CN110277839B - Diffraction-free controllable electromagnetic field generation method - Google Patents
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- H—ELECTRICITY
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- H—ELECTRICITY
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- H02J50/10—Circuit arrangements or systems for wireless supply or distribution of electric power using inductive coupling
- H02J50/12—Circuit arrangements or systems for wireless supply or distribution of electric power using inductive coupling of the resonant type
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Abstract
The invention provides a method for generating a diffraction-free controllable electromagnetic field. According to a required electromagnetic field distribution model under a given waveguide model, an optimal excitation coil set is calculated in a coil to be selected by using an orthogonal matching pursuit algorithm; calculating an autocorrelation matrix of the electromagnetic field distribution of each coil, and calculating a cross-correlation matrix of the electromagnetic field distribution of each coil and the required magnetic field distribution, so as to solve the optimal drive current vector of each coil; applying the corresponding optimal driving current vector to each coil, measuring to obtain a corresponding voltage vector, and calculating an impedance matrix among the coils and a load capacitance of each coil according to the current vector and the voltage vector; calculating a compensation capacitance for bringing the coil into resonance; and concentrically arranging the coils, configuring a compensation capacitor and applying an optimal driving current, wherein the generated electromagnetic field distribution is the required electromagnetic field distribution. The generated electromagnetic field has the characteristic of no diffraction, is adjusted and controlled according to the requirement, and has high transmission efficiency and strong anti-interference capability when being used for wireless power transmission.
Description
Technical Field
The invention belongs to the technical field of wireless power supply, and particularly relates to a method for generating a diffraction-free controllable electromagnetic field.
Background
Research has shown that when the size of an electromagnetic field emitting device is smaller than the wavelength of the electromagnetic field emitted by the device, the electromagnetic field emitted by the device has the characteristic of no diffraction. The electromagnetic field with excellent characteristics can be used in the fields of microwave ablation, wireless power transmission and the like, and particularly can improve the transmission efficiency of wireless power transmission and improve the anti-interference capability during transmission when being used for wireless power transmission. However, to date, there has been no practical solution for generating such diffraction-free electromagnetic fields with excellent properties.
Disclosure of Invention
In order to solve the technical problem, the invention provides a method for generating a diffraction-free controllable electromagnetic field.
In order to achieve the purpose, the invention adopts the technical scheme that the method for generating the diffraction-free controllable electromagnetic field comprises the following steps:
step 1: giving a required electromagnetic field distribution model under a waveguide model, and calculating an optimal excitation coil set in a coil to be selected by using an orthogonal matching pursuit algorithm;
step 2: calculating an autocorrelation matrix of a time function of electromagnetic field distribution of each coil, calculating a cross-correlation matrix of the time function of the electromagnetic field distribution of each coil and the time function of the magnetic field distribution required by each coil, and solving an optimal driving current vector of each coil according to the autocorrelation matrix and the cross-correlation matrix;
and step 3: applying corresponding optimal driving current vectors to the coils in the optimal excitation coil set, measuring to obtain voltage vectors applied to two ends of the coils, and calculating impedance matrixes among the coils and load capacitances of the coils according to the optimal driving current vectors and the voltage vectors at the two ends of the coils;
and 4, step 4: calculating a compensation capacitance for bringing the coil into resonance;
and 5: concentrically placing an optimal excitation coil to concentrate each coil, configuring a compensation capacitor and applying optimal driving current to obtain the electromagnetic field distribution generated at the moment;
preferably, the required electromagnetic field distribution model in step 1 is:
establishing a space rectangular coordinate system, and establishing a required electromagnetic field distribution model H under a waveguide model according to the required electromagnetic field size and space distribution given in advance d (x,y,z)；
The step 1 of calculating the optimal excitation coil set by using an orthogonal matching pursuit algorithm in the coils to be selected comprises the following steps:
step 1.1: h is to be d Is set as a residual H e I.e. H e ＝H d ；
Establishing an optimal excitation coil set model as S l ＝{l 1 ,l 2 ,...,l n }, the initial state is empty set
Wherein l i For the ith selected coil, i ∈ [1, n ]]N is less than or equal to N, N is the number of selected coils, and N is the total number of the selectable coils;
inputting the type of a lead, the shape of the coil, the size of the coil, the number of turns of the coil, the permeability of a medium, the relative dielectric constant of the medium and the frequency of a driving current into all coils to be selected, and establishing all selectable coils l under a waveguide model j Space electromagnetic field distribution model H j (x, y, z) where j ∈ [1,N ]]；
Setting an algorithm stop condition:
the upper limit m of the number of coils, wherein m is less than or equal to N, and the maximum allowable error H eMAX In which H eMAX ≥0；
Step 1.2: computing each H by orthogonal matching pursuit algorithm j And H e Set of degree of matching S c ＝{c 1 ,c 2 ,...,c N-n And selecting the electromagnetic field distribution with the highest matching degree, and marking as H b Adding the corresponding coil into the optimal excitation coil set S l And according to H b Updating residual H using orthogonal matching pursuit algorithm e ；
Step 1.3: repeating step 1.2 until the number of selected turns reaches the upper limit, i.e. n = m, or the residual H e Less than or equal to the maximum allowable error, i.e. H e ≤H eMAX 。
Preferably, the step 2 of calculating the autocorrelation matrix of the time function of the magnetic field distribution of each coil is as follows:
according to an autocorrelation function model of the periodic power signal:
according to the drive current period, i.e. T 0 Time difference τ, and the optimal excitation coil set S in step 1 l Time function H of magnetic field distribution of each coil i (t) modeling by the autocorrelation functionType calculation of each H i (t) autocorrelation matrix R ss ；
In step 2, the cross-correlation matrix for calculating the time function of the magnetic field distribution of each coil and the time function of the magnetic field distribution required by each coil is as follows:
using the cross-correlation function model:
according to the drive current period, i.e. T 0 Time difference τ, the optimal excitation coil set S in step 1 l Time function H of magnetic field distribution of each coil i (t) and the time function H of the desired magnetic field distribution d (t), calculating each H i (t) and H d (t) cross-correlation matrix V sd ；
In the step 2, solving the optimal driving current vector of each coil according to the autocorrelation matrix and the cross-correlation matrix is as follows:
I＝[I 1 I 2 … I n ] T
preferably, the optimal driving current vector in step 3 is: i = [ I = 1 I 2 … I n ] T ；
I i For the optimum drive current for the ith coil, i e [1, n ]]；
In step 3, the voltage vectors at the two ends of the coil are as follows: v = [ V ] 1 V 2 … V n ] T
V i For the voltage across the ith coil, i e [1, n ]]；
The step 3 of calculating the impedance matrix Z between the coils specifically includes:
Z＝VI -1
the step 3 of calculating the load capacitance of each coil specifically includes:
C loadi ＝1/(ω 0 Im(Z ii -Z Ti ))
wherein, Z Ti Is the load impedance of the i-th coil, C loadi Load capacitance of i-th coil, V i Is the voltage across the ith coil, I i And I m Optimum drive currents for the i-th and m-th coils, respectively, Z im Is an element of the impedance matrix Z in the ith row and the mth column, Z ii Is an element of the impedance matrix Z at row i and column i.
S Cload ＝{C load1 ,C load2 ,...,C loadn Is the load capacitance vector;
preferably, the calculation in step 4 is to calculate the compensation capacitance for the coil to reach resonance as follows:
Z t ＝V i /I i
C e ＝1/(ω 0 Im(Z t ))
wherein Z is t Is the equivalent impedance across the ith coil, C e Is the equivalent capacitance across the ith coil, I i Optimum drive current, V, for the ith coil i Is the voltage across the ith coil, C loadi Is the load capacitance of the i-th coil, C Ti A compensation capacitor for the ith coil;
S CT ＝{C T1 ,C T2 ,...,C Tn -is the compensation capacitance vector;
preferably, the optimal excitation coil set in step 5 is S l ＝{l 1 ,l 2 ,...,l n }；
In step 5, the configuration compensation capacitor is:
according to the compensation capacitance vector S CT ＝{C T1 ,C T2 ,...,C Tn Allocating a compensation capacitor for each coil;
in step 5, the optimal driving current is applied as follows:
according to the optimal drive current vector I = [ ] 1 I 2 … I n ] T Applying an optimal drive current to each coil;
the electromagnetic field distribution generated at this time in step 5 is the required electromagnetic field distribution H in step 1 d (x,y,z)；
Generated electromagnetic field distribution H d (x, y, z) depends on the ratio between the optimum driving currents applied to the respective coils, and the electromagnetic field strength depends on the magnitude of the optimum driving current, and control of the electromagnetic field distribution and strength can be achieved by varying the ratio and magnitude of the optimum driving currents.
The invention has the beneficial effects that: the generated electromagnetic field has the excellent characteristic of no diffraction, and has the transmission characteristics of higher transmission efficiency, stronger anti-interference capability and the like when being used for wireless power transmission; and the distribution and the size of the generated electromagnetic field can be adjusted and controlled according to needs.
Drawings
FIG. 1: a method flow diagram of the invention;
FIG. 2 is a schematic diagram: the invention relates to a flow chart of an orthogonal matching algorithm;
FIG. 3: the excitation coil, the compensation capacitor and the driving current source are connected in a graph;
FIG. 4 is a schematic view of: the invention discloses an overall schematic diagram of a diffraction-free electromagnetic field generating device.
Detailed Description
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 only a part of the embodiments of the present invention, and not all of the embodiments. 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.
The following describes a specific embodiment of the present invention with reference to the drawings, and a flow chart of the method of the present invention is shown in fig. 1, and comprises the following steps:
step 1: giving a required electromagnetic field distribution model under a waveguide model, and calculating an optimal excitation coil set in a coil to be selected by using an orthogonal matching pursuit algorithm;
the required electromagnetic field distribution model in the step 1 is as follows:
establishing a space rectangular coordinate system, and establishing a required electromagnetic field distribution model H under a waveguide model according to the required electromagnetic field size and space distribution given in advance d (x,y,z)；
In step 1, an orthogonal matching pursuit algorithm is used to calculate an optimal excitation coil set in a coil to be selected, and a flowchart of the orthogonal matching pursuit algorithm is shown in fig. 2, and includes the following steps:
step 1.1: h is to be d Is set as a residual H e I.e. H e ＝H d ；
Establishing an optimal excitation coil set model as S l ＝{l 1 ,l 2 ,...,l n The initial state is an empty set
Wherein l i For the ith selected coil, i ∈ [1, n ]]N is less than or equal to N, N is the number of selected coils, and N is the total number of the selectable coils;
inputting the type of a lead, the shape of the coil, the size of the coil, the number of turns of the coil, the relative magnetic permeability of a medium, the relative dielectric constant of the medium and the frequency of a driving current into all coils to be selected, and establishing all selectable coils l under a waveguide model j Space electromagnetic field distribution model H j (x, y, z) where j ∈ [1, N ]]；
In the embodiment, the type of the used lead wire is 0.1 multiplied by 400 litz wire, the coil is wound into a round shape, the radius of the coil is 4mm-50mm, and the number of turns of the coil is 1 turn; the relative permeability and the relative permittivity of the medium are both values in air, i.e. mu r ＝1，ε r =1; the driving current source is a high-frequency alternating current source, and the frequency is 13.56MHz. In practical application, according to the required electromagnetismDifferent types of wires can be selected according to different field distribution and sizes and different driving current frequencies, different coil shapes, coil sizes and coil turns can be wound, and the coil size is smaller than the wavelength of a required electromagnetic field; the relative magnetic permeability and relative dielectric constant of the medium are determined by the medium surrounding the coil; the frequency of the driving current source is selected according to actual requirements.
Setting an algorithm stop condition:
the upper limit m of the number of coils, wherein m is less than or equal to N, and the maximum allowable error H eMAX In which H is eMAX ≥0；
Step 1.2: computing each H by orthogonal matching pursuit algorithm j And H e Set of degree of matching S c ＝{c 1 ,c 2 ,...,c N-n And selecting the electromagnetic field distribution with the highest matching degree, and marking as H b Adding the corresponding coil into the optimal excitation coil set S l And according to H b Updating residual H using orthogonal matching pursuit algorithm e ；
Step 1.3: repeating step 1.2 until the number of selected turns reaches the upper limit, i.e. n = m, or the residual H e Less than or equal to the maximum allowable error, i.e. H e ≤H eMAX 。
Step 2: calculating an autocorrelation matrix of a time function of electromagnetic field distribution of each coil, calculating a cross-correlation matrix of the time function of the electromagnetic field distribution of each coil and the time function of the magnetic field distribution required by each coil, and solving an optimal driving current vector of each coil according to the autocorrelation matrix and the cross-correlation matrix;
in step 2, the autocorrelation matrix of the time function of the magnetic field distribution of each coil is calculated as follows:
according to an autocorrelation function model of the periodic power signal:
according to the period of the drive current, i.e. T 0 Time difference τ, and the optimal excitation coil set S in step 1 l Time function of magnetic field distribution of each coilNumber H i (t) calculating each H by the autocorrelation function model i (t) autocorrelation matrix R ss ；
The driving current period in this embodiment is T 0 =0.02s, the time difference is τ =0.005s. In practical application, the period of the driving current is determined by the frequency of the driving current, and the time difference is selected according to needs.
In step 2, the cross-correlation matrix of the time function of the magnetic field distribution of each coil and the time function of the magnetic field distribution required by each coil is calculated as follows:
using the cross-correlation function model:
according to the period of the drive current, i.e. T 0 Time difference τ, the optimal excitation coil set S in step 1 l Time function H of the magnetic field distribution of each coil i (t) and the time function H of the desired magnetic field distribution d (t), calculating each H i (t) and H d (t) cross-correlation matrix V sd ；
In the step 2, solving the optimal driving current vector of each coil according to the autocorrelation matrix and the cross-correlation matrix is as follows:
I＝[I 1 I 2 … I n ] T
step 3, applying the corresponding optimal driving current vector to each coil in the optimal excitation coil set, measuring to obtain voltage vectors applied to two ends of each coil, and calculating an impedance matrix between the coils and the load capacitance of each coil according to the optimal driving current vector and the voltage vectors at the two ends of each coil;
in step 3, the optimal driving current vector is: i = [ I = 1 I 2 … I n ] T ；
I i For optimal driving of the ith coilCurrent, i ∈ [1, n ]]；
In step 3, the voltage vectors at the two ends of the coil are as follows: v = [ V = 1 V 2 … V n ] T
V i Is the voltage across the ith coil, i ∈ [1, n ]]；
The step 3 of calculating the impedance matrix Z between the coils specifically includes:
Z＝VI -1
the calculating of the load capacitance of each coil in step 3 is specifically as follows:
C loadi ＝1/(ω 0 Im(Z ii -Z Ti ))
wherein Z is Ti Is the load impedance of the i-th coil, C loadi Is the load capacitance of the i-th coil, V i Is the voltage across the ith coil, I i And I m Optimum drive currents for the i-th and m-th coils, respectively, Z im Is an element of the impedance matrix Z in the ith row and the mth column, Z ii Is an element of the impedance matrix Z at row i and column i.
and 4, step 4: calculating a compensation capacitance for bringing the coil into resonance;
in step 4, the compensation capacitance for enabling the coil to achieve resonance is calculated as follows:
Z t ＝V i /I i
C e ＝1/(ω 0 Im(Z t ))
wherein, Z t Is the equivalent impedance across the ith coil, C e Is the equivalent capacitance across the ith coil, I i Is the optimum drive current, V, of the ith coil i Is the voltage across the ith coil, C loadi Load capacitance of the i-th coil, C Ti A compensation capacitor for the ith coil;
and 5: concentrically placing an optimal excitation coil to concentrate each coil, configuring a compensation capacitor and applying an optimal driving current to obtain the electromagnetic field distribution generated at the moment;
fig. 3 shows a connection diagram of the excitation coil, the compensation capacitor and the driving current source, and fig. 4 shows an overall schematic diagram of the non-diffraction electromagnetic field generating device of the present embodiment.
In step 5, the optimal excitation coil set is S l ＝{l 1 ,l 2 ,...,l n }；
In step 5, the configuration compensation capacitor is:
according to the compensation capacitance vector
Configuring a compensation capacitor for each coil;
in step 5, the optimal driving current is applied as follows:
according to the optimal drive current vector I = [ ] 1 I 2 … I n ] T Applying an optimal drive current to each coil;
the electromagnetic field distribution generated at this time in step 5 is the required electromagnetic field distribution H in step 1 d (x,y,z)；
Generated electromagnetic field distribution H d (x, y, z) depends on the ratio between the optimum driving currents applied to the respective coils, and the electromagnetic field strength depends on the magnitude of the optimum driving current, and control of the electromagnetic field distribution and strength can be achieved by varying the ratio and magnitude of the optimum driving currents.
It should be understood that parts of the specification not set forth in detail are of the prior art.
It should be understood that the above description of the preferred embodiments is given for clarity and not for any purpose of limitation, and that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (6)
1. A method for generating a controllable electromagnetic field without diffraction, comprising the steps of:
step 1: giving a required electromagnetic field distribution model under a waveguide model, and calculating an optimal excitation coil set in a coil to be selected by using an orthogonal matching pursuit algorithm;
step 2: calculating an autocorrelation matrix of a time function of electromagnetic field distribution of each coil, calculating a cross-correlation matrix of the time function of the electromagnetic field distribution of each coil and the time function of the magnetic field distribution required by each coil, and solving an optimal driving current vector of each coil according to the autocorrelation matrix and the cross-correlation matrix;
and step 3: applying corresponding optimal driving current vectors to the coils in the optimal excitation coil set, measuring to obtain voltage vectors applied to two ends of the coils, and calculating impedance matrixes among the coils and load capacitances of the coils according to the optimal driving current vectors and the voltage vectors at the two ends of the coils;
and 4, step 4: calculating a compensation capacitance for bringing the coil into resonance;
and 5: and concentrically placing the optimal excitation coil to concentrate each coil, configuring a compensation capacitor and applying optimal driving current to obtain the electromagnetic field distribution generated at the moment.
2. The method of claim 1, wherein the model of the electromagnetic field distribution of step 1 is:
establishing a space rectangular coordinate system according to the preset required electromagnetic field size sumSpatial distribution, establishing a required electromagnetic field distribution model H under a waveguide model d (x,y,z)；
The step 1 of calculating the optimal excitation coil set in the coil to be selected by using an orthogonal matching pursuit algorithm comprises the following steps:
step 1.1: will H d Is set as a residual H e I.e. H e ＝H d ；
Establishing an optimal excitation coil set model as S l ＝{l 1 ,l 2 ,...,l n }, the initial state is empty set
Wherein l i For the ith selected coil, i ∈ [1, n ]]N is less than or equal to N, N is the number of selected coils, and N is the total number of the selectable coils;
inputting the type of a lead, the shape of the coil, the size of the coil, the number of turns of the coil, the permeability of a medium, the relative dielectric constant of the medium and the frequency of a driving current into all coils to be selected, and establishing all selectable coils l under a waveguide model j Spatial electromagnetic field distribution model H j (x, y, z) where j ∈ [1,N ]]；
Setting an algorithm stop condition:
the upper limit m of the number of coils, wherein m is less than or equal to N, and the maximum allowable error H eMAX In which H is eMAX ≥0；
Step 1.2: computing each H by orthogonal matching pursuit algorithm j And H e Set of degree of matching S c ＝{c 1 ,c 2 ,...,c N-n And selecting the electromagnetic field distribution with the highest matching degree, and marking as H b Adding the corresponding coil into the optimal excitation coil set S l And according to H b Updating residual H using orthogonal matching pursuit algorithm e ；
Step 1.3: repeating step 1.2 until the number of selected turns reaches the upper limit, i.e. n = m, or the residual H e Less than or equal to the maximum allowable error, i.e. H e ≤H eMAX 。
3. The method of claim 1, wherein the step 2 of calculating the autocorrelation matrix of the time function of the magnetic field distribution of each coil is:
according to an autocorrelation function model of the periodic power signal:
according to the drive current period, i.e. T 0 Time difference τ, and the optimal excitation coil set S in step 1 l Time function H of magnetic field distribution of each coil i (t) calculating each H by the autocorrelation function model i (t) autocorrelation matrix R ss ；
In step 2, the cross-correlation matrix for calculating the time function of the magnetic field distribution of each coil and the time function of the magnetic field distribution required by each coil is as follows:
using the cross-correlation function model:
according to the period of the drive current, i.e. T 0 Time difference τ, the optimal excitation coil set S in step 1 l Time function H of the magnetic field distribution of each coil i (t) and the time function H of the desired magnetic field distribution d (t), calculating each H i (t) and H d (t) cross-correlation matrix V sd ；
In step 2, solving the optimal driving current vector of each coil according to the autocorrelation matrix and the cross-correlation matrix is as follows:
I＝[I 1 I 2 …I n ] T 。
4. according toThe method of generating a diffraction-free controllable electromagnetic field according to claim 1, wherein the optimal driving current vector in step 3 is: i = [ I = 1 I 2 …I n ] T ；
I i For the optimum drive current for the ith coil, i e [1, n ]]；
In step 3, the voltage vectors at the two ends of the coil are as follows: v = [ V ] 1 V 2 …V n ] T
V i Is the voltage across the ith coil, i ∈ [1, n ]]；
The step 3 of calculating the impedance matrix Z between the coils specifically includes:
Z＝VI -1
the step 3 of calculating the load capacitance of each coil specifically includes:
C loadi ＝1/(ω 0 Im(Z ii -Z Ti ))
wherein Z is Ti Is the load impedance of the i-th coil, C loadi Is the load capacitance of the i-th coil, V i Is the voltage across the ith coil, I i And I m Optimum drive currents for the i-th and m-th coils, respectively, Z im Is an element of the impedance matrix Z in the ith row and the mth column, Z ii Is an element of the ith row and the ith column of the impedance matrix Z;
5. The method of generating a diffraction-free controllable electromagnetic field according to claim 1, wherein the calculating of the compensation capacitance for bringing the coil into resonance in step 4 is:
Z t ＝V i /I i
C e ＝1/(ω 0 Im(Z t ))
wherein Z is t Is the equivalent impedance across the ith coil, C e Is the equivalent capacitance across the ith coil, I i Is the optimum drive current, V, of the ith coil i Is the voltage across the ith coil, C loadi Load capacitance of the i-th coil, C Ti A compensation capacitor for the ith coil;
6. The method of claim 1, wherein the optimal excitation coil set in step 5 is S l ＝{l 1 ,l 2 ,...,l n }；
In step 5, the configuration compensation capacitor is:
according to the compensation capacitance vector
Configuring a compensation capacitor for each coil;
in step 5, the optimal drive current is applied as follows:
according to the optimal drive current vector I = [ ] 1 I 2 …I n ] T Applying an optimal drive current to each coil;
the electromagnetic field distribution generated at this time in step 5 is the required electromagnetic field distribution H in step 1 d (x,y,z)；
Generated electromagnetic field distribution H d (x, y, z) is determined by the ratio between the optimum driving currents applied to the respective coils, and the intensity of the electromagnetic field is determined by the magnitude of the optimum driving current, which can be realized by varying the ratio and magnitude of the optimum driving currentsThe electromagnetic field distribution and intensity are now controlled.
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