RU2776621C1 - Method for landing a group of unmanned aerial vehicles with a random structure on a landing platform - Google Patents

Abstract

FIELD: unmanned aerial vehicles.

SUBSTANCE: invention relates to a method for landing a group of unmanned aerial vehicles (UAVs) on a landing platform. For UAV landing, information exchange is carried out over the direct and reverse communication channels of the UAV requiring landing with the landing platform and subsequent correction of its movement during landing, while for the rest of the UAVs from the group, a waiting area and service priority are formed in a certain way.

EFFECT: air traffic safety of the UAV group is improved.

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Description

The invention relates to a method for landing a group of unmanned aerial vehicles (UAVs) on at least one landing platform (LP). It can be used in the modernization of existing landing systems for UAV swarm structures at CPs, the creation of promising transit terminal stations for servicing UAVs with a high intensity of their arrival for landing to be served by one or more platforms and network interaction of many such stations.

In the prior art, a method is known to control a large number of commercial UAVs in controlled airspace around an airport according to the patent "Alternative controls for a large number of commercial unmanned aerial vehicles over airports and settlements" (US US9754497B1 Charles R. Smith Northrop Grumman Systems Corporation, Priority 2017-01 -27, Filed 2017-01-27, Granted 2017-09-05, Published 2017-09-05). The invention describes a method for ensuring the safe flight of a large number of commercial UAVs in an area controlled by an air traffic control system around an airport. The method includes providing an outgoing corridor from the carrier's facility through the airport's air traffic control system-controlled space, which is intended for the flight of a swarm of UAVs and prohibits the presence of any other aircraft in it, while allowing the UAV to leave the outgoing corridor from the airport's air traffic control system not required. The method also includes providing an inbound corridor through the space controlled by the air traffic control system to the carrier facility that does not allow any other air object to be in it, and allows the UAV to return to the carrier facility through the space controlled by the air traffic control system, flying through incoming corridor without the need for air traffic control. The invention proposes to use commercial UAVs to deliver packages from an air carrier's facility to the final destination of the packages or another air carrier's facility, depending on distance, UAV size, and other factors, rather than requiring the packages to be transported from the airport by truck or other vehicle. In one embodiment, a large swarm of UAVs form as a group on the ground in a gathering area away from all other air and ground traffic at the airport, take to the air as a swarm under the control of an air traffic control system in the gathering area, and fly out of that area along an outgoing corridor as a group. . As soon as a group of UAVs leave the air traffic control system, they disperse as independent UAVs to their destination to deliver their cargo. After delivering its cargo, the UAV is sent to a pre-designated re-collection zone outside the space controlled by the air traffic control system, where it, along with other UAVs that have completed the task, are combined into a swarm for further movement to the airport zone. After the UAV swarm is fully formed, it returns back to the airport through the space controlled by the air traffic control system, lands in the collection area to be ready to reconfigure the group for other cargo. The use of the air traffic control system in this document is for either ground control or airport airspace control. The presented patent allows organizing specially allocated corridors in a limited space - the airfield area for the safe flight of UAVs, however, it does not solve the problem of landing UAV swarm structures on at least one landing site.

As a prototype, the method of landing a UAV swarm on a mobile platform was chosen [Anam Tahir, Jari Bӧling, Mohammad-Hashem Haghbayan, Juha Plosila. Navigation System For Landing A Swarm Of Autonomous Drones On A Movable Surface. Communications of the ECMS, Volume 34, Issue 1, Proceedings, Mike Steglich, Christian Mueller, Gaby Neumann, Mathias Walther (Editors). ISBN: 978-3-937436-68-5/978-3-937436-69-2(CD)].

The prototype considers the problem of landing a swarm of a fixed number (ten) UAVs on a moving platform with linear speed and the effect of vibrations. The essence of the invention is as follows. A swarm of ten UAVs has a hierarchical structure with a designated leader having the highest level of the hierarchy. Associated with it are UAV followers of the next level of the hierarchy, which in turn have their UAV followers. To take into account the mobility of the platform, the UAV leader has feedback from the mobile platform and corrects its position. UAV followers following the leader correct their positions in the swarm, while solving the problem of collision avoidance, taking into account the safe distances between neighboring UAVs in the group, then this problem is solved by UAV followers of subsequent levels of the hierarchy. The swarm is responsible for tracking the desired trajectories, as well as hovering in the desired positions for predetermined time intervals. The trajectory of the leader is independent and determines the trajectory of the UAV swarm structure. The trajectory of each follower is determined based on the orientation and actions of the respective leader. In terms of movement, each follower depends on the movement of their respective leader using a safe distance strategy. Each follower is responsible for efficiently tracking the trajectory of the respective leader, keeping the distance between the two respective objects. When solving the task of landing a swarm, reference commands from the PP station are continuously transmitted to the leader as feedback, describing the phenomenon of tracking mutual movement. The leader's local control unit then corrects its location and generates a signal to stabilize it upon landing. This process continues until the desired goal is reached - the landing of the UAV on the BCP. Since in the hierarchical swarm structure, based on the initial definition of UAV chains of the leader-follower type and their continuous interaction, the mutual orientation of the UAV and the corresponding correction of routes are carried out in it, the choice of the next UAV for landing is not required, while each next UAV for landing after the UAV -leader performs a similar interaction with the PP via direct and reverse communication channels.

The disadvantages of the considered method are: landing a group of UAVs with a random structure on the SP in this way is impossible due to the lack of implementation of the corresponding protocol for accessing the SP, in the considered prototype, the choice of the next UAV for landing is determined by the very hierarchical structure of the UAV swarm due to leader-follower chains; there is no possibility of landing a random flow of UAVs with high intensity due to the lack of a holding area with safe air traffic; the method does not allow organizing the priority service of the UAV during landing; there is no possibility of the landing system influence on the UAV swarm in order to improve flight safety in the landing area.

Currently, methods and devices are unknown, in accordance with which it is possible to land a group of UAVs with a random structure or a stochastic flow of high-intensity UAVs at a landing station with one or more landing sites, when the intervals between incoming UAVs for landing are less than the UAV landing time by at least one PP.

The aim of the invention is to ensure the landing of groups of UAVs with a random structure on the SP, as well as stochastic flows of UAVs with an average time interval between UAV arrivals less than the minimum required time interval for landing a single UAV on the SP; construction of the UAV waiting area, taking into account the problem of air traffic safety in the landing area; priority UAV service by a landing station with at least one launch site; accounting for the number of UAVs and the intensity of their arrival by the landing station to improve air traffic safety in the UAV landing zone.

The set goal of the method of landing a group of UAVs with a random structure on a SP is achieved by creating a queuing system for landing a group of UAVs on at least one SP, which includes: storage device of the queuing system of the landing system of the UAV group and providing UAV input streams with a set of non-intersecting routes, as well as regularizing the total UAV input stream using the Landing Line Multiple Access Protocol, i.e. converting the UAV stochastic input stream into a regular gate stream; Landing Buffer Zone (LZP), which ensures equalization of the UAV speed when leaving the PVZO and arriving at the starting point of the landing line at the BCP, as well as allowing to adjust the utilization factor of at least one BCP; at least one PP, characterized by the landing time of a single UAV, which is a service device of the landing queuing system for a group of UAVs. At the same time, the method of landing a group of UAVs with a random structure based on data on the statistics of service by the landing station, information on the input flow of UAVs, data from neighboring transit-terminal UAV landing stations, UAV technical characteristics and data from the weather station provides for the formation by the landing system of the structure and size of the PVZO, which allows to ensure the safe presence of a certain number of UAVs in the PVZO in flight mode, to form UAV flight routes in the PVZO, which are characterized by the frequency of the UAV passing spatial points of the PVZO to leave the holding area in the BZP and further landing, which determines the priority of the UAV service. The choice of one UAV from a set of applicants for exiting the PVZO, with the aim of further landing at the BCP, is decided on the basis of the landing line multiple access protocol and the air traffic safety analysis algorithm in the landing zone. The transformation of the stochastic UAV input stream into a regular UAV output stream for landing under conditions of high loading of the landing system is carried out by a uniform distribution of incoming UAVs in the PVZO on a set of non-intersecting and space-ordered closed routes that provide UAVs with periodic passage of exit points for landing with different frequency, while in Each such route organizes the ordered movement of the UAVs entering the PVZO through a safe time interval, which corresponds to the time compaction of the UAVs in a given route. As a variant of the spatial structure of the PVZO, a two-dimensional ring structure is proposed - a toroidal self-similar structure, which is a spatial ring structure, the basis of which is a ring structure formed by a regular polygon (hereinafter - the elementary ring structure), which represents a ring structure of small radius of a two-dimensional ring structure (at infinite set of points, an elementary ring structure corresponds to a circle that rotates around an axis that lies in the plane of this circle and does not intersect it), the number of its vertices determines the number of sectors uniformly distributed around a circle of large radius of a two-dimensional ring structure. The set of points (vertices) of all elementary ring structures form the coordinate space for UAV movement in it. An increase in the number of vertices in an elementary ring structure leads to an increase in the number of routes with different priorities, the number of UAVs spatially distributed in the structure, and an increase in the radii of rotation of a two-dimensional ring structure, namely, a small one - the radius of an elementary ring structure and a large one - a radius corresponding to the removal of the centers of elementary ring structures from the axis of their rotation, increases the safety of UAV air traffic by increasing the minimum allowable distance between UAVs in the PVZO.

The technical result is achieved by the fact that the information and computing means of the landing station landing system analyzes information about the statistics of UAV arrivals for landing in a given time interval, the intensity of UAV arrivals, UAV traffic information from neighboring transit terminal landing stations, weather conditions and technical characteristics of UAVs served, in as a result, the landing system forms the PVZO structure, identifies the objects requesting landing, and, if the service decision is positive, each UAV of the incoming group, or a single UAV in a stochastic flow, is issued via the communication channel, landing permission, time and spatial coordinates for entering the PVZO, route, UAV movement speed in PVZO. During the movement of the UAV in the PVZO in a discrete time interval, several UAVs, approaching the points of exit from the PVZO, together with the landing system, implement the landing line access protocol, as a result of which at least one UAV leaves the PVZO for landing, the rest continue to move to the PVZO along closed routes. The UAV leaving the PVZO is given the route to the BZP and the coordinates of the landing line when using technical means of landing, including using technical vision, the UAV is landing at the BCP.

The difference between the invention and the prototype is that on the basis of the proposed method, a queuing system for landing groups of UAVs with random structures is created, in which, based on the variable structure of the PVZO and the set of routes that do not intersect in it, buffering of a different number of UAVs, regularization of UAV input streams and provision of conditions UAV priority service during landing. As a result, it is possible to land not only groups of UAVs with different structures, but also a stochastic flow of UAVs with an UAV arrival rate higher than the landing speed of a single UAV on the landing platform in a certain time interval. The change in the structure of the PVZO depends on the analysis of the statistics of the arrival of the UAV for landing, the characteristics of the UAV traffic, taking into account the information of information interaction with other transit terminal landing stations, meteorological conditions and the technical characteristics of the UAV. An increase in the radii of the structural elements of the two-dimensional ring structure of the PVZO, while maintaining the number of vertices of the elementary ring structure, makes it possible to increase the safety of UAV air traffic in the landing zone.

In FIG. 1a) presents a model of the system for landing UAV swarm groups on the launch site in the form of a queuing system consisting of the main blocks:

1 - PVZO;

2 - BZP;

3 - PP.

In FIG. 1b) shows a model of a queuing system for UAV groups with several RPs: RP ₁ , …, RP _n .

In FIG. Figure 2 shows the structure of the PVZO with two UAV routes.

Line 1-2 corresponds to the flight of the UAV along the route with the highest priority, corresponding to the phase shift "0"; line 1-3-4-5 corresponds to a route with a reduced priority of two levels and the corresponding phase shift "2Δ"; lines 2-6 and 5-6 correspond to the movement of the UAV in BZP 2, and the paired line 6-7 corresponds to the landing line of the UAV at CP 3.

In FIG. 3 shows the algorithm for interaction between the landing system of the landing station and the UAV.

The queuing system for landing a group of UAVs with a random structure (Fig.1a) consists of series-connected PVZO 1, BZP 2 and PP 3, the input of which is a swarm of UAVs with a random structure, or a stochastic flow of UAVs with intensity γ [UAV/unit. time]. In the presence of several, in the general case, n, PP 3, UAVs from the exit of PVZO 1, as an option from different spatial points, enter the BZP and then follow in parallel to the points of the beginning of the landing lines of the corresponding PP 3 (Fig. 1b). PVZO 1 performs the functions of accumulating UAVs waiting to land, regularizing the incoming flow of UAVs and ensuring the safety of UAV air traffic in it, BZP 2 equalizes the UAV movement speeds when the UAV leaves PVZO 1 and enters the point of the landing line of LS 3, at a high speed of service of LS 3 provides an efficient utilization factor, alternatively, by loading the BZP 2 with several UAVs. Structurally, the PVZO (Fig. 2) is a limited UAV location space, in which there is a spatial figure, the coordinates of the nodal points of which determine the points of passage of a plurality of independent UAV routes during their movement with the condition that air traffic safety requirements are met.

A variant of the PVZO, which has a large number of non-intersecting closed paths, is a two-dimensional ring structure - a toroidal structure with self-similarity, i.e. in it, identical elementary ring structures of small radius, representing, for example (Fig. 2), a regular hexagon, define a spatial hexagonal ring structure of a regular shape of large radius, the vertices of which correspond to elementary ring structures of small radius. As a result, sectors are formed in the toroidal structure, the middles of which correspond to elementary ring structures (Fig. 2), through which the UAV enters and exits PVZO 1. Depending on the UAV traffic analysis, UAV characteristics and weather conditions, the landing system can change the dimension of the elementary ring structure. structure, as a result of which the number and density of sectors in the structure changes. So, for example, with fixed values of the radii r and R (Fig. 2), for an elementary ring structure with 12 nodes, the PVZO structure will have 12 sectors, which makes it possible to form a greater number of independent routes in the structure with a simultaneous increase in the UAV density. Reducing the distances between UAVs in the PVZO involves taking into account the task of safe air traffic in the landing area. With a fixed value of the maximum allowable number of UAVs in the PVZO, an increase in r and R leads to an expansion of space with a simultaneous increase in air traffic safety. The vertices of the spatial toroidal structure form the coordinate space of UAV routes. The direction of UAV flights in the PVZO is chosen as one, for example, counterclockwise (see Fig. 2). Thus, the spatial factor characterizing the PVZO resource is determined by its structure and closed independent routes in it, and the time factor is determined by the allowable time intervals between two successive UAVs in one route. The entry points of the UAV into the PVZO and the exit of the UAV from it are determined by the features of the relative position of the SP and PVZO and the weather conditions. In FIG. 2, the top points of the structure are selected. The route for the movement of the UAV in the PVZO is determined by the entry point into the spatial structure and the fixed phase shift in the elementary ring structure. Moving counterclockwise along the route in the toroidal structure, the UAV in each sector has a target coordinate (one of the vertices of the elementary ring structure of the next sector) to change the direction of movement. It is obtained by adding a certain phase shift in the route (Fig. 2, the route with the phase shift "0" corresponds to the path 1-2, the route with the phase shift "2Δ" corresponds to the path 1-3-4-5, while in each subsequent sector the target coordinate is equally shifted counterclockwise by two vertices, i.e. by 2Δ). With a fixed value of the small radius, the value of Δ, equal to Δ=360/n, depends on the number of vertices n in the elementary ring structure, affects, as well as the geometric parameters of the toroidal structure, air traffic safety and must be greater than the minimum allowable relative position of neighboring UAVs. In elementary ring structures, the target coordinates for different routes are different and differ in phase shifts in the plane of the elementary ring structure: Δ, 2Δ, 3Δ, … n/2Δ. Since the period of revolution in a two-dimensional ring structure is equal to 4π (except for the route with zero phase shift, where the period is equal to 2π, it is determined by the movement of the UAV only in one plane and corresponds to the movement of the UAV along a large radius ring), when moving in a two-dimensional structure, for example, against clockwise, the UAVs move from sector to sector (in a circle), while making a shift by their phase shift in the elementary ring structure in each sector, then for the period of circulation along the large radius ring, depending on the route, the UAV makes a different number of accesses along the ring small radius structure. This makes it possible for the UAV to go to the coordinate points from which the landing gate is determined with different frequencies. Priority service during landing is determined by the route, which, with the corresponding value of the phase shift, has the highest frequency of passing through a point in the toroidal structure, which, in turn, allows landing from the PVZO. Using the ordering in the elementary ring structure, i.e. by linking each coordinate to a certain level (degree) of belonging to the given functional subsets (solutions), it is possible not only to correctly control the UAV using fuzzy (soft) subsets when accessing the landing line, but also to implement emergency landing options. A variant of a simple emergency landing is the independent landing of the UAV in the sector, for example, when passing the lowest point of the elementary ring structure. The toroidal structure of the PVZO can be used simultaneously for UAV takeoff, provided that the direction of UAV movement in the structure is observed and the corresponding algorithmic division of the space-time resource of the waiting area for takeoff and landing is observed. The algorithm for the interaction of the landing station landing system with the UAV (Fig. 3) provides for the availability of technical means of control in order to prevent unauthorized access to the launch site and ensure the safety of air traffic in the PVZO.

The proof of the technical feasibility of the method is the availability of the necessary technical and computational resources of the UAV swarm landing system, technical vision, control systems with video and IR channels, wireless communication systems in the landing area, providing two-way digital communication between the central unit of the landing system and a plurality of UAVs.

Claims (5)

1. A method for landing a group of unmanned aerial vehicles (UAVs) on a landing platform, which consists in information exchange via forward and reverse communication channels of a UAV requiring landing with a landing platform and subsequent correction of its movement during landing, characterized in that for the purpose of safe landing of a group of UAVs with random structure and service priorities, as well as an incoming stochastic UAV flow with a high intensity, a UAV group landing queuing system is created with at least one landing platform, including a space-time UAV waiting area that is tunable at discrete times, but fixed at a given time interval a spatial structure, the vertices of which correspond to the coordinates of the UAV movement routes, in which a set of UAV movement routes that do not intersect in space and determine the UAV service priorities during landing are formed. 2. The method according to claim 1, characterized in that the spatio-temporal waiting area of the UAV has a toroidal self-similar structure, in which the number of vertices of the small radius ring structure is equal to the number of sectors of the large radius ring structure corresponding to the small radius ring structure, the UAV movement routes in the spatial ring structure are set in one of two directions, for example, counterclockwise, when entering the holding area, each UAV is given the coordinates of the entry point corresponding to one of the vertices of the ring structure of the small radius sector specified by the landing system, the time of entry into the holding area, the route of movement in it and the speed of the UAV along the route. 3. The method according to claim 2, characterized in that the UAV movement route in the spatio-temporal waiting area is set by the coordinates of the sequence of points of the two-dimensional ring structure, taking into account its movement in a cycle in the large radius ring structure and the movement of the UAV, taking into account the phase shift in the small ring structure the radius of the spatial structure of the waiting area. 4. The method according to claims 1 and 2, characterized in that the space-time waiting area and the parameters of the toroidal spatial structure change at discrete times depending on the requirements of air traffic safety, UAV traffic, weather conditions and UAV technical characteristics without changing the system operation algorithms landing of the UAV group. 5. The method according to claim 1, characterized in that in order to equalize the speed of the UAV when leaving the holding area and entering the landing line, as well as to increase the utilization of the landing platform when landing a group of UAVs, a buffer landing zone is used with UAV flight routes that allow distribute them to more than one landing platform, and in high-speed conditions of at least one landing platform, generate UAV traffic when leaving the holding area for landing along one or more traffic routes in the landing buffer zone in the direction of the landing platform.

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