A robust multi-coverage placement method for directional wireless chargers

Abstract

The present invention discloses a method for robust multi-coverage placement of a directional wireless charger, including: setting a set of rechargeable sensors; defining a placement strategy of a directional wireless charger; formalizing the robust multi-coverage problem of a directional wireless charger; using a region partitioning method to obtain a discretized finite set of sub-regions and a set of candidate coverage sensors; calling the directional wireless charger placement strategy discretization algorithm to obtain a finite directional wireless charger placement strategy space; calling the directional wireless charger robust multi-coverage placement algorithm to obtain a placement plan for the position and charging direction of the directional wireless charger. The method provided by the present invention enables a wireless rechargeable sensor network to charge normally even when there are a small number of faulty chargers, ensures that each sensor is covered by multiple chargers, minimizes the number of placed chargers, and meets the charging robustness requirements of the wireless rechargeable sensor network at the lowest cost.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless rechargeable sensor networks, and in particular to a robust multi-coverage placement method for directional wireless chargers. Background Art

[0002] Wireless energy transmission has been widely used in wireless rechargeable sensor networks. Sensors in the network obtain energy from wireless chargers through receivers. Directional wireless charging and directional sensors have attracted widespread attention from academia and the business community because of their more efficient and stable energy transmission. That is, energy can be transmitted when the charger and sensor are in their respective fan-shaped sensing areas.

[0003] At present, there are few studies on the robust placement of wireless chargers. Only a few scholars have studied the robustness of transmission energy fluctuations and electromagnetic radiation fluctuations caused by electromagnetic jitter. Since directional wireless chargers are precision electronic instruments with a large number of electronic components, these components may have various faults, such as packaging faults, contact faults, printed circuit board faults, relay faults, etc. In addition, the external environment may also cause directional wireless chargers to fail. For example, lightning can generate electromagnetic pulses and damage directional wireless chargers by generating overvoltage and surges. Dust may also affect the reliability of printed circuit board assembly. At the same time, vibration, aging, corrosion, humidity, cold and heat can cause human and non-human failures. However, current research does not take into account the charging robustness problem caused by directional wireless charger failures, which is common in precision electronic instruments such as directional wireless chargers. Summary of the invention

[0004] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0005] In view of the above-mentioned problems, the present invention is proposed.

[0006] Therefore, the technical problem solved by the present invention is that a large number of electronic components in the current directional wireless charger may have various faults, such as packaging faults, contact faults, printed circuit board faults, relay faults, etc. In addition, the external environment may also cause the directional wireless charger to fail, and its failure will bring about the common problem of charging robustness.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions: a directional wireless charger robust multi-coverage placement method, comprising:

[0008] Set up a collection of rechargeable sensors;

[0009] Define placement strategies for directional wireless chargers;

[0010] Formalize the robust multi-coverage problem of directional wireless chargers;

[0011] The region partitioning method is used to obtain a discretized limited sub-region set and its candidate coverage sensor set;

[0012] Calling the directional wireless charger placement strategy discretization algorithm to obtain a limited directional wireless charger placement strategy space;

[0013] The directional wireless charger robust multi-coverage placement algorithm is called to obtain a placement solution of the position and charging direction of the directional wireless charger.

[0014] As a preferred solution of the directional wireless charger robust multi-coverage placement method described in the present invention, wherein: the rechargeable sensor set is: a rechargeable sensor set S with fixed position and direction = {s1, s2, ..., s n}, the charging area is a two-dimensional plane Ω, wherein the directional wireless charger is placed in the charging area Ω.

[0015] As a preferred solution of the robust multi-coverage placement method of the directional wireless charger described in the present invention, before defining the placement strategy of the directional wireless charger, the charging power of the directional wireless charger is functionalized, and the charging power is the charging power of the rechargeable sensor s i From directional wireless charger o j The obtained value is expressed as:

[0016]

[0017] Wherein, the directional wireless charger and the rechargeable sensor have charging angles A and s and receiving angle A o , α and β are two constants determined by the magnetic field environment and hardware parameters of the directional wireless charger and the rechargeable sensor, D is the maximum charging distance at which positive power can be obtained from the directional wireless charger, d(s i ,o j ) is a directional wireless charger o j With rechargeable sensors i The distance between For directional wireless charger o j The charging direction vector, For rechargeable sensors i The receiving direction vector, when d(s i ,o j)≤D, and , the rechargeable sensor always obtains positive power.

[0018] As a preferred solution of the robust multi-coverage placement method of the directional wireless charger described in the present invention, the placement strategy of the directional wireless charger includes:

[0019] Obtain the selection situation x(o) of the directional wireless charger placement strategy j ,θ j )

[0020]

[0021] Among them, (o j ,θ j ) represents directional wireless charger o j Location j and direction θ j , i.e., the placement strategy of the directional wireless charger; represents the set of placement strategies for deployed directional wireless chargers, is the placement strategy space consisting of all possible placement strategies on plane Ω;

[0022] Define the directional wireless charger placement strategy (o j ,θ j ) under all non-zero power of the rechargeable sensor set S(o j ,θ j )

[0023] S(o j ,θ j )={s i |P(s i ,o j ,φ i ,θ j )>0} (3)

[0024] Among them, P(s i ,o j ,φ i ,θ j ) is a rechargeable sensor s i From directional wireless charger o j The charging power obtained.

[0025] As a preferred solution of the directional wireless charger robust multi-coverage placement method described in the present invention, the formalized directional wireless charger robust multi-coverage problem includes:

[0026] Establishing constraints Among them, λ iis a positive constant representing the rechargeable sensor s i At least need to be i Directional wireless charger coverage;

[0027] Establish constraints j ∈Ω,0≤θ j <2π;

[0028] Minimizing the number of directional wireless chargers deployed is the optimization goal, and the directional wireless charger robust multi-coverage problem is defined as:

[0029]

[0030]

[0031] o j ∈Ω,0≤θ j <2π (6)

[0032] As a preferred solution of the directional wireless charger robust multi-coverage placement method described in the present invention, the area division method includes:

[0033] For each of the rechargeable sensors s i ∈S, with rechargeable sensor s i As the center of the circle, with the maximum charging radius D as the radius, a sector is constructed according to the receiving direction and receiving angle of the rechargeable sensor;

[0034] Segmenting all sub-areas according to the geometric relationship of all the constructed sectors;

[0035] For each of the sub-regions, let F i , define the sub-region F i The rechargeable sensor set that can cover the sub-area is the candidate coverage sensor set

[0036] As a preferred solution of the directional wireless charger robust multi-coverage placement method described in the present invention, the directional wireless charger placement strategy discretization algorithm includes:

[0037] R1: Select a sub-region F that has not been calculated. i ;

[0038] R2: Select the sub-region F i The candidate coverage sensor set Any pair of rechargeable sensors in , set as s1 and s2;

[0039] R3: execute projection partitioning algorithm;

[0040] R4: execute translation partitioning algorithm;

[0041] R5: Repeat steps R2 to R4 until the candidate coverage sensor set Each pair of rechargeable sensors has been selected;

[0042] R6: Execute the rotation partitioning algorithm in the sub-area F i A point is randomly selected from the boundary as the deployment position of the directional wireless charger, and its charging direction is rotated counterclockwise from 0 degrees to 360 degrees to cover the rechargeable sensors one by one. First, the direction of the directional charger is initialized to 0 degrees. During the rotation process, if some covered rechargeable sensor nodes will be uncovered, the current charging direction is marked as the dominant direction. Then continue to rotate. If some covered rechargeable sensors will be uncovered after the new sensor nodes are covered, the current direction is marked as the dominant direction. During the rotation process, if the rotation angle is greater than 360 degrees, the rotation is terminated, and all the dominant directions obtained are combined with the current charger deployment position into a directional wireless charger placement strategy, and the directional wireless charger placement strategy is incorporated into the directional wireless charger placement strategy space.

[0043] R7: Placement strategy space in directional wireless chargers Delete the placement strategies that are a subset of other directional charger placement strategies;

[0044] R8: Repeat steps R1 to R7 until all the sub-regions F i The strategies have been chosen;

[0045] R9: Return to the limited directional wireless charger placement strategy space

[0046] As a preferred solution of the method for robust multi-coverage placement of directional wireless chargers described in the present invention, the projection partitioning algorithm is to set a straight line passing through s1 and s2, and extend the straight line to intersect with the sub-area boundary. The charger is placed at these intersections, and its direction is adjusted so that s1 and s2 are exactly located on the clockwise boundary of the directional wireless charger coverage area, and the current directional wireless charger placement strategy is obtained and incorporated into the directional wireless charger placement strategy space.

[0047] As a preferred solution of the directional wireless charger robust multi-coverage placement method described in the present invention, the translation partitioning algorithm is to set two arcs passing through s1 and s2 and forming an angle A with them. sThen calculate the intersection points of the trajectory and the partition boundary, place the chargers at these intersections, and make s1 and s2 exactly on the two boundaries of the charger coverage area, obtain the current charger placement strategy, and incorporate it into the directional wireless charger placement strategy space

[0048] As a preferred solution of the directional wireless charger robust multi-coverage placement method of the present invention, the directional wireless charger robust multi-coverage placement algorithm includes:

[0049] A1: Initialize the placement strategy set of the deployed directional wireless charger is an empty set;

[0050] A2: For each of the rechargeable sensors s i ∈S, initialize its remaining coverage times λ i ′ is λ i ;

[0051] A3: Strategically place space on all directional wireless chargers Get the placement strategy with the largest effective coverage (o j ,θ j ), that is, in Is the directional wireless charger placement strategy (o h ,θ h ) effective coverage;

[0052] A4: j ,θ j ) merged into In, that is

[0053] A5: Update each of the rechargeable sensors i ∈S(o j ,θ j )’s remaining coverage, that is, let λ′ i =λ i ′-min{1,λ i '};

[0054] A6: Repeat steps A3 to A5 until the sum of the remaining coverage times of all rechargeable sensors is 0, that is,

[0055] A7: Returns the placement strategy set of deployed directional wireless chargers

[0056] Beneficial effects of the invention: The invention aims at the problem that wireless chargers may fail in wireless rechargeable sensor networks, and provides a method for robust multi-coverage placement of directional wireless chargers, so that the wireless rechargeable sensor network can be charged normally even when there are a small number of faulty chargers. The invention minimizes the number of placed chargers while ensuring that each sensor is covered by multiple chargers, and meets the charging robustness requirements of the wireless rechargeable sensor network at the lowest cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0058] Figure 1 A flowchart of a method for robust multi-coverage placement of a directional wireless charger provided by an embodiment of the present invention;

[0059] Figure 2 A schematic diagram of sensor deployment in a robust multi-coverage placement method for a directional wireless charger provided by an embodiment of the present invention;

[0060] Figure 3 A schematic diagram of sub-regions after the middle region is segmented in a method for robust multi-coverage placement of a directional wireless charger provided by an embodiment of the present invention;

[0061] Figure 4 A flowchart of a charger placement strategy discretization algorithm in a directional wireless charger robust multi-coverage placement method provided by an embodiment of the present invention;

[0062] Figure 5 A schematic diagram of projection division in a robust multi-coverage placement method for a directional wireless charger provided by an embodiment of the present invention;

[0063] Figure 6 A schematic diagram of translational partitioning in a robust multi-coverage placement method for a directional wireless charger provided by an embodiment of the present invention;

[0064] Figure 7 A schematic diagram of rotation partitioning in a robust multi-coverage placement method for a directional wireless charger provided by an embodiment of the present invention;

[0065] Figure 8 A flowchart of a directional wireless charger robust multi-coverage placement algorithm in a directional wireless charger robust multi-coverage placement method provided by one embodiment of the present invention;

[0066] Fig. 9 A directional charger placement scheme outputted from a directional wireless charger robust multi-coverage placement method provided by an embodiment of the present invention;

[0067] Fig.10 A comparison diagram of the effects of a robust multi-coverage placement method for a directional wireless charger provided in the third embodiment of the present invention;

[0068] Fig.11 A physical experiment diagram of a robust multi-coverage placement method for a directional wireless charger provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0069] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0070] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0071] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0072] The present invention is described in detail with reference to schematic diagrams. When describing the embodiments of the present invention, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0073] At the same time, in the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper, lower, inner and outer" are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first, second or third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0074] In the present invention, unless otherwise clearly specified and limited, the terms "install, connect, connect" should be understood in a broad sense, for example: it can be a fixed connection, a detachable connection or an integral connection; it can also be a mechanical connection, an electrical connection or a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0075] Example 1

[0076] Reference Figure 1 , 4 -8, is an embodiment of the present invention, providing a directional wireless charger robust multi-coverage placement method, comprising:

[0077] S1: Set the rechargeable sensor set;

[0078] Specifically, the rechargeable sensor set is: a rechargeable sensor set S with fixed position and direction = {s1, s2, ..., s n}, the charging area is a two-dimensional plane Ω, wherein the directional wireless charger is placed in the charging area Ω.

[0079] S2: define the placement strategy of the directional wireless charger;

[0080] Furthermore, before defining the placement strategy of the directional wireless charger, the charging power of the directional wireless charger is functionalized, and the charging power is the rechargeable sensor s i From directional wireless charger o j The obtained value is expressed as:

[0081]

[0082] The directional wireless charger and the rechargeable sensor have charging angles A and B respectively. s and receiving angle A o , α and β are two constants determined by the magnetic field environment and hardware parameters of the directional wireless charger and the rechargeable sensor. D is the maximum charging distance at which positive power can be obtained from the directional wireless charger. d(s i ,o j ) is a directional wireless charger o j With rechargeable sensors i The distance between For directional wireless charger o j The charging direction vector, For rechargeable sensors i The receiving direction vector, when d(s i ,o j )≤D, and The rechargeable sensor always draws positive power.

[0083] Specifically, the placement strategies for directional wireless chargers include:

[0084] Get the selection of directional wireless charger placement strategy x(o j ,θ j )

[0085]

[0086] Among them, (o j ,θ j ) represents directional wireless charger o j Location j and direction θ j , i.e., the placement strategy of directional wireless chargers; represents the set of placement strategies for deployed directional wireless chargers, is the placement strategy space consisting of all possible placement strategies on plane Ω;

[0087] Define directional wireless charger placement strategy (o j ,θ j ) is the set of all non-zero-power rechargeable sensors S(o j ,θ j )

[0088] S(o j ,θ j )={s i |P(s i ,o j ,φ i ,θ j )>0} (3)

[0089] Among them, P(s i ,o j ,φ i ,θ j ) is a rechargeable sensor s i From directional wireless charger o j The charging power obtained.

[0090] S3: Formalizing the robust multi-coverage problem of directional wireless chargers;

[0091] Furthermore, the formalized directional wireless charger robust multi-coverage problem includes:

[0092] Establishing constraints The purpose is to ensure that all rechargeable sensors meet their coverage requirements, where λ iis a positive constant representing the rechargeable sensor s i At least need to be i Directional wireless charger covers,

[0093] It should be noted that rechargeable sensors i The more important it is to the sensor network, the i The bigger;

[0094] Establish constraints j ∈Ω,0≤θ j <2π, the purpose is to ensure that all directional wireless chargers can be placed at any position in any charging direction;

[0095] Minimizing the number of directional wireless chargers deployed is the optimization goal, and the directional wireless charger robust multi-coverage problem is defined as:

[0096]

[0097]

[0098] o j ∈Ω,0≤θ j <2π (6)

[0099] S4: Use the region partitioning method to obtain a discretized finite set of sub-regions and their candidate coverage sensor sets;

[0100] Specifically, the regional division method includes:

[0101] For each rechargeable sensor i ∈S, with rechargeable sensor s i As the center of the circle, with the maximum charging radius D as the radius, a sector is constructed according to the receiving direction and receiving angle of the rechargeable sensor;

[0102] Divide all sub-areas according to the geometric relationship of all constructed sectors;

[0103] For each sub-region, let F i , define sub-region F i The rechargeable sensor set that can cover the sub-area is the candidate coverage sensor set

[0104] S5: calling the directional wireless charger placement strategy discretization algorithm to obtain a limited directional wireless charger placement strategy space;

[0105] Specifically, the discretization algorithm of the directional wireless charger placement strategy includes:

[0106] R1: Select a sub-region F that has not been calculated i ;

[0107] R2: Select sub-region F i The candidate coverage sensor set Any pair of rechargeable sensors in , set as s1 and s2;

[0108] R3: execute projection partitioning algorithm;

[0109] Specifically, the projection partitioning algorithm sets a straight line passing through s1 and s2 and extends the straight line to intersect with the sub-area boundary. The charger is placed at these intersections and its direction is adjusted so that s1 and s2 are exactly located on the clockwise boundary of the directional wireless charger coverage area. The current directional wireless charger placement strategy is obtained and incorporated into the directional wireless charger placement strategy space.

[0110] R4: execute translation partitioning algorithm;

[0111] Specifically, the translation partitioning algorithm is to set two arcs passing through s1 and s2, and form an angle A with them. s Then calculate the intersection points of the trajectory and the partition boundary, place the chargers at these intersections, and make s1 and s2 exactly on the two boundaries of the charger coverage area, obtain the current charger placement strategy, and incorporate it into the directional wireless charger placement strategy space

[0112] R5: Repeat steps R2 to R4 until the candidate coverage sensor set is Each pair of rechargeable sensors has been selected;

[0113] R6: Execute the rotation partitioning algorithm, in sub-region F i A point is randomly selected from the boundary as the deployment location of the directional wireless charger, and its charging direction is rotated counterclockwise from 0 degrees to 360 degrees to cover the rechargeable sensors one by one. First, the direction of the directional charger is initialized to 0 degrees. During the rotation process, if some covered rechargeable sensor nodes will be uncovered, the current charging direction is marked as the dominant direction. Then continue to rotate. If some covered rechargeable sensors will be uncovered after the new sensor nodes are covered, the current direction is marked as the dominant direction. During the rotation process, if the rotation angle is greater than 360 degrees, the rotation is terminated, and all the dominant directions obtained are combined with the current charger deployment position into a directional wireless charger placement strategy, and the directional wireless charger placement strategy is incorporated into the directional wireless charger placement strategy space.

[0114] R7: Placement strategy space in directional wireless chargers Delete the placement strategies that are a subset of other directional charger placement strategies;

[0115] R8: Repeat steps R1 to R7 until all sub-regions F i The strategies have been chosen;

[0116] R9: Return to the limited directional wireless charger placement strategy space

[0117] S6: calling the directional wireless charger robust multi-coverage placement algorithm to obtain a placement plan for the position and charging direction of the directional wireless charger.

[0118] Specifically, the directional wireless charger robust multi-coverage placement algorithm includes:

[0119] A1: Initialize the placement strategy set of deployed directional wireless chargers is an empty set;

[0120] A2: For each rechargeable sensor i ∈S, initialize its remaining coverage times λ i ′ is λ i ;

[0121] A3: Strategically place space on all directional wireless chargers Get the placement strategy with the largest effective coverage (o j ,θ j ), that is, in Is the directional wireless charger placement strategy (o h ,θ h ) effective coverage;

[0122] It should be noted that in this step, finding the layout strategy with the maximum effective coverage takes The time, where the calculation It takes O(n) time. Since each time a charger is selected, at least one sensor can be covered, so steps A3 to A5 take a total of The area division method in step S4 can divide the charging area Ω into no more than 5n 2 -5n+2 sub-regions. Each sub-region generates at most O(n 2 ) charger placement strategies. Therefore, there are In summary, the time complexity of the directional wireless charger robust coverage scheduling algorithm is That is, the directional wireless charger robust coverage scheduling algorithm is a polynomial time algorithm.

[0123] A4: j ,θj ) merged into In, that is

[0124] A5: Update each rechargeable sensor i ∈S(o j ,θ j )’s remaining coverage, that is, let λ′ i =λ i ′-min{1,λ i '};

[0125] A6: Repeat steps A3 to A5 until the sum of the remaining coverage times of all rechargeable sensors is 0, that is,

[0126] A7: Returns the placement strategy set of deployed directional wireless chargers

[0127] It should be noted that the directional wireless charger robust multi-coverage placement algorithm is a polynomial time algorithm and can be executed in a relatively fast time.

[0128] At the same time, the approximation ratio of the directional wireless charger robust multi-coverage placement algorithm is H n , compared with the optimal solution, its performance error can be guaranteed at the logarithmic level, that is, fewer chargers need to be placed.

[0129] In order to prove that its approximation ratio is H n , you can see the following description:

[0130] According to the definition of the objective function in S3, it is proved that the directional wireless charger robust coverage problem can be reduced to the set multi-cover problem in polynomial time. Since the set multi-cover problem is NP-hard, the directional wireless charger robust coverage problem is also NP-hard. In addition, there is a polynomial time solution for the set multi-cover problem.

[0131] First, the mathematical model of the original problem is linearly transformed

[0132]

[0133]

[0134]

[0135] Consider a set S(o j ,θ j ). The sensor nodes are numbered in the order that meets their coverage requirements. Let the sorted element sequence be s1, s2, …, s q. Assume that the last node covered by the last iteration of the algorithm is s i In the above case, S(o j ,θ j ) contains at least q-i+1 unsatisfied sensor nodes. Therefore, in this iteration, S(o j ,θ j )The maximum coverage cost is 1 / (q-i+1). (The coverage cost is the number of chargers required to cover the sensor nodes.) At the same time, cost(s i ,λ i )≤1 / (q-i+1). Obviously, cost(s i ,1)≤cost(s i ,2)≤…≤cost(s i ,λ i ), let y i = cost(s i ,λ i ) / H n , where H n is the harmonic function.

[0136] Then, according to the above, construct a set of vectors y = (y1, y2, ..., y n ), we can get the following formula

[0137] Therefore, y is a set of feasible solutions to the DP problem.

[0138] Let cost(s i ,S(o j ,θ j )) as sensors i The set S(o j ,θ j ) The cost of coverage. Let OPT′ and OPT be the optimal solutions of the problems DP and CPRC, then we can obtain the following inequality.

[0139]

[0140] Therefore, the approximation ratio of the directional wireless charger robust coverage scheduling algorithm is H n .

[0141] This proves that compared with the optimal solution, its performance error can be guaranteed at the logarithmic level, which means that fewer chargers need to be placed.

[0142] Example 2

[0143] Reference Figure 1-9, is an embodiment of the present invention. In step S1 of this embodiment, the set of rechargeable sensors is S = {s1, s2, s3, s4, s5, s6, s7}, and the deployment of sensors is as follows Figure 2 As shown in the figure, 7 sensors are deployed in a 4m×4m two-dimensional plane Ω, and the charging area is a 4m×4m 2D plane area Ω. Each sensor has a fan-shaped receiving area. The information of each sensor is shown in Table 1, where Ω takes the lower left corner as the coordinate origin, that is, the coordinate of the lower left corner is (0, 0), and the coordinate of the upper right corner is (4.4).

[0144] Table 1 Sensor information table

[0145]

[0146] In this example, α=100, β=40 are set in the charging power of the functionalized directional wireless charger, the maximum charging distance D=1.5m, and the charging angle A of the directional wireless charger is s =45°, the sensor receiving angle is A o = 60°, therefore, d(s i ,o j )≤D, therefore When , the sensor can always obtain positive power. Therefore, substituting the parameters into formula (1), we get:

[0147]

[0148] This embodiment includes the following steps in step S2:

[0149] Get the selection of charger placement strategy x(o j ,θ j )

[0150]

[0151] Among them, (o j ,θ j ) represents the charger o j Location j and direction θ j , i.e., the placement strategy of the charger; represents the placement strategy of the deployed chargers, For all placement strategies;

[0152] Obtained by the charging strategy (o j ,θ j ) obtains the sensor set S(o j ,θ j )

[0153] S(o j ,θ j )={s i |P(s i ,o j ,φ i ,θ j )>0} (3)

[0154] Among them, P(s i ,o j ,φ i ,θ j ) is the sensor s i From the charger j The charging power obtained;

[0155] In step S3 of this embodiment, the steps are as follows:

[0156] Establishing constraints Ensure that all rechargeable sensors meet their coverage requirements, where λ i Represents rechargeable sensors i At least need to be i Directional wireless charger covers, rechargeable sensors i The more important it is to the sensor network, the i The larger the value, in this example, λ1=1, λ2=1, λ3=1, λ4=1, λ5=1, λ6=1, λ7=1;

[0157] Establish constraints j ∈Ω,0≤θ j <2π, ensuring that all rechargeable sensors can be placed at any position in any charging direction;

[0158] Minimizing the number of wireless chargers deployed is the optimization goal, and a unified formal wireless charging robust coverage problem is obtained:

[0159]

[0160]

[0161] o j ∈Ω,0≤θ j <2π (6)

[0162] In this embodiment, the sub-regions after the region segmentation are as follows: Figure 3 As shown, this embodiment includes the following steps in step S4:

[0163] For each sensor s i ∈S, with sensor s iAs the center of the circle, with the maximum charging radius D as the radius, a sector is constructed according to the receiving direction and receiving angle of the sensor;

[0164] All sub-areas are divided according to the geometric relationship of all constructed sectors. For the convenience of explanation, Figure 3 It shows that sensors s1 and s2 segmented three sub-regions, defined as F1, F2, and F3;

[0165] Define the candidate coverage sensor set of F1, F2, and F3

[0166] The flowchart of the charger placement strategy discretization algorithm in step S5 of this embodiment is as follows Figure 4 As shown, the following steps are included:

[0167] R1: Select an uncalculated sub-region F obtained in step S4 i , in this example, sub-region F1 is selected for detailed description;

[0168] R2: Select the candidate coverage sensor set for sub-area F1 Any pair of sensors in is set as s1 and s2;

[0169] R3: Figure 5 As shown, this embodiment performs projection partitioning on s1 and s2 to obtain the strategy (o1, θ1), (o2, θ1), the sensor set covered by (o1, θ1) is {s1, s2}, and the sensor set covered by (o2, θ1) is {s1, s2, s3}.

[0170] R4: Figure 6 As shown, this embodiment performs translation partitioning on s4 and s5 to obtain strategies (o3, θ2) and (o4, θ3), which can cover the sensor sets {s4, s5, s6} and {s4, s5, s7} respectively.

[0171] R5: Repeat steps R2 to R4 until Each pair of sensors has been selected.

[0172] R6: Figure 7 As shown, in sub-area F i A point o5 is randomly selected from the boundary of the charger as the deployment position of the charger, and its charging direction is rotated counterclockwise from 0 degrees to 360 degrees to cover the sensors one by one. First, the direction of the charger is initialized to 0 degrees, such as Figure 7As shown in (a), during the rotation process, if some covered sensor nodes will be uncovered, the current charging direction is marked as the dominant direction. Then continue to rotate. If some covered sensors will be uncovered after the new sensor nodes are covered, the current direction is marked as the dominant direction. During the rotation process, if the rotation angle is greater than 360 degrees, the rotation is terminated. Figure 7 Three dominant directions were obtained, namely Figure 7 (b), covering sensors {s1,s2}, Figure 7 (c) Covering sensor {s3}, Figure 7 (d) Covering sensors {s4, s5}, all dominant directions obtained are combined with the current deployment position into a charger placement strategy and incorporated into the charger placement strategy space

[0173] R7: Identify and delete some placement strategies in the strategy space. {s1, s2} is included in {s1, s2, s3}, {s3} is included in {s1, s2, s3}, and {s4, s5} is included in {s4, s5, s6}. Finally, the set of placement strategies is obtained as shown in Table 2.

[0174] R8: Repeat steps R1 to R7 until all sub-regions F i The strategies have been chosen;

[0175] R9: Return to limited charger placement strategy space

[0176] Table 2 Deployment strategy set in sub-region F1

[0177] Deployment strategy Covering sensor collection <![CDATA[{o2,θ1}]]> <![CDATA[{s1,s2,s3}]]> <![CDATA[{o3,θ2}]]> <![CDATA[{s4,s5,s6}]]> <![CDATA[{o4,θ3}]]> <![CDATA[{s4,s5,s7}]]>

[0178] In this embodiment, the specific steps of the directional wireless charger robust multi-coverage placement algorithm in step S6 are as follows: Figure 8 As shown:

[0179] A1: Initialization, the placement strategy of the deployed chargers is an empty set;

[0180] A2: According to each sensor S = {s1, s2, s3, s4, s5, s6, s7} in this example, initialize their remaining coverage times λ′1 = λ1 = 1, λ′2 = λ2 = 1, λ′3 = λ3 = 2, λ′4 = λ4 = 1, λ′5 = λ5 = 1, λ′5 = λ5 = 1, λ′6 = λ6 = 1, λ′7 = λ7 = 1;

[0181] A3: In all placement strategies Get the placement strategy with the largest effective coverage (o j ,θj ),Right now According to this example, the placement strategy with the largest effective coverage is {o2,θ1};

[0182] A4: Merge (o1,θ1) into the placement strategy of the already deployed chargers Right now

[0183] A5: For each sensor s i ∈S(o3,θ1), in this example, it is sensor {s3,s4}, and its remaining coverage times are updated, that is, λ′ i =λ i ′-min{1,λ i ′}, in this example, λ′1=λ1′-1, λ′2=λ2′-1, λ′3=λ3′-1;

[0184] A6: Repeat steps A3 to A5 until the sum of the remaining coverage times of the sensor is 0. In this example, (o2,θ1), (o3,θ2), and (o4,θ3) are selected in sequence;

[0185] A7: Returns the placement strategy of deployed chargers The directional charger placement scheme finally output by this embodiment is shown in Fig. 9 , the fan-shaped area is the charging area.

[0186] Example 3

[0187] Reference Fig.10 , which is another implementation case of the present invention. In order to verify and illustrate the technical effect adopted in the present method, this embodiment involves three schemes for comparative testing with the present invention method.

[0188] (1) Random Position and Dominant Direction Algorithm: This algorithm places chargers in an iterative manner, and randomly selects positions and dominant directions in each iteration as long as the selected strategy can increase the coverage of at least one sensor node.

[0189] (2) Random Position and Maximum Dominant Direction Algorithm: This algorithm places chargers in an iterative manner, and in each iteration, randomly selects a position and a dominant direction that covers most sensor nodes.

[0190] (3) Random Position and Maximum Edge Dominant Direction Algorithm: This algorithm places chargers in an iterative manner, and each iteration randomly selects a position and a dominant direction with maximum edge coverage.

[0191] Parameter setting: Distribute the sensor nodes evenly in a 60m×60m square area. Set α=100, β=40, D=6m, n=100, A s =π / 2,A o =2π / 3,. For each s i ∈S,λ i The values ​​of key parameters are varied uniformly distributed in [1,3] to explore the impact on the design algorithm. All simulations are run on a Windows machine equipped with an Intel(R) Xeon(R) CPU E5-2603 v2 and 16GB of memory. Each measurement is averaged over 100 random topologies.

[0192] like Fig.10 As shown, the directional wireless charger robust multi-coverage placement algorithm is compared with the other three algorithms.

[0193] Number of sensors: Fig.10 (a), the directional wireless charger robust multi-coverage placement algorithm outperforms the random position and dominant direction algorithm, the random position and maximum dominant direction algorithm, and the random position and maximum edge dominant direction algorithm by 22.32%, 18.65%, and 17.48%, respectively. In terms of the maximum coverage requirement, Fig.10 (b), the directional wireless charger robust multi-coverage placement algorithm outperforms the random position and dominant direction algorithm, the random position and maximum dominant direction algorithm, and the random position and maximum edge dominant direction algorithm by 28.09%, 23.95%, and 21.47%, respectively.

[0194] In terms of receiving angle, Fig.10 (c), the directional wireless charger robust multi-coverage placement algorithm is 28.91%, 24.99%, and 22.18% better than the random position and dominant direction algorithm, the random position and maximum dominant direction algorithm, and the random position and maximum edge dominant direction algorithm, respectively.

[0195] Charging angle, such as Fig.10 (d), the average performance of the directional wireless charger robust multi-coverage placement algorithm is 29.35%, 24.91%, and 22.65% better than the random position and dominant direction algorithm, the random position and maximum dominant direction algorithm, and the random position and maximum edge dominant direction algorithm, respectively.

[0196] Example 4

[0197] Reference Fig.11, is another implementation case of the present invention. To verify the technical effect of the method, an experiment is conducted in a 4m×4m area, where four sensor nodes are placed at any position in the area with coordinates of (1.72, 0.95), (2.75, 2.16), (0.84, 1.94) and (3.22, 1.91), and the coverage requirements are 2, 1, 2 and 1. The detailed strategies of the four algorithms are as follows Fig.11 and Table 3. The random position and dominance direction algorithm is as follows Fig.11 As shown in (a), the random position and maximum dominant direction algorithm is as follows Fig.11 As shown in (b), the random position and maximum edge dominance direction algorithm is as follows Fig.11 As shown in (c), the directional wireless charger robust multi-coverage placement algorithm is as follows Fig.11 (d) It can be seen that the directional wireless charger robust multi-coverage placement algorithm only uses 5 chargers to cover all sensor nodes. However, the number of chargers for the random position and dominant direction algorithm, the random position and maximum dominant direction algorithm, and the random position and maximum edge dominant direction algorithm are 11, 8, and 9, respectively.

[0198] Table 3 Charger placement strategies of different algorithms

[0199]

[0200] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for robust multi-coverage placement of directional wireless chargers, characterized in that: include: Set up a collection of rechargeable sensors; Define placement strategies for directional wireless chargers; Formalize the robust multi-coverage problem of directional wireless chargers; The formalized directional wireless charger robust multi-coverage problem includes: Establishing constraints Among them, (o j ,θ j ) is the placement strategy with the largest effective coverage; i is a positive constant representing the rechargeable sensor s i At least need to be i directional wireless charger covers; S is a collection of rechargeable sensors; Establish constraints j ∈Ω,0≤θ j <2π; Minimizing the number of directional wireless chargers deployed is the optimization goal, and the directional wireless charger robust multi-coverage problem is defined as: o j ∈Ω,0≤θ j <2π Where Ω is the charging area, which is a two-dimensional plane; x(o j ,θ j ) is the selection of the directional wireless charger placement strategy; is the placement strategy space consisting of all possible placement strategies on plane Ω; The region partitioning method is used to obtain a discretized limited sub-region set and its candidate coverage sensor set; Calling the directional wireless charger placement strategy discretization algorithm to obtain a limited directional wireless charger placement strategy space; Invoking a directional wireless charger robust multi-coverage placement algorithm to obtain a placement plan for the position and charging direction of the directional wireless charger; The directional wireless charger robust multi-coverage placement algorithm includes: A1: Initialize the placement strategy set of the deployed directional wireless charger is an empty set; A2: For each rechargeable sensor i ∈S, initialize its remaining coverage times λ i ′ is λ i ; A3: Strategically place space on all directional wireless chargers Get the placement strategy with the largest effective coverage (o j ,θ j ), that is, in Is the directional wireless charger placement strategy (o h ,θ h ) effective coverage; A4: j ,θ j ) merged into In, that is A5: Update each rechargeable sensor i ∈S(o j ,θ j )’s remaining coverage, that is, let λ′ i =λ i ′-min{1,λ i '}; A6: Repeat steps A3 to A5 until the sum of the remaining coverage times of all rechargeable sensors is 0, that is, A7: Returns the placement strategy set of deployed directional wireless chargers 2. The method for robust multi-coverage placement of directional wireless chargers according to claim 1, characterized in that: The rechargeable sensor set is: a rechargeable sensor set S with fixed position and direction = {s1, s2, ..., s n }, the charging area is a two-dimensional plane Ω, wherein the directional wireless charger is placed in the charging area Ω.

3. The method for robust multi-coverage placement of a directional wireless charger according to claim 1 or 2, characterized in that: Before defining the placement strategy of the directional wireless charger, the charging power of the directional wireless charger is functionalized, and the charging power is the charging power of the rechargeable sensor s i From directional wireless charger o j The obtained value is expressed as: Wherein, the directional wireless charger and the rechargeable sensor have charging angles A and s and receiving angle A o , α and β are two constants determined by the magnetic field environment and hardware parameters of the directional wireless charger and the rechargeable sensor, D is the maximum charging distance at which positive power can be obtained from the directional wireless charger, d(s i ,o j ) is a directional wireless charger o j With rechargeable sensors i The distance between Directional wireless charger j The charging direction vector, For rechargeable sensors i The receiving direction vector, when d(s i ,o j )≤D, and , the rechargeable sensor always obtains positive power.

4. The method for robust multi-coverage placement of a directional wireless charger according to claim 3, characterized in that: The placement strategy of the directional wireless charger includes: Obtain the selection situation x(o) of the directional wireless charger placement strategy j ,θ j ) Among them, (o j ,θ j ) represents directional wireless charger o j Location j and direction θ j , i.e., the placement strategy of the directional wireless charger; represents the set of placement strategies for deployed directional wireless chargers, is the placement strategy space consisting of all possible placement strategies on plane Ω; Define the directional wireless charger placement strategy (o j ,θ j ) under all non-zero power of the rechargeable sensor set S(o j ,θ j ) S(o j ,i j )={s i |P(s i ,o j ,f i ,i j )>0} Among them, P(s i ,o j ,φ i ,θ j ) is a rechargeable sensor s i From directional wireless charger o j The charging power obtained.

5. The method for robust multi-coverage placement of a directional wireless charger according to claim 4, characterized in that: The area division method comprises: For each of the rechargeable sensors s i ∈S, with rechargeable sensor s i As the center of the circle, with the maximum charging radius D as the radius, a sector is constructed according to the receiving direction and receiving angle of the chargeable sensor; Segmenting all sub-areas according to the geometric relationship of all the constructed sectors; For each of the sub-regions, let F i , define the sub-region F i The rechargeable sensor set that can cover the sub-area is the candidate coverage sensor set 6. The method for robust multi-coverage placement of a directional wireless charger according to claim 5, characterized in that: The directional wireless charger placement strategy discretization algorithm includes: R1: Select a sub-region F that has not been calculated. i ; R2: Select the sub-region F i The candidate coverage sensor set Any pair of rechargeable sensors in , set as s1 and s2; R3: execute projection partitioning algorithm; R4: execute translation partitioning algorithm; R5: Repeat steps R2 to R4 until the candidate coverage sensor set Each pair of rechargeable sensors has been selected; R6: Execute the rotation partitioning algorithm in the sub-region F i A point is randomly selected from the boundary as the deployment position of the directional wireless charger, and its charging direction is rotated counterclockwise from 0 degrees to 360 degrees to cover the rechargeable sensors one by one. First, the direction of the directional charger is initialized to 0 degrees. During the rotation process, if some covered rechargeable sensor nodes will be uncovered, the current charging direction is marked as the dominant direction; then the rotation continues. If some covered rechargeable sensors will be uncovered after the new sensor nodes are covered, the current direction is marked as the dominant direction; during the rotation process, if the rotation angle is greater than 360 degrees, the rotation is terminated, and all the dominant directions obtained are combined with the current charger deployment position into a directional wireless charger placement strategy, and the directional wireless charger placement strategy is incorporated into the directional wireless charger placement strategy space. R7: Placement strategy space in directional wireless chargers Delete the placement strategies that are a subset of other directional charger placement strategies; R8: Repeat steps R1 to R7 until all the sub-regions F i The strategies have been chosen; R9: Return to the limited directional wireless charger placement strategy space 7. The method for robust multi-coverage placement of a directional wireless charger according to claim 6, characterized in that: The projection partitioning algorithm is to set a straight line passing through s1 and s2, and extend the straight line to intersect with the boundary of the sub-area, place the charger at these intersections, and adjust its direction so that s1 and s2 are exactly located on the clockwise boundary of the directional wireless charger coverage area, obtain the current directional wireless charger placement strategy, and incorporate it into the directional wireless charger placement strategy space 8. The method for robust multi-coverage placement of a directional wireless charger according to claim 7, characterized in that: The translation partitioning algorithm is to set two arcs passing through s1 and s2 and forming an angle A with them. s Then calculate the intersection points of the trajectory and the partition boundary, place the chargers at these intersections, and make s1 and s2 exactly on the two boundaries of the charger coverage area, obtain the current charger placement strategy, and incorporate it into the directional wireless charger placement strategy space

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