A design method for millimeter wave coverage reflective surface for mobile robots

Abstract

The present invention discloses a design method for a millimeter wave covered reflective surface for a mobile robot. The present invention produces a reflective surface by optimizing the three-dimensional geometric structure of a planar unit array, which can cover the reflected electromagnetic wave to a special trajectory, thereby achieving signal enhancement and weakening in a specific robot moving trajectory area. The present invention first determines the trajectory of the mobile robot based on known path planning information; widens the trajectory of the mobile robot to obtain a target electromagnetic wave coverage area, and converts the target electromagnetic wave coverage area into a binary image to obtain an electromagnetic projection pattern; then performs electromagnetic caustic optimization based on geometric relationships to obtain a three-dimensional model of the reflective surface; and finally produces a millimeter wave covered reflective surface based on the three-dimensional model of the reflective surface. The present invention can cover electromagnetic waves of a special trajectory through a low-cost 3D printed reflective surface, making it possible to accurately control the distribution of electromagnetic waves, which helps to enhance the strength of communication signals and facilitates large-scale deployment.

Description

Technical Field

[0001] The invention belongs to the field of radio frequency control of wireless communications and relates to a design method for a millimeter wave coverage reflection surface for a mobile robot. Background Art

[0002] In the field of wireless communications, the obstruction of wireless signals has always been a major bottleneck. In order to solve this problem, the directional reflection of electromagnetic waves can be achieved by designing a reflective surface, so that the wireless signal can bypass obstacles. The existing intelligent reflective surface adjusts the different states of the reflective unit to reflect electromagnetic waves in a specific direction. However, this solution has high cost, slow adjustment speed, and large fluctuations in communication rate, making it difficult to support fast-moving robot communications. Therefore, the present invention designs a millimeter-wave covered reflective surface for mobile robots, which does not require the use of circuit structures, greatly reduces costs, and can cover electromagnetic waves on the robot's moving trajectory, ensuring highly reliable and high-speed wireless communications. Summary of the invention

[0003] In view of the serious obstruction of 6G wireless signals and the shortcomings of existing intelligent reflective surface solutions, such as high cost, slow adjustment speed and large fluctuation in communication rate, the present invention provides a design method for a millimeter-wave coverage reflective surface for mobile robots.

[0004] The object of the present invention is achieved through the following technical solution: a design method for a millimeter wave coverage reflection surface for a mobile robot, the method comprising the following steps:

[0005] S1, determine the trajectory of the mobile robot based on known path planning information;

[0006] S2, widening the trajectory of the mobile robot to obtain a target electromagnetic wave coverage area, and converting the target electromagnetic wave coverage area into a binary image to obtain an electromagnetic projection pattern;

[0007] S3, perform electromagnetic caustics optimization to obtain a three-dimensional model of the reflection surface, specifically:

[0008] S3.1, reflection surface-projection area grid mapping: mapping the reflection surface grids one by one to the robot trajectory of the projection area, where the projection area is the smallest rectangular area containing the robot trajectory;

[0009] S3.2, optimization of the normal vector of the reflection surface unit: relying on the geometric relationship, the plane normal vector is adjusted to meet the requirements by adjusting the height of the grid node, thereby reflecting the electromagnetic wave to the target projection area;

[0010] S3.3, phase superposition and constructive phase adjustment based on height control: Based on the phase characteristics of electromagnetic waves, the phases of different electromagnetic waves reflected on the same projection trajectory grid are superimposed and constructive through the height phase adjustment algorithm;

[0011] S4, manufacturing a millimeter wave covering reflection surface according to the three-dimensional reflection surface model.

[0012] Furthermore, for the p ×N p The projection area of ​​the grid contains N t The robot trajectory in the projection area of ​​the grid contains M r ×N r grids of reflection surfaces, and let each robot trajectory grid correspond to n reflection surface grids. in Indicates rounding down. At this time, N t ×n reflection surface grid mapping is completed, and for the remaining M reflection surfaces r ×N r -N t ×n grids, randomly mapping them to t The projection area of ​​the grid is on the robot trajectory.

[0013] Furthermore, the placement position of the reflecting surface must satisfy that all lines connecting the access point and the reflecting surface are not blocked by obstacles, and all lines connecting the reflecting surface and the projection track are not blocked by obstacles; the closer the distance between the reflecting surface and the projection track or the access point, the better.

[0014] Furthermore, for any point Q on the trajectory of the mobile robot i , when the reflective surface is used to eliminate the obstacle, the power P received by the robot at point Qi r (Q i ) is expressed as:

[0015]

[0016] Connect the access point to the robot trajectory point Q i The distance between them is denoted as d AP,i , connect the access point-reflection surface center and the access point-robot trajectory point Q i The angle between them is denoted as α RP,i , the access point - robot trajectory point Q i The angle between the center of the reflection surface and the robot trajectory point Qi is expressed as α AR,i , then according to the geometric relationship, the power P received by the robot at point Qi r (Q i ) is expressed as:

[0017]

[0018] Among them, σ max Indicates the maximum value of the radar cross-sectional area corresponding to the reflecting surface; η iIt represents the millimeter wave reflection loss introduced by the reflecting surface. The formula is as follows:

[0019]

[0020] For point Q on the trajectory of the mobile robot i In order to obtain the optimal reflective surface deployment position and orientation of the robot on the entire trajectory, the optimization goal is set to make the power P received by the robot at point Qi r (Q i ) is the largest; the optimization problem is expressed as follows:

[0021]

[0022] subject to:α AR,i ∈[α AR,min ,α AR,max ],α RP,i ∈[α RP,min ,α RP,max ]

[0023] Among them, [α AR,min ,α AR,max ] represents the α corresponding to the reflecting surface that enables the millimeter wave to bypass obstacles AR,i Range, [α RP,min ,α RP,max ] represents the α corresponding to the reflecting surface that enables the millimeter wave to bypass obstacles RP,i Scope; solve the optimization problem, and the optimal solution obtained includes the position and orientation of the reflecting surface;

[0024] For different points Q i The optimal deployment position and orientation of the reflecting surface are obtained respectively, and the centroid of different reflecting surface positions is taken as the actual deployment position of the reflecting surface. Since the position and orientation of the reflecting surface are coupled with each other, the actual deployment orientation of the reflecting surface is obtained.

[0025] Furthermore, the size of the reflection surface is determined by weighing the transmission power of the access point, the size of the projection track, the distance between the access point and the transmission surface, and the distance between the transmission surface and the projection area.

[0026] Furthermore, the number of grids of the emitting surface is determined by balancing the complexity of solving the reflection surface shape and the accuracy of electromagnetic caustics, and depends on the Rayleigh roughness criterion; in order to enable each reflection surface unit to have precise control capabilities, it is necessary to ensure that the roughness height difference h of the entire reflection surface satisfies h>λ / 8, where λ is the wavelength of the electromagnetic wave.

[0027] Furthermore, the S3.2 is specifically:

[0028] For the M r ×Nr The reflection unit corresponding to any one grid of the grid reflection surface is connected clockwise in sequence as ABDC, and the normal vector of the plane corresponding to the reflection unit is adjusted to vector N, which is obtained by the geometric relationship between the positions of the access point, the reflection unit, and the projection point;

[0029] For triangle ABC, take A as the coordinate origin of the reflection unit, fix the position of point A, fix the horizontal positions of points B and C, adjust the heights of points B and C so that the normal vector of triangle ABC is adjusted to vector N, solve the following equations to obtain the heights of points B and C:

[0030]

[0031] For triangle BDC, the positions of points B and C are known, and the horizontal position of point D is fixed. By adjusting the heights of points B and C, the normal vector of triangle BDC is adjusted to vector N. Solve the following equation to find the height of point D:

[0032]

[0033] Obtain the reflection surface M r ×N r The node height of each reflection unit is calculated to obtain the three-dimensional structure of the reflection surface.

[0034] Furthermore, S3.3 is specifically as follows: for j reflected waves projected onto the same projection track grid i, the superposition effect of the far-field function on the projection track grid i is f i :

[0035]

[0036] Among them, f e is the far-field function of the access point, is the distance from the access point to the reflector element i j The distance is the reflection surface unit i j The distance to the projection trajectory grid i, k0 = 2π / λ is the wave number in free space, λ is the wavelength of the electromagnetic wave, and i' represents the imaginary part;

[0037] In order to maximize the intensity of the electromagnetic wave projected onto the projection track grid i, it is necessary to ensure that the j reflected waves projected onto the same projection track grid i are constructed in phase, which can be formally expressed as follows:

[0038]

[0039] Where mod means taking the remainder; this means that for the reflection surface unit i projected onto the projection trajectory grid i jFor all reflective surface units i j All reflectors are labeled 1. 1 Keep the phase consistent, that is, the absolute value of the phase difference is approximately 0; this phase condition is met by further fine-tuning the grid point height of each reflection surface unit.

[0040] Furthermore, the fine adjustment of the grid point height of each reflective surface unit is implemented based on a height phase adjustment algorithm, specifically:

[0041] For each reflective surface unit i j , calculate the distance from the access point to the reflection surface unit i j Distance With the reflection surface unit i j Distance to the projection trajectory grid i The sum is recorded as Compare reflective surface unit i 1 With each reflective surface unit i j The phase difference from the access point through the reflection surface unit to the projection unit is recorded as Need for guarantee So if where Δd t is the maximum phase difference threshold, then the following iterative solution is performed:

[0042] if We should try to increase the distance from the access point to the reflector unit i j Distance With the reflection surface unit i j Distance to the projection trajectory grid i By reducing the reflection surface unit i j Height To achieve this, the reflective surface unit i j Height Each time the step size is reduced to z step The height of

[0043] if We should try to reduce the distance from the access point to the reflector element i j Distance With the reflection surface unit i j Distance to the projection trajectory grid i By increasing the reflective surface unit i j Height To achieve this, the reflective surface unit i j Height Each time the step size is increased to z step The height of

[0044] For each reflective surface unit i j Checking the phase difference condition If not, the above height adjustment operation is performed repeatedly until the phase difference condition is met. Until, and finally make it pass through the reflection surface unit i j The electromagnetic waves reaching the projection track grid i all maintain the same phase.

[0045] Furthermore, the S4 specifically includes: using 3D printing technology to produce a reflective surface geometric structure, and performing metal plating on the surface of the structure.

[0046] The beneficial effects of the present invention are as follows: the present invention optimizes the three-dimensional geometric structure of the planar unit array to produce a reflective surface, which can cover the reflected electromagnetic waves to a special track, thereby achieving signal enhancement and weakening in a specific robot movement track area. The present invention can cover electromagnetic waves of a special track through a low-cost 3D printed reflective surface, making it possible to precisely control the distribution of electromagnetic waves, which helps to enhance the communication signal strength and facilitates large-scale deployment. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. 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 paying creative labor.

[0048] Figure 1 It is a schematic diagram of the use scenario of the present invention;

[0049] Figure 2 is a schematic diagram of an idealized rectangular metal reflective surface model for oblique incidence of millimeter waves provided by an embodiment of the present invention;

[0050] Figure 3 is a schematic diagram of a reflection surface-projection area grid mapping provided by an embodiment of the present invention;

[0051] Figure 4 It is a schematic diagram of a reflector power and deployment position orientation model provided by an embodiment of the present invention;

[0052] Figure 5 is a schematic diagram of optimizing the normal vector of a reflection surface unit provided by an embodiment of the present invention;

[0053] Figure 6 It is a schematic diagram of phase superposition constructiveness based on height regulation provided by an embodiment of the present invention;

[0054] Figure 7 This is a schematic diagram of a 3D printed reflective surface with aluminum foil provided in an embodiment of the present invention;

[0055] Figure 8 It is a diagram of electric field strength covered by electromagnetic waves of different trajectories provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0056] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0057] It should be clear that the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0058] The embodiment of the present invention provides a design method for a millimeter wave coverage reflective surface for a mobile robot, the method comprising the steps of robot trajectory input, electromagnetic projection mode calculation, electromagnetic caustics optimization, reflective surface production, etc. The specific implementation method of each step is described in detail below.

[0059] Step 1: Robot trajectory input. Figure 1 The robot trajectory input depends on the known path planning information, which can be expressed in multiple points (such as Figure 1 The known path planning information can be the trajectory of the mobile robot with any parameters such as shape, size, and length.

[0060] Step 2: Electromagnetic projection pattern calculation. The input of the electromagnetic projection pattern calculation is the specified robot trajectory, and the output is the electromagnetic projection pattern. The electromagnetic projection pattern calculation is to widen the input robot trajectory to obtain the target electromagnetic wave coverage area, and convert the target electromagnetic wave coverage area into a binary image to obtain the electromagnetic projection pattern.

[0061] Step 3: Electromagnetic caustics optimization. The basic assumption of electromagnetic caustics optimization is to compare millimeter wave reflection to optical reflection. Since the smallest unit of any shape of reflective surface can be equivalent to a plane according to the principle of calculus, we first model the idealized rectangular metal reflective surface for oblique incidence of millimeter waves, as shown in the following figure: Figure 2 As shown, specifically: the access point acts as a transmitter, and the propagation direction vector of the incident electromagnetic wave emitted is a t , the electric field direction vector is The magnetic field direction vector is The size of the idealized rectangular metal reflective surface is L×L', the direction of the reflective surface is along the n vector direction, the vector directions of the two adjacent sides of the rectangle are l and l' respectively, after the incident electromagnetic wave is reflected by the rectangular metal plane, the propagation direction vector of the outgoing wave reaching the receiver (i.e., the communication module on the mobile robot) is a r, then for the receiver, the radar cross section (RCS) of the idealized rectangular metal reflector is:

[0062]

[0063] Among them, · represents the vector dot product, × represents the vector cross product, and λ represents the wavelength of the electromagnetic wave. It can be seen that when the size of the ideal rectangular metal reflector satisfies the condition L, L'≥λ, the Radar Cross Section (RCS) of the ideal rectangular metal reflector is:

[0064]

[0065] in, The above formula shows that when the size of the ideal rectangular metal reflective surface is much larger than the wavelength of the electromagnetic wave, the reflection of the electromagnetic wave passing through the ideal rectangular metal reflective surface is similar to optical reflection (or mirror reflection), that is, the incident angle is equal to the reflection angle. This condition is also the basic assumption and condition of the reflective surface design of the present invention.

[0066] Electromagnetic caustics optimization includes steps such as reflection surface-projection area grid mapping, reflection surface unit normal vector optimization, and phase superposition constructiveness based on height control.

[0067] Step 3.1: Reflection surface-projection area mesh mapping. Figure 3 Schematic diagram of reflection surface-projection area grid mapping provided by an embodiment of the present invention. Reflection surface-projection area grid mapping is to map the reflection surface grids one by one to a special track (i.e., a specified robot track) on the projection area, such as Figure 3 The N-shaped trajectory shown. p ×N p The projection area of ​​the grid contains N t The special trajectory of the projection area of ​​the grid contains M r ×N r Each special track grid corresponds to n reflection surface grids, where n is defined as follows:

[0068]

[0069] in, Indicates rounding down; at this time, N t ×n reflection surface mesh mapping is completed. r ×N r -N t ×n grids, randomly mapping them to t The projection area of ​​the grid is on a special track.

[0070] Specifically, the projection area is the smallest rectangular area containing the robot trajectory, which is evenly discretized into M p ×N p Grids, M p N p ≤M r N r .

[0071] Specifically, the placement position of the reflecting surface must satisfy the requirement that all lines connecting the access point and the reflecting surface are not blocked by obstacles, and all lines connecting the reflecting surface and the projection track are not blocked by obstacles; in order to make the signal of the projection track as strong as possible, the closer the distance between the reflecting surface and the projection track or the access point is, the better.

[0072] Specifically, Figure 4 is a schematic diagram of the reflector power and deployment position orientation model provided by an embodiment of the present invention. For any point Q on the trajectory of the mobile robot i For example, when the reflective surface is used to eliminate the obstacle, the robot is at point Q i The received power P r (Q i ) can be expressed as:

[0073]

[0074] Among them, P t is the power of the millimeter wave transmitted by the access point, G t is the millimeter wave antenna gain of the access point, G r is the millimeter wave antenna gain of the receiver (i.e., the communication module on the mobile robot), d AR,i is the distance from the access point to the center of the reflecting surface, d RP,i The point Q from the center of the reflection surface to the robot trajectory i The distance, σ i is the radar cross-sectional area RCS corresponding to the reflecting surface. Further, the access point and the robot trajectory point Q i The distance between them is denoted as d AP,i , connect the access point-reflection surface center and the access point-robot trajectory point Q i The angle between them is denoted as α RP,i , the access point - robot trajectory point Q i and the center of the reflective surface - robot trajectory point Q i The angle between them is denoted as α AR,i , then according to the geometric relationship, the power P received by the robot at point Qi r (Q i ) can be expressed as:

[0075]

[0076] in, represents the millimeter wave reflection loss introduced by the reflecting surface. Specifically, the numerator represents the grazing loss introduced by the reflecting surface in different directions, and the denominator represents the path loss introduced by the reflecting surface in different positions; σ max Indicates the maximum value of the radar cross-sectional area RCS corresponding to the reflecting surface. For point Q on the trajectory of the mobile robot i In order to obtain the optimal reflective surface deployment position and orientation of the robot on the entire trajectory, the optimization goal can be set to make the power P received by the robot at point Qi r (Q i ) is the largest. Therefore, the optimization problem can be written as follows:

[0077]

[0078] subject to:α AR,i ∈[α AR,min ,α AR,max ],α RP,i ∈[α RP,min ,α RP,max ]

[0079] Among them, [α AR,min ,α AR,max ] represents the α corresponding to the reflecting surface that enables the millimeter wave to bypass obstacles AR,i Range, [α RP,min ,α RP,max ] represents the α corresponding to the reflecting surface that enables the millimeter wave to bypass obstacles RP,i The above optimization problem can be solved by optimization algorithms such as stochastic gradient descent and greedy algorithm. The optimal solution obtained includes the position and orientation of the reflective surface. In order to obtain the optimal reflective surface deployment position and orientation of the robot on the entire trajectory, it is necessary to discretize the entire trajectory of the robot first, that is, to represent it as different points Q i ; Then, for different points Q i The optimal deployment position and orientation of the reflecting surface are obtained respectively, and finally the centroid of different reflecting surface positions is taken as the actual deployment position of the reflecting surface. Since the position and orientation of the reflecting surface are coupled with each other, the actual deployment orientation of the reflecting surface can be directly obtained.

[0080] Specifically, the overall size of the rectangular reflection surface is determined by weighing the transmission power of the access point, the size of the projection track, the distance between the access point and the transmission surface, and the distance between the transmission surface and the projection area.

[0081] Specifically, M r ×N rIt is determined by balancing the complexity of solving the shape of the reflecting surface and the accuracy of electromagnetic caustics, and relies on the Rayleigh roughness criterion. In order to enable each reflecting surface unit to have precise control capabilities, it is necessary to ensure that the roughness height difference h of the entire reflecting surface satisfies h>λ / (8cosθ), where λ is the wavelength of the electromagnetic wave and θ is the incident angle of the electromagnetic wave. In order to obtain the lower limit of the roughness height difference h of the entire reflecting surface, it is necessary to ensure that h>λ / 8. In order to describe the roughness height difference h of the reflecting surface, it is defined from the horizontal and vertical aspects respectively. The roughness height differences in the horizontal and vertical directions are

[0082]

[0083]

[0084] Among them, h i ' ,j Represents the height of the lower right corner of the reflective surface unit in the i-th row and j-th column.

[0085] Step 3.2: Optimize the normal vector of the reflection surface element. Figure 5 Schematic diagram of the optimization of the normal vector of the reflector unit provided by the embodiment of the present invention. The optimization of the normal vector of the reflector unit depends on the geometric relationship. By adjusting the height of the grid node, the plane normal vector meets the requirements, and then the electromagnetic wave is reflected to the target projection area. r ×N r The reflection unit corresponding to any grid of the grid reflection surface is connected clockwise in sequence as ABDC. The normal vector of the plane corresponding to the reflection unit is adjusted to vector N, and vector N can be obtained from the geometric relationship of the position of the access point, the reflection unit, and the projection point. For the triangle ABC, A is used as the coordinate origin of the reflection unit, the position of point A is fixed, and the horizontal positions of points B and C are fixed. The normal vector of triangle ABC is adjusted to vector N by adjusting the height of points B and C. Solve the following equation to obtain the height of points B and C:

[0086]

[0087] Similarly, for the triangle BDC, the positions of points B and C are known, the horizontal position of point D is fixed, and the normal vector of triangle BDC is adjusted to vector N by adjusting the heights of points B and C. Solve the following equation to find the height of point D:

[0088]

[0089] By analogy, we can obtain the reflection surface M r ×N r The node height of each reflection unit is calculated, and then the three-dimensional structure of the reflection surface is obtained.

[0090] Step 3.3: Constructive phase superposition based on height control. Figure 6 Schematic diagram of phase superposition and constructive phase adjustment based on height control provided by an embodiment of the present invention. Phase superposition and constructive phase adjustment based on height control takes into account the phase characteristics of electromagnetic waves. Through the height phase adjustment algorithm, the phases of different electromagnetic waves reflected on the same projection trajectory grid are superimposed and constructive, thereby improving the electromagnetic wave signal strength on the projection trajectory. For j reflected waves projected onto the same projection trajectory grid i, the superposition effect of the far-field function on the projection trajectory grid i is f i :

[0091]

[0092] Among them, f e is the far-field function of the access point, is the distance from the access point to the reflector element i j The distance is the reflection surface unit i j The distance to the projection trajectory grid i, k0 = 2π / λ is the wave number in free space, λ is the wavelength of the electromagnetic wave, and i' represents the imaginary part.

[0093] In order to maximize the intensity of the electromagnetic wave projected onto the projection track grid i, it is necessary to ensure that the j reflected waves projected onto the same projection track grid i are constructed in phase, which can be formally expressed as follows:

[0094]

[0095] Where mod means taking the remainder; this means that for the reflection surface unit i projected onto the projection trajectory grid i j For all reflective surface units i j All reflectors are labeled 1. 1 Keep the phase consistent, that is, the absolute value of the phase difference is approximately 0. This phase condition can be met by further fine-tuning the grid point height of each reflector unit.

[0096] Fine-tuning the grid point height of each reflective surface unit can be achieved based on a height phase adjustment algorithm. Specifically, for each reflective surface unit i j , calculate the distance from the access point to the reflection surface unit i j Distance With the reflection surface unit i j Distance to the projection trajectory grid i The sum is recorded as Compare reflective surface unit i 1 With each reflective surface unit i j The phase difference from the access point through the reflection surface unit to the projection unit is recorded as Need for guarantee So if where Δd t is the maximum phase difference threshold, then the following iterative solution is performed:

[0097] if This means that from the access point to the reflector element i 1 Distance With the reflection surface unit i 1 Distance to the projection trajectory grid i Exceeds the distance from the access point to the reflector element i j Distance With the reflection surface unit i j Distance to the projection trajectory grid i Therefore, we should try to increase the distance from the access point to the reflector unit i j Distance With the reflection surface unit i j Distance to the projection trajectory grid i This can be achieved by reducing the reflective surface unit i j Height To achieve, specifically, the reflection surface unit i j Height Each time the step size is reduced to z step The height of if This means that from the access point to the reflector element i 1 Distance With the reflection surface unit i 1 Distance to the projection trajectory grid i Less than the distance from the access point to the reflector unit i j Distance With the reflection surface unit i j Distance to the projection trajectory grid i Therefore, we should try to reduce the distance from the access point to the reflection surface unit i j Distance With the reflection surface unit i j Distance to the projection trajectory grid i This can be achieved by increasing the reflective surface unit i j Height To achieve, specifically, the reflection surface unit i j Height Each time the step size is increased to z step The height of where z step By balancing the speed of iterative solution and the accuracy of phase superposition and constructiveness, z in this embodiment is determined. step Take λ / 20.

[0098] Then, for each reflective surface unit i j Checking the phase difference condition If not, the above height adjustment operation is performed repeatedly until the phase difference condition is met. Until, and finally make it pass through the reflection surface unit i j The electromagnetic waves reaching the projection track grid i all maintain the same phase. t Need to be greater than z step , so that the phase superposition and constructive phase can converge. In this embodiment, Δd t Take λ / 10.

[0099] Step 4: Reflective surface production. The reflective surface can be produced through 3D printing technology, including 3D printing, metal plating and other steps. 3D printing is the use of 3D printing technology to produce a special reflective surface geometry, with no special requirements for material and structural strength; metal plating is the process of tightly covering the reflective surface with a metal material with high conductivity. The methods of metal plating include but are not limited to aluminum foil and electroplating. Figure 7 It is a schematic diagram of a 3D printed reflective surface with aluminum foil provided in an embodiment of the present invention.

[0100] The emitting surface is designed by the method of the present invention, and the design effect of the present invention is demonstrated through HFSS simulation experiments. Figure 8 This is a diagram of the electric field strength covered by electromagnetic waves with different trajectories during the experiment. It can be seen that under the four projection trajectories of N, E, S, and C, the trajectories of the 3D printed reflective surface are clear.

[0101] The above description is merely a preferred embodiment of one or more embodiments of the present specification and is not intended to limit one or more embodiments of the present specification. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of one or more embodiments of the present specification shall be included in the scope of protection of one or more embodiments of the present specification.

Claims

1. A design method for a millimeter wave coverage reflective surface for a mobile robot, characterized in that: include: S1, determine the trajectory of the mobile robot based on known path planning information; S2, widening the trajectory of the mobile robot to obtain a target electromagnetic wave coverage area, and converting the target electromagnetic wave coverage area into a binary image to obtain an electromagnetic projection pattern; S3, perform electromagnetic caustics optimization to obtain a three-dimensional model of the reflection surface, specifically: S3.1, reflection surface-projection area grid mapping: mapping the reflection surface grids one by one to the robot trajectory of the projection area, where the projection area is the smallest rectangular area containing the robot trajectory; For any point Q on the trajectory of the mobile robot i , when the reflective surface is used to eliminate the obstacle, the power P received by the robot at point Qi r (Q i ) is expressed as: Among them, P t is the power of the millimeter wave transmitted by the access point, G t is the millimeter wave antenna gain of the access point, G r is the receiver’s millimeter-wave antenna gain, d RP,i The point Q from the center of the reflection surface to the robot trajectory i The distance, σ i is the radar scattering cross-sectional area corresponding to the reflecting surface, λ is the wavelength of the electromagnetic wave; the access point and the robot trajectory point Q i The distance between them is denoted as d AP,i , connect the access point-reflection surface center and the access point-robot trajectory point Q i The angle between them is denoted as α RP,i , the access point - robot trajectory point Q i and the center of the reflective surface - robot trajectory point Q i The angle between them is denoted as α AR,i , then according to the geometric relationship, the robot is at point Q i The received power P r (Q i ) is expressed as: Among them, σ max Indicates the maximum value of the radar cross-sectional area corresponding to the reflecting surface; η i It represents the millimeter wave reflection loss introduced by the reflecting surface. The formula is as follows: For point Q on the trajectory of the mobile robot i In order to obtain the optimal reflective surface deployment position and orientation of the robot on the entire trajectory, the optimization goal is set to make the power P received by the robot at point Qi r (Q i ) is the largest; the optimization problem is expressed as follows: subject to:a AR,i ∈[a AR,min ,a AR,max ],a RP,i ∈[a RP,min ,a RP,max ] Among them, [α AR,min ,α AR,max ] represents the α corresponding to the reflecting surface that enables the millimeter wave to bypass obstacles AR,i Range, [α RP,min ,α RP,max ] represents the α corresponding to the reflecting surface that enables the millimeter wave to bypass obstacles RP,i Scope; solve the optimization problem, and the optimal solution obtained includes the position and orientation of the reflecting surface; For different points Q i The optimal deployment position and orientation of the reflective surface are obtained respectively, and the centroid of different reflective surface positions is taken as the actual deployment position of the reflective surface. Since the position and orientation of the reflective surface are coupled with each other, the actual deployment orientation of the reflective surface is obtained; S3.2, optimization of the normal vector of the reflection surface unit: relying on the geometric relationship, the plane normal vector is adjusted to meet the requirements by adjusting the height of the grid node, thereby reflecting the electromagnetic wave to the target projection area; S3.3, phase superposition and constructive phase adjustment based on height control: Based on the phase characteristics of electromagnetic waves, the phases of different electromagnetic waves reflected on the same projection trajectory grid are superimposed and constructive through the height phase adjustment algorithm; S4, manufacturing a millimeter wave covering reflection surface according to the three-dimensional reflection surface model.

2. The design method of a millimeter wave coverage reflective surface for a mobile robot according to claim 1, characterized in that: For the M p ×N p The projection area of ​​the grid contains N t The robot trajectory in the projection area of ​​the grid contains M r ×N r grids of reflection surfaces, and let each robot trajectory grid correspond to n reflection surface grids. in Indicates rounding down. At this time, N t ×n reflection surface grid mapping is completed, and for the remaining M reflection surfaces r ×N r -N t ×n grids, randomly mapping them to t The projection area of ​​the grid is on the robot trajectory.

3. The design method of a millimeter wave coverage reflective surface for a mobile robot according to claim 1, characterized in that: The placement position of the reflecting surface must satisfy that all lines connecting the access point and the reflecting surface are not blocked by obstacles, and all lines connecting the reflecting surface and the projection track are not blocked by obstacles; the closer the distance between the reflecting surface and the projection track or the access point, the better.

4. The design method of a millimeter wave coverage reflective surface for a mobile robot according to claim 1, characterized in that: The size of the reflection surface is determined by weighing the transmission power of the access point, the size of the projection track, the distance between the access point and the transmission surface, and the distance between the transmission surface and the projection area.

5. The design method of a millimeter wave coverage reflective surface for a mobile robot according to claim 1, characterized in that: The number of grids of the reflecting surface is determined by balancing the complexity of solving the reflecting surface shape and the accuracy of electromagnetic caustics, and depends on the Rayleigh roughness criterion; in order to enable each reflecting surface unit to have precise control capabilities, it is necessary to ensure that the roughness height difference h of the entire reflecting surface satisfies h>λ / 8, where λ is the wavelength of the electromagnetic wave.

6. The design method of a millimeter wave coverage reflective surface for a mobile robot according to claim 1, characterized in that: The S3.2 is specifically: For the M r ×N r The reflection unit corresponding to any one grid of the grid reflection surface is connected clockwise in sequence as ABDC, and the normal vector of the plane corresponding to the reflection unit is adjusted to vector N, which is obtained by the geometric relationship between the positions of the access point, the reflection unit, and the projection point; For triangle ABC, take A as the coordinate origin of the reflection unit, fix the position of point A, fix the horizontal positions of points B and C, adjust the heights of points B and C so that the normal vector of triangle ABC is adjusted to vector N, solve the following equations to obtain the heights of points B and C: For triangle BDC, the positions of points B and C are known, and the horizontal position of point D is fixed. By adjusting the heights of points B and C, the normal vector of triangle BDC is adjusted to vector N. Solve the following equation to find the height of point D: Obtain the reflection surface M r ×N r The node height of each reflection unit is calculated to obtain the three-dimensional structure of the reflection surface.

7. The design method of a millimeter wave coverage reflection surface for a mobile robot according to claim 1, characterized in that: S3.3 is specifically: for j reflected waves projected onto the same projection track grid i, the superposition effect of the far-field function on the projection track grid i is f i : Among them, f e is the far-field function of the access point, is the distance from the access point to the reflector element i j The distance is the reflection surface unit i j The distance to the projection trajectory grid i, k0 = 2π / λ is the wave number in free space, λ is the wavelength of the electromagnetic wave, and i' represents the imaginary part; In order to maximize the intensity of the electromagnetic wave projected onto the projection track grid i, it is necessary to ensure that the j reflected waves projected onto the same projection track grid i are constructed in phase, which can be formally expressed as follows: Where mod means taking the remainder; this means that for the reflection surface unit i projected onto the projection trajectory grid i j For all reflective surface units i j All reflectors are labeled 1. 1 Keep the phase consistent, that is, the absolute value of the phase difference is approximately 0; this phase condition is met by further fine-tuning the grid point height of each reflection surface unit.

8. The design method of a millimeter wave coverage reflective surface for a mobile robot according to claim 7, characterized in that: The fine adjustment of the grid point height of each reflective surface unit is implemented based on a height phase adjustment algorithm, specifically: For each reflective surface unit i j , calculate the distance from the access point to the reflection surface unit i j Distance With the reflection surface unit i j Distance to the projection trajectory grid i The sum is recorded as Compare reflective surface unit i 1 With each reflective surface unit i j The phase difference from the access point through the reflection surface unit to the projection unit is recorded as Need for guarantee So if where Δd t is the maximum phase difference threshold, then the following iterative solution is performed: if We should try to increase the distance from the access point to the reflector unit i j Distance With the reflection surface unit i j Distance to the projection trajectory grid i By reducing the reflection surface unit i j Height To achieve this, the reflective surface unit i j Height Each time the step size is reduced to z step The height of if We should try to reduce the distance from the access point to the reflector element i j Distance With the reflection surface unit i j Distance to the projection trajectory grid i By increasing the reflective surface unit i j Height To achieve this, the reflective surface unit i j Height Each time the step size is increased to z step The height of For each reflective surface unit i j Checking the phase difference condition If not, the above height adjustment operation is performed repeatedly until the phase difference condition is met. Until, and finally make it pass through the reflection surface unit i j The electromagnetic waves reaching the projection track grid i all maintain the same phase.

9. The design method of a millimeter wave coverage reflective surface for a mobile robot according to claim 1, characterized in that: The S4 specifically includes: using 3D printing technology to produce a reflective surface geometric structure, and performing metal coating on the surface of the structure.

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