of the Beidou second pulse signal; the frequency division pulse output module is used for outputting a timing pulse signal which is coherent with the phase of the master vibration frequency signal; and the central control module is used for monitoring the state of each module and performing coordination control.

On the basis of the content of the system embodiment, the Beidou coherent system for unmanned aerial vehicle detection and positioning provided by the embodiment of the invention further comprises: and the key display module is used for carrying out state display and key control on the device under the control of the central control module.

On the basis of the content of the system embodiment, the Beidou coherent system for unmanned aerial vehicle detection and positioning provided by the embodiment of the invention further comprises: and the unmanned aerial vehicle detection positioning system is used for carrying out state monitoring on the Beidou coherent system for unmanned aerial vehicle detection positioning through the central control module.

On the basis of the content of the system embodiment, the Beidou coherent system for unmanned aerial vehicle detection and positioning provided in the embodiment of the present invention outputs a master oscillation frequency source signal, including: and performing power distribution and frequency multiplication on the original frequency signal output by the rubidium atomic clock module, and outputting a main vibration frequency source signal related to the phase of the original frequency signal.

On the basis of the content of the system embodiment, the Beidou coherent system for unmanned aerial vehicle detection and positioning, provided by the embodiment of the invention, for locking the phase of the original frequency signal and the phase of the Beidou second pulse signal comprises: the phase detection is carried out on the Beidou second pulse signal output by the operation modeling module and the main vibration frequency source signal output by the power division frequency multiplication output module, a frequency adjusting code is output to the rubidium atomic clock module, and the phase of the original frequency signal output by the rubidium atomic clock module and the phase of the Beidou second pulse signal output by the operation modeling module are locked.

On the basis of the content of the system embodiment, the Beidou coherent system for unmanned aerial vehicle detection and positioning provided in the embodiment of the present invention outputs the timing pulse signal coherent with the phase of the master oscillation frequency signal, and includes: and directly dividing the frequency of the main vibration frequency signal output by the power division and frequency multiplication output module, and outputting a timing pulse signal which is coherent with the phase of the main vibration frequency signal.

On the basis of the content of the system embodiment, the Beidou coherent system for unmanned aerial vehicle detection and positioning provided by the embodiment of the invention is also used for receiving timing pulse output of the frequency division pulse output module and coherent master vibration frequency output of the power division frequency multiplication output module.

On the basis of the content of the system embodiment, the Beidou coherent system for unmanned aerial vehicle detection and positioning provided by the embodiment of the invention further comprises: and the satellite antenna module is used for receiving the Beidou satellite signals.

In a second aspect, an embodiment of the present invention provides an electronic device, including:

at least one processor; and

at least one memory communicatively coupled to the processor, wherein:

the memory stores program instructions executable by the processor, and the processor calls the program instructions to execute the Beidou coherent system for unmanned aerial vehicle detection and positioning provided by any one of the various implementation manners of the first aspect.

In a third aspect, an embodiment of the present invention provides a non-transitory computer-readable storage medium, where the non-transitory computer-readable storage medium stores computer instructions, and the computer instructions enable a computer to implement the Beidou coherent system for unmanned aerial vehicle detection and positioning provided in any one of the various implementation manners of the first aspect.

According to the Beidou coherent system and the equipment for unmanned aerial vehicle detection and positioning, provided by the embodiment of the invention, the satellite receiving module, the operation modeling module, the rubidium atomic clock module, the power division and frequency multiplication output module, the coherent phase locking module, the frequency division pulse output module and the central control module are subjected to system integration, so that a timing pulse signal and a coherent main vibration frequency source signal synchronous with a Beidou second signal can be generated, the detection and positioning time of the unmanned aerial vehicle is shortened, and the detection and positioning accuracy of the unmanned aerial vehicle is improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, a brief description will be given below to the drawings required for the description of the embodiments or the prior art, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a Beidou coherent system for unmanned aerial vehicle detection and positioning according to an embodiment of the present invention;

fig. 2 is a schematic physical structure diagram of an electronic device according to an embodiment of the present invention;

fig. 3 is a schematic structural diagram of another Beidou coherent system for unmanned aerial vehicle detection and positioning according to an embodiment of the present invention;

fig. 4 is a schematic structural diagram of a Beidou coherent system for unmanned aerial vehicle detection and positioning according to an embodiment of the present invention;

fig. 5 is a schematic structural diagram of another Beidou coherent system for unmanned aerial vehicle detection and positioning according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. In addition, technical features of various embodiments or individual embodiments provided by the present invention may be arbitrarily combined with each other to form a feasible technical solution, and such combination is not limited by the sequence of steps and/or the structural composition mode, but must be realized by a person skilled in the art, and when the technical solution combination is contradictory or cannot be realized, such a technical solution combination should not be considered to exist and is not within the protection scope of the present invention.

Locking a rubidium atomic clock frequency signal to a Beidou second signal in a phase-locked mode, generating a main oscillation frequency signal with a stable phase relation in a phase-locked frequency multiplication mode, and finally directly dividing the main oscillation frequency signal into a timing pulse signal so as to output a timing pulse signal synchronized with the Beidou second high precision and a coherent main oscillation frequency source signal. Based on this idea, an embodiment of the present invention provides a Beidou coherent system for unmanned aerial vehicle detection and positioning, referring to fig. 1, where the system includes: the satellite receiving module is used for demodulating and analyzing the Beidou satellite signals and generating original Beidou second pulse signals and Beidou duration signals; the operation modeling module is used for optimizing a Beidou satellite constellation model and generating a Beidou second pulse signal; the rubidium atomic clock module is used for providing an original frequency signal; the power division and frequency multiplication output module is used for outputting a master vibration frequency source signal; the phase-coherent phase-locked module is used for locking the phase of the original frequency signal with the phase of the Beidou second pulse signal; the frequency division pulse output module is used for outputting a timing pulse signal which is coherent with the phase of the master vibration frequency signal; and the central control module is used for monitoring the state of each module and performing coordination control.

Specifically, referring to fig. 3, based on the content of the above system embodiment, as an optional embodiment, the Beidou coherent system for unmanned aerial vehicle detection and positioning provided in the embodiment of the present invention further includes: and the key display module is used for carrying out state display and key control on the device under the control of the central control module. The key display module performs state display and key control of the device under the control of the central control module.

Specifically, referring to fig. 4, based on the content of the above system embodiment, as an optional embodiment, the Beidou coherent system for unmanned aerial vehicle detection and positioning provided in the embodiment of the present invention further includes: and the unmanned aerial vehicle detection positioning system is used for carrying out state monitoring on the Beidou coherent system for unmanned aerial vehicle detection positioning through the central control module. The unmanned aerial vehicle detection positioning system receives timing pulse output of the frequency division pulse output module and coherent master vibration frequency output of the power division and frequency multiplication output module, and performs state monitoring on the device through the central control module.

Based on the content of the above system embodiment, as an optional embodiment, the output master oscillation frequency source signal of the Beidou coherent system for unmanned aerial vehicle detection and positioning provided in the embodiment of the present invention includes: and performing power distribution and frequency multiplication on the original frequency signal output by the rubidium atomic clock module, and outputting a main vibration frequency source signal related to the phase of the original frequency signal.

Based on the content of the above system embodiment, as an optional embodiment, the Beidou coherent system for unmanned aerial vehicle detection and positioning provided in the embodiment of the present invention, the locking the phase of the original frequency signal and the phase of the Beidou second pulse signal, includes: the phase detection is carried out on the Beidou second pulse signal output by the operation modeling module and the main vibration frequency source signal output by the power division frequency multiplication output module, a frequency adjusting code is output to the rubidium atomic clock module, and the phase of the original frequency signal output by the rubidium atomic clock module and the phase of the Beidou second pulse signal output by the operation modeling module are locked.

Based on the content of the above system embodiment, as an optional embodiment, the Beidou coherent system for unmanned aerial vehicle detection and positioning provided in the embodiment of the present invention outputs a timing pulse signal coherent to the phase of the master oscillation frequency signal, including: and directly dividing the frequency of the main vibration frequency signal output by the power division and frequency multiplication output module, and outputting a timing pulse signal which is coherent with the phase of the main vibration frequency signal.

Based on the content of the system embodiment, as an optional embodiment, the Beidou coherent system for unmanned aerial vehicle detection and positioning provided in the embodiment of the present invention is further configured to receive timing pulse output of the frequency division pulse output module and coherent master vibration frequency output of the power division and frequency multiplication output module.

Specifically, the satellite receiving module is used for demodulating and analyzing a Beidou satellite signal and generating an original Beidou second pulse signal and a Beidou time signal; the operation modeling module is used for optimizing a Beidou satellite constellation model and generating a high-precision Beidou second pulse signal; the rubidium atomic clock module provides an original frequency signal; the power division and frequency multiplication output module performs power distribution and frequency multiplication according to the original frequency signal output by the rubidium atomic clock module, and outputs a plurality of paths of main vibration frequency source signals with stable phase relation with the original frequency signal; the coherent phase locking module carries out phase detection and outputs a frequency adjusting code to the rubidium atomic clock module according to the high-precision Beidou second pulse signal output by the operational modeling module and the main vibration frequency source signal output by the power division frequency doubling output module, so that the phase of the original frequency signal output by the rubidium atomic clock module is locked to the high-precision Beidou second pulse signal output by the operational modeling module; the frequency division pulse output module directly divides the frequency of the main vibration frequency signal output by the power division and frequency multiplication output module and outputs a timing pulse signal which is coherent with the phase of the main vibration frequency signal; the central control module is connected with each module to monitor and coordinate the state of each module.

Specifically, referring to fig. 5, based on the content of the above system embodiment, as an optional embodiment, the Beidou coherent system for unmanned aerial vehicle detection and positioning provided in the embodiment of the present invention further includes: and the satellite antenna module is used for receiving the Beidou satellite signals.

According to the Beidou coherent system and the equipment for unmanned aerial vehicle detection and positioning, provided by the embodiment of the invention, the satellite receiving module, the operation modeling module, the rubidium atomic clock module, the power division and frequency multiplication output module, the coherent phase locking module, the frequency division pulse output module and the central control module are subjected to system integration, so that a timing pulse signal and a coherent main vibration frequency source signal synchronous with a Beidou second signal can be generated, the detection and positioning time of the unmanned aerial vehicle is shortened, and the detection and positioning accuracy of the unmanned aerial vehicle is improved.

According to the Beidou coherent system and the equipment for unmanned aerial vehicle detection and positioning, provided by the embodiment of the invention, a timing pulse signal with extremely small jitter is generated by adopting the frequency high stability characteristic of a rubidium atomic clock; by adopting an external phase locking method, the problem that the rubidium atomic clock can only lock frequency and can not lock phase in the prior art is solved; the problem that the output frequency is not coherent with the timing pulse in the prior art is solved by a direct frequency division method; generating a timing pulse signal and a coherent master vibration frequency source signal which are synchronous with the Beidou second high precision, and providing the timing pulse signal and the coherent master vibration frequency source signal to an unmanned aerial vehicle detection positioning system, so that the detection positioning time is shortened, and the detection positioning precision is improved; the device is suitable for single base station, double base stations and multi-base station systems, and is suitable for static systems and dynamic systems.

Among many positioning detection technologies, radio detection and positioning technologies are widely applied to a plurality of engineering fields such as communication reconnaissance, aerospace, electronic countermeasure, and radio detection and positioning technologies are also widely adopted in current unmanned aerial vehicle detection and positioning systems. The unmanned aerial vehicle detection positioning system generally comprises a transmitting radar station and a plurality of receiving radar stations, an unmanned aerial vehicle target is detected through a radar, and the radar performs target detection and target parameter extraction by utilizing electromagnetic waves so as to realize the positioning of the target. Specifically, electromagnetic waves are intensively emitted to a certain range through a radar antenna of a bistatic radar or a multistatic radar, are emitted by a target and then are received by the radar, and the positioning is realized by utilizing the Time Difference (TDOA) between the emission of the electromagnetic waves from the radar to the target and the reception of the electromagnetic waves. In order to improve the accuracy of TDOA detection location, it is most important to consider the timing accuracy, i.e. the accuracy of the timing pulse and the carrier frequency phase, and the acquired phase time error will be directly converted into the error of distance measurement to finally determine the location error. These errors are roughly divided into two parts: first, the uncertainty in the time recorded by each radar station of the probe positioning system depends on the accuracy of the timing pulse used by each station; second, the accuracy of carrier frequency phase synchronization between each station depends on the accuracy of phase synchronization of the master frequency of each station.

Because a plurality of radar stations of the unmanned aerial vehicle detection positioning system are distributed in a long distance, each station uses an independent time frequency device, the main vibration frequency and the timing pulse can not be completely homologous like a single-base radar, each independent time frequency device can only receive Beidou satellite signals and directly synchronize the timing pulse to the Beidou second pulse to realize quasi-homology, the positioning precision is directly influenced by the precision of the timing pulse of the quasi-homology, and the synchronization process is not related to the main vibration frequency; furthermore, in order to improve the quasi-homologous accuracy and obtain better time keeping accuracy in a satellite signal loss state, a time frequency device needs to be internally provided with a rubidium atomic clock, the rubidium atomic clock provides original frequency output for the main vibration frequency, but the rubidium atomic clock cannot directly achieve output frequency phase synchronization to the Beidou second due to the limitation of a physical mechanism, namely, no correlation or non-coherent exists between the phase of the main vibration frequency and the timing pulse. The method of uncorrelated synchronization of the timing pulse and the master vibration frequency leads to difficulty in improving the TDOA positioning accuracy and accelerating the positioning time when the unmanned aerial vehicle detection positioning system performs signal level data processing.

The big dipper coherent system and the equipment for unmanned aerial vehicle detection and positioning provided by the embodiment of the invention are different from the prior art scheme in that the timing pulse is obtained by frequency division and phase shift of the main vibration frequency directly, rather than locking the timing pulse to the big dipper second pulse directly, thereby overcoming the defect that the rubidium atomic clock can not carry out frequency phase locking coherent.

The system of the embodiment of the invention is realized by depending on the electronic equipment, so that the related electronic equipment is necessarily introduced. To this end, an embodiment of the present invention provides an electronic apparatus, as shown in fig. 2, including: the system comprises at least one processor (processor), a communication Interface (communication Interface), at least one memory (memory) and a communication bus, wherein the at least one processor, the communication Interface and the at least one memory are communicated with each other through the communication bus. The at least one processor may invoke logic instructions in the at least one memory to implement the various systems provided in the system embodiments.

In addition, the logic instructions in the at least one memory may be implemented in software functional units and stored in a computer readable storage medium when sold or used as a stand-alone product. Based on such understanding, the technical solution of the present invention may be substantially implemented or contributed to by the prior art, or the technical solution may be implemented in a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the system according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.

The above-described embodiments of the apparatus are merely illustrative, and the units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.

Through the above description of the embodiments, those skilled in the art will clearly understand that each embodiment can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware. With this understanding in mind, the above-described technical solutions may be embodied in the form of a software product, which can be stored in a computer-readable storage medium, such as ROM/RAM, magnetic disk, optical disk, etc., and includes instructions for enabling a computer device (which may be a personal computer, a server, or a network device, etc.) to implement the methods or systems of the various embodiments or some parts of the embodiments.

The flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present invention. Based on this recognition, each block in the flowchart or block diagrams may represent a module, a program segment, or a portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

In this patent, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.