CN110881195B - Multi-frequency multi-target selective wireless energy transmission method and system - Google Patents

Multi-frequency multi-target selective wireless energy transmission method and system Download PDF

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CN110881195B
CN110881195B CN201910789365.XA CN201910789365A CN110881195B CN 110881195 B CN110881195 B CN 110881195B CN 201910789365 A CN201910789365 A CN 201910789365A CN 110881195 B CN110881195 B CN 110881195B
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钟成
赵德双
刘要红
包金龙
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University of Electronic Science and Technology of China
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Abstract

The invention discloses a multi-frequency multi-target selective wireless energy transmission method and system, and belongs to the technical field of electromagnetic wave wireless energy transmission. The method comprises the following steps: constructing a receiving device group and a transmitting device group of a multi-frequency energy transmission system; discretizing the energy transmission bandwidth range adopted by the system according to the measured maximum multipath time delay in the energy transmission environment, and extracting the energy transmission channel parameters of the energy transmission system at each frequency point; selecting an optimal energy transmission frequency point according to the extracted energy transmission channel parameters and a calculation formula; and determining the optimal feed-in signal corresponding to the selected frequency point by using an optimization algorithm to realize multi-target selective parallel energy transmission. The invention solves the problem that the existing multi-target selective energy transmission technical method is difficult to give consideration to energy transmission efficiency and side lobe values, and realizes high-efficiency and low-side-lobe multi-target selective parallel energy transmission.

Description

Multi-frequency multi-target selective wireless energy transmission method and system
Technical Field
The invention belongs to the technical field of electromagnetic wave wireless energy transmission, and particularly relates to a multi-frequency multi-target selective energy transmission method and system.
Background
Wireless Power Transfer (WPT) is a leading research edge in the current energy transmission field, and is also a research hotspot which is concerned by the scientific and industrial fields in recent years. Compared with wired energy transmission, the WPT can completely get rid of the constraint of a power transmission cable, can supply energy to electronic equipment uninterruptedly, conveniently, flexibly and anytime anywhere in all weather, is a revolutionary energy transmission technology, can be widely applied to various fields in national economy, and has scientific research significance and application value inferior to the current wireless communication technology.
At present, a large number of wireless energy transmission methods mainly aim at single-target energy transmission and are difficult to meet the application requirements of a plurality of devices to be transmitted in an energy transmission environment. In recent years, in order to solve the problem of multi-target parallel energy transmission, researchers have proposed a new Wireless energy transmission technology, namely "Time Reversal Wireless Power Transfer (TR-WPT)". Different from the traditional WPT, the TR-WPT has the space-time focusing characteristic, and electromagnetic energy radiated by an antenna is accurately conveyed to a target point in a 'point focusing wave' mode. TR-WPT is expected to realize multi-target selective parallel energy output by means of the unique energy output mechanism.
In recent years, many researchers have proposed different approaches to multi-objective parallel wireless energy delivery. An invention patent with patent application number CN201810698828.7 discloses a method for parallel energy transmission of multiple energy receiving targets by using a single transmitting device using multi-frequency signals, but this method cannot realize multi-target selective energy transmission, and a single transmitting antenna transmits energy by radiating to the periphery, most of the energy is dissipated in space, and the overall energy transmission efficiency is low. An invention patent with patent application number CN201810580750.9 discloses a method for realizing multi-target selective wireless energy transmission by using single-frequency signals, but when the method transmits energy to a plurality of targets to be transmitted selected from some multi-targets, the energy transmission efficiency is low, and large side lobes are generated at the same time. The invention patent with the application patent number of CN201810580731.6 discloses a method for realizing selective energy transmission of a plurality of transmitting devices to a plurality of energy receiving targets by adopting a frequency division multiple access mode, which utilizes different frequency signals to carry out energy transmission on different energy receiving targets and can realize independent energy transmission of each target in multiple targets, so that when a plurality of selected targets are subjected to parallel energy transmission, side lobes hardly occur, each energy receiving antenna can only receive appointed single frequency energy, and the energy of other frequency points at the position of the energy receiving antenna is greatly wasted, so that the energy transmission efficiency of the multiple targets is reduced.
In summary, the existing multi-target selective wireless energy transmission method has some inherent defects, and it is difficult to consider both low side lobe and high energy transmission efficiency under the condition of any multi-target selective energy transmission.
Disclosure of Invention
In order to overcome the inherent defects of the conventional multi-target selective wireless energy transmission method, the invention provides a multi-frequency multi-target selective energy transmission method and a system, which specifically comprise the following steps:
step 1, selecting energy transmission frequency points of a multi-frequency energy transmission system
Step 1-1. construction of energy transmission system
Placing M receiving devices EC in the target energy transmission area1～ECMThe set of receiving devices ECG constituting the energy delivery system.
N transmitting devices TR are arranged around the outside of the energy transmission area1～TRNAnd forming a transmitting device set TRM of the energy transmission system.
Step 1-2, extracting channel parameters of the energy transmission system
The energy transmission system constructed based on the step 1-1 detects the maximum multipath time delay tau in the energy transmission systemmaxThereby obtaining a corresponding coherence bandwidth of
Figure RE-GDA0002361348840000021
In order to ensure that the energy transmission channels between two arbitrarily selected frequency points do not belong to the same flat fading channel, the energy transmission bandwidth range [ f ] adopted by the system is divided into 2 delta B frequency intervalsL,fH]Discretizing to obtain K frequency points f1,…fk,…fK，1≤k≤K。
Extracting system energy transmission channel parameters under the K different frequency points, and specifically operating the following steps:
(1) will have a frequency f1By receiving means EC1～ECMTransmitting, N transmitting means TR1～TRNReceiving and recording the sinusoidal signal, i.e. M groups of frequencies f in total1Is expressed as H1＝[h11,...hm1,...hM1]T∈CM×NWherein h ism1Denotes the m-th receiving device ECmWith N transmitting means TR1～TRNHas a frequency of f1M is more than or equal to 1 and less than or equal to M, superscript T represents matrix transposition, CM×NA complex matrix representing M N;
(2) in addition, the frequency is selected to be f2,…fk,…fKSequentially repeating the above operations to extract f2,…fk,…fKLower sinusoidal signal channel parameter matrix H2，…Hk,…HK。
Step 1-3. selection of frequency point of energy transmission system
Selecting all receiving devices EC in the energy transmission area1～ECMThe total efficiency of energy output of the M energy output targets represents the total efficiency of the whole energy output area.
Under K different energy transmission frequency points, the energy transmission efficiency of all receiving devices is calculated by a formula
Figure RE-GDA0002361348840000031
To solve, wherein etakK is more than or equal to 1 and less than or equal to K and lambda represents the energy transmission efficiency under the K frequency pointmax(. cndot.) represents the maximum eigenvalue of the matrix,
Figure RE-GDA0002361348840000032
represents the channel matrix HkThe conjugate transpose of (c).
The method comprises the following specific operation steps:
(1) utilizing the sine signal channel parameter matrix H extracted in the step 1-21,…,HKIn combination with the formula
Figure RE-GDA0002361348840000033
Calculating the matrix under K different frequencies
Figure RE-GDA0002361348840000034
Maximum eigenvalue of
Figure RE-GDA0002361348840000035
(2) Sequentially arranging the K maximum characteristic values according to the size sequence, and selecting A maximum values
Figure RE-GDA0002361348840000036
Figure RE-GDA0002361348840000036
1≤ka≤kANot more than K, and the corresponding frequency points are respectively
Figure RE-GDA0002361348840000037
Then the a frequency points are the energy transmission frequency points selected by the energy transmission system.
It should be noted that the larger the value a is, the more the selected energy transmission frequency points are, which may make the energy transmission effect of the system better, but at the same time, the size, cost and implementation difficulty of the energy transmission system may also be increased, so that the selection of the actual number of frequency points must take into account the actual energy transmission requirement and the complexity and cost of the energy transmission system.
Step 2, realizing multi-target selective wireless energy transmission
Step 2-1, setting system optimization variables and optimization indexes
E receiving devices needing energy transmission are selected according to actual application requirements
Figure RE-GDA0002361348840000038
The rest M-E receiving devices are used as the targets to be transmitted
Figure RE-GDA0002361348840000039
Namely the non-energy-to-be-transmitted target.
The system optimization variables are set as follows:
setting the weighting factors under the selected A different energy transmission frequency points as
Figure RE-GDA00023613488400000310
Wherein
Figure RE-GDA0002361348840000041
Figure RE-GDA0002361348840000042
Is expressed in frequency
Figure RE-GDA0002361348840000043
Weighting factor of the next mth receiving device, if ECmBelong to E targets to be transported
Figure RE-GDA0002361348840000044
For complex variables containing magnitude-phase information, if ECmBelong to M-E non-energy-transmission targets, then
Figure RE-GDA0002361348840000045
The system optimization index is set as follows
(1) M-E non-energy-transmission target positions
Figure RE-GDA0002361348840000046
Received maximum power value and E targets to be transmitted
Figure RE-GDA0002361348840000047
The ratio of the minimum received power value is defined as a side lobe value SLL of the multi-frequency energy transmission system;
(2) e targets to be transported
Figure RE-GDA0002361348840000048
Total received power and N transmitting devices TR1～TRNThe ratio of the total emitted power is defined as the efficiency value eta of the multi-frequency energy transmission system;
(3) in order to take two energy output indexes of the system into consideration, a maximum efficiency threshold eta is setthAnd a minimum side lobe threshold SLLthAnd expressing the joint optimization indexes of the two by using a COST function COST: COST ═ w1·(SLL-SLLth)+w2·(ηth-η)，w1、w2Represents the optimal weight coefficient between SLL and η.
Step 2-2. optimization of system feed-in signal
In practical application, according to actual demand, setting power distribution ratio w 'between E energy targets to be transmitted as [ w'1,w'2,…,w'E]I.e. satisfy
Figure RE-GDA0002361348840000049
Wherein
Figure RE-GDA00023613488400000410
Representing E targets to be energy-delivered
Figure RE-GDA00023613488400000411
Respectively receiving the energy of the multi-frequency signal. In order to obtain the optimal feed-in signal under A energy transmission frequency points of the system, a weighting factor is used as an optimization variable, and the two indexes of a side lobe value SLL and energy transmission efficiency eta of the system are jointly optimized, wherein the specific optimization problem can be represented as follows:
Figure RE-GDA00023613488400000412
Figure RE-GDA00023613488400000413
for solving the problem, a global optimization algorithm (such as simplex algorithm, genetic algorithm and ant colony algorithm) can be adopted to obtain a series of optimal weighting factors which minimize COST
Figure RE-GDA0002361348840000051
The feed-in signal under A energy transmission frequency points can be obtained as
Figure RE-GDA0002361348840000052
Wherein
Figure RE-GDA0002361348840000053
Figure RE-GDA0002361348840000053
1≤ka≤kA≤K。
Step 2-3. transmission of system feed-in signal
The feed-in signals of all frequency points are obtained through the optimization
Figure RE-GDA0002361348840000054
Superimposed to form an aggregate feed signal
Figure RE-GDA0002361348840000055
The total feed-in signals are respectively fed into the corresponding N transmitting devices TR1～TRNAnd in the middle, the high-efficiency and low-sidelobe energy transmission can be realized for the expected E energy targets to be transmitted.
The invention has the beneficial effects that:
(1) the method can realize wireless energy transmission with high efficiency and low side lobe under the condition of arbitrary multi-target selective energy transmission;
(2) the invention can select the energy transmission frequency of the system according to the specific energy transmission scene to achieve the optimal energy transmission effect;
(3) the invention realizes the free selection of the frequency of the energy transmission system, and can avoid the conflict between the energy transmission frequency and the existing communication frequency in the energy transmission environment;
(4) the invention realizes that the receiving power among a plurality of targets to be transmitted is in any proportion;
(5) the invention can realize multi-target selective wireless energy transmission according to the practical application requirements and different emphasis on energy transmission efficiency and side lobe values.
Drawings
Fig. 1 is a schematic structural diagram of a multi-frequency wireless energy transmission system;
fig. 2 is a block diagram of a receiving device set of the multi-frequency wireless energy transmission system;
fig. 3 is a block diagram of a transmitting device set of the multi-frequency wireless energy transmission system;
the metal reverberation cavity model employed in the example of fig. 4;
FIG. 5 is a block diagram of a receiver block architecture employed in the example;
FIG. 6 is a block diagram of a transmit bank architecture employed in the example;
pair EC in the example of FIG. 74,EC5,EC6A field distribution pattern of energy transfer;
FIG. 8(a) is a graph comparing the side lobe values of multi-frequency and single-frequency energy transmission in the example;
FIG. 8(b) is a graph of efficiency comparison of multi-frequency versus single-frequency power delivery in the example;
FIG. 8(c) is a graph of COST values for multiple frequency versus single frequency energy delivery in the example.
Detailed Description
The invention is further described below with reference to the figures and examples.
The present embodiment provides a multi-frequency multi-target selective energy transmission method and system, the structural diagram of the system is shown in fig. 1, where 1 represents the receiving device group ECG, 2 is the selected non-energy transmission device, 3 is the selected energy transmission device, and 4 is the transmitting device TR2～TRNAnd 5 is a transmitting device set TRM.
The structure of the receiving device group is shown in fig. 2, and includes: energy-receiving antenna AR1～ARMFor transmitting a sinusoidal detection signal and receiving an energy transmission signal; signal source OSC1～OSCMFor generating a probe signal of a selected frequency; LOAD1～LOADMThe device load which needs to be supplied with power is driven by direct current; rectifier PRU1～PRUMFor coupling a receiving device EC1～ECMThe received multi-frequency sinusoidal energy transmission signal is converted into direct current energy and is provided to a LOAD LOAD1～LOADM(ii) a Switch S1～SMFor switching the powered antenna AR1～ARMAnd a signal source OSC1～OSCMOr rectifying means PRU1～PRUMTo be connected to each other. The connection relationship is as follows: energy-receiving antenna AR1～ARMBy means of a switch S1～SMRespectively connected with signal source OSC1～OSCMAnd a rectifying unit PRU1～PRUMPRU connecting and rectifying device1～PRUMRear end connected with LOAD1～LOADM。
The structure of the transmitting device set is shown in fig. 3, and includes: energy transmission antenna AT1～ATNFor receiving a probing signal and transmitting an energy transmission signal; band-pass filter BPF1～BPFNFor filtering outL,fH]Clutter outside of bandwidth; waveform detection module WDM1～WDMNThe device is used for recording the waveform of the detection signal transmitted by the receiving device group; combinerSUM1～SUMNRespectively at a frequency of
Figure RE-GDA0002361348840000061
Synthesizing a multi-tone signal by the plurality of sinusoidal energy transmission signals; microwave power source OSC _ F1～OSC_FARespectively for generating a frequency of
Figure RE-GDA0002361348840000062
The sine energy transmission signal; power divider PD _ F1～PD_FAN equal power dividers are respectively used for connecting the microwave power source OSC _ F1～OSC_FAThe generated sinusoidal signals are divided into N paths with equal power, and the amplitude and the phase of the signals are the same; adjustable power amplifier PA1_F1～PAN_F1,…,PA1_FA～PAN_FARespectively for adjusting each channel frequency to
Figure RE-GDA0002361348840000071
The single tone energy transmission signal amplitude of (a); phase shifter PS1_F1～PS16_F1,…,PS1_FA～PS16_FAFor adjusting the frequency to
Figure RE-GDA0002361348840000072
The single-tone energy transmission signal phase; switch R1～RNFor switching band-pass filters BPF1～BPFNWDM with waveform detection module1～WDMNOr combiner SUM1～SUMNThe connection of (2). The connection relationship is as follows: energy transmission antenna AT1～ATNDirect and band pass filter BPF1～BPFNConnected with each other, the back end passes through a switch R1～RNSeparately connected waveform detection module WDM1～WDMNSUM combiner SUM1～SUMN. At the transmitting device TR1In, combiner SUM1Each of the two circuits is respectively connected with an adjustable power amplifier PA1_F1～PA1_FAConnected at their rear ends with phase shifters PS, respectively1_F1～PS1_FAAre connected with the power divider PD _ F respectively1～PD_FAIs connected to the first port of the other transmitting devices TR2～TRNSUM of combiner2～SUMNBack end connection mode and combiner SUM1The same is true. Power divider PD _ F1～PD_FARespectively corresponding to the microwave power source OSC _ F1～OSC_FAAre connected.
The invention increases the number of the energy transmission frequency points of the system by increasing part of the topological structure of the transmitting device group; the arrangement of the transmitting device groups can be determined according to the boundary shape of a specific energy transmission scene, can be square, circular, irregular graphs and the like, and can also be arranged by adopting a non-equidistant sparse array; the antennas adopted in the transceiver group can be selected according to the actual application requirements, and can be omnidirectional dipole antennas or microstrip patch antennas, and the resonance point and the bandwidth of the antennas are determined according to the application requirements of an actual system; in order to avoid the multi-frequency signal being fed into the adjustable power amplifier at the same time to generate the intermodulation signal component, the embodiment controls only the single-frequency energy transmission signal through the adjustable power amplifier and the phase shifter, and then the combiner is used for superposition to generate the multi-frequency signal, thereby avoiding the energy loss caused by the intermodulation component.
Based on the above device, the multi-frequency multi-target selective energy transmission method and system of the embodiment specifically comprise:
step 1, selecting energy transmission frequency points of a multi-frequency energy transmission system
Step 1-1. construction of energy transmission system
The system model adopted in this example is, as shown in fig. 4, in a metal reverberation chamber of 60cm × 60cm × 15cm, for a target energy transmission area of 12cm × 12cm in the middle, 9 receiving devices are respectively placed at positions where energy transmission is required, and numbered EC from left to right and from top to bottom1～EC9The set of receiving devices ECG constituting the energy delivery system is shown in fig. 5.
Meanwhile, 16 transmitting devices are arranged at the periphery of the metal reverberation cavity at 12cm intervals at equal intervals and are arranged from the top left vertexHour hand number TR1～TR16A group TRM of transmitting means constituting the energy transmission system is shown in fig. 6. The 9 receiving devices and the 16 transmitting devices adopt patch monopole antennas with the center frequency of 2.45GHz and the bandwidth of 500 MHz.
Step 1-2, extracting channel parameters of the energy transmission system
Based on the energy transmission system constructed above, the maximum multipath time delay tau in the energy transmission system is detectedmax40ns, corresponding to a coherence bandwidth of
Figure RE-GDA0002361348840000081
Discretizing the energy transmission bandwidth range of the system from 2.2GHz to 2.7GHz at the frequency interval of 50MHz to obtain 10 frequency points f1,…,f10。
Extracting system energy transmission channel parameters under the 10 different frequency points, wherein the specific operation steps are as follows:
(1) at the receiving device group, OSC1～OSC9All select frequency points as f1Of the sinusoidal signal source of, make the switch S1And OSC1To each other, the rest S2～S9Then respectively communicate with PRU2～PRU9Connected to a signal source OSC1The generated detection signal is fed into a receiving device EC1Performing the following steps;
(2) at the transmitting set of devices, switch R1～R16Respectively with WDM1～WDM16Connected from WDM1～WDM16Respectively extracting frequency points f from the recorded waveforms1The amplitude and phase of (2) constitute the receiving means EC1And a transmitting set TR1～TR16At frequency point f1Lower sinusoidal signal channel parameter matrix h11∈C16×1；
(3) With successive replacement of the receiving means EC2…,EC9Repeating the steps (1) and (2) to enable the device, and respectively measuring the TR with the surrounding transmitting device group1～TR16The channel parameter matrix in between is h21,…,h91That is, at frequency point f1Channel parameter of lower sinusoidal signalThe number matrix is: h1＝[h11,...,h91]T∈C9×16；
(4) By varying the OSC of the feed of the receiving means separately1～OSC9Has a frequency point of f2,…,f10Repeating the steps (1), (2) and (3) to obtain the frequency point f2,…,f10The following energy transmission system sinusoidal signal channel parameter matrix is: h2，…，H10。
Step 1-3. selection of frequency point of energy transmission system
Selecting all receiving devices EC in the energy transmission area1～EC9As the targets to be energy-transferred, the total efficiency of energy transfer for these 9 targets to be energy-transferred represents the total efficiency of the entire energy transfer area.
Utilizing the energy transmission channel parameter H extracted in the step 1-21,…,H10Calculating matrix under 10 different frequencies by using MATLAB software
Figure RE-GDA0002361348840000091
The calculation results are shown in table 1. Selecting the frequency points corresponding to the two maximum values in the table according to the size sequence, i.e. selecting the frequency points corresponding to the two maximum values in the table
Figure RE-GDA0002361348840000092
And taking the two frequency points as energy transmission frequency points of the system.
TABLE 1.10 maximum eigenvalues of the matrix at different frequency points
Figure RE-GDA0002361348840000093
Step 2, realizing multi-target selective wireless energy transmission
Step 2-1, setting system optimization variables and optimization indexes
Selecting a receiving device needing energy transmission, and respectively selecting 3 to-be-transmitted energy targets EC from 9 receiving devices4、EC5、EC6And the other 6 non-energy-transmission targets are EC1、EC2、EC3、EC7、EC8、 EC9。
The system optimization variables are set as follows:
setting two frequencies
Figure RE-GDA0002361348840000094
And
Figure RE-GDA0002361348840000095
weighting factor x of the underfed signal1＝[0,0,0,x41,x51,x61,0,0,0]T、x2＝[0,0,0,x42,x52,x62,0,0,0]T。
The system optimization indexes are set as follows:
the indexes considered by the multi-frequency energy transmission system are a side lobe value SLL and an efficiency value eta, and in order to consider the two energy transmission indexes of the system, a system maximum efficiency threshold eta is setth0.8 and minimum side lobe threshold SLLthSetting the optimized weight coefficient of the two as w to be-10 dB1＝1、w2The two joint optimization indexes are expressed by a COST function COST as 10: COST ═ w1·(SLL-SLLth)+w2·(ηth-η)。
Step 2-2. optimization of system feed-in signal
According to the selected 3 targets EC to be energy-transmitted4、EC5、EC6The power distribution ratio w' between the 3 targets to be supplied is set to [1,1]I.e. satisfy Pr,4＝Pr,5＝Pr,6. In order to obtain the optimal feed signal of the system under 2 energy transmission frequency points, a weighting factor x is used1、x2In order to optimize variables, the two indexes of the side lobe value SLL and the energy transmission efficiency eta of the system are jointly optimized, and the specific optimization problem can be represented as follows:
Figure RE-GDA0002361348840000101
s.t.Pr,4＝Pr,5＝Pr,6
to this questionSolving the problem, wherein the simplex algorithm is adopted to obtain the optimal weighting factor which minimizes the COST as x1 opt、x2 optFrequency of available
Figure RE-GDA0002361348840000102
And
Figure RE-GDA0002361348840000103
the lower feed-in signals are respectively
Figure RE-GDA0002361348840000104
Step 2-3. transmission of system feed-in signal
The feed-in signals s of all frequency points are obtained through the calculation or optimization1、s2Adding the signals s to s1+s2The total feed-in signal is fed into N transmitting devices TR respectively1～TRNIn the middle, 3 expected targets EC to be energy-output can be realized4、EC5、EC6And the energy transmission with high efficiency and low side lobe is carried out.
The specific operation steps are divided into the following three steps:
(1) at the receiver group, switch S1～S9And PRU1～PRU9Connecting; at the transmitting set of devices, switch R1～R16And combiner SUM1～SUM16Connected to, OSC _ F1Selecting a microwave power source, OSC _ F, capable of generating sinusoidal signals with a frequency of 2.45GHz2Selecting a microwave power source capable of generating a sinusoidal signal with the frequency of 2.55 GHz;
(2) according to 2.45GHz1Adjusting the amplitude and phase of each path in the PA filter to adjust the PA1_F1～PA16F1 and PS1_F1～PS16_F1Each path generates 2.45GHz sinusoidal signals with corresponding amplitude and phase; similarly, according to 2.55GHz feed signal s2Adjusting the amplitude and phase of each path in the PA filter to adjust the PA1_F2～PA16_F2And PS1_F2～PS16_F2Each path generates 2.55GHz sinusoidal signals with corresponding amplitude and phase; each path of the generated single-tone sinusoidal signals with two frequencies passes through a combiner SUM1～SUM16Synthesizing a two-tone signal to feed into the antenna in the transmitting device group;
(3) at the receiver group, 3 receivers EC of the expected energy output4、EC5、EC6The antenna receives the dual-frequency energy transmission signals transmitted by the transmitting device group at the same time, and the dual-frequency energy transmission signals pass through the PRU4、PRU5、PRU6Converting the received dual-frequency energy transmission signal into LOAD supply LOAD4,LOAD5,LOAD6The direct current energy used. At the same time, the other 6 receiving devices EC with unexpected energy transmission1、EC2、EC3、EC7、EC8、 EC9And lower side lobe energy is generated.
If the energy transmission scene is changed, skipping to the step 1, selecting the frequency of the multi-frequency wireless energy transmission system again, and then sequentially executing the operation in the step 2; if the energy transmission scene is not changed and only the target to be transmitted is changed, the user only needs to jump to the step 2 and sequentially executes the related operations in the step 2 again, and then selective wireless energy transmission of the newly selected target can be achieved.
In the embodiment, the electromagnetic simulation software CST Studio Suite 2016 is used for simulating the receiving device EC4,EC5,EC6The field distribution pattern for energy transfer is shown in fig. 7. It is evident from the figure that the energy is almost exclusively in EC4,EC5,EC6Three targets to be transmitted are gathered, and the energy distribution in the rest positions is small.
In order to verify the universality and the effectiveness of the method, 5 groups of targets to be energy-transmitted are optionally selected in addition in the example for simulation verification, and 6 groups of targets to be energy-transmitted in the simulation of the example are numbered as serial numbers 1-6 in sequence, and respectively: number 1 (EC)4,EC5,EC6) Number 2 (EC)1,EC3,EC5,EC8) Number 3 (EC)1,EC4,EC7,EC8) Serial number of4(EC1,EC2,EC3,EC5,EC8) Number 5 (EC)2,EC4,EC6,EC8) Number 6 (EC)1,EC2,EC3,EC5,EC7,EC8,EC9). These 6 sets of simulation results are compared, as shown in fig. 8, wherein fig. 8(a) is a graph comparing single-frequency and multi-frequency side lobe values, fig. 8(b) is a graph comparing single-frequency and multi-frequency efficiency values, and fig. 8(c) is a graph comparing single-frequency and multi-frequency COST values. It can be seen from the figure that, under the condition of multi-target energy transmission of any combination, the side lobe value and the efficiency value of the multi-frequency energy transmission signal are optimal compared with a single frequency, and the joint optimization index COST of the side lobe value and the efficiency value is always at the minimum value, which indicates that the wireless energy transmission mode of the multi-frequency energy transmission signal is an energy transmission method which can give consideration to both high efficiency and low side lobe.

Claims (2)

1. A multi-frequency multi-target selective wireless energy transmission method comprises the following steps:
step 1, selecting energy transmission frequency points of a multi-frequency energy transmission system
Step 1-1. construction of energy transmission system
Placing M receiving devices EC in the target energy transmission area1～ECMA group of receiving devices ECG forming an energy delivery system;
n transmitting devices TR are arranged around the outside of the energy transmission area1～TRNForming a transmitting device set TRM of the energy transmission system;
step 1-2, extracting channel parameters of the energy transmission system
The energy transmission system constructed based on the step 1-1 detects the maximum multipath time delay tau in the energy transmission systemmaxThereby obtaining a corresponding coherence bandwidth of
Figure FDA0003139129460000011
The energy transmission bandwidth range [ f ] adopted by the system is divided into frequency intervals of 2 delta BL，fH]Discretizing to obtain K frequency points f1，…fk，…fKK is more than or equal to 1 and less than or equal to K, and the channel parameter moments of the energy transmission system under the K different frequency points are extractedMatrix H1，…Hk，…HKThe method comprises the following steps:
(1) will have a frequency f1By receiving means EC1～ECMTransmitting, N transmitting means TR1～TRNReceiving and recording the sinusoidal signal, i.e. M groups of frequencies f in total1Is expressed as H1＝[h11，...hm1，...hM1]T∈CM×NWherein h ism1Denotes the m-th receiving device ECmWith N transmitting means TR1～TRNHas a frequency of f1M is more than or equal to 1 and less than or equal to M, superscript T represents matrix transposition, CM×NA complex matrix representing M N;
(2) in addition, the frequency is selected to be f2，…fk，…fKThe above operations are repeated in sequence to extract the frequency f2，…fk，…fKChannel parameter matrix H of lower energy transmission system2，…Hk，…HK；
Step 1-3. selection of frequency point of energy transmission system
Selecting all receiving devices EC in the energy transmission area1～ECMAs the energy to be transmitted, the total efficiency of energy transmission of the M energy to be transmitted represents the total efficiency of the whole energy transmission area;
under K different frequency points, the energy transmission efficiency of all receiving devices is calculated by a formula
Figure FDA0003139129460000012
Solving of where etakDenotes the energy transfer efficiency at the k-th frequency point, λmax(. cndot.) represents the maximum eigenvalue of the matrix,
Figure FDA0003139129460000014
matrix H for representing channel parameters of energy transmission systemkThe conjugate transpose of (1);
the selection operation steps of the energy transmission frequency point are as follows:
(1) utilizing the energy transmission system channel parameters extracted in the step 1-2Number matrix H1，…，HKIn combination with the formula
Figure FDA0003139129460000013
Calculating the matrix under K different frequency points
Figure FDA0003139129460000021
Maximum eigenvalue of
Figure FDA0003139129460000022
(2) Sequentially arranging the K maximum characteristic values according to the size sequence, and selecting A maximum values
Figure FDA0003139129460000023
1≤ka≤kANot more than K, and the corresponding frequency points are respectively
Figure FDA0003139129460000024
The A frequency points are the energy transmission frequency points selected by the energy transmission system;
step 2, realizing multi-target selective wireless energy transmission
Step 2-1, setting system optimization variables and optimization indexes
E receiving devices needing energy transmission are selected according to actual application requirements
Figure FDA0003139129460000025
The rest M-E receiving devices are used as the targets to be transmitted
Figure FDA0003139129460000026
Namely the target is the non-energy-to-be-transmitted target;
the system optimization variables are set as follows:
setting the weighting factors under the selected A different energy transmission frequency points as
Figure FDA0003139129460000027
Wherein
Figure FDA0003139129460000028
Figure FDA0003139129460000029
Is expressed in frequency
Figure FDA00031391294600000210
Weighting factor of the next mth receiving device, if ECmBelong to E targets to be transported
Figure FDA00031391294600000211
For complex variables containing magnitude-phase information, if ECmBelong to M-E non-energy-transmission targets, then
Figure FDA00031391294600000212
The system optimization indexes are set as follows:
(1) M-E non-energy-transmission target positions
Figure FDA00031391294600000213
Received maximum power value and E targets to be transmitted
Figure FDA00031391294600000214
The ratio of the minimum received power value is defined as a side lobe value SLL of the energy transmission system;
(2) e targets to be transported
Figure FDA00031391294600000215
Total received power and N transmitting devices TR1～TRNThe ratio of the total emitted power is defined as the efficiency value eta of the energy transmission system;
(3) in order to take two energy output indexes of the system into consideration, a maximum efficiency threshold eta is setthAnd a minimum side lobe threshold SLLthAnd expressing the joint optimization indexes of the two by using a COST function COST: COST ═ w1·(SLL-SLLth)+w2·(ηth-η)，w1、w2Expressing an optimized weight coefficient between SLL and eta;
step 2-2. optimization of system feed-in signal
According to actual requirements, setting power distribution ratio w 'to [ w ] among E energy targets to be transmitted'1，w′2，…，w′E]I.e. satisfy
Figure FDA00031391294600000216
Wherein
Figure FDA00031391294600000217
Representing E targets to be energy-delivered
Figure FDA00031391294600000218
Respectively receiving the power of the energy transmission signals; in order to obtain the optimal feed-in signal under A energy transmission frequency points of the system, a weighting factor is used as an optimization variable, and the two indexes of a side lobe value SLL and energy transmission efficiency eta of the system are jointly optimized, wherein the specific optimization problem is characterized as follows:
Figure FDA0003139129460000031
Figure FDA0003139129460000032
a global optimization algorithm is adopted to obtain a series of optimal weighting factors which minimize COST
Figure FDA0003139129460000033
The feed-in signal under A energy transmission frequency points can be obtained as
Figure FDA0003139129460000034
Wherein
Figure FDA0003139129460000035
Step 2-3. transmission of system feed-in signal
The feed-in signals of all frequency points are obtained through the optimization
Figure FDA0003139129460000036
Superimposed to form an aggregate feed signal
Figure FDA0003139129460000037
The total feed-in signals are respectively fed into the corresponding N transmitting devices TR1～TRNAnd in the middle, the high-efficiency and low-sidelobe energy transmission can be realized for the expected E energy targets to be transmitted.
2. The multi-frequency multi-target selective energy delivery method of claim 1, wherein in step 2-2, the global optimization algorithm is a simplex algorithm, a genetic algorithm, or an ant colony algorithm.
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