阅读说明：本技术 无线电信标系统 (Radio beacon system ) 是由 D·皮亚扎 G·梅纳 L·雷佳尼 于 2018-06-13 设计创作，主要内容包括：一种被配置为帮助一个或多个无人飞行器(UAV)的自主飞行的无线电信标系统,其中,所述无线电信标系统包括：-无人机装置(200),其被配置为安装在UAV上并且包括无线电收发器；以及-无线电信标装置(100),其被配置为安装在地面上并且包括：N个天线阵列(110、120),其中,N≥2；被配置为与无人机装置(200)的无线电收发器通信的一个或多个无线电收发器；以及至少一个处理单元(130),其中,每个天线阵列(110、120)具有与相应的波束成形电子权重w(n,m)相关联的M个天线元件(115、125),其中,M≥2,n的范围为1至N,m的范围为1至M,其中,所述至少一个处理单元(130)被配置为执行用于帮助UAV的自主飞行的自适应波束成形方法。(radio beacon system configured to facilitate autonomous flight of or more Unmanned Aerial Vehicles (UAVs), wherein the radio beacon system comprises-a drone apparatus (200) configured to be mounted on a UAV and comprising a radio transceiver, and-a radio beacon apparatus (100) configured to be mounted on the ground and comprising N antenna arrays (110, 120), wherein N ≧ 2, or more radio transceivers configured to communicate with the radio transceiver of the drone apparatus (200), and at least processing units (130), wherein each antenna array (110, 120) has M antenna elements (115, 125) associated with respective beamforming electronic weights w (N, M), wherein M ≧ 2, N ranges from 1 to N, M ranges from 1 to M, wherein the at least processing units (130) are configured to perform an adaptive beamforming method for assisted autonomous flight of the UAV.)

1, an adaptive beamforming method for facilitating autonomous flight of a UAV on which an unmanned aerial device (200) comprising a radio transceiver is mounted, the adaptive beamforming method comprising the steps of:

A. setting (700) beamforming electronic weights w (n, m) to respective initial values w₀(n, m) ofWhere N ranges from 1 to N and M ranges from 1 to M, where a beamforming electronic weight w (N, M) is associated with N antenna arrays (110, 120) of a ground-mounted radio beacon device (100), where N ≧ 2, the radio beacon device (100) including or more radio transceivers configured to communicate with a radio transceiver of the drone device (200), where each antenna array (110, 120) has M antenna elements (115, 125), where M ≧ 2, where an initial value w of the beamforming electronic weight w (N, M) is₀(N, m) directing the main beam (1150, 1250) of the array directivity function (1100, 1200) of the N antenna arrays (110, 120) in respective N directions at different angles to each other with respect to an axis orthogonal to the ground, whereby the distance (d) between the N antenna arrays (110, 120) and the drone device (200) and of the N antenna arrays (110, 120) when the N antenna arrays (110, 120) receive a signal from a radio transceiver of the drone device (200)_n) Correlated, at least received signal quantity measures M selected from sets of physical parameters of the received signal_n,k(d_n) Is different for each of the N antenna arrays (110, 120);

B. calculating (710) a difference vector Δ M 'having or more elements'_kThe or more elements are at least at least sample times t_kA subset of the at least received signal quantities measure differences between each of all combinations of two antenna arrays among the N antenna arrays (110, 120);

C. will be difference vector delta M'_k or a plurality of elements of and a target vector Δ M_TRGIs compared (720) with corresponding or more target values, the or more target values defining at least Defined Zones (DZI)₁；DZI₂)；

D. Outputting (730) one or more commands (C)_j) To assist the UAV with respect to the at least defined regions (DZI)₁；DZI₂) And the or more commands (C)_j) To the drone device (200);

E. updating (740) the beamforming electronic weights w (n, m) such thatDifference vector delta M'_kIs maximized at altitude h and/or in a particular position of the drone device (200) above ground, and returns to performing step B until an end event occurs.

2. The adaptive beamforming method according to claim 1, wherein the at least received semaphore measures are changed according to a previous execution of step B when returning from step E to the execution of step B.

3. The adaptive beamforming method according to claim 1 or 2, wherein after returning from step E to performing step B, in step C, the difference vector Δ M 'is added'_k or a plurality of elements of and a target vector Δ M_TRGIs compared to corresponding or more target values, the or more target values defining at least Defined Zones (DZI) as previously defined₁；DZI₂) At least distinct demarcated regions (DZI)₁；DZI₂) Thus, a gradually changing trajectory of the UAV's flight plan is defined.

4. The adaptive beamforming method according to any of the preceding claims, wherein the set of physical parameters comprises or consists of received signal strength, phase rotation and propagation time.

5. The adaptive beamforming method of any of the preceding claims, wherein the difference vector Δ M'_kIs the difference between each of all combinations of two antenna arrays among the N antenna arrays (110, 120) of the at least received semaphore measures, whereby a difference vector Δ M_kWith a number of elements equal to the number of 2-combinations of N elements.

6. The adaptive beamforming method according to any of the preceding claims , wherein the difference vector Δ isM’_kIs an average E [ Δ M ] over time of a time series of differences of the at least received semaphore measures between two antenna arrays among the N antenna arrays (110, 120)_q(p)]Optionally a weighted average.

7. The adaptive beamforming method according to any of the preceding claims , wherein the target vector Δ Μ_TRGThe or more target values are dependent on a time according to a flight plan of the UAV and/or an altitude h of the drone device (200) above ground.

8. The adaptive beamforming method according to any of the preceding claims , wherein the at least delimited areas (DZI)₁；DZI₂) Is a spatial volume and/or surface and/or line and/or a single point.

9. The adaptive beamforming method according to any of the preceding claims , wherein the at least delimited areas (DZI)₁；DZI₂) As a function of altitude h above ground and/or as a function of time.

10. The adaptive beamforming method according to any of the preceding claims, wherein, in step E, the beamforming electronic weights w (n, m) are updated by calculating the beamforming electronic weights w (n, m) according to:

a) retrieving from a look-up table; and/or

b) The recursive technique operates to optimize the objective cost function.

11. The adaptive beamforming method according to any of the preceding claims , wherein in step E, the end event is UAV descent, or a difference vector Δ M'_k or a plurality of elements of and a target vector Δ M_TRGOr a drone mission end, or a drone device(s) of the corresponding or more target values of (a)200) Exiting from the signal transmission range of the N antenna arrays (110, 120).

12, , the radio beacon system configured to facilitate autonomous flight of or more Unmanned Aerial Vehicles (UAVs), wherein the radio beacon system comprises:

-an unmanned aerial vehicle device (200), the unmanned aerial vehicle device (200) being configured to be mounted on a UAV, and comprising a radio transceiver, an

-a radio beacon device (100), the radio beacon device (100) being configured to be mounted on the ground and comprising N antenna arrays (110, 120), wherein N ≧ 2; or more radio transceivers configured to communicate with the radio transceiver of the drone device (200), and at least processing units (130), wherein each antenna array (110, 120) has M antenna elements (115, 125) associated with respective beamforming electronic weights w (N, M), wherein M ≧ 2, N ranges from 1 to N and M ranges from 1 to M,

wherein the at least processing units (130) are configured to perform the adaptive beamforming method according to any of claims 1-11 of to assist in autonomous flight of the UAV.

Technical Field

The present invention relates to radio beacon systems and related methods that make it possible to facilitate autonomous flight of Unmanned Aerial Vehicles (UAVs), also known as drones, in an efficient, reliable, versatile, extremely precise and inexpensive way, said systems requiring low environmental and visual impact, since the necessary equipment requires low energy, involves low power radio frequency emissions, has a limited size that is easily adaptable to the environment (and can be hidden in the environment).

Background

It is known that, although originally developed for military applications, drones have been increasingly used for civil applications such as surveillance, inspection, package delivery, pilot training, games and hobbies over the past few decades. In particular, applications in infrastructure are investment monitoring, inspection, maintenance and inventory, in which context the use of assets such as electric lines, natural gas and other renewable energy power plants for inspection of Transport System Operators (TSOs) and Distribution System Operators (DSOs) is of particular interest.

Operators in the field of UAV technology have developed systems for UAV (drone) positioning and landing, and estimating distance and angle of arrival (particularly by using antenna arrays), such as electromechanical adaptive antenna tracking devices on UAV machines disclosed in document US2017059688, landing systems disclosed in documents WO2015160230a1 and US5716032, and systems for estimating distance disclosed in US7580378, WO2001094974a2, and WO1996025673a 1.

Furthermore, positioning systems based on signal processing techniques for deriving the relative or absolute coordinates of moving or fixed objects, where the use of antenna arrays is usually associated with an estimation of the angle of arrival of the signals received by the object, have been disclosed as shown, for example, in D.Macagnano et al, in "A comprehensive project on localization: Algorithm and performance analysis tools", International Journal of Wireless information networks, Vol.19, No. 4, p.290, 314, 2012.

Furthermore, systems for UAV positioning with reference to Terrain (where UAV position is deduced by comparing measured images or signals to known patterns) have been disclosed as mentioned, for example, in s.carreno et al, "a Survey on Terrain base navigation for UAVs", OCEANS 2010 MTS/IEEE, pages 1-7, 2010.

Furthermore, phase Interferometry based systems have been adopted for UAV applications, where the location of the signal source is derived or processed from the phase difference measured at the receiver as disclosed in R.F. Handsen, "radio interference: Data Interpretation and Error Analysis", Netherlands and transmitting Magazine, 2001 and A.Moreira et al, "A & tutorial synthetic aperture", IEEE geosciences and Remote Sensing, Vol.1, No. 1, pages 6-43, month 3 2013.

Such prior art solutions, however, have drawbacks, primarily due to the fact that UAV applications specifically require higher spatial resolution than that achieved by the prior art techniques and the ability to also define regions, rather than individual points.

Disclosure of Invention

It is therefore an object of the present invention to facilitate autonomous flight of UAVs in an efficient, reliable, versatile, extremely accurate and inexpensive manner.

It is a further object of the present invention to provide such assistance with low energy requirements, low power radio frequency transmission and limited size devices.

A particular subject of the invention is an adaptive beamforming method for aiding the autonomous flight of a UAV as defined in claim 1.

Further embodiments of the adaptive beamforming method are defined in the dependent claims.

A radio beacon system configured to facilitate the autonomous flight of or more unmanned aerial vehicles, as defined in claim 10, is also a particular subject of the present invention.

The present invention is an radio beacon system configured to facilitate autonomous flight of a flying vehicle (e.g., a UAV) based on a method that supports precise positioning of the UAV by means of identification of the area in which the vehicle is flying and the area in which the vehicle is allowed to fly or not (referred to below as a "defined area").

The drone device is a simple radio-frequency transceiver (hereinafter, also simply indicated as a radio transceiver), or more radio-frequency transceivers (hereinafter, also simply indicated as radio transceivers), at least processing units (e.g., microprocessors) for implementing the method according to the invention, and optionally (at least) landing stations.

The method according to the invention, performed by a radio beacon device, is based on adaptive beamforming for delimiting the area around the radio beacon device and improving the accuracy of the identification of this area by optimization of the resolution of the measurements, in particular or more semaphore measurements obtained with the physical layer of the radio system and, according to them, adapting the beamforming weights of the antenna array for improving the accuracy of the identification of or more delimited areas around the radio beacon device.

The main advantage of the radio beacon system and the related method according to the present invention over prior art solutions is the affordable positioning accuracy at a cost.

In fact, the radio beacon system according to the present invention is configured to identify or more -like regions in space (which may be a 3D zone, a 2D zone, a 1D zone, or a single point) with high accuracy.

In addition, radio beacon systems according to the present invention can be used for autonomous package delivery, which greatly minimizes the risk of package delivery of errant objects and eliminates the need for ground vehicle transportation, thus reducing fuel costs and vehicle fleet costs.

Advantageously, the radio beacon system according to the invention can be applied to any possible service offered by the UAV team, such as monitoring, inspection, package delivery, pilot training, games and hobbies.

Drawings

The present invention will now be described, by way of illustration and not limitation, according to preferred embodiments thereof, with particular reference to the figures of the accompanying drawings, in which:

fig. 1 schematically shows a top plan view of a radio beacon device according to an embodiment of the radio beacon system of the invention;

fig. 2 schematically shows a perspective view of the portion of the radio beacon system of fig. 1;

fig. 3 shows an example of the array directivity function of the radio beacon system of fig. 1;

fig. 4 shows an example of a graph of signals processed by the radio beacon system of fig. 2;

fig. 5 schematically shows a block diagram of the radio beacon apparatus of fig. 1;

fig. 6 schematically shows the radio beacon system of fig. 2 according to an operating mode;

fig. 7 schematically shows a block diagram of a preferred embodiment of the adaptive beamforming method according to the present invention;

fig. 8a schematically shows a top plan view of part of a radio beacon device of a second embodiment of a radio beacon system according to the invention, fig. 8b schematically shows a top plan view of a delimited area identified by the radio beacon device of fig. 8 a;

fig. 9a schematically shows a top plan view of part of a radio beacon device of a third embodiment of a radio beacon system according to the invention, fig. 9b schematically shows a top plan view of a delimited area identified by the radio beacon device of fig. 9 a;

fig. 10a schematically shows a top plan view of part of a radio beacon device according to a fourth embodiment of the radio beacon system of the present invention, fig. 10b schematically shows top plan views of two delimited areas identified by the radio beacon device of fig. 10 a;

figure 11a schematically shows a top plan view of the arrangement of the linear antenna arrays of the radio beacon device of the th embodiment of the radio beacon system according to the invention, figure 11b plots the phase difference between the signals at the outputs of the two arrays "array 1" and "array 2" as a function of the distance d the UAV moves from a location (x, y) ═ 0,0 at an altitude h of 10 meters for three different sets of beamforming electronic weights, along the diagonal direction identified by the arrow in figure 11a, and

fig. 12a schematically shows a top plan view of the arrangement of the linear antenna array of the radio beacon apparatus of fig. 11a, where the defined area is the plane at y-0, and fig. 12b plots the RSSI difference between the signals at the outputs of the two arrays "array 1" and "array 2" as a function of the distance d of the location (x, y) — (0,0) at an altitude h (h-10 m) of the UAV 10 meters above the ground for two different sets of beamforming electronic weights.

In the drawings, like reference numerals will be used for like elements throughout.

Detailed Description

In the following description, an th embodiment of a radio beacon system and related method according to the present invention will be primarily discussed, including radio beacon devices and drone devices with two parallel linear antenna arrays however, it must be understood that a radio beacon system and related method according to the present invention may have multiple drone devices and/or multiple radio beacon devices, and that a radio beacon device may have any configuration of antenna arrays configured to perform beamforming, for example, two-dimensional or circular arrays and more than two antenna arrays, while remaining within the scope of the invention as defined by the appended claims.

Referring to fig. 1 and 2, an th embodiment of the radio beacon system includes a ground-mounted radio beacon device 100 and an unmanned aerial vehicle device 200 mounted on a UAV (not shown), the unmanned aerial vehicle device 200 being provided with a radio transceiver.

Radio beacon device 100 has two parallel linear antenna arrays 110 and 120, each having (as viewed from the top) four antenna elements 115 and 125, respectively, represented by squares in the figure, however, it must be noted that radio beacon device 100 may have any N antenna arrays, where N ≧ 2, and/or each antenna array may have any M antenna elements, where M ≧ 2. furthermore, radio beacon device 100 is provided with a processing unit 130 (e.g., which includes or more processors, as shown in fig. 5), processing unit 130 being configured to perform beamforming in N antenna arrays 110 and 120 by modifying a set of beamforming electronic weights w (N, M) associated with each of M array elements 115 and 125 with N (index N indicating the nth antenna array to which the electronic weight belongs) in the range of 1 to N ═ 2 and M (index M indicating the mth antenna array to which the electronic weight under consideration is associated with) in the range of 1 to M ═ 4.

Assuming that the reference frame is a cartesian coordinate system having an x-axis parallel to and equidistant from the lines along which the two antenna arrays 110 and 120 extend, the antenna element spacings Δ x are typically all equal to fractions of the wavelength λ, typically λ/2, the antenna element spacing Δ y may be selected according to the size constraints of the radio beacon device 100 and range considerations with respect to the defined area. The altitude h of the UAV above the ground, and thus the altitude h of the drone device 200, is measured relative to the plane (x, y) or z-0 (i.e., relative to the ground), while the distance of the drone device 200 from the center of the antenna arrays 110 and 120 is measured by d₁And d₂And (4) indicating. It should be noted that in the figures, the measures and sizes are not to scale: h. d₁And d₂Typically much higher than the size, ax, and ay of the radio beacon device 100.

As shown in fig. 3 and 6, the two antenna arrays 110 and 120 (extending along a line parallel to the x-axis) are configured to have their own main beams of the array directivity functions 1100 and 12001150 and 1250 are turned at opposite angles equal to + theta and-theta, respectively, with respect to an axis parallel to the z-axis passing through the respective centers of the same antenna arrays 110 and 120, to this point , although fig. 6 schematically represents such a mode of operation, fig. 3 shows examples of precise array directivity functions 1100 and 1200 of the two antenna arrays 110 and 120, respectively, thus, the received signal strength (also referred to as RSSI) (i.e., the power of the received signal) at the two antenna arrays 110 and 120 will be different because the beam direction along the x-axis with respect to the position of the drone 200 is different, while, as shown in fig. 2, the difference in RSSI Δ RSSI at the two antenna arrays 110 and 120 defines the region DZI only at the (plane) defined by the plane (y, z) (where x ═ 0)₁The upper will be exactly equal to 0 (zero), i.e., Δ RSSI ═ 0. Obviously, in practice, this plane is not infinite, since in practice it is limited by the range of transmission of the signal; meanwhile, the condition Δ RSSI of 0 unambiguously identifies DZI in the neighborhood of x 0 (in which the radio beacon is located)₁That is, until the side lobes of the array create other regions in the space characterized by Δ RSSI ═ 0 for this point, FIG. 4 shows when the drone device 200 is along a point (-x)₀,-y₀H 10m) and (+ x)₀,-y₀H 10m) as a function of the position of the drone 200 along the x-axis, in other words, when the signal quantity measure processed by the radio beacon device 100 is RSSI, the two main beams 1150 and 1250 of the two antenna arrays 110 and 120 are rotated by opposite angles with respect to the plane (y, z) (where x is 0) in order to identify the delimited area DZI by means of the measure Δ RSSI being 0₁。

In fact, the signal phase α at the output of each antenna array depends on the length of the propagation path and the term given by the antenna array.A phase difference Δ α between the outputs of the two antenna arrays 110 and 120 is only at the second (plane) boundary defined by the plane (x, z) (where y is 0) when a sinusoidal signal from the drone device 200 is received by the two antenna arrays 110 and 120Localized area DZI₂Equal to 0 (zero) (shown in the (x, y) plane in fig. 1), i.e., Δ α ═ 0, where the second delimited region DZI₂And define region DZI₁Again, the condition Δ α -0 unambiguously identifies DZI in the neighborhood of y-0₂Since it is well known that the phase associated with a propagation path is characterized by a periodicity equal to the wavelength, which corresponds to a 360 ° rotation; this ambiguity does not exist when the receiver uses the propagation time, rather than the phase, as a semaphore measure.

As shown in more detail in fig. 5, each of the two antenna arrays 110 and 120 of the radio beacon apparatus 100 is provided with a multiplier 116 and 126 for each antenna element 115 and 125, wherein each multiplier 116 or 126 is configured to multiply the signal received at the respective antenna element 115 or 125 by a respective beam-forming electronic weight w (n, m), the four multipliers 116 and 126 of each antenna array 110 and 120 are followed by a corresponding adder 117 and 127, the adders 117 and 127 determining characteristics of the array directivity functions 1100 and 1200 of the antenna arrays 110 and 120, the processing unit 130 is configured to estimate a signal quantity measure from the output signals of the adders 117 and 127, i.e. in this case the RSSI and/or signal phase α (as represented by blocks 131 and 132 in fig. 5) and their difference Δ RSSI and/or Δ α (as represented by block 133 in fig. 5), furthermore, the processing unit 130 is configured to perform the adaptive beam-forming method according to the invention (possibly represented by means of at least specific microprocessors in fig. 134 in fig. 5) as will be described in more detail later.

, the signal metric processed by the radio beacon device 100 may be any physical parameter related to the distance between the drone device 200 and the radio beacon device 100. in particular, the radio beacon device 100 is optionally configured to process at least signal metric measurements selected from the set of physical parameters consisting of RSS, phase rotation and propagation time, or RSSI, phase rotation and propagation time.

The radio beacon device has the following capabilities: the degrees of freedom provided by the set of beamforming weights are exploited to improve the resolution and hence accuracy of commands sent to the UAV for complying with the defined territory.

In the case where the semaphore is RSSI, the metric resolution can be increased by using beamforming electronic weights with the same amplitude and different phase that steer the beam in order to improve the local signal strength variation relative to the variation in the distance of the UAV from the defined area (this feature of the invention will be illustrated with additional details in step E of the inventive method).

In case the semaphore measure is phase rotated, the angular resolution can be improved by using beamforming electronic weights w (n, m) that do not have the same amplitude, unlike the case where the semaphore measure is RSSI, where all beamforming electronic weights w (n, m) typically, if not necessarily, have normalized amplitudes equal to 1. The processing performed according to the method of the invention improves the signal contribution from pairs of antenna elements that accumulate a higher phase difference with respect to the particular trajectory that the UAV is following. By way of example, and not limitation, this is useful when the type of allowable commands to be sent to the drone are "back" or "forward" on a particular trajectory that is independent of the particular geometry of the array and/or the drone orientation and cannot be controlled or changed by the system according to the invention. In this case, the system according to the invention is able to enhance the response from the antenna elements, which ensures a better response to phase changes.

Fig. 11a shows a top plan view of the arrangement of the linear antenna arrays of a radio beacon device of an th embodiment of the radio beacon system according to the invention (where the viewpoint is rotated clockwise, whereby the x-axis and the y-axis are interchanged with respect to fig. 1), comprising two linear antenna arrays indicated as "array 1" and "array 2", each antenna array having four antenna elements, respectively (these antenna elements are represented by squares as seen from the top), the system according to the invention being able to locally adapt the weights and improve the accuracy with respect to the phase rotation according to, for example, the orientation and/or trajectory of the UAV on which the unmanned aerial device is mounted, the defined area being the plane at x-0 (in fig. 11a being denoted by x-0Shown as a line) identified by the equal phase received at the two arrays "array 1" and "array 2" parallel to the y-axis. FIG. 11b plots electronic weights w for beamforming₁W (1, m) and w₂Three different sets S of ═ w (1, m) (where m ranges from 1 to 4)_W1、S_W2And S_W3The phase difference between the signals at the outputs of the two arrays "array 1" and "array 2" as a function of the distance d of (0,0) from the location (x, y) ═ 10m at an altitude h (h ═ 10m) of 10 meters above the ground, and which is moving in the diagonal direction identified by the arrows in fig. 11a (which is due to, for example, previous commands and/or trajectories). It can be observed that the initial set of electronic weights S relative to the beamforming_W3For UAV to stabilize at location (x, y) — (0,0), set S_W1Or set S_W2Similarly, by also taking into account SNR, the set of beamforming electronic weights may be optimized to better respond to local position changes of the UAV along any direction.

In the case where the semaphore measure is the propagation time T, it is clear that it is related to the phase rotation byStrictly related:

wherein f is_txIs the frequency of the signals transmitted (and received) by the radio frequency transceivers of the drone devices and radio beacon devices of the system according to the invention. Thus, using travel time as a signal metric is equivalent to using phase rotation for small scale variations around a defined region (since phase utilization is significantly limited by a 360 ° period). According to theseBy way of limitation, RSSI may be used as a signal quantity measure for large scale (or coarse) determinations bounding an area, while phase rotation (or time of propagation) may be advantageously used for small scale (or fine) determinations bounding an area, and thus, with greater accuracy.

In other words, the method according to the invention makes it possible to define the bounding region and to update the beamforming electronic weights w (n, m) using different physical parameters: for example, first, a coarsely defined RSSI used to bound a region, and then a phase rotation or propagation time used for finer verification with respect to the location of the bound region.

In addition, , the radio beacon device 100 has N antenna arrays, where N ≧ 2.

Further, the radio beacon device 100 is provided with radio transceivers per antenna array, i.e. with two radio transceivers (not shown in the figure) configured to communicate with the radio transceivers of the drone device 200.

It should be noted that in other embodiments of the radio beacon system according to the invention, the radio beacon device may be provided with only radio transceivers in which case the signal communications between the single radio transceiver of the radio beacon device and the radio transceiver of the drone device required to obtain the signal quantity measure for each antenna array occur sequentially by using the same single radio transceiver of the radio beacon device (i.e. the signal communication sequence for each antenna array), which is feasible because the movement time of the UAV on which the drone device is mounted is several orders of magnitude longer than the electronic processing response time.

Assume that the radio beacon device 100 is based on a sampling period T_SOperating then the n-th antenna array is at the sampling time t_k＝kT_SProcessed semaphore measure M_n,k(d_n) (where N ranges from 1 to N (where N is 2 for the th embodiment shown in the figure)) depends on the distance d of the (center of the) nth antenna array of the radio beacon device 100 from the drone device 200_n。

N semaphore measurements M based on all N antenna arrays_n,k(d_n) A preferred embodiment of the adaptive beamforming method according to the present invention, performed by a radio beacon device, outputs:

at a command time t_j＝jT_C or more commands C for autonomous flight or correction of UAVs on which drone device 200 is mounted_jIn which T_CIs a command cycle in which or more commands C_jIs sent by the drone device 200 to the UAV flight board in order to keep the UAV passing through N semaphore measures M_n,k(d_n) Identified or more demarcated areas inside or outside, and

-an update of the set of beamforming electronic weights w (N, M) associated with each of the M array elements of each of the N antenna arrays.

generally, command period T_CIs the sampling period T_SIs usually greater than the sampling period T_SMuch longer. Typical Command C_jIt may be that the drone 200 is rotated 360 deg. in the same position for enhanced phase measurements, kept advancing in the same direction, returned in the opposite direction, and rotated by an angle phi with respect to the current flight direction, where phi may advantageously be equal to 90 deg. or-90 deg..

In more detail, referring to fig. 7, a preferred embodiment of the adaptive beamforming method according to the present invention includes the steps described below.

Step A (700) is to set the beamforming electronic weights w (n, m) to initial values w₀(N, M) (N-1, …, N; M-1, …, M) wherein the initial value w is₀The array of (n, M) depends on the selected semaphore measure M to be used_n,k(d_n) Type of (e.g., RSSI, phase rotation, or propagation time) and or more defined regions to be identified.

In step B (710), the method computes a difference vector having P elements, P being equal to the number of 2-combinations of N elements:

where each element is the difference of out of all possible combinations of two antenna arrays out of the N antenna arrays of the radio beacon device 100, for example, where N is 2, P is 1, i.e., Δ M_kHas elements:

△M_k＝△M_k(p)＝{M_1,k(d₁)-M_2,k(d₂) Where P is 1;

in the case where N is 3, P is 3, i.e., Δ M_kHas three elements:

△M_k＝△M_k(p)＝{[M_1,k(d₁)-M_2,k(d₂)],[M_1,k(d₁)–M_3,k(d₃)],[M_2,k(d₂)–M_3,k(d₃)]wherein P ranges from 1 to P ═ 3; in the case where N is 4, P is 6, i.e., Δ M_kHas six elements:

△M_k＝△M_k(p)＝{[M_1,k(d₁)-M_2,k(d₂)],[M_1,k(d₁)–M_3,k(d₃)],[M_1,k(d₁)–M_4,k(d₄)],[M_2,k(d₂)–M_3,k(d₃)],[M_2,k(d₂)–M_4,k(d₄)],[M_3,k(d₃)–M_4,k(d₄)]}

wherein P ranges from 1 to P ═ 6.

Other embodiments of the method according to the invention may have that in step B the method transforms the difference vector Δ M_kIs calculated as over time (i.e., along the series of Q sample times t)_q＝qT_S) Of two antenna arrays of the N antenna arrays_n,k(d_n) Average (possibly weighted average) E [ Δ M ] of a continuous set of differences between_q(p)]Wherein Q ranges from (k-Q +1) to k, wherein Q sample times include a current sample time k and (Q-1) previous sample times; advantageously, QT_S≤T_BFWherein, T_BFIs the beamforming weight update period. In this way, the method is able to compensate for possible temporary changes in the flight path (for example, due to any sudden temporary event, such as wind).

It must be noted that in other embodiments of the method according to the invention, in step B, the method calculates a difference vector Δ M 'having P' elements (where P '≧ 1)'_kP 'is less than the number of 2-combinations of N elements, where the difference vector Δ M'_kIncluding a subset of all possible differences for all possible combinations of two antenna arrays among the N antenna arrays of the radio beacon device, where 1 ≦ P'<P。

In step C (720), the method provides a difference vector Δ M_kP elements of (a) and a target vector Δ M of a specific target value_TRGDefining a defined region in space, and in general, may depend on the altitude h of drone device 200 (e.g., provided by GPS sensors or other suitable devices included in drone device 200 and/or radio beacon device 100)_TRGThe defined bounded region, which may be a 3D region (i.e., a volume in space), a 2D region (i.e., a surface), a 1D region (i.e., a line), or a single point, is(3D or 2D or 1D or single point) trajectories of points satisfying the condition that can be written as follows:

for each P in the range of 1 to P,

△M_k(p)＝△M_TRG(p) or

△M_k(p)>△M_TRG(p) or

△M_k(p)≥△M_TRG(p) or

△M_k(p)<△M_TRG(p) or

△M_k(p)≤△M_TRG(p)

In particular, the comparison may comprise calculating the vector Δ M_kP elements of (a) and a target vector Δ M_TRGIs calculated, i.e. is calculated (Δ M)_TRG–ΔM_k). Further, regarding Δ M_kAny of the preceding conditions of (p) may be written with reference to absolute values (e.g., | Δ M_k(p)|＝|ΔM_TRG(p) |). For the embodiments of the radio beacon system shown in fig. 1, 2 and 6, where N is 2 and P is 1, the target vector Δ M_TRGMay be an empty Δ M_TRG＝[0]Wherein, when the semaphore measures M_n,k(d_n) When RSSI is employed, the defined region is the (y-z) plane DZI₁Where x is 0 (i.e., perpendicular to the x-axis), or, when the semaphore measure M_n,k(d_n) When the phase is rotated α, the defined region is the (x-z) plane DZI₂Where y is 0 (i.e., perpendicular to the y-axis). As described above, from the target vector Δ M_TRGThe defined demarcated areas may be:

identifying planes of straight lines on the ground (as shown in figures 1 and 2), which can therefore be used to give flight trajectories or to define exclusion zones;

identifying a point on the ground (as shown in fig. 1) and possibly two planes of or more reference descent lines for descent, generally perpendicular to each other;

-like combinations of lines and points on a plane and therefore on the ground that can identify more complex forbidden areas or flight corridors and trajectories for autonomous or assisted UAV flight, in particular these -like combinations of areas can also be generated and managed with a specific time plan in order to assist UAV flight on specific gradually changing trajectories.

However, the technician then also obtains the target vector Δ M_TRGOther configurations of defined demarcated areas may be obtained by means of different antenna array configurations.

In step D (730), the method output is at command time t_j＝jT_C or more commands C for autonomous flight or correction of UAVs on which drone device 200 is mounted_jSo as to measure M from the N semaphore measures in step C_n,k(d_n) The conditions to be met keep the UAV at a value defined by the target vector Δ M_TRGInside (or outside) a defined area, or more commands C_jIs sent to the UAV flight board by the drone device 200. For the embodiments of the radio beacon system shown in fig. 1, 2 and 6, it is assumed that Δ M_TRG＝[0]Then current Δ M_kDetermines whether the UAV on which the drone 200 is mounted is closer to antenna arrays or another antenna arrays, i.e., when the semaphore measure M_n,k(d_n) Is RSSI, the UAV is relative to the (y-z) plane DZI₁To which side is occupied, or, when the semaphore measure M is_n,k(d_n) Is phase rotation α, UAV is relative to (x-z) plane DZI₂To which side is occupied.

In step E (740), the method proceeds at time t_r＝rT_BFUpdating beamforming electronic weights w associated with each of each M array elements of the N antenna arrays_rSet of (n, m), wherein T_BFIs the beamforming weight update period. Beamforming weight update period T_BFTypically a sampling period T_SMultiple of (1), usually to T_SMuch longer, the weight update typically depends on or more of the altitude h of the drone 200, its current location, its configuration (such as orientation and type of commands allowed), current measure, bounding terrain shapeA trade-off of complexity in the antenna array configuration and the method according to the invention.

In this regard at , it must be noted that when commanding a period T_CAnd/or a beamforming weight update period T_BFIs the sampling period T_SIs configured to not only take into account time t by calculating the mean value of the measure over a time period in order to reduce the noise of the measure_j＝jT_CTime and/or time t_r＝rT_BFA semaphore measure of time, but also a trend of such a semaphore measure over time, to generate or more commands C_jAnd/or updating beamforming electronic weights w_rA set of (n, m); in this way, additional information may also be obtained, for example, ascertaining whether the UAV is closer to, or farther away from, the radio beacon device.

Beamforming electronic weights w_r(n, M) has a dual role in the system and associated method according to the present invention, , along with the antenna array layout and target vector Δ M_TRGWhich identify defined regions (such as DZI shown in fig. 1 and 2₁And DZI₂) Secondly, they may be updated and improved (during execution of the method according to the invention) in order to minimize the identification error delimiting the region, wherein such improvement may be made in accordance with or more of the altitude h of the drone device 200 (e.g. provided by a GPS sensor or other suitable device comprised in the drone device 200 and/or the radio beacon device 100), its location (e.g. provided by a GPS sensor or provided by the same calculations and/or measurements made by the method steps), its configuration (e.g. orientation or type of available commands), the difference vector Δ M_k(p) a current value of the element. With respect to this improvement, the method according to the invention makes the difference vector Δ M of the unmanned aerial vehicle device 200 given a delimited area_kMaximization: extending the range of variation of the semaphore measure (i.e. the signal useful for estimating the position of the drone device 200 relative to the radio beacon device) while the spatial distance Δ d from the target line remains fixed improves the resolution δ Δ d/Δ M_k. In particular, the beamforming electronic weights w may be calculated according to the following manner_r(n,m)：

a) A fixed pre-calculated table stored in memory as a look-up table (open loop weight control); and/or

b) Recursive techniques (closed-loop weight control) for optimizing the operation of the objective cost function.

As a related example of this process, in step E (740), the method updates the beamforming electronic weights for increasing the current Δ RSSI by steering main beams 1150 and 1250 of antenna directivity functions 1100 and 1200 of antenna arrays 110 and 120 relative to an axis parallel to the z-axis that passes through the respective centers of the same antenna arrays 110 and 120 (i.e., by changing the angle), keeping the position of the drone device 200 fixed. Referring to fig. 3 and 6, this corresponds to a slight increase in the opposite angles + θ and- θ of the array directivity functions 1100 and 1200 of the antenna arrays 110 and 120 in order to increase the ratio Δ M at a given altitude h of the drone device 200_kΔ d, i.e. increasing δ by Δ d/Δ M_k. Thus, prior to beamforming weight update, the resolution is given by the following equation:

δ_initial＝|x₂|/ΔRSSI_{2_initial}

and after the beamforming weights are updated, the resolution is given by the following equation:

δ_updated＝|x₂|/ΔRSSI_{2_updated}<δ_initial

this means that the same distance | x₂I is checked with a larger Δ RSSI margin, resulting in performance advantages and accuracy improvements in embodiments of the method according to the invention, the beamforming electronic weights w may be updated_r(n, m) for improved resolution and while keeping the UAV position fixed (i.e., constant), e.g., during periods of no flight command transmission.

As an example for the phase measure, the method updates the beamforming electronic weights w according to the following principle_r(n, m) increasing the weight from the current UAV by using not to have amplitude The particular trajectory followed accumulates the signal contributions of the pairs of antenna elements of higher phase differences (this is useful, for example, when the type of command allowed to be sent to the drone is "return" or "forward" on a particular trajectory irrespective of the particular geometric layout of the array and/or of the orientation of the drone which may be neither controlled by the system according to the invention nor managed by the system according to the invention). The system according to the invention can thus enhance the response from the antenna elements that ensure a better response to phase changes (see also the previous description of fig. 11a and 11 b).

At the end of step E (740), the method may return to perform:

step B (710) until an end event occurs, such as a UAV landing (e.g. on a landing stage of the radio beacon apparatus 100), or the achievement of a difference vector Δ M_kP elements of (a) and a target vector Δ M_TRGTo the P target values (so that the difference vector Δ M_kWith a target vector Δ M_TRGMeets or more conditions (other than tolerance values) for longer than the threshold time of stability, e.g., if within the threshold time of stability (e.g., of a few seconds), the condition is Δ M_k(p)＝ΔM_TRG(p) when (Δ M)_TRG-ΔM_k) Equal to 0 (except for tolerance values), such stable equalization is achieved), or the drone mission ends or the drone device 200 exits from the signal transmission range of the antenna arrays 110 and 120 of the radio beacon device 100; or

Step B (710), in which the signal metric to be used is changed (for example, from RSSI to phase rotation in order to improve the accuracy in the defined area definition) until an end event occurs, such as UAV landing, or achievement of Δ M relative to a target vector_TRGStable equalization of the target value of, or the drone mission ends or the drone device 200 exits from the signal transmission range of the antenna arrays 110 and 120 of the radio beacon device 100; or

-a step C (720) in which the defined area is changed according to the scheduled flight plan or trajectory of the UAV.

According to the invention, based on steps A and E (i.e. definition of the delimited areas and accuracy optimization), each delimited area (which may be any of the following: 3D area, i.e. volume; 2D area, i.e. plane; 1D area, i.e. line; single point) or part of the delimited area is identified and the accuracy is optimized by means of a two-stage mechanism.

With respect to defining the territory, these are by means of corresponding target vectors Δ M_TRGCorresponding to or more signal quantity measures (e.g. RSSI and/or phase rotation and/or propagation time) at the output of the processing unit 130 shown in fig. 5. in this point, the same bounding region may be defined by a number of equivalent weight vector combinations greater than 1 (if not infinite in most cases).

Regarding accuracy optimization, updating the method according to the invention gradually improves the accuracy by updating the beamforming electronic weights. Utilizing redundant sets of beamforming electronic weight vectors to select those combinations that ensure better performance in the current particular configuration of the UAV (with reference to, e.g., altitude, position, orientation, type of command accepted), i.e., the difference vector Δ M as a function of the position offset Δ d_kThe larger the slope of (A), the larger the ratio Δ d/Δ M_kThe smaller.

Fig. 12a shows a top plan view of the arrangement of the linear antenna array of the radio beacon device of fig. 11a, where the defined area is a plane (shown as a line in fig. 12 a) at y-0 identified by equal RSSI received at the two arrays "array 1" and "array 2", where Δ RSSI-0. FIG. 12b plots the electronic weights w for beamforming₄W (1, m) and w₅Two different sets S of ═ w (1, m) (where m ranges from 1 to 4)_W4And S_W5RSSI difference between signals at the outputs of the two arrays "array 1" and "array 2" as a function of distance d of location (x, y) — (0,0) at altitude h (h ═ 10m) of 10 meters above ground for the UAV on which the drone device is mounted, where set S is_W4The main beam of the directional function of the array is directed at an angle of +/-36,and set S_W5The main beam of the directional function of the steering array is directed at an angle of +/-20 deg.. Set S_W4And S_W5These two sets define the defined area as the plane at y-0, and when the UAV on which the drone device is mounted approaches such defined area, S_W4Is preferred because it ensures a better slope of the system response (i.e., RSSI difference Δ RSSI) as a function of the UAV's position offset d, providing higher sensitivity and better accuracy. The method according to the invention may use the set S in step A_W5As initial values for the beamforming electronic weights w (n, m) because they ensure a larger region where the signal from the UAV provides valid commands towards a defined region (indicated as "attraction zone" in fig. 12 b).

Obviously, the scheduled flight plan or trajectory of the UAV may be formed by a sequence of different targets, each defining a sequence of defined areas that the UAV is required to reach, e.g., a sequence of target points; in this case, the method according to the invention (a preferred embodiment of which is shown in fig. 7) is performed for each object of the sequence.

It has to be noted that in other embodiments of the radio beacon system according to the invention, the number N of antenna arrays may be larger than 2 (i.e. N>2). When a radio beacon device is provided with an even number N of antenna arrays, the signals of such antenna arrays (and thus their beam-forming electronic weights w)_r(n, m)) may be processed in pairs such that the array directivity functions of each pair of antenna arrays are processed along opposite angles with respect to the angle theta_0,u、θ_0,u+θ_uAnd theta_0,u-θ_uWherein U ranges from 1 to N/2 (in this embodiment, the angle θ)_0,uDefining a defined area); in this case, in step E, the method according to the invention may update the beamforming electronic weights for use by slightly increasing the opposite angle θ_0,u+θ_uAnd decrease theta_0,u-θ_uSo with respect to θ_0,uIncreasing the angular distance between the array directivity functions of each pair of antenna arrays increases the current semaphore measure (e.g., Δ RSSI)) The position of the drone device 200 is kept fixed. When a radio beacon device is provided with an odd number N of antenna arrays, the signals of such antenna arrays (and thus their beam-forming electronic weights w)_r(n, m)) may be processed in pairs in addition to a single "pivoting" antenna array, such that the array directivity function of the single "pivoting" antenna array is processed along the angle θ₀Guiding (e.g. theta)₀0 deg., parallel to the z-axis orthogonal to the ground), and the array directivity functions of each pair of antenna arrays are directed along opposite angles theta_0,u+θ_nAnd theta_0,u-θ_uWherein U ranges from 1 to (N-1)/2; in this case, in step E, the method according to the invention updates the beamforming electronic weights for the opposite angle θ for the array directivity function by slightly increasing the array directivity function of each pair of antenna arrays_0,u+θ_uAnd theta_0,u-θ_uAngle θ that enables array directivity function for a single "pivoting" antenna array₀Remain fixed to increase the current semaphore metric (e.g., Δ RSSI) so that the position of the drone device 200 remains fixed.

However, it must also be noted that the signals of the antenna array of the radio beacon device (and therefore its beam-forming electronic weights w)_r(n, m)) pairs of processing, and arrangement parallel to the linear antenna array (even a linear configuration of the antenna array) are not essential to the invention.

As an th example, FIG. 8a shows a top plan view of the arrangement of the linear antenna arrays of a radio beacon device of a second embodiment of the radio beacon system according to the invention, which comprises two linear antenna arrays 110A and 120A, each having four antenna elements 115A and 125A, respectively (these antenna elements are represented by squares as seen from the top). in this second embodiment, the two linear antenna arrays 110A and 120A are arranged along lines rotated +45 and-45, respectively, with respect to the x-axis (and y-axis), whereby the two linear antenna arrays 110A and 120A are arranged along lines that are orthogonal to each other, rather than parallel lines_n,k(d_n) Is RSSI and target vector Δ M_TRGIs empty Δ M_TRG＝[0]In this case, by using the beam forming electronic weight so that the initial values of the angles of the array directivity functions of the antenna arrays 110A and 120A are both 0 °, the bounding region is the (y-z) plane DZI represented by two vertical lines intersecting each other at the origin in fig. 8b₁And (x-z) plane DZI₂. In addition, by setting the target vector Δ M_TRGIs set equal to a very small value (e.g. equal to 0.2), a small area around the origin (actually around the z-axis at an altitude h of 20m, as shown in fig. 8 b) is also passed through the following condition, together with the (y-z) plane DZI₁And (x-z) plane DZI₂ are identified:

△M_k(p)≤△M_TRG(p)；

in fig. 8b, the points indicated with "X" marks are those that satisfy such a condition with respect to Δ RSSI. In this case, the initial value of the angle of the array directivity function of the antenna arrays 110A and 120A is 0 °, that is, the array directivity function of the antenna arrays 110A and 120A is parallel to the z-axis.

As a second example, fig. 9a shows a top plan view of the arrangement of a linear antenna array of a radio beacon device according to a third embodiment of the radio beacon system of the present invention, said radio beacon device comprising two linear antenna arrays 110B and 120B, each having four antenna elements 115B and 125B, respectively (these antenna elements are indicated by squares when viewed from the top). In this third embodiment, the two linear antenna arrays 110B and 120B are arranged along lines close to the origin, parallel to the x-axis and the y-axis, respectively, whereby the two linear antenna arrays 110B and 120B are arranged along lines orthogonal to each other, rather than parallel lines. In this case, when the semaphore measure M_n,k(d_n) Is RSSI and target vector Δ M_TRGIs equal to a very small value (e.g., equal to 0.2), the initial values of the angles of the array directivity functions of the antenna arrays 110B and 120B are 0 ° and 15 °, respectively, approximately centered at the origin, by using the beam forming electronic weights so that the initial values are 0 ° and 15 °, respectivelyThe arc-like region (e.g. at about 4-5 meters) of the core (actually around the z-axis at an altitude h of 20m, as shown in fig. 9 b) is identified by the following condition:

|△M_k(p)|≤|△M_TRG(p)|

this condition can be used, for example, for inspection around the lattice structure of the overhead power line; in fig. 9b, the points indicated with "X" marks are those that satisfy such a condition with respect to | Δ RSSI |.

As a third example, FIG. 10a shows a top plan view of the arrangement of the linear antenna arrays of a radio beacon device according to a fourth embodiment of the radio beacon system of the present invention, said radio beacon device comprising three linear antenna arrays 110C, 120C and 140C, each having four antenna elements 115C, 125C and 145C, respectively (these antenna elements are represented by squares as seen from the top). in this fourth embodiment, the th linear antenna array 110C, the second linear antenna array 120C and the third linear antenna array 140C are arranged parallel to the x-axis, whereby the three linear antenna arrays 110C, 120C and 140C are parallel to each other_n,k(d_n) Is RSSI and target vector Δ M_TRGIncluding two particular target values (thus a subset of the three elements, consisting of all possible 2 combinations of 3 elements) that are both equal to null, i.e., including the target value for the RSSI difference of the second antenna array 120C and the antenna array 110C and the target value for the RSSI difference of the third antenna array 140C and the second antenna array 120C, by using asymmetric beam-forming electronic weights (i.e., not having the beams at opposite angles + θ, as in other embodiments of the present invention)_uAnd-theta_uSteering) such that the initial values of the angles of the array directivity functions of antenna arrays 110C, 120C and 140C are 0 °, 10 ° and 15 °, respectively, parallel to the y-axis, to the right of the radio beacon device (i.e., at the positive x-coordinate) (as shown in fig. 10b, in fact parallel to (y-z) plane DZI at an altitude h of 20m₁) The corridor of (a) is identified by the following condition:

|△RSSI_2-1|＝|△RSSI_{2-1_TRG}|＝0

|△RSSI_3-2|＝|△RSSI_{3-2_TRG}|＝0

this condition can be used for inspection of overhead power lines; in fig. 10b, the points indicated with "X" marks are those that satisfy such a condition. By reversing the initial values of the angles of the array directivity functions of antenna arrays 110C, 120C and 140C, parallel to the y-axis, to the left of the radio beacon device (i.e., at the negative x-coordinate) (as shown in fig. 10b, in fact parallel to (y-z) plane DZI at an altitude h of 20m₁) Are identified by the same conditions.

The use of adaptive beamforming, achieved by the method according to the invention, therefore has the dual role of aspect, region definition, and aspect, with improved accuracy by means of updating the measurement resolution as the UAV approaches the target-defined region.

Indeed, the radio beacon system and related method according to the present invention achieves high positioning accuracy (e.g., relative to GSP sensors, etc.), is inexpensive to implement (e.g., when compared to lidar systems), is independent of the current rotation of the UAV, can define or more line limits, can manage and control multiple UAVs, and does not require any knowledge of the absolute azimuth or altitude of the UAV.

The foregoing has described preferred embodiments of the present invention and suggested several variations, but it will be understood that other variations and modifications may be effected therein by those skilled in the art without departing from the scope of the invention as defined in the appended claims.