Time difference measurement and correction method for multi-sensor cooperative system

Abstract

The invention relates to a time difference measuring and correcting method for a multi-sensor cooperative system, which comprises the following steps of: judging relative time difference in a receiving and transmitting time slot period between nodes by using envelope time width of a signal in a sensor receiving wave gate, and correcting; and demodulated node timestamps and position information are used to demodulate and correct integer multiples of ambiguity and time difference of a receiving and transmitting time slot period. The method comprises the following steps: firstly, judging a relative time difference in a receiving and transmitting time slot period between nodes by using an envelope time width of a signal in a sensor receiving wave gate, and revising the relative time difference to realize complete receiving and transmitting and correct demodulation of the signal; and demodulated node timestamps and position information are utilized to demodulate and correct integer multiples of ambiguity and time difference of a receiving and transmitting time slot period, so that time synchronization among nodes of the multi-sensor cooperative system under the condition of no unified time reference is realized.

Description

Technical Field

[0001] The present invention relates to the cross field of multi-sensor collaboration and wireless communication, and particularly to a method for measuring and correcting time difference in a multi-sensor collaboration system. Background Art

[0002] Time synchronization is one of the key technologies in multi-sensor collaboration systems. Especially in an integrated exploration and communication multi-sensor collaboration system, the radio frequency front-end is generally a time-division duplex channel. The time synchronization between the transceiver parties needs to meet a certain accuracy to ensure the complete reception of signals, and then realize communication and collaboration functions. At the same time, the time synchronization accuracy also directly affects the collaborative detection efficiency and the supported collaborative modes.

[0003] Common time reference devices generally have one or more time service means such as Beidou, GPS, short wave, and long wave, and can automatically switch according to the set priority: when the high-priority time service means is not powered on or fails, it automatically switches to the secondary-priority device. When there is no external unified time service system, or the time synchronization devices of the nodes in the multi-sensor collaboration system fail and the time service means are inconsistent, there may be a large time error between multiple nodes, resulting in a reduction in collaborative efficiency, or even inability to communicate and collaborate.

[0004] Measuring the time synchronization performance between nodes of a multi-sensor collaboration system with long-distance distribution is a difficult problem in the industry. Usually, the third-party high-precision reference clock comparison method or the high-precision and high-stability clock source relocation measurement method can be used. The time service accuracy of the former and its consistency on distributed mobile multi-nodes are difficult to guarantee; the latter clock source is expensive and has extremely high requirements for transportation, storage, calibration, etc., and is difficult to implement under the condition of node movement. Therefore, when the system performance degrades or cannot work properly due to large time synchronization errors, it is often difficult to quickly complete the time difference measurement and high-precision time difference correction. Two-way time comparison can achieve high-precision time synchronization but requires a two-way communication link support. Based on the functions of the multi-sensor collaboration system itself, realizing the rapid measurement and correction of time synchronization parameters is of great significance for ensuring the stable operation of the multi-sensor collaboration system.

[0005] Reference [1] studied a method for improving the accuracy of two-way ranging and time synchronization systems by using carrier phase smoothed pseudorange technology and device delay calibration technology. Reference [2] analyzed the error factors of two-way one-way pseudorange measurement time synchronization and gave an improved synchronization accuracy algorithm for the case of UAV maneuver. Reference [3] sorted out common time synchronization algorithms and gave the specific design and test results of a two-way time synchronization system. Reference [4] designed a synchronization signal based on sorting out the parameter measurement methods and error analysis of radio two-way time synchronization, and gave the synchronization accuracy analysis in the case of distributed node static and mobile conditions. Patent [5] proposed a two-way time comparison technology based on radar pulse communication, and a method for realizing high-precision time synchronization between master and slave nodes in a network.

[0006] None of the above-mentioned literature and patents involve the rapid measurement and correction of time differences in the case of time asynchronization between multiple nodes of a multi-sensor collaborative system.

[0007] References:

[0008] 【1】Li Meng, Research on Methods for Improving Measurement Accuracy of Two-Way Ranging and Time Synchronization System: Dissertation of University of Chinese Academy of Sciences, 2014

[0009] 【2】Lei Mengke, Research on UAV Time Synchronization Method Based on Two-Way One-Way Pseudorange Measurement: Dissertation of Xi'an University of Technology, 2022

[0010] 【3】Song Chao, Research and Implementation of Remote Timing Synchronization Technology: Dissertation of University of Electronic Science and Technology of China, 2018

[0011] 【4】Han Yijing, Research on Distributed Radio Time Synchronization Technology: Dissertation of National University of Defense Technology, 2019

[0012] 【5】Zhu Jun, Yang Jianxin, Dong Yang, etc., Time Comparison Synchronization Algorithm Suitable for Radar Pulse Communication Equipment Networking: ZL201810710936.1, 2018 Summary of the Invention

[0013] To solve the existing technical problems, the present invention provides a method for measuring and correcting time differences in a multi-sensor collaborative system.

[0014] The specific content of the present invention is as follows: A method for measuring and correcting time differences in a multi-sensor collaborative system first uses the envelope time width of the signal in the sensor receiving wave gate to judge and revise the relative time difference within the receiving and transmitting time slot period between nodes, and then uses the demodulated node timestamps and position information to solve the ambiguity of the integer multiple of the receiving and transmitting time slot period and the time difference and perform correction.

[0015] Further, the time difference measurement and correction specifically include the following steps:

[0016] S1: Node A transmits a measurement signal with a time width of τ under timing control. The measurement signal contains the transmission timestamp T 0(A) and the position information P1 of node A;

[0017] S2: Node B receives and samples at the set receiving time slot under timing trigger and records the sampled data;

[0018] S3: Node B analyzes the recorded sampled data and extracts the receiving frame sampling start time T 0(B) , the first signal sampling point time t r of the received signal, and the last signal sampling point time t e, calculate the time width of the received signal: ;

[0019] S4: Judgment Whether it is equal to 0, if so, go to step S6; if not, go to step S5;

[0020] S5: After adjusting the starting time of the receiving time slot of Node B according to the Δτ obtained in step S4, go to step S1;

[0021] S6: Time slot period fuzzy judgment and correction;

[0022] S7: Calculate the relative time difference within the transceiver time slot period;

[0023] S8: Judge whether the time difference Δt is less than the set threshold: if so, go to step S10, if not, go to step S9;

[0024] S9: Adjust the starting time of the receiving time slot of Node B according to the relative time difference within the transceiver time slot period obtained in step S7, and go to step S1;

[0025] S10: The time difference measurement process ends.

[0026] Furthermore, in S3, the time t of the first sampling point of the received signal r is obtained by adding the frame sampling start time and the sampling deviation within the frame: , where is the sampling period count from the first signal sampling point to the frame start, is the AD sampling frequency;

[0027] The time t of the last sampling point of the received signal e is obtained by adding the frame sampling start time and the sampling deviation within the frame: , where is the sampling period count from the last signal sampling point to the frame start.

[0028] Furthermore, S6 includes;

[0029] S601: Node B demodulates the received signal and parses out the transmission timestamp information T of Node A in the signal 0(A) and the location information P1;

[0030] S602: Calculate whether ΔT = T 0(B) - T 0(A) is equal to 0 to judge whether the time slot period is aligned: if so, go to step S7; if not, go to step S603;

[0031] S603: Adjust the timestamp of Node B according to ΔT and then go to step S1.

[0032] Furthermore, S7 includes:

[0033] S701: Node B calculates the distance d between the two nodes based on the local position information P2 and the calculated position P1 of Node A.

[0034] S702: Node B calculates the signal propagation delay t between the two nodes from d D = d / c, where c is the speed of light in free space;

[0035] S703: Calculate the time difference Δt between the two nodes: 。

[0036] Furthermore, the nodes participating in the measurement have half-duplex wireless signal transceiver channels, and the start time of the transceiver time slot can be controlled by parameters.

[0037] Furthermore, in the transmitted measurement signal, the transmission time width τ and the transceiver time slot moments are known to both the transmitter and the receiver, and the signal carries the transmission time of the current frame of the transmitting node and the node position information.

[0038] The present invention first uses the envelope time width of the signal in the sensor receiving wave gate to judge and revise the relative time difference within the transceiver time slot period between nodes, so as to achieve the complete transceiver and correct demodulation of the signal; furthermore, it uses the demodulated node time stamps and position information to solve the ambiguity and time difference of integer multiples of the transceiver time slot period and correct them, so as to achieve time synchronization between nodes in a multi-sensor collaborative system without a unified time reference. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The present invention will be further illustrated below with reference to the accompanying drawings.

[0040] Figure 1 It is a time-division multiplexing sounding and integration time frame schematic diagram;

[0041] Figure 2 Schematic diagram of the position of the signal in the receiving time window under time synchronization;

[0042] Figure 3 Schematic diagram of the position of the signal in the receiving time window when the receiving station time is advanced;

[0043] Figure 4 Schematic diagram of the position of the signal in the receiving window when the receiving station time lags behind and is less than the propagation delay;

[0044] Figure 5 Schematic diagram of the position of the signal in the receiving window when the receiving station time lags behind and is greater than the propagation delay;

[0045] Figure 6 Flowchart of time difference measurement and correction of the multi-sensor collaborative system of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0046] Combined with Figures 1 - 5, the present invention proposes a method for measuring the time difference between nodes by using the envelope width and arrival timestamp of the multi-sensor collaborative system signal in the receiving wavegate of the receiving sensor, and can correct the node time difference according to the measurement result to achieve the time synchronization of the multi-sensor collaborative system.

[0047] 1. System Overview

[0048] In a detection-communication integrated system that operates in a time-division manner for detection and communication, the system divides the working cycle T (referred to as a time frame) of the sensor into a detection time window T M and a communication time window T C . Within the communication time window T C , N bursts with a period of T S (referred to as time slots) are arranged for communication. The pulse width within each time slot is τ, and the rest is the receiving time, as shown in Figure 1 . The width of τ and the ratio of τ to T [[ID=!7]] S satisfy the restrictions of the radio frequency front-end on the pulse width and duty cycle.

[0049] The information communication of the system has a two-way symmetric architecture, the radio frequency front-end supports time-division duplex, the communication nodes are divided into two types of timing: transmit first and receive later, and receive first and transmit later. The two communication parties transmit signals to the opposite end under the predetermined timing trigger, and set the start time T 0B of the receiving wavegate and the transmission time T 0A of the transmitting station to be the same moment. The end of the receiving wavegate is not less than the sum of the communication pulse width τ and the maximum transmission delay t Dmax ( , d max is the farthest communication distance, c is the speed of light). Through timing design, it can be ensured that the signal is completely transmitted and received under the condition of time synchronization between the two nodes.

[0050] When the two nodes are time-synchronized, the arrival time of the signal in the receiving wavegate of the receiving station (relative to the starting position of the receiving wavegate) is the propagation delay t D , that is, the arrival time of the signal at the receiving end , as shown in Figure 2 .

[0051] When there is a time difference between the two nodes, the arrival time t r of the signal in the receiving wavegate of the receiving station is: the start time T 0(B) of the receiving wavegate + propagation delay t D + relative time difference Δt within the time slot period (Δt is defined as positive when B station is ahead and negative when it is lagging, with an ambiguity of an integer multiple of the time slot period), as shown in Figure 3 . At this time, there is:

[0052] (1)

[0053] Case of time lag Δt at Node B:

[0054] When ≤t D The position of the signal sent by A and received by B within the receiving window of Node B is shown as Figure 4 shown. The calculation of the relative time difference Δt within the period is the same as formula (1).

[0055] When is greater than t D , as shown in Figure 5 , Node B cannot completely receive the signal from Node A, and the signal is truncated (τ ’ <τ). At this time, there is:

[0056] (2)

[0057] 2. Implementation steps

[0058] To achieve the purpose of the present invention, the following technical solutions are adopted in the present invention:

[0059] Combined with Figure 6 , the method for measuring and correcting time difference in the multi-sensor collaborative system of the present invention includes the following steps:

[0060] S1: Node A emits a measurement signal with a time width of τ under timing control. The measurement signal contains the transmission timestamp T 0(A) of Node A and the position information P1;

[0061] S2: Node B performs reception, sampling, and records the sampled data under timing trigger according to the set reception time slot. In the case of time synchronization, the start time T 0(B) of each reception time slot and the transmission time T 0(A) of Node A are numerically consistent.

[0062] S3: Node B analyzes the recorded sampled data, and extracts the start time T 0(B) of frame sampling, the time t r of the first signal sampling point of the received signal, and the time t e of the last signal sampling point of the received signal from the timing control message of this node, and calculates the time width of the received signal; ; where:

[0063] The time t r of the first sampling point of the received signal is obtained by adding the frame sampling start time and the sampling deviation within the frame: ( is the sampling period count from the first signal sampling point to the start of the frame, is the AD sampling frequency);

[0064] The time t of the last sampling point of the received signale Obtained by adding the frame sampling start time and the in-frame sampling deviation: ( is the sampling period count from the last signal sampling point to the start of the frame, is the AD sampling frequency);

[0065] S4: Decision Is it equal to 0? If so, go to step S6; if not, go to step S5: By comparing the received signal time width with the transmitted signal time width, judge the integrity of the received signal, and adjust the receiving node timing control according to the judgment result to achieve the complete transceiver of the signal;

[0066] S5: After adjusting the start time of the receiving time slot of node B according to Δτ obtained in step S4, go to step S1;

[0067] S6: Time slot period ambiguity decision and correction: Perform ambiguity criterion and correction of the time slot period integer by comparing the start time stamps of the received signal and the signal of this node;

[0068] S601: Node B demodulates the received signal and parses out the transmission time stamp information T 0(A) and location information P1 of node A in the signal;

[0069] S602: Calculate ΔT = T 0(B) - T 0(A) Is it equal to 0 to judge whether the time slot period is aligned: If so, go to step S7; if not, go to step S603;

[0070] S603: After adjusting the time stamp of node B according to ΔT, go to step S1;

[0071] S7: Calculation of relative time difference within the transceiver time slot period

[0072] S701: Node B calculates the distance d between the two nodes according to the local location information P2 and the resolved location P1 of node A;

[0073] S702: Node B calculates the signal propagation delay t between the two nodes from d D = d / c (c is the speed of light in free space);

[0074] S703: Calculate the time difference Δt between the two nodes according to formula (1): ;

[0075] S8: Judge whether the time difference Δt is less than the set threshold: If so, go to step S10; if not, go to step S9; Judge the measured time difference, and judge that the time difference less than the judgment threshold is synchronized, and end the time difference measurement process; For the time difference greater than the judgment threshold, adjust the start time stamp of the receiving node according to the measured time difference until it is less than the judgment threshold;

[0076] S9: Adjust the start time of the receiving time slot of node B according to the Δt obtained in step S703, and go to step S1;

[0077] S10: The time difference measurement process ends.

[0078] Preferably in this embodiment, the nodes participating in the measurement have half-duplex wireless signal transceiver channels, and the start time of the transceiver time slot can be controlled by parameters. In the transmitted measurement signal, the transmission time width τ and the transceiver time slot time are known to both the transmitter and the receiver, and the signal carries the transmission time of the current frame of the transmitting node and the node position information. The receiving end performs high-speed sampling, recording, and demodulation on the received signal envelope.

[0079] Under the condition of no external high-precision time measurement device and high-precision time reference standard, the present invention first uses the envelope time width of the signal in the sensor receiving wave gate to judge and revise the relative time difference within the transceiver time slot period between nodes, so as to realize the complete transceiver and correct demodulation of the signal; furthermore, it uses the demodulated node timestamps and position information to solve the ambiguity and time difference of integer multiples of the transceiver time slot period and correct them, so as to realize time synchronization between nodes in a multi-sensor collaborative system without a unified time reference. The present invention provides a fast time difference measurement and correction method based on the on-site conditions of equipment use for multi-sensor collaborative systems, greatly reducing the guarantee requirements for time synchronization equipment in multi-sensor collaborative systems and improving the system's ability to respond to emergencies. It can be applied to wireless communication networks and wireless sensor networks with high-precision time synchronization requirements, and is particularly suitable for multi-sensor collaborative systems based on integrated exploration and communication, with good economic benefits and promotion value.

[0080] In the above description, many specific details are set forth in order to provide a thorough understanding of the present invention. However, the above description is only a preferred embodiment of the present invention, and the present invention can be implemented in many other ways different from those described herein. Therefore, the present invention is not limited by the specific embodiments disclosed above. At the same time, any person skilled in the art can make many possible changes and modifications to the technical solution of the present invention, or modify it into an equivalent embodiment with equivalent changes, without departing from the scope of the technical solution of the present invention. Any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for time difference measurement and correction of a multi-sensor collaborative system, characterized in that: First, the relative time difference within the transceiver time slot period between nodes is judged and revised by using the envelope time width of the signal in the sensor receiving wave gate, and then the ambiguity of the integer multiple of the transceiver time slot period and the time difference are solved and corrected by using the demodulated node time stamps and position information.

2. The method for time difference measurement and correction of the multi-sensor collaborative system according to claim 1, wherein: The time difference measurement and correction specifically include the following steps: S1: Node A transmits a measurement signal with a time width of τ under timing control. The measurement signal contains the transmission timestamp T 0(A) and the location information P1 of Node A; S2: Node B performs reception, sampling at a timing trigger according to the set reception time slot, and records the sampling data; S3: Node B analyzes the sampled data of the record, and extracts the receiving frame sampling start time T from the timing control message of this node 0(B) , the first signal sampling point time t of the received signal r , the last signal sampling point time t e , and calculates the time width of the received signal: ; S4: Judgment Check whether it is equal to 0. If yes, go to step S6; if no, go to step S5; S5: Adjust the starting time of the reception time slot of Node B according to Δτ obtained in step S4, and then go to step S1; S6: Time slot period ambiguity judgment and correction; S7: Calculation of the relative time difference within the transceiver time slot period; S8: Judge whether the time difference Δt is less than the set threshold: if yes, go to step S10; if not, go to step S9; S9: Adjust the starting time of the reception time slot of Node B according to the relative time difference within the transceiver time slot period obtained in step S7, and go to step S1; S10: The time difference measurement process ends.

3. The multi-sensor collaborative system time difference measurement and correction method according to claim 2, characterized in that: In S3, the time t of the first sampling point of the received signal r is obtained by adding the frame sampling start time and the in-frame sampling deviation: , where is the sampling period count from the first signal sampling point to the start of the frame, is the AD sampling frequency; The time t of the last sampling point of the received signal e is obtained by adding the frame sampling start time and the in-frame sampling deviation: , where is the sampling period count from the last signal sampling point to the start of the frame.

4. The method for time difference measurement and correction of the multi-sensor collaborative system according to claim 2, characterized in that: S6 includes; S601: Node B demodulates the received signal and extracts the transmission timestamp information T and location information P1 of Node A in the signal. 0(A) and location information P1; S602: Calculate ΔT = T 0(B) - T 0(A) and determine whether it is equal to 0 to judge whether the time slot period is aligned. If so, go to step S7; otherwise, go to step S603; S603: Adjust the time stamp of Node B according to ΔT, and then go to step S1.

5. The method for time difference measurement and correction of the multi-sensor collaborative system according to claim 2, characterized in that: S7 includes: S701: Node B calculates the distance d between the two nodes according to the local position information P2 and the calculated position P1 of Node A; S702: Node B calculates the signal propagation delay t between two nodes from d D = d / c, where c is the speed of light in free space; S703: Calculate the time difference Δt between two nodes: .

6. The method for time difference measurement and correction of the multi-sensor collaborative system according to claim 1, characterized in that: The nodes participating in the measurement have half-duplex radio signal transceiver channels, and the starting time of the transceiver time slot can be controlled by parameters.

7. The method for time difference measurement and correction of the multi-sensor collaborative system according to claim 2, wherein: In the transmitted measurement signal, the transmission time width τ, the transceiver time slot moments are known to both the transmitter and the receiver, and the signal carries the transmission time of the current frame of the transmitting node and the node position information.

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