Reliability Evaluation Method for UAV Data Link Services

Abstract

This invention provides a method for evaluating the reliability of UAV datalink services, used for modeling complex, dynamic, and coupled UAV datalinks. Based on the analysis of UAV datalink characteristics, this invention focuses on three major services: uplink remote control / flight control / mission control data transmission, downlink telemetry data transmission, and downlink mission payload data transmission. It proposes using service reliability to describe the reliability of the UAV datalink. A reliability simulation model of the dynamically changing UAV datalink services is constructed based on GSPN (Germanic Stochastic Petri Net) and Monte Carlo simulation. The model describes various resources, states, behaviors, and collaborative relationships in the datalink system through concepts such as resources, locations, and transitions. Specific random variables represent component states and their durations, simulating the dynamic operation of the system services and achieving accurate evaluation of UAV datalink service reliability.

Description

Technical Field

[0001] This invention belongs to the field of dynamic reliability modeling of UAV data links, and specifically relates to a method for evaluating the service reliability of UAV data links. Background Technology

[0002] With the gradual promotion and application of joint operations, data links play a crucial role in this new model. As an information "glue," they enable data exchange, interconnection, and sharing among various combat platforms, acting as a force multiplier. As an important form of data link, the reliability of UAV data links is receiving increasing attention.

[0003] The most commonly used reliability modeling methods, such as Reliability Block Diagram (RPD) and Fault Tree Analysis (FTA), are static modeling and analysis methods, which are difficult to describe the complex temporal and dynamic relationships between data link systems. Markov models can solve dynamic problems; however, the most significant characteristic of Markov models is that the system's next state depends only on the current state and is independent of previous states, but many real-world systems do not meet this condition. Traditional UAV data link reliability modeling methods are no longer sufficient to meet the needs of dynamic behavior modeling for data link reliability. Summary of the Invention

[0004] The technical problem to be solved by this invention is to construct a UAV data link service reliability evaluation method based on GSPN network. The method focuses on the service implementation and link connectivity of the data link to carry out UAV data link service reliability modeling, considers the complex characteristics of strong coupling nonlinearity under multi-source heterogeneous attribute characteristics, fully characterizes the dynamic behavior of the data link, and performs Monte Carlo simulation on the constructed GSPN model to achieve a more accurate evaluation of the data link reliability level.

[0005] To address the above problems, this invention provides a method for evaluating the reliability of UAV data link services, comprising the following steps:

[0006] S1. Define the service failure criteria for the UAV system: Select the service attribute parameters of uplink remote control, flight control and manned data transmission as the reflection of service capability indicators. Based on the assessment requirements of service reliability, set the threshold values ​​of service capability indicators as service failure criteria.

[0007] S2. Obtain the business functions, basic relationships between events, dynamic behaviors, and static flowchart data of the unmanned aerial vehicle system;

[0008] S3. Construct a GSPN network for reliability simulation of dynamic changes in UAV data link services: Use places to represent the state of data link system devices and tokens to represent the resources carried on the system; according to the system's operation logic, use time migration and instantaneous migration to connect the places representing device states, and express the dynamic operation process of data link services through sequential relationships, parallel relationships and conflict relationships.

[0009] S31. Construct a Petri net model for uplink remote control, flight control, and user control data transmission services of the UAV system: Within line-of-sight, C+UHF band link equipment is prioritized. During takeoff and descent, the first C-band antenna is used for communication, and after reaching the cruise phase, it switches to the second C-band antenna. Remote control commands issued from the user control computer, link monitoring computer, and flight control computer are transmitted via a third optical transceiver to the second and first optical transceivers, respectively. The second optical transceiver then connects to the C-band terminal processor and the UHF band terminal processor via a switch. The C-band signal is modulated and encrypted by the C-band terminal processor, and then converted from intermediate frequency signal to radio frequency signal by a C-band inverter-upconverter. It is then transmitted by the first C-band antenna and the second C-band antenna via a C-band power amplifier and a C-band duplexer through a switching switch. The UHF band signal is modulated and encrypted by the UHF band terminal processor and then transmitted via the UHF band antenna.

[0010] S32. Construct a Petri net model for downlink telemetry data transmission services of the UAV system: Within line of sight, C-band and UHF bands are used preferentially for data transmission, and the selection of C-band antenna depends on the flight phase; beyond line of sight, data is transmitted through satellite communication links.

[0011] S33. Construct a Petri net model for downlink mission payload data transmission services of the unmanned aerial vehicle system;

[0012] S4. Calculate the GSPN network constructed for dynamic reliability simulation of UAV data link services using Monte Carlo simulation, and obtain the average number of tokens, 95% confidence interval, and service reliability of each location in the UAV data link service:

[0013] S41. GSPN Net Setup: Based on the Petri net model constructed in step S33, a delay following a certain distribution is associated with the changes in the state of the storage facility to form the GSPN model; the distribution function that the changes follow is set by setting the RATE parameter of the excitation rate in the changes; the RATE parameter values ​​of the changes associated with equipment failure in the Petri net model are all set to their corresponding failure rates for simulation.

[0014] S42. Simulation settings: Add the correct number of tokens to the storage area. In GSPN, the weight represents the number of tokens m consumed from the storage area above the arc and the number of tokens n transmitted to the downstream storage area after the transition below the arc is enabled and fired. m is not necessarily the same as n. The state of system components and the stage of the task are modeled as the corresponding storage area. A storage area with successful data transmission is used to represent that the data is finally transmitted through the antenna. A storage area with failed data transmission is used to represent the data transmission failure caused by packet loss and bit error in the optical terminal on the primary and backup paths of the service data transmission. After the above storage areas are constructed, transitions and arcs are used to connect the storage areas. The weight of each arc is 1 by default. Enabling this transition consumes 1 token.

[0015] S43. Simulation: Simulate the continuous data transmission process;

[0016] S44. Service reliability calculation: Service reliability is defined as the probability that a target task will successfully transmit data from one end to another under specified conditions and within a specified time. In the GSPN model, it is the ratio of the average number of tokens corresponding to the data transmission success database to the sum of the average number of tokens corresponding to both the data transmission success database and the data transmission failure database. Specifically, it is expressed as follows:

[0017]

[0018] Where R represents service reliability, N s N represents the number of tokens in the database where data was successfully sent. f Indicates the number of tokens in the database where data transmission failed;

[0019] S45. Calculate the average number of tokens and the 95% confidence interval of each location using Monte Carlo simulation to obtain the operational reliability of the UAV data link.

[0020] Preferably, the system service functions in step S2 include uplink remote control, flight control and / or mission control data transmission services, downlink telemetry data transmission services, and downlink mission payload data transmission services.

[0021] Preferably, step S31 specifically includes the following steps:

[0022] S311. Construct a Petri net model for forwarding service data information of optical transceivers: When the data from the control computer arrives at the third optical transceiver, a place is used to represent the information queue waiting to be processed on the third optical transceiver. The data processing rule is to process the data in order of arrival time. There are two directions for data transmission on the third optical transceiver: the first optical transceiver and the second optical transceiver. The first optical transceiver serves as a redundancy backup and switches over when either the second optical transceiver or the switch fails. Their states are described by a place, where normal is the OK place and faulty is the Fail place. The probability of the OK place reaching the Fail place is determined based on the equipment failure rate. When any place becomes the Fail place, the data token of that place enters the place of the first optical transceiver to continue the transmission.

[0023] S312. Construct a Petri net model for data transmission in C-band equipment: The location of the Petri net model for the transmission process of service data information is the name of the corresponding component, indicating that the data arrives at the component; the transition is the data processing in the component, indicating the occurrence of the data transmission event in the component. If the time for the component to process the data needs to be considered, the transition is represented by a <hollow bar> to indicate the signal processing delay; otherwise, it is represented by a <solid bar> to indicate that the transition occurs immediately.

[0024] S313. Construct a Petri net model of the data transmission process at the antenna end: Use two places to represent the arrival of data at the first C-band antenna and the second C-band antenna respectively. For data arriving at the switching switch place, connect these data with a transition respectively; add two places to represent the transmission stage, which are used as their enabling input places to jointly determine the enabling of the transition.

[0025] Preferably, step S32 specifically includes the following steps:

[0026] S321. Construct a Petri net model for receiving antenna service data information: Determine the service data transmission mode through the conflict relationship model composed of three libraries: in-line-of-sight / beyond-line-of-sight and data source; determine the transmission path of service data in the C-band through the conflict relationship model composed of three libraries: the flight phase, the first C-band antenna, and the second C-band antenna.

[0027] S322. Construct a Petri net model for data transmission in C-band equipment: The location of service data in the Petri net model during this process represents the processing of service data in the component; transitions are the success or failure of service data transmission by the component, indicating the occurrence of the service data transmission event; considering the time for the component to process data, the transition is represented by a <hollow bar> to indicate the signal processing delay, otherwise it is represented by a <solid bar> to indicate that the transition occurs immediately;

[0028] S323. Constructing a Petri net model for service data forwarding in terminal units: After service data arrives at the C-band terminal processor, a placeholder is used to represent the queue of information waiting to be processed. The data processing rule is to process data in the order of arrival time. Service data on the terminal unit has two transmission directions: one is to transmit it to the switch, and then to the third optical terminal via the first optical terminal; the other is to transmit it to the third optical terminal via the first optical terminal when the switch or the second optical terminal fails. The switch and the second optical terminal each use two placesholders to represent service data in the component and when the component fails. The placeholder representing the failure is switched to the first optical terminal after transition. The placeholder representing the first optical terminal is then switched to the placeholder representing the third optical terminal, thereby realizing dynamic reconfiguration.

[0029] S324. Constructing a Petri net model for service data arrival in the seat computers: After service data arrives at the third optical transceiver, the next hop is forwarded to the seat computers. Successful forwarding to all three seat computers is considered successful data transmission. A place is used to represent the processing of service data in the third optical transceiver. A place indicates that three computers are available, i.e., the receiving end is normal. For each of the three seat computers, three places are used to represent their normal status, and each is indicated by a transition pointing to the computer being available, i.e., the data receiving end is normal. A transition points to the place indicating that the computer is faulty. Only one backup seat computer is set up. When more than one computer fails, they will compete for the backup seat computer, forming a conflict relationship. The transition indicating the conflict relationship points to the seat computer that the backup seat computer replaces.

[0030] Preferably, step S33 specifically includes the following steps:

[0031] S331. Construct a Petri net model for receiving antenna service data: Construct a conflict model based on the aircraft's flight status. The conflict relationship model consisting of the three libraries of line-of-sight / beyond line-of-sight and data source determines whether the data is transmitted through the C-band link or the satellite communication link. The conflict relationship model consisting of the three libraries of the flight phase, the first C-band antenna, and the second C-band antenna determines whether the service data in the C-band is transmitted through the first antenna or the second antenna.

[0032] S332. Construct a Petri net model for data transmission in C-band equipment: The location of the service data in the Petri net model during this process represents "service data being processed in the component"; the transition is the success or failure of the service data being sent by the component, indicating the occurrence of the service data transmission event. If the time for the component to process the data needs to be considered, the transition is represented by a <hollow bar> to indicate the signal processing delay; otherwise, it is represented by a <solid bar> to indicate that the transition occurs immediately.

[0033] S333. Constructing a Petri net model for service data forwarding in the terminal: After service data arrives at the C-band terminal processor, a placeholder is used to represent the queue of information waiting to be processed. The data processing rule is to process data in order of arrival time. Service data on the terminal has two transmission directions: one is to transmit to the switch, and then to the third optical terminal via the second optical terminal; the other is that when the switch or the second optical terminal fails, the first optical terminal transmits the data to the third optical terminal. The switch and the second optical terminal use two placesholders to represent whether the service data forwarding in this component is successful or unsuccessful. Placeholders representing failures are transitioned to the first optical terminal, and placeholders representing the first optical terminal are transitioned to placeholders representing the third optical terminal.

[0034] S334. Service data arriving at the Petri net model from the seat computer: After the service data arrives at the third optical transceiver, the next hop is forwarded to the seat computer. Successful forwarding to all three seat computers is considered a successful data transmission. Successful data transmission requires that the data arrives at the third optical transceiver and that all three seat computers are available. A place is used to represent that the service data is being processed in the third optical transceiver, and a place represents that all three computers are available. The three seat computers share a backup seat computer. When one computer fails, the backup seat computer can serve as redundancy, ensuring that all three computers are available. The three seat computers are represented by three places to indicate that their status is normal, and each is indicated by a transition pointing to the available computer, i.e., the data receiving end is normal, and a transition points to the place indicating that the computer is faulty. There is only one backup seat computer. When more than one computer fails, they will compete for the backup seat computer, forming a conflict relationship. The transition indicating the conflict relationship points to the seat computer that the backup seat computer replaces.

[0035] Compared with existing technologies, the technical effects of this solution are as follows:

[0036] (1) It is proposed to use service reliability to describe the reliability of UAV data links. UAV data links have many functions, all of which are realized by the three major data transmission services of UAV uplink remote control, downlink telemetry and downlink mission payload. Services are a class of functions, which are more suitable for characterizing the reliability of UAVs.

[0037] (2) It is proposed to use the six-tuple of GSPN to express the dynamic changes of the data link. According to the operation logic of the system, time migration and instantaneous migration are used to connect these libraries representing the device status. Through model languages ​​such as sequential relationship, parallel relationship and conflict relationship, the dynamic operation process of data link business can be effectively expressed.

[0038] (3) The introduction of Monte Carlo simulation makes up for the shortcomings of GSPN in model solving. By calculating the constructed GSPN network through Monte Carlo simulation, the average number of tokens in each place can be obtained, thereby obtaining a more accurate business reliability of UAV data link. Attached Figure Description

[0039] Figure 1 A flowchart illustrating the reliability evaluation method for unmanned aerial vehicle (UAV) data link services;

[0040] Figure 2 A schematic diagram when the basic relationship between events in an unmanned aerial vehicle (UAV) system is a sequential relationship;

[0041] Figure 3 This is a diagram illustrating the basic relationship between events in an unmanned aerial vehicle (UAV) system when the relationship is concurrent.

[0042] Figure 4 A diagram illustrating the basic relationship of events in an unmanned aerial vehicle (UAV) system when the relationship is one of conflict.

[0043] Figure 5 The diagram illustrates the basic relationships of events in an unmanned aerial vehicle (UAV) system during dynamic reconfiguration.

[0044] Figure 6 A schematic diagram of the reliability model for uplink remote control and flight control / arbitrary control data transmission services of an unmanned aerial vehicle (UAV) system;

[0045] Figure 7 A schematic diagram of the reliability model for downlink telemetry data transmission services in an unmanned aerial vehicle (UAV) system.

[0046] Figure 8 This is a schematic diagram of the reliability model for downlink payload data transmission services in an unmanned aerial vehicle (UAV) system. Detailed Implementation

[0047] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings. Unless otherwise specified, the embodiments and features described in the present application can be combined with each other.

[0048] Down Figure 1 This invention discloses a method for evaluating the reliability of UAV data link services, which includes the following steps:

[0049] S1. Define the fault criteria for the UAV system: Select the service attribute parameters of uplink remote control, flight control, and arbitrary control data transmission as the reflection of service capability indicators. Based on the assessment requirements of service reliability, set the threshold values ​​of service capability indicators as the criteria for service faults.

[0050] S2. Obtain the business functions, basic relationships of events, dynamic behaviors, and static flowchart data of the unmanned aerial vehicle system.

[0051] When using Petri nets to model the GCS of a drone, the dynamic behavior of the system is reflected through the relationships between events. In Petri nets, the basic relationships between events include: sequential relationships, concurrent relationships, and conflict relationships.

[0052] like Figure 2 The diagram shows the basic sequential relationship of events in an unmanned aerial vehicle (UAV) system. Let PN = (P, T; F, M0) be a Petri net, and t1 and t2 be two transitions in PN. If an identifier M of PN makes (1) M[t1> but (2) M[t1>M1→M1[t2>), that is, under the label M, t1 is enabled while t2 is not enabled, and enabling t1 will enable t2, then t1 and t2 have an order relationship.

[0053] like Figure 3 The diagram illustrates the basic relationship of concurrency in an unmanned aerial vehicle (UAV) system. Let PN = (P, T; F, M0) be a Petri net, and t1 and t2 be two transitions in PN. If an identifier M of PN allows M[t1> and M[t2>), then if M[t1>M1→M1[t2> and M[t2>M2→M2[t1>), meaning that under identifier M, both t1 and t2 are enabled, and triggering either transition will not disable the other, then t1 and t2 are said to be concurrent in M.

[0054] like Figure 4 The diagram illustrates the fundamental conflict relationships in an unmanned aerial vehicle (UAV) system. Let PN = (P, T; F, M0) be a Petri net, and t1 and t2 be two transitions in PN. If an identifier M in PN such that M[t1> and M[t2>), then if... If, under the label M, there exists a situation where both t1 and t2 are enabled, and the triggering of any one of their transitions will cause the other transition to be disabled, then t1 and t2 are said to be in conflict under M.

[0055] For the dynamic behaviors involved in the UAV GCS, such as the data transmission link consisting of the optical transceiver and switch 1, and the data receiving / transmitting end consisting of four host computers, the reconfiguration behavior of these two parts can be described by combining the above basic relationships. Taking the C-band transmission link in the downlink mission payload data transmission service as an example, when link 1, consisting of the switch and the second optical transceiver, fails, the data is transferred to the ASI optical transceiver for transmission. For this link reconfiguration behavior, two libraries are used to represent each component on link 1, namely "data is processed in switch 1 (optical transceiver 2)" and "switch 1 (optical transceiver 2) fails, data transmission fails". The token in the "Data processed in switch 1 (optical transceiver 2)" location transitions through a change indicating "Data successfully sent by switch 1 (optical transceiver 2)" to the "Data processed in optical transceiver 2 (optical transceiver 3)" location, or through a change indicating "Switch 1 (optical transceiver 2) failed" to the "Switch 1 (optical transceiver 2) failed, data transmission failed" location, and then through an instantaneous change to the location indicating "Data processed in ASI optical transceiver". At this point, the link reconfiguration is complete. For transitions after the switch and the second optical transceiver, such as T1 and T3, because switch 1 either successfully sends data or fails, only one can be triggered when both T1 and T3 are enabled; this can be described as a "conflict relationship". However, for T1 and T2, because optical transceiver 2 can send data after the switch successfully sends data (i.e., T2 is enabled), this can be described as a "sequential relationship". The dynamic reconfiguration diagram of the UAV system is shown below. Figure 5 As shown in the figure. In the figure, optical transceiver 1 represents the first optical transceiver, optical transceiver 2 represents the second optical transceiver, and optical transceiver 3 represents the third optical transceiver.

[0056] Business functions are often described using flowcharts. However, flowcharts are only static representations of processes and are a low-level method for describing problems. They cannot represent the nature and specific implementation of the actual system, nor can they analyze potential conflicts, parallelism, or other resource contention within the system. Therefore, flowcharts need to be standardized to prepare for Petri nets.

[0057] S3. Construct a GSPN network for reliability simulation of dynamic changes in UAV data link services: Use places to represent the state of data link system devices and tokens to represent the resources carried on the system; according to the system's operation logic, use time migration and instantaneous migration to connect the places representing device states, and express the dynamic operation process of data link services through sequential relationships, parallel relationships and conflict relationships.

[0058] S31. Construct a Petri net model for uplink remote control, flight control, and user control data transmission services of the UAV system. Within line-of-sight, prioritize the use of C+UHF band link equipment. During takeoff and descent, use the first C-band antenna for communication, and switch to the second C-band antenna after reaching the cruise phase. Remote control commands issued from the user control computer, link monitoring computer, and flight control computer are transmitted via the third optical transceiver to the second and first optical transceivers, respectively. The second optical transceiver then connects to the C-band terminal processor and the UHF band terminal processor via a switch. The C-band signal is modulated and encrypted by the C-band terminal processor, then converted from intermediate frequency to radio frequency by a C-band inverter-upconverter. It is then transmitted via a C-band power amplifier and a C-band duplexer, and finally merged with the second C-band antenna through a switching switch. The UHF band signal is modulated and encrypted by the UHF band terminal processor and finally transmitted via the UHF band antenna.

[0059] The transmission channels consisting of the switch and the second optical transceiver are redundantly designed, and the transmission channels consisting of the first optical transceiver are redundantly designed. The seats are designed with a control seat computer, a link monitoring computer, a flight control seat computer, and a spare parts seat computer, which can be used when any seat fails.

[0060] The optical transceiver's information receiving end is connected to three data sources: the task control computer, the link monitoring computer, and the flight control computer. Therefore, the first step is to construct a data arrival model on optical transceivers 3 and 5 based on the arrival patterns of the service information from these data sources. Since the "backup computer" is used to replace the other three computers in case of failure, but only one replacement is allowed if multiple computers fail simultaneously, the three task function computers compete for resources against one backup computer. Therefore, we use two storage locations to represent the normal and fault states of the task function computers, and one storage location to represent the working state of the backup computer. A transition is used to connect the fault state storage location and the backup computer working state storage location, and the capacity of the backup computer working storage location is set to 1, indicating that enabling one transition can only complete the data reconstruction of one task function computer.

[0061] S311. Construct a Petri net model for forwarding service data information of optical transceivers; when the data from the control computer arrives at the third optical transceiver, a place is used to represent the "information queue waiting to be processed" on the third optical transceiver, and the data processing rule is "processing according to the arrival time order"; there are two directions of data transmission on the third optical transceiver: the second optical transceiver and the first optical transceiver. The first optical transceiver serves as a redundancy backup and switches over when either the second optical transceiver or the switch fails. Their states are described by a place, where "OK" represents normal and "Fail" represents failure. The probability of "OK" reaching "Fail" is determined by the failure rate of the equipment. When "Fail" occurs in either place, the data token enters the place of the first optical transceiver to continue transmission.

[0062] S312. Construct a Petri net model for data transmission in band equipment; the location of the Petri net model for the transmission process of service data information is the name of the corresponding component (C-band terminal processor, cryptographic machine, C-band frequency converter, C-band power amplifier, C-band duplexer), indicating that the data arrives at the component; the transition is the data processing in the component, indicating the occurrence of the component's data transmission event. If the time for the component to process the data needs to be considered, the transition is represented by a <hollow bar> to indicate the signal processing delay; otherwise, it is represented by a <solid bar> to indicate that the transition occurs immediately.

[0063] S313. Construct a Petri net model of the data transmission process at the antenna end. According to the system function description, data arriving at the "switching switch" will be transmitted by either the first C-band antenna or the second C-band antenna. The choice of different transmitting antennas actually comes from the different mission phases of the system. That is, the first C-band antenna is used for communication during the takeoff and descent phases, and the system switches to the second C-band antenna after reaching the cruise phase. Two places are used to represent the arrival of data at the "first C-band antenna" and the "second C-band antenna" respectively. For data arriving at the "switching switch" place, a transition is used to connect them respectively. According to the requirements of the data switching scenario, that is, only one of the two transitions can occur, and the other cannot occur. This is a typical "conflict relationship" in Petri net modeling. In addition to the arrival of data at the "switching switch", the conditions for the two transitions to occur are also related to the mission phase of data transmission. Therefore, two more places representing the transmission phase need to be added as their enabling input places to jointly determine the enabling of the transition.

[0064] The Petri net model for the uplink remote control, flight control, and / or arbitrary control data transmission services of the constructed UAV system is as follows: Figure 6 As shown in the figure. In the figure, C-band antenna 1 is the first C-band antenna, and C-band antenna 2 is the second C-band antenna.

[0065] S32. Construct a Petri net model for downlink telemetry data transmission services of the UAV system; downlink telemetry data transmission services are affected by whether the data is within line of sight and the flight phase. Similar to uplink remote control / flight control / route control data transmission functions; within line of sight, C-band and UHF bands are preferentially used for data transmission, and the selection of C-band antennas depends on the flight phase; beyond line of sight, data is transmitted through satellite communication links.

[0066] S321. Construct a Petri net model for antenna service data reception. Service data reception is affected by whether it is within line of sight and the flight phase. Only one of the two states, within line of sight and beyond line of sight, exists. The same applies to the flight phase (takeoff, descent / cruise). Therefore, two conflict models need to be constructed based on the aircraft's flight state. The conflict relationship model formed by the three libraries of within line of sight / beyond line of sight and the data source determines whether service data is transmitted via C-band, UHF band, or satellite communication link. The conflict relationship model formed by the three libraries of the flight phase, the first C-band antenna, and the second C-band antenna determines whether service data in the C-band is transmitted via the first C-band antenna or the second C-band antenna.

[0067] S322. Construct a Petri net model for data transmission in C-band equipment; taking the "C-band data transmission" process as an example, the location of the service data in the Petri net model of this process represents "service data processing in components (switching switches, C-band duplexers, C-band inverters-down-converters, C-band terminal processing)"; the transition is the success / failure of the service data being sent by the component, indicating the occurrence of the service data transmission event; considering the time for the component to process the data, the transition is represented by a <hollow bar> to indicate the signal processing delay, otherwise it is represented by a <solid bar> to indicate that the transition occurs immediately.

[0068] S323. Construct a Petri net model for business data forwarding in the terminal. Taking a "C-band terminal processor" as an example, after business data arrives at the C-band terminal processor, it is represented by a placeholder as the "information queue waiting to be processed". The data processing rule is "processing according to the arrival time order". The business data on the terminal has two transmission directions: one is to transmit to the switch, and then to the third optical terminal via the first optical terminal; the other is to transmit to the third optical terminal via the first optical terminal when the switch or the second optical terminal fails. The switch and the second optical terminal both use two placesholders to represent "business data in this component" and "this component is faulty". The placeholder representing the fault is switched to the first optical terminal after transition. The placeholder representing the first optical terminal is then switched to the placeholder representing the third optical terminal, thereby realizing dynamic reconstruction.

[0069] S324. Construct a Petri net model for service data arrival in the seat computers. After the service data arrives at the third optical transceiver, the next hop is forwarded to the seat computers. Successful forwarding to all three seat computers is considered a successful data transmission. A place is used to represent "service data is being processed in the third optical transceiver" and "three computers are available", i.e., the receiving end is normal. For each of the three seat computers, three places are used to represent their normal status, and each is indicated by a transition pointing to the computer being available, i.e., the data receiving end is normal. A transition points to the place indicating that the computer is faulty. There is only one backup seat computer. When more than one computer fails, they will compete for the backup seat computer, forming a conflict relationship. The transition indicating the conflict relationship points to the seat computer that the backup seat computer replaces.

[0070] The Petri net model for the "downlink telemetry data transmission service" of the constructed information system equipment is as follows: Figure 7 As shown.

[0071] S33. Construct a Petri net model for downlink mission payload data transmission services of the unmanned aerial vehicle system.

[0072] S331. Construct a Petri net model for receiving antenna service data information; construct a conflict model based on the aircraft's flight status; the conflict relationship model consisting of the three libraries of line-of-sight / beyond line-of-sight and data source determines whether data is transmitted through the C-band link or the satellite communication link; the conflict relationship model consisting of the three libraries of the first C-band antenna and the second C-band antenna during the flight phase determines whether service data in the C-band is transmitted through the first antenna or the second antenna.

[0073] S332. Construct a Petri net model for data transmission in C-band equipment; taking the "C-band data transmission" process as an example, the location of the service data in the Petri net model of this process represents "service data processing in components (switching switches, C-band duplexers, C-band inverters-down-converters, C-band interrupt handling)"; the transition is the success / failure of the service data being sent by the component, indicating the occurrence of the service data transmission event. If the time for component data processing needs to be considered, the transition is represented by a <hollow bar> to indicate the signal processing delay, otherwise it is represented by a <solid bar> to indicate that the transition occurs immediately.

[0074] S333. Construct a Petri net model for business data forwarding in the terminal. Taking a "C-band terminal processor" as an example, after business data arrives at the C-band terminal processor, it is represented by a placeholder as the "information queue waiting to be processed". The data processing rule is "processing according to the arrival time order". The business data on the terminal has two transmission directions: one is to transmit to the switch, and then to the third optical terminal via the second optical terminal; the other is that when the switch or the second optical terminal fails, the first optical terminal transmits the data to the third optical terminal. The switch and the second optical terminal use two placesholders to represent whether the business data forwarding in this component is successful or unsuccessful. The placeholder representing failure is switched to the first optical terminal after transition, and the placeholder representing the first optical terminal is then switched to the placeholder representing the third optical terminal.

[0075] S334. Service data from the seat computers arrives at the Petri net model. After the service data arrives at the third optical transceiver, the next hop is forwarded to the seat computers. Successful forwarding to all three seat computers is considered successful data transmission. Successful data transmission requires that the data arrives at the third optical transceiver and that all three seat computers are available. A place is used to represent that the service data is being processed in the third optical transceiver, and a place represents that all three computers are available. The three seat computers share a backup seat computer. When one computer fails, the backup seat computer can serve as redundancy, ensuring that all three computers are available. The three seat computers are represented by three places to indicate that their status is normal, and each is indicated by a transition pointing to the availability of the computer, i.e., the data receiving end is normal, and a transition points to the place indicating that the computer is faulty. There is only one backup seat computer. When more than one computer fails, they will compete for the backup seat computer, forming a conflict relationship. The transition indicating the conflict relationship points to the seat computer that the backup seat computer replaces.

[0076] The Petri net model for the "downlink telemetry data transmission service" of the constructed information system equipment is as follows: Figure 8 As shown.

[0077] S4. The GSPN network constructed for dynamic change reliability simulation of UAV data link services is calculated using Monte Carlo simulation to obtain the average number of tokens, 95% confidence interval and service reliability of each location of UAV data link services.

[0078] S41. GSPN Net Setup: Based on the Petri net model constructed in step S33, a delay following a certain distribution is associated with the transition of the storage state to form the GSPN model; the distribution function of the transition is set by setting the RATE parameter of the excitation rate in the transition; the RATE parameter values ​​of the transitions associated with equipment failure in the Petri net model are all set to their corresponding failure rates for simulation.

[0079] S42. Simulation settings: Add the correct number of tokens to the storage area. In GSPN, the weight represents the number of tokens m consumed from the storage area above the arc and the number of tokens n transmitted to the downstream storage area after the transition below the arc is enabled and fired. m is not necessarily the same as n. The state of system components and the stage of the task are modeled as the corresponding storage area. A storage area with successful data transmission is used to represent that the data is finally transmitted through the antenna. A storage area with failed data transmission is used to represent the data transmission failure caused by packet loss and bit error on the primary and backup paths of the service data transmission. After the above storage areas are constructed, transitions and arcs are used to connect the storage areas. The weight of each arc is 1 by default. Enabling this transition consumes 1 token.

[0080] S43. Simulation: Pipe2.5 (Platform Independent Petri Net Editor) software tool is used to formally describe the GSPN of a certain type of UAV data link system, expressing resource contention such as signal collisions and parallelism. The RATE parameter values ​​of the transitions associated with equipment failure are all set to the failure rate of the corresponding equipment. The Simulation module is used to analyze the model, and random firing is performed 20,000 times (i.e. Monte Carlo simulation times) to simulate the continuous data transmission process, repeated 5 times.

[0081] S44. Service reliability calculation: Service reliability is defined as the probability that a target task will successfully transmit data from one end to another under specified conditions and within a specified time. In the GSPN model, it is the ratio of the average number of tokens corresponding to the databases with successful data transmission to the sum of the average number of tokens corresponding to the databases with successful data transmission and those with failed data transmission. Specifically, it is expressed as follows:

[0082]

[0083] Where R represents service reliability, N s N represents the number of tokens successfully sent from the repository. f This indicates the number of tokens that failed to send data to the repository.

[0084] S45. By calculating the average number of tokens and the 95% confidence interval for each location using Monte Carlo simulation, the operational reliability of the UAV data link is obtained as follows:

[0085]

[0086] Taking "uplink data transmission service" as an example, ignoring its dynamic reconfiguration behavior, it is simplified to a series-parallel system. RBD is selected to verify the correctness of the GSPN simulation model. The data transmission path depends on whether the aircraft is within visual line of sight or beyond visual line of sight. Assuming the aircraft is in both states with equal probability, the calculated reliability is 0.99856. Considering dynamic reconfiguration behavior, the GSPN simulation model's calculation result is slightly higher than the RBD calculation result, which is consistent with the actual situation. This indicates that the results of this method for reliability modeling and analysis of UAV data link services are correct and reasonable.

[0087] Finally, it should be noted that the above embodiments are for illustration only and not for limiting the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention without departing from the spirit and scope of the present invention. Any modifications or partial substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for evaluating the reliability of unmanned aerial vehicle (UAV) data link services, characterized in that, It includes the following steps: S1. Define the service failure criteria for the UAV system: Select the service attribute parameters of uplink remote control, flight control and manned data transmission as the reflection of service capability indicators. Based on the assessment requirements of service reliability, set the threshold values ​​of service capability indicators as service failure criteria. S2. Obtain the business functions, basic relationships between events, dynamic behaviors, and static flowchart data of the unmanned aerial vehicle system; S3. Construct a GSPN network for reliability simulation of dynamic changes in UAV data link services: Use places to represent the state of data link system devices and tokens to represent the resources carried on the system; according to the system's operation logic, use time migration and instantaneous migration to connect the places representing device states, and express the dynamic operation process of data link services through sequential relationships, parallel relationships and conflict relationships. S31. Construct a Petri net model for uplink remote control, flight control, and user control data transmission services of the UAV system: Within line-of-sight, C+UHF band link equipment is prioritized. During takeoff and descent, the first C-band antenna is used for communication, and after reaching the cruise phase, it switches to the second C-band antenna. Remote control commands issued from the user control computer, link monitoring computer, and flight control computer are transmitted via a third optical transceiver to the second and first optical transceivers, respectively. The second optical transceiver then connects to the C-band terminal processor and the UHF band terminal processor via a switch. The C-band signal is modulated and encrypted by the C-band terminal processor, and then converted from intermediate frequency signal to radio frequency signal by a C-band inverter-upconverter. It is then transmitted by the first C-band antenna and the second C-band antenna via a C-band power amplifier and a C-band duplexer through a switching switch. The UHF band signal is modulated and encrypted by the UHF band terminal processor and then transmitted via the UHF band antenna. S32. Construct a Petri net model for downlink telemetry data transmission services of the UAV system: Within line of sight, C-band and UHF bands are used preferentially for data transmission, and the selection of C-band antenna depends on the flight phase; beyond line of sight, data is transmitted through satellite communication links. S33. Construct a Petri net model for downlink mission payload data transmission services of the unmanned aerial vehicle system; S4. Calculate the GSPN network constructed for dynamic reliability simulation of UAV data link services using Monte Carlo simulation, and obtain the average number of tokens, 95% confidence interval, and service reliability of each location in the UAV data link service: S41. GSPN Net Setup: Based on the Petri net model constructed in step S33, a delay following a certain distribution is associated with the changes in the state of the storage facility to form the GSPN model; the distribution function that the changes follow is set by setting the RATE parameter of the excitation rate in the changes; the RATE parameter values ​​of the changes associated with equipment failure in the Petri net model are all set to their corresponding failure rates for simulation. S42. Simulation settings: Add the correct number of tokens to the storage area. In GSPN, the weight represents the number of tokens m consumed from the storage area above the arc and the number of tokens n transmitted to the downstream storage area after the transition below the arc is enabled and fired. m is not necessarily the same as n. The state of system components and the stage of the task are modeled as the corresponding storage area. A storage area with successful data transmission is used to represent that the data is finally transmitted through the antenna. A storage area with failed data transmission is used to represent that the data transmission failure may be caused by packet loss and bit error on the primary and backup paths of the service data transmission. After the above storage areas are constructed, transitions and arcs are used to connect the storage areas. The weight of each arc is 1 by default. Enabling this transition consumes 1 token. S43. Simulation: Simulate the continuous data transmission process; S44. Service reliability calculation: Service reliability is defined as the probability that a target task will successfully transmit data from one end to another under specified conditions and within a specified time. In the GSPN model, it is the ratio of the average number of tokens corresponding to the data transmission success database to the sum of the average number of tokens corresponding to both the data transmission success database and the data transmission failure database. Specifically, it is expressed as follows: Where R represents service reliability, N s N represents the number of tokens in the database where data was successfully sent. f Indicates the number of tokens in the database where data transmission failed; S45. Calculate the average number of tokens and the 95% confidence interval for each repository by Monte Carlo simulation of the constructed GSPN model, thereby obtaining the operational reliability of the UAV data link.

2. The method for evaluating the reliability of UAV data link services according to claim 1, characterized in that, The system service functions described in step S2 include uplink remote control, flight control and / or mission control data transmission services, downlink telemetry data transmission services, and downlink mission payload data transmission services.

3. The method for evaluating the reliability of UAV data link services according to claim 1, characterized in that, Step S31 specifically includes the following steps: S311. Construct a Petri net model for forwarding service data information of optical transceivers: When the data from the control computer arrives at the third optical transceiver, a place is used to represent the information queue waiting to be processed on the third optical transceiver. The data processing rule is to process the data in order of arrival time. There are two directions for data transmission on the third optical transceiver: the first optical transceiver and the second optical transceiver. The first optical transceiver serves as a redundancy backup and switches over when either the second optical transceiver or the switch fails. Their states are described by a place, where normal is the OK place and faulty is the Fail place. The probability of the OK place reaching the Fail place is determined based on the equipment failure rate. When any place becomes the Fail place, the data token of that place enters the place of the first optical transceiver to continue the transmission. S312. Construct a Petri net model for data transmission in C-band equipment: The location of the Petri net model for the transmission process of service data information is the name of the corresponding component, indicating that the data arrives at the component; the transition is the data processing in the component, indicating the occurrence of the data transmission event in the component. If the time for the component to process the data needs to be considered, the transition is represented by a <hollow bar> to indicate the signal processing delay; otherwise, it is represented by a <solid bar> to indicate that the transition occurs immediately. S313. Construct a Petri net model of the data transmission process at the antenna end: Use two places to represent the arrival of data at the first C-band antenna and the second C-band antenna respectively. For data arriving at the switching switch place, connect these data with a transition respectively; add two places to represent the transmission stage, which are used as their enabling input places to jointly determine the enabling of the transition.

4. The method for evaluating the reliability of UAV data link services according to claim 1, characterized in that, Step S32 specifically includes the following steps: S321. Construct a Petri net model for receiving antenna service data information: Determine the service data transmission mode through the conflict relationship model composed of three libraries: in-line-of-sight / beyond-line-of-sight and data source; determine the transmission path of service data in the C-band through the conflict relationship model composed of three libraries: the flight phase, the first C-band antenna, and the second C-band antenna. S322. Construct a Petri net model for data transmission in C-band equipment: The location of service data in the Petri net model during this process represents the processing of service data in the component; transitions are the success or failure of service data transmission by the component, indicating the occurrence of the service data transmission event; considering the time for the component to process data, the transition is represented by a <hollow bar> to indicate the signal processing delay, otherwise it is represented by a <solid bar> to indicate that the transition occurs immediately; S323. Constructing a Petri net model for service data forwarding in terminal units: After service data arrives at the C-band terminal processor, a placeholder is used to represent the queue of information waiting to be processed. The data processing rule is to process data in the order of arrival time. Service data on the terminal unit has two transmission directions: one is to transmit it to the switch, and then to the third optical terminal via the first optical terminal; the other is to transmit it to the third optical terminal via the first optical terminal when the switch or the second optical terminal fails. The switch and the second optical terminal each use two placesholders to represent service data in the component and when the component fails. The placeholder representing the failure is switched to the first optical terminal after transition. The placeholder representing the first optical terminal is then switched to the placeholder representing the third optical terminal, thereby realizing dynamic reconfiguration. S324. Constructing a Petri net model for service data arrival in the seat computers: After service data arrives at the third optical transceiver, the next hop is forwarded to the seat computers. Successful forwarding to all three seat computers is considered successful data transmission. A place is used to represent the processing of service data in the third optical transceiver. A place indicates that three computers are available, i.e., the receiving end is normal. For each of the three seat computers, three places are used to represent their normal status, and each is indicated by a transition pointing to the computer being available, i.e., the data receiving end is normal. A transition points to the place indicating that the computer is faulty. Only one backup seat computer is set up. When more than one computer fails, they will compete for the backup seat computer, forming a conflict relationship. The transition indicating the conflict relationship points to the seat computer that the backup seat computer replaces.

5. The method for evaluating the reliability of UAV data link services according to claim 1, characterized in that, Step S33 specifically includes the following steps: S331. Construct a Petri net model for receiving antenna service data information; construct a conflict model based on the aircraft's flight status; the conflict relationship model composed of the three libraries of line-of-sight / beyond line-of-sight and data source determines whether the data is transmitted through the C-band link or the satellite communication link; the conflict relationship model composed of the three libraries of the first C-band antenna and the second C-band antenna during the flight phase determines whether the service data in the C-band is transmitted through the first antenna or the second antenna. S332. Construct a Petri net model for data transmission in C-band equipment; the location of service data in the Petri net model during this process represents "service data being processed in the component"; transitions indicate the occurrence of the service data transmission event when the service data is successfully / failed to be sent by the component. If the time for the component to process the data needs to be considered, the transition is represented by a <hollow bar> to indicate the signal processing delay; otherwise, it is represented by a <solid bar> to indicate that the transition occurs immediately. S333. Constructing a Petri net model for service data forwarding in the terminal: After service data arrives at the C-band terminal processor, a placeholder is used to represent the queue of information waiting to be processed. The data processing rule is to process data in order of arrival time. Service data on the terminal has two transmission directions: one is to transmit to the switch, and then to the third optical terminal via the second optical terminal; the other is that when the switch or the second optical terminal fails, the first optical terminal transmits the data to the third optical terminal. The switch and the second optical terminal use two placesholders to represent whether the service data forwarding in this component is successful or unsuccessful. Placeholders representing failures are transitioned to the first optical terminal, and placeholders representing the first optical terminal are transitioned to placeholders representing the third optical terminal. S334. Service data arriving at the Petri net model from the seat computer: After the service data arrives at the third optical transceiver, the next hop is forwarded to the seat computer. Successful forwarding to all three seat computers is considered a successful data transmission. Successful data transmission requires that the data arrives at the third optical transceiver and that all three seat computers are available. A place is used to represent that the service data is being processed in the third optical transceiver, and a place represents that all three computers are available. The three seat computers share a backup seat computer. When one computer fails, the backup seat computer can serve as redundancy, ensuring that all three computers are available. The three seat computers are represented by three places to indicate that their status is normal, and each is indicated by a transition pointing to the available computer, i.e., the data receiving end is normal, and a transition points to the place indicating that the computer is faulty. There is only one backup seat computer. When more than one computer fails, they will compete for the backup seat computer, forming a conflict relationship. The transition indicating the conflict relationship points to the seat computer that the backup seat computer replaces.

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