A method and system for event-triggered safety control of a multi-UAV system

Abstract

The present disclosure provides a method and system for event-triggered safety control of a multi-UAV system, which relates to the field of automatic control technology. The method includes obtaining the topological structure of the multi-UAV communication network and establishing the dynamic equations of the UAV leader and followers; according to the topological structure of the communication network, each UAV sets the dynamic equation of the estimator of its neighbors, defines the triggering interval sampling error, designs a distributed event-triggered communication strategy and the interval of time-triggering; according to the designed estimator and the distributed event-triggered communication strategy, designs a consensus control protocol based on the network topological relationship; according to the designed distributed event-triggered communication strategy, designs the switching strategy of the estimator and the controller, and uses the information obtained from the last successful communication as the initial value of the estimator state, and conducts simulation verification; the present disclosure overcomes the problem that the multi-UAV system cannot obtain the neighbor control input information during an attack, and saves computing resources at the same time.

Description

Technical Field

[0001] The present disclosure relates to the field of automatic control technology, and particularly relates to a method and system for event-triggered safety control of a multi-UAV system. Background Art

[0002] The statements in this part merely provide background technical information related to the present disclosure and do not necessarily constitute prior art.

[0003] With the wide application of UAVs, many scholars have focused on the consensus control method of multi-UAV systems, that is, a method that enables the states of each UAV to eventually converge. The consensus of multi-UAV systems includes leaderless average consensus and leader-follower consensus. However, these consensus control protocols highly rely on network communication, so the security control problem of multi-UAV systems is becoming increasingly important.

[0004] The cyberattacks suffered by multi-UAV systems are mainly divided into two types: denial-of-service attacks and spoofing attacks. A denial-of-service attack refers to an attack method that makes it impossible for UAVs to normally exchange information. The specific implementation process is as follows: the attacker sends a large number of false request messages to the target channel to consume the communication resources of the target UAV. Eventually, the target UAV has no resources to process normal communication requests, resulting in packet loss.

[0005] For the purpose of saving communication resources, many studies have proposed an event-triggered control method. The basic idea of this method is that communication will only be carried out when the conditions of the set event trigger function are met. This existing method of continuous communication and periodic communication will greatly increase the communication frequency. Summary of the Invention

[0006] In order to solve the above problems, the present disclosure proposes a control method for achieving the consensus of a multi-UAV system under a denial-of-service attack and conducts communication optimization. A set of estimators is set in each UAV to estimate the states of neighbors based on the obtained information, and an event-triggered method is designed to reduce the communication frequency during normal communication while ensuring the convergence of the multi-UAV system.

[0007] According to some embodiments, the present disclosure adopts the following technical solutions:

[0008] A method for event-triggered safety control of a multi-UAV system, comprising:

[0009] Obtain the topological structure of the multi-UAV communication network and establish the dynamic equations of UAV leaders and followers;

[0010] According to the topological structure of the communication network, set the dynamic equations of estimators for neighbors in each UAV, define the triggering interval sampling error, and design a distributed event-triggered communication strategy and the interval of time triggering;

[0011] According to the designed estimator and distributed event-triggered communication strategy, design a consensus control protocol based on the network topology relationship; according to the designed distributed event-triggered communication strategy, design a switching strategy for the estimator and the controller, and use the information obtained from the last successful communication as the initial value of the estimator state, and conduct simulation verification.

[0012] According to some embodiments, the present disclosure adopts the following technical solutions:

[0013] A multi-UAV system event-triggered safety control system, comprising:

[0014] A dynamic equation construction module, configured to obtain the topology of the multi-UAV communication network and establish the dynamic equations of the UAV leader and followers;

[0015] A strategy definition module, configured to set the dynamic equations of the estimators of the neighbors for each UAV according to the topology of the communication network, define the triggering interval sampling error, design a distributed event-triggered communication strategy, and the interval of time-triggering;

[0016] A control switching module, configured to design a consensus control protocol based on the network topology relationship according to the designed estimator and distributed event-triggered communication strategy; according to the designed distributed event-triggered communication strategy, design a switching strategy for the estimator and the controller, and use the information obtained from the last successful communication as the initial value of the estimator state, and conduct simulation verification.

[0017] According to some embodiments, the present disclosure adopts the following technical solutions:

[0018] A computer-readable storage medium, in which multiple instructions are stored, and the instructions are adapted to be loaded and executed by a processor of a terminal device for the described multi-UAV system event-triggered safety control method.

[0019] According to some embodiments, the present disclosure adopts the following technical solutions:

[0020] A terminal device, comprising a processor and a computer-readable storage medium, the processor is used to implement each instruction; the computer-readable storage medium is used to store multiple instructions, and the instructions are adapted to be loaded and executed by the processor for the described multi-UAV system event-triggered safety control method.

[0021] Compared with the prior art, the beneficial effects of the present disclosure are:

[0022] 1. To address the problem that UAVs cannot communicate with each other under a denial-of-service attack, a set of estimators is introduced to reconstruct the lost state information during the attack using known information. The estimators do not require control inputs, overcoming the problem that multi-UAV systems cannot obtain neighbor control input information during the attack and saving computational resources at the same time;

[0023] 2. To save communication resources, an event-triggered control method is adopted. The designed event-triggering function is fully distributed, which can avoid continuously monitoring the states of neighbors and can also avoid Zeno behavior. In addition, a periodic time-triggered strategy is designed to detect the end of the attack. The two triggering strategies determine which one to use according to whether an attack occurs;

[0024] According to whether UAVs can communicate with each other, the control protocol is designed in two parts: using the real state values during normal communication periods and using the estimated state values during periods when communication is unavailable. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings forming a part of this disclosure are used to provide a further understanding of this disclosure. The schematic embodiments of this disclosure and their descriptions are used to explain this disclosure and do not constitute an improper limitation of this disclosure.

[0026] Figure 1 It is a flowchart of an event-triggered security control method for a multi-UAV system based on estimators according to this disclosure;

[0027] Figure 2 It is a system block diagram of an event-triggered security control method for a multi-UAV system based on estimators according to this disclosure;

[0028] Figure 3 It is a schematic diagram of the triggering moment of an event-triggered security control method for a multi-UAV system based on estimators according to this disclosure;

[0029] Figure 4 It is a communication network topology diagram of a multi-UAV system in an embodiment of this disclosure;

[0030] Figure 5 It is a time series schematic diagram of a denial-of-service attack in an embodiment of this disclosure;

[0031] Figure 6 It is a state trajectory diagram of the leader and followers of a multi-UAV system in an embodiment of this disclosure; DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] The present disclosure will be further described below in conjunction with the accompanying drawings and embodiments.

[0033] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present disclosure. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present disclosure belongs.

[0034] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present disclosure. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0035] Embodiment 1

[0036] In one embodiment of the present disclosure, a multi - UAV system event - triggered safety control method is provided, including:

[0037] S1: Obtain the topological structure of the multi - UAV communication network and establish the dynamic equations of the UAV leader and followers;

[0038] S2: According to the topological structure of the communication network, each UAV sets the dynamic equation of the estimator of its neighbors, defines the triggering interval sampling error, and designs a distributed event - triggered communication strategy and the time - triggered interval;

[0039] S3: According to the designed estimator and the distributed event - triggered communication strategy, design a consensus control protocol based on the network topological relationship;

[0040] S4: According to the designed distributed event - triggered communication strategy, design the switching strategy of the estimator and the controller, and use the information obtained from the last successful communication as the initial value of the estimator state, and conduct simulation verification.

[0041] As an embodiment, obtaining the topological structure of the multi - UAV communication network and establishing the dynamic equations of the UAV leader and followers includes the following steps:

[0042] The multi - UAV system consists of one leader and N followers. The dynamic equations of each UAV are established as follows:

[0043]

[0044] where \(x_0\in R\) n represents the state of the leader, \(x\) i \(\in R\) n represents the state of the \(i\) - th UAV, \(u\) i \(\in R\) nDenote the control input of the \(i\)-th UAV. \(A\) is the system matrix and \(B\) is the input matrix, both of which are time-invariant.

[0045] Among them, the dynamic model of the leader considers no control input.

[0046] Furthermore, according to the topology of the communication network, the steps of setting the dynamic equation of the estimator for the neighbors of each UAV, defining the triggering interval sampling error, and designing the distributed event-triggered communication strategy and the time-triggered interval include:

[0047] According to the topology of the communication network, calculate the values of the adjacency matrix and the \(H\) matrix, and configure the estimator for the neighbors of each follower. The adjacency matrix is:

[0048]

[0049] If UAV \(i\) and UAV \(j\) are neighbors of each other, then \(a_{ij}=a_{ji}=1\); otherwise, \(a_{ij}=a_{ji}=0\), and it is assumed that \(a_{ii}=0\). ij =a ji =1, otherwise, a ij =a ji =0, and assume a ii =0;

[0050] Laplacian matrix:

[0051]

[0052] where and \(l_{ij}=-a_{ij}\), \(i\neq j\); ij =-a ij , \(i\neq j\);

[0053] \(\Delta\) matrix: \(\Delta=\text{diag}\{a_{11},\ldots,a_{nn}\}\). If UAV \(i\) is a neighbor of the leader UAV, then \(a_{ii}=1\); otherwise, \(a_{ii}=0\). 10 ,…,a N0}, if UAV \(i\) is a neighbor of the leader UAV, then a i0 =1, otherwise, a i0 =0;

[0054] Calculate the \(H\) matrix:

[0055] Establish the dynamic equation of the estimator for the \(i\)-th UAV as follows:

[0056]

[0057] where are the state estimates of the leader, the \(i\)-th UAV, and the neighbors of the \(i\)-th UAV respectively. Only the neighbors of the leader need to estimate the state of the leader.

[0058] Define the sampling error as:

[0059]

[0060] wherein is the triggering moment of the i-th drone. During the normal communication time interval, the triggering moment is determined by the following event triggering function:

[0061]

[0062] When f i (t)>0, the state value is updated, and this moment is the triggering moment

[0063] The definition method of the time triggering interval is as follows: During the normal communication time interval, the triggering moment is determined by the event triggering function, and the moment when the function updates the state value is the triggering moment; during the time interval when communication is unavailable, a fixed-period triggering method is adopted. The moment when the attack starts is defined as the first triggering moment, and then it is triggered once every fixed period until successful communication is established between the drone and its neighbors. During the time interval when communication is unavailable due to an attack, a fixed-period triggering method is adopted. The moment when the attack starts is the first triggering moment, and then it is triggered once every θ time until successful communication is established between the drone and its neighbors. During this period, a communication attempt is made each time it is triggered. The θ time is artificially selected. The shorter this time is, the better the performance, but more resources are required, and vice versa for a longer time.

[0064] Furthermore, according to the described event-triggered security control method for a multi-drone system based on an estimator, according to the designed estimator and distributed event-triggered communication strategy, the specific implementation method of the consensus control protocol based on the network topology relationship includes the following steps:

[0065] According to the estimator and triggering strategy, the calculation process of the i-th drone controller is as follows:

[0066]

[0067] wherein are the state values updated at the triggering moment of the leader, the i-th drone, and the neighbors of the i-th drone respectively, are the state estimation values of the leader, the i-th drone, and the neighbors of the i-th drone respectively. K1 and K2 represent the gain matrices of the controller in two modes. The specific calculation process of K1 is as follows:

[0068] According to the Riccati algebraic equation: QA + A T Q - 2λ min (H)QBB T Q + ∈I < 0, select an appropriate positive number ∈, and obtain the matrix Q by combining the system matrix A, the input matrix B, and the H matrix. Then calculate K1 = B T Q, wherein, λmin (H) is the minimum eigenvalue of the H matrix.

[0069] According to the described estimator-based multi-UAV system event-triggered safety control method, in step S4, based on the detection of the triggering protocol, the system is divided into two modes: the case where normal communication is possible and the case where communication is impossible due to an attack. Different control protocols are used in the two cases: in the interval where normal communication is possible, the actual obtained state values are used by the controller; when an attack occurs, the estimated state values are switched to be used. In addition, the estimator only starts after an attack occurs, and the information obtained from the last successful communication is used as the initial value of the estimator state, which is specifically expressed as follows:

[0070]

[0071] where, assume t ζ is the start time of the attack.

[0072] The above triggering protocol is:

[0073]

[0074] where assume

[0075] The above-mentioned method is verified by simulation, as Figures 4 - 6 shown.

[0076] The communication topology diagram is as Figure 4 shown. The simulated system considered includes 1 leader (labeled 0) and 4 followers (labeled 1, 2, 3, 4). According to Figure 4 calculated

[0077]

[0078] Let the controllable matrix pair (A, B) of the system be as follows

[0079]

[0080] Select ∈ = 0.5, σ = 0.0018 and θ = 0.1, and then according to QA + A T Q - 2λ min (H) QBB T Q + ∈I < 0 calculated

[0081]

[0082] From the above data, through the formula K1 = B T Q, it is calculated that K1 = [0.9107 0.5521], and K2 is appropriately selected as [0.1 0.1].

[0083] The parameters in the event-triggered function are: a = 0.1, b = 0.4, and N = 4. Simulate for 50 s, and the DoS attack sequence is as Figure 5 shown, where the shaded part represents the time when the attack occurs.

[0084] Represent the system state vector as x i =[x i,1 ,x i,2 T , i = 0, 1, …, 4, set the initial state of each UAV as x0(0) = [-1, 1] T , x1(0) = [-2, 2] T , x2(0) = [-3, 3] T , x3(0) = [-4, 4] T , x4(0) = [-5, 5] T , and then set the external disturbance of the system as d0(t) = 0.01sin(0.1t) × [1, 1] T , d1(t) =

[0085] 0.01sin(0.1t + 10) × [1, 1] T , d2(t) = 0.01sin(0.1t + 20) × [1, 1] T , d3(t) =

[0086] 0.01sin0.1t + 30 × [1, 1] T , d4(t) = 0.01sin(0.1t + 40) × [1, 1] T , and finally, the simulation results are as Figure 6 shown, and the states of each UAV tend to be consistent.

[0087] Embodiment 2

[0088] In an embodiment of the present disclosure, a multi-UAV system event-triggered safety control system is provided, including:

[0089] A dynamic equation construction module, configured to obtain the topological structure of the multi-UAV communication network and establish the dynamic equations of the UAV leader and followers;

[0090] A strategy definition module, configured to set the dynamic equations of the estimators of the neighbors for each UAV according to the topological structure of the communication network, define the triggering interval sampling error, and design a distributed event-triggered communication strategy and the time-triggered interval;

[0091] ​The control switching module is used to design a consensus control protocol based on the network topology relationship according to the designed estimator and the distributed event-triggered communication strategy; design the switching strategy of the estimator and the controller according to the designed distributed event-triggered communication strategy, and use the information obtained from the last successful communication as the initial value of the estimator state, and conduct simulation verification.

[0092] Embodiment 3

[0093] In an embodiment of the present disclosure, a computer-readable storage medium is provided, in which multiple instructions are stored, and the instructions are suitable for being loaded and executed by a processor of a terminal device to perform the steps of the multi-UAV system event-triggered security control method.

[0094] Embodiment 4

[0095] A terminal device includes a processor and a computer-readable storage medium. The processor is used to implement each instruction; the computer-readable storage medium is used to store multiple instructions, and the instructions are suitable for being loaded and executed by the processor to perform the steps of the multi-UAV system event-triggered security control method.

[0096] The present disclosure is described with reference to the flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present disclosure. It should be understood that each process and / or block in the flowcharts and / or block diagrams, and the combination of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for implementing the functions specified in one process Figure 1 one process or multiple processes and / or blocks Figure 1 or multiple blocks.

[0097] These computer program instructions can also be loaded onto a computer or other programmable data processing devices, so that a series of operation steps are performed on the computer or other programmable devices to generate a computer-implemented process, and thus the instructions executed on the computer or other programmable devices provide steps for implementing the functions specified in one process Figure 1 one process or multiple processes and / or blocks Figure 1 or multiple blocks.

[0098] Although the specific implementation manners of the present disclosure are described above in conjunction with the accompanying drawings, it is not a limitation to the protection scope of the present disclosure. Those skilled in the art should understand that based on the technical solutions of the present disclosure, various modifications or deformations that can be made by those skilled in the art without creative efforts are still within the protection scope of the present disclosure.

Claims

1. A method for event-triggered safety control of a multi-UAV system, characterized in that, Including: Obtain the topological structure of the multi-UAV communication network and establish the dynamic equations of UAV leaders and followers; The dynamic model of the leader has no control input; According to the topological structure of the communication network, each UAV sets the dynamic equation of the estimator of its neighbors, defines the triggering interval sampling error, designs a distributed event-triggered communication strategy and the interval of time-triggering. Specifically: establish the dynamic equation of the estimator of the i-th UAV: where are the state estimates of the leader, the i-th UAV, and the neighbors of the i-th UAV, respectively. Only the neighbors of the leader need to estimate the state of the leader; A is the system matrix; Define the sampling error as: where \(x_0\in\mathbb{R}\) n represents the state of the leader, and \(x\) i \(\in\mathbb{R}\) n represents the state of the \(i\)-th UAV; \(t_i\) is the triggering time of the \(i\)-th UAV. During the normal communication time interval, the triggering time is determined by the event-triggering function, specifically: When \(f\) i (t)>0, the state value is updated, and this moment is the triggering time where \(e\) i (t) is the sampling error; \(N\) is the number of followers; if UAV \(i\) is a neighbor of the leader UAV, then \(a\) i0 \( = 1\), otherwise, \(a\) i0 \( = 0\); According to the designed estimator and distributed event-triggered communication strategy, design a consensus control protocol based on the network topological relationship; according to the designed distributed event-triggered communication strategy, design the switching strategy of the estimator and the controller, and use the information obtained from the last successful communication as the initial value of the estimator state, and conduct simulation verification; according to the detection of the triggering protocol, divide the system into two modes: the case where normal communication is possible and the case where communication is impossible due to an attack; different control protocols are used in the two cases. In the interval of normal communication, the controller uses the actually obtained state value; when an attack occurs, switch to using the estimated state value, and the estimator only starts after the attack occurs, and uses the information obtained from the last successful communication as the initial value of the estimator state.

2. The method for event-triggered safety control of a multi-UAV system according to claim 1, wherein The UAV system consists of one leader and multiple followers. Establish the dynamic equations of each UAV as: where \(x_0\in\mathbb{R}\) n represents the state of the leader, \(x\) i \(\in\mathbb{R}\) n represents the state of the \(i\)-th UAV, \(u\) i \(\in\mathbb{R}\) n represents the control input of the \(i\)-th UAV, \(A\) is the system matrix, \(B\) is the input matrix, both of which are invariant; \(N\) represents the number of followers.

3. A method for event-triggered safety control of a multi-UAV system according to claim 1, characterized in that, The way for each UAV to set the dynamic equation of the estimator of its neighbors is to calculate the values of the adjacency matrix and the H matrix according to the topological structure of the communication network, configure the estimator of its neighbors for each follower, and establish the dynamic equation of the estimator of the UAV.

4. The safety control method for multi-UAV system event triggering according to claim 1, characterized in that, The definition method of the time-triggering interval also includes: in the time interval when communication is impossible, adopt the fixed-period triggering method, define the start time of the attack as the first triggering time, and then trigger once every fixed period until successful communication between the UAV and its neighbors.

5. A multi-UAV system event-triggered safety control system, characterized in that, Including: A dynamic equation construction module, which is used to obtain the topological structure of the multi-UAV communication network and establish the dynamic equations of UAV leaders and followers; The dynamic model of the leader has no control input; A strategy definition module, which is used to set the dynamic equation of the estimator of the neighbors for each UAV according to the topological structure of the communication network, define the triggering interval sampling error, design a distributed event-triggered communication strategy and the interval of time-triggering. Specifically: establish the dynamic equation of the estimator of the i-th UAV: wherein are the state estimation values of the leader, the i-th UAV, and the neighbors of the i-th UAV, respectively. Only the neighbors of the leader need to estimate the state of the leader; A is the system matrix; Define the sampling error as: where \(x_0\in\mathbb{R}\) n represents the state of the leader, and \(x\) i \(\in\mathbb{R}\) n represents the state of the \(i\)-th UAV; is the triggering moment of the \(i\)-th UAV. During the normal communication time interval, the triggering moment is determined by the event-triggering function, specifically: When \(f\) i (t)>0, the state value is updated, and this moment is the triggering moment where \(e\) i (t) is the sampling error; \(N\) is the number of followers; if UAV \(i\) is a neighbor of the leader UAV, then \(a\) i0 \( = 1\), otherwise, \(a\) i0 \( = 0\); A control switching module is used to design a consensus control protocol based on the network topology relationship according to the designed estimator and distributed event-triggered communication strategy; design the switching strategy of the estimator and the controller according to the designed distributed event-triggered communication strategy, and use the information obtained from the last successful communication as the initial value of the estimator state, and conduct simulation verification; divide the system into two modes according to the detection of the triggering protocol: the case where normal communication can be carried out and the case where communication cannot be carried out due to an attack; different control protocols are used in the two cases. In the normal communication interval, the controller uses the actually obtained state value; when an attack occurs, it switches to using the estimated state value, and the estimator also only starts after the attack occurs, and uses the information obtained from the last successful communication as the initial value of the estimator state.

6. A computer-readable storage medium, characterized in that, It stores multiple instructions, and the instructions are suitable for being loaded and executed by a processor of a terminal device to perform a multi-UAV system event-triggered security control method according to any one of claims 1-4.

7. A terminal device, characterized in that, It includes a processor and a computer-readable storage medium. The processor is used to implement each instruction; the computer-readable storage medium is used to store multiple instructions, and the instructions are suitable for being loaded and executed by the processor to perform a multi-UAV system event-triggered security control method according to any one of claims 1-4.

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