Formation navigation method

Abstract

The invention discloses a formation navigation method, and belongs to the technical field of aviation autonomous navigation, and the method comprises the steps that formation members completing a network access process perform information interaction according to a preset time slot distribution strategy of a network; each formation member carries out positioning calculation according to the information of other formation members and the own information; and the lead aircraft in the formation sends a cooperation instruction to the wing aircrafts. According to the invention, high-precision autonomous relative navigation of the aviation platform in a satellite navigation denial environment can be realized.

Description

Technical Field

[0001] The present application belongs to the field of aviation autonomous navigation technology, and in particular, relates to a formation navigation method. Background Art

[0002] Early airborne radio navigation equipment included TACAN, rangefinder, Volt, microwave landing, instrument landing, radio compass / beacon, etc., which could provide pilots with formation, route, approach and landing guidance. Before the 1990s, they were the main radio navigation means for aircraft, also known as traditional radio navigation means.

[0003] Since the 1890s, with the emergence of satellite navigation systems, traditional radio navigation is no longer the main means. These means are either about to be eliminated or retained and used as backup systems for satellite navigation, thus losing the motivation for system evolution. Satellite navigation can provide all-day, all-weather, global coverage, high-precision, real-time and continuous time and position information, becoming the main means of aviation navigation.

[0004] The landing power of satellite navigation signal is about -130dBm, which is very easy to be interfered. In some environments, satellite navigation is at risk of being interfered. In some environments, due to the lack of ground infrastructure support, air-to-air TACAN is an available navigation means, which can provide navigation measurement capabilities in denied environments, but the existing air-to-air TACAN system is outdated, and its formation capacity, ranging accuracy, navigation and time synchronization capabilities cannot meet current needs. Summary of the invention

[0005] The purpose of this application is to provide a formation navigation method to overcome the defects of the prior art, aiming to provide high-precision time synchronization, ranging and relative navigation services in a denied environment.

[0006] The purpose of this application is achieved through the following technical solutions:

[0007] A formation navigation method, the method comprising:

[0008] The formation members who have completed the network access process exchange information according to the network's preset time slot allocation strategy;

[0009] Each formation member performs positioning and solving based on the information of other formation members and its own information;

[0010] The leader in the formation issues coordination instructions to the wingman.

[0011] Furthermore, the network access process specifically includes:

[0012] The leader sends a network access signal to the out-of-band wingman, and receives a network access request returned by the wingman in response to the network access signal;

[0013] The leader agrees that the wingman can access the network and sends a confirmation message to the wingman.

[0014] Furthermore, in the method, the structure of the time slot includes a protection segment, a carrier segment, a timing waveform, a data payload and a protection time slot, and the timing waveform is used for signal synchronization and demodulation.

[0015] Furthermore, the preset time slot allocation strategy includes:

[0016] When the distance between the formation members for information exchange is less than the first preset distance, the close-range collaborative time slot is selected;

[0017] When the distance between the formation members for information exchange is not less than the first preset distance, the long-distance coordination time slot is selected;

[0018] The protection time slot of the short-distance coordination time slot is smaller than the protection time slot of the long-distance coordination time slot.

[0019] Furthermore, the time slot adopts a GMSK modulation method with high spectrum utilization.

[0020] Furthermore, the information interaction includes the following steps:

[0021] When sending information, the enable signal, message type and message content are message encoded to generate an original information sequence;

[0022] Performing cyclic redundancy check encoding on the original information sequence to generate a first check sequence;

[0023] The first check sequence is appended to the original information sequence, and then RS error correction coding is performed to output the data payload.

[0024] Furthermore, the method further comprises:

[0025] Timing sequences are added before, in the middle and after the data payload so that a complete time slot contains information of a first preset size.

[0026] Furthermore, the content of the information interaction includes time synchronization, ranging and navigation message distribution.

[0027] Furthermore, the information interaction further includes the following steps:

[0028] When receiving information, the time slot is used to estimate the Doppler frequency deviation and perform mixing processing on the time slot waveform.

[0029] The beneficial effects of this application are:

[0030] This application can provide high-precision time synchronization, ranging and relative navigation services in a denied environment, and realize high-precision autonomous relative navigation of aviation platforms in a satellite navigation denied environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a flowchart of a formation navigation method according to an embodiment of the present application;

[0032] Figure 2 It is a schematic diagram of the hardware architecture of the system of the embodiment of the present application;

[0033] Figure 3 This is a schematic diagram of link time slot allocation in an embodiment of the present application;

[0034] Figure 4 This is a schematic diagram of the data frame structure of an embodiment of the present application;

[0035] Figure 5 This is a signal receiving and sending processing structure diagram of an embodiment of the present application;

[0036] Figure 6 This is a structural diagram of the comprehensive processing of relative navigation information in an embodiment of the present application. DETAILED DESCRIPTION

[0037] The following describes the embodiments of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. The present application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0038] Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of this application.

[0039] In some environments, due to the lack of ground infrastructure support, air-to-air TACAN is an available navigation means that can provide navigation measurement capabilities in a denied environment. However, the existing air-to-air TACAN system is outdated, and its formation capacity, ranging accuracy, navigation and time synchronization capabilities cannot meet current needs.

[0040] In order to solve the above technical problems, the following embodiments of a formation navigation method of the present application are proposed.

[0041] Reference Figure 1 ,like Figure 1 The figure is a flowchart of a formation navigation method according to an embodiment of the present application, and the method specifically comprises the following steps:

[0042] Step 201: The formation leader aircraft 103 sends a network access signal to an out-of-formation wingman aircraft.

[0043] Step 202: After receiving the network access signal, the wingman 105 sends a network access request.

[0044] Step 203, after receiving the network access request from the wingman 105, the formation leader aircraft 103 agrees to the network access and sends a confirmation message.

[0045] Step 204, the wingman 105 completes the network access confirmation.

[0046] Step 205: The network allocates user time slots according to the changes in the number of members and the distance interval.

[0047] Step 206: The formation members perform time synchronization, ranging, and periodic distribution of navigation messages according to network time slot allocation.

[0048] Step 207: The local machine integrates the ranging and navigation information of other network users and combines it with the local machine's navigation sensor data to perform positioning calculation.

[0049] Step 208: The lead aircraft gives instructions on formation coordination.

[0050] Reference Figure 2 ,like Figure 2 The figure shows a schematic diagram of the hardware architecture of the system of the embodiment of the present application, wherein the upper part is a transmitter link, including information processing 301, signal processing 302, digital-to-analog converter 303, baseband low-pass filter 304, I / Q modulator 305, intermediate frequency oscillator 306, phase shifter 322, mixer 307, intermediate frequency amplifier 308, local oscillator 319, RF up-conversion 309, RF amplifier 310, power amplifier 311 and isolator 312. The lower part is a receiver link, including a low noise amplifier 315, RF bandpass filter 316, RF amplifier 317, RF down-converter 318, local oscillator 319, intermediate frequency amplifier 320, I / Q demodulator 321, intermediate frequency oscillator 326, baseband low-pass filter 323, baseband amplifier 324, analog-to-digital converter 325, signal processing 302 and information processing 301. The output 327 of the transmitter and the input 328 of the receiver are connected to the integrated transmitting and receiving antenna 314 through a duplexer 313 .

[0051] The information processing module 301 transmits the generated navigation information 329 to the signal processing module 302. After coding and modulation, the digital baseband signal 330 is converted into a corresponding analog baseband signal by the digital-to-analog converter 303 in the baseband module. After baseband filtering 304, the baseband signal is up-converted to an intermediate frequency signal. In the I / Q modulator 305, the intermediate frequency signal in the Q channel is more phase-shifted by 90° than the signal in the I channel during up-conversion. The mixer 307 mixes the intermediate frequency signals of the I-channel 331 and the Q-channel 332 output of the I / Q modulator. The mixed intermediate frequency signal is amplified by the intermediate frequency amplifier 308, and the signal is moved to the radio frequency band by the radio frequency amplifier 309. The radio frequency amplifier 317 amplifies the signal to a power level capable of driving the power amplifier 311. After deducting the insertion loss of the isolator 312 and the duplexer 313, the power amplifier 311 needs to provide a peak power of about 400 watts to meet the requirement of a maximum range of 300 kilometers. The duplexer 313 is composed of two bandpass filters, one of which is used as a transmitter filter to suppress passband noise and stray radiation, and the other is a pre-filter of the receiver to suppress the transmission energy leaking to the receiver.

[0052] When the electromagnetic wave signal is received by the antenna 314 and converted into a high-frequency current signal, it is connected to the receiver input 328 via a feeder. The signal first passes through a low-noise amplifier 315 to improve signal quality and improve system sensitivity, and then passes through an RF bandpass filter 316 to further suppress transmission leakage, image and other interference. The RF amplifier 317 provides a sufficiently large gain for the receiving link, so that the noise of the RF downconverter 318 and the subsequent stage has only a slight effect on the noise coefficient and sensitivity of the receiver. The RF downconverter 318 converts the RF signal into an intermediate frequency signal, which is amplified by the intermediate frequency amplifier 320 and moved to the baseband through the I / Q demodulator 321. The I / Q demodulator 321 includes two mixers, which convert the intermediate frequency signal into two mutually orthogonal I and Q signals. After mixing, it passes through a baseband low-pass filter 323 to filter out out-of-band interference. The I and Q baseband signals are amplified by the amplifier 324, and then the analog-to-digital converter 325 converts the analog baseband signal into a digital baseband signal 333. In the signal processing module 302, the received digital baseband signal 333 undergoes a series of signal processing such as demodulation, and transmits the time synchronization, distance measurement and navigation information 334 to the information processing module 301 for positioning solution.

[0053] Reference Figure 3 ,like Figure 3The figure shows a schematic diagram of link time slot allocation in an embodiment of the present application. The maximum number of network members is 32. The basic unit of member transmission is a time slot. There are two types of time slots. The first type of time slot is a short-distance collaborative time slot 401, which is 200 microseconds long and is mainly used for close-distance members to broadcast quickly and regularly in sequence. This time slot has a shorter protection time slot and can support high-precision synchronization between members within a range of about 30km. The second type of time slot 402 is a long-distance collaborative time slot, which is mainly used for long-distance members to broadcast slowly and regularly. This time slot has a longer protection time slot and can support high-precision synchronization between members within a range of about 300km. 32 short-distance collaborative time slots and 1 long-distance collaborative time slot constitute a basic time frame 403, which is 7.6 milliseconds long. 32 time frames constitute a superframe, which is 243.2ms long.

[0054] Reference Figure 4 ,like Figure 4 The data frame structure diagram of the embodiment of the present application is shown. A time slot is composed of a 1us protection segment 501, a 1.2us single carrier 502, three 1.6us timing waveforms 503, 505, 507, two 465us data payloads 504, 506 and a protection time slot 508. According to the division of the time slot 30km and 300km working distance, the protection time slot is 100us and 1ms respectively. The data adopts cyclic redundancy check and RS error correction coding, the bit rate is 10Mbps, and the modulation adopts Gaussian minimum frequency shift keying (GMSK) with a code element constraint length of 3 and BT=0.2.

[0055] Reference Figure 5 ,like Figure 5The figure shows the signal receiving and transmitting processing structure diagram of the embodiment of the present application. The upper part is the generation process of the baseband transmission signal. The information processing module 301 provides the enabling signal, the message type and the message content. After the message encoding 601, the generated original information sequence is first subjected to the cyclic redundancy check (CRC) encoding 602 to generate a 16-bit check sequence, and the check sequence is attached to the information sequence and then RS (31, 23) error correction encoding 603 is performed, and the output is a data payload, so that the signal has error detection and correction capabilities. Then, a protection sequence and a single carrier sequence 604 are added before the time frame, and a timing sequence is added before, in the middle and after the data payload, so that a complete time slot contains 1000 bits of information. The binary bit stream data is then bipolar encoded 605. Considering that the sampling rate of the digital-to-analog converter 303 is 40MHz, it is sampled 606 with a sampling factor of 4 and then passed through a 12th-order digital Gaussian low-pass filter 607 with a code element constraint length of 3 and a product of 3dB bandwidth and code element period of 0.2 to form a smoother signal waveform. The signal is integrated 608 to obtain phase information. The phase signal is divided into two paths, and the I path 611 and Q path 612 baseband signals are obtained by table lookup calculation of cosine 609 and sine function 610 respectively. The data payload 504, 506 contains multiple data types, mainly divided into: platform attribute information, network management information, time synchronization message, navigation positioning information. Platform attribute information includes: device model, identity identifier, leader / subordinate identification, etc. Network management information includes: detection request, network access application, network access confirmation, etc. Time synchronization messages include: RTT transmission and RTT reception. Navigation and positioning information includes: platform latitude, platform longitude, barometric altitude, eastward speed, northward speed, celestial speed, position quality, speed quality, TOA measurement value, etc.

[0056] The lower part is the solution process of the baseband received signal, and the analog-to-digital converter 325 provides the I / Q baseband digital signal. First, the Doppler frequency deviation is estimated 613 using the single carrier waveform in the front section of the time slot, and then the time slot waveform is mixed 614 to eliminate the influence of the frequency deviation. Then, the cross-correlation between the signal waveform and the local reference timing waveform is obtained 615, and the cross-correlation curve is curve-fitted 616 using the autocorrelation curve of the reference timing waveform. The arrival time is estimated 618 by interpolating the three-segment timing waveform to obtain the cross-correlation peak 617, and then the timing synchronization is performed 619 in combination with the loopback timing message (RTT) in the solution message, so that the signal can achieve a synchronization accuracy of 10 nanoseconds under the condition of a 40M sampling rate. Using the arrival time estimation 618 and the timing synchronization information 619, the transmission delay of the signal can be obtained, and the distance between the terminals can be calculated 620. At the same time, using the common one-bit differential feedback demodulation algorithm of GMSK modulation, the signal is delayed by one codeword 621 and phase-shifted by 90° 622, mixed with the original signal 623, and the phase value at this time is calculated 624 to obtain the phase increment of the GMSK modulated signal, and the sampling judgment is performed 625 to restore the codeword information. After removing the overhead such as the timing sequence 626, the data payload is subjected to RS error detection and correction decoding 627, which can eliminate some transmission errors caused by channel mutations. If the codeword after error correction can complete CRC error detection verification 628, the transmitted message 629 can be obtained, and finally the timing synchronization, distance measurement, and navigation messages are passed to the information processing module 301.

[0057] Reference Figure 6 ,like Figure 6The figure shows the structure diagram of the relative navigation information comprehensive processing of the embodiment of the present application. The navigation information processing does not only use the data provided by the formation navigation function 701, but also includes the data of the airborne inertial group 702 and the data of the non-traditional navigation sensor 703. With the formation navigation network as the core, a distributed sensor system is constructed, and all available navigation data in and between aircrafts are integrated and processed using the all-source navigation architecture to obtain the optimal navigation result of the group. The formation navigation function provides the arrival time measurement TOA, two-way time comparison RTT, navigation messages of other aircraft and other types of data. The airborne inertial group 702 provides the attitude, position, speed, high pressure, magnetic heading and other data of the aircraft. The non-traditional navigation sensor 703 includes airborne data link, air collision avoidance and photoelectric / infrared, etc., and provides measurement information such as TOA, RTT, and azimuth. The relevant measurement information is first standardized 704, and the data is provided to the formation navigation comprehensive information processing 705 part according to the unified interface. For different platforms, only the data standardization part needs to be modified to connect the sensor to the system, and there is no need to modify the comprehensive information processing 705 software again. According to the type of navigation measurement information, the formation navigation comprehensive information processing 705 automatically matches the state model component 708 and the observation model component 709, and provides the system mathematical model and measurement data for the filter processing component 710. The filter processing component 710 performs state propagation and observation correction to obtain the optimal estimate of the relative position and time of the aircraft, and assembles it into the aircraft navigation information 707 for broadcast. The relevant information is converted into the user's required local navigation information through coordinate transformation, and is combined with the received other aircraft navigation message 706 for calculation to obtain the other aircraft navigation information at the same time and provide it to the upper-level application. The integrity monitoring component is responsible for fault detection and isolation, accuracy assessment, and gives an alarm signal when the navigation system accuracy cannot meet the mission requirements.

[0058] This embodiment supports formation navigation of 36 nodes within a range of 200km, adopts a structure based on superframes, time frames, and time slots, divides two different types of time slots among members according to the operating range and navigation performance requirements, and can dynamically allocate time slot resources. The data frame structure is composed of a protection segment, a single carrier, a timing waveform, a data payload, and a protection time slot, which is used to complete high-precision synchronous measurement and navigation message interaction between nodes. It adopts an all-source navigation technology architecture, integrates relative measurement, navigation messages, platform navigation, and non-navigation sensor information, and maximizes the formation's collaborative navigation capability through information filtering and fusion. Based on the general software radio hardware and spectrum resources of the airborne integrated communication, navigation, and identification system, the formation's collaborative navigation capability is formed through waveform, protocol, and processing software upgrades without increasing additional resource consumption.

[0059] In this embodiment, the link time slots are divided into two types: long and short. The long time slot length is 1.2 milliseconds and is used for long-distance relative measurement and time synchronization. The short time slot length is 200 microseconds and is used for short-distance relative measurement. At the same time, the short time slots can be dynamically allocated according to needs to improve the utilization rate of link time slot resources.

[0060] The time slot structure of this embodiment consists of 1 protection segment, 1 single carrier segment, 3 timing waveform segments, 2 data payload segments and 1 protection time slot. It adopts the GMSK modulation method with high spectrum utilization. During reception processing, the 3 timing waveforms are combined to perform high-precision signal synchronization and demodulation, supporting nanosecond arrival time measurement and 900-bit data payload.

[0061] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A formation navigation method, characterized in that: The method comprises: The formation members who have completed the network access process exchange information according to the network's preset time slot allocation strategy; Each formation member performs positioning and solving based on the information of other formation members and its own information; The leader in the formation issues coordination instructions to the wingman.

2. The formation navigation method according to claim 1, characterized in that: The network access process specifically includes: The leader sends a network access signal to the out-of-band wingman, and receives a network access request returned by the wingman in response to the network access signal; The leader agrees to the wingman to join the network and sends a confirmation message to the wingman.

3. The formation navigation method according to claim 1, characterized in that: The structure of the time slot in the method includes a protection segment, a carrier segment, a timing waveform, a data payload and a protection time slot, and the timing waveform is used for signal synchronization and demodulation.

4. The formation navigation method according to claim 3, characterized in that: The preset time slot allocation strategy includes: When the distance between the formation members for information exchange is less than the first preset distance, the close-range collaborative time slot is selected; When the distance between the formation members for information exchange is not less than the first preset distance, the long-distance coordination time slot is selected; The protection time slot of the short-distance coordination time slot is smaller than the protection time slot of the long-distance coordination time slot.

5. The formation navigation method according to claim 3, characterized in that: The time slot adopts the GMSK modulation mode with high spectrum utilization rate.

6. The formation navigation method according to claim 1, characterized in that: The information interaction comprises the following steps: When sending information, the enable signal, message type and message content are message encoded to generate an original information sequence; Performing cyclic redundancy check encoding on the original information sequence to generate a first check sequence; The first check sequence is appended to the original information sequence, and then RS error correction coding is performed to output the data payload.

7. The formation navigation method according to claim 6, characterized in that: The method further comprises: Timing sequences are added before, in the middle and after the data payload so that a complete time slot contains information of a first preset size.

8. The formation navigation method according to claim 1, characterized in that: The content of the information interaction includes time synchronization, ranging and navigation message distribution.

9. The formation navigation method according to claim 7, characterized in that: The information interaction further comprises the following steps: When receiving information, the time slot is used to estimate the Doppler frequency deviation and perform mixing processing on the time slot waveform.

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