A fast and accurate positioning method based on UWB in a well

Abstract

This invention relates to a rapid and accurate underground positioning method based on UWB, belonging to the field of communication technology. The method includes the following steps: S1: Designing the identification card's network entry, initial ranging, and normal ranging; S2: Designing the communication protocol for the network entry and ranging stages; S3: Performing underground positioning. The identification card requests network access by randomly broadcasting a network entry request frame. Because a random interval is used for broadcasting, and the channel is monitored for idleness before broadcasting, the probability of collision with other signals during the broadcast of the network entry request frame is reduced. After the reader performs unilateral ranging with the identification card, bilateral ranging is achieved by combining the sending and receiving timestamps of the identification card's network entry request frame or the previous ranging response frame. That is, unilateral ranging between the identification card and the reader can achieve bilateral ranging positioning accuracy, meeting the high-precision positioning application scenarios in coal mines. The identification card can simultaneously perform ranging with the reader's bilateral antennas, optimizing the ranging process and improving ranging efficiency.

Description

Technical Field

[0001] This invention belongs to the field of communication technology and relates to a method for rapid and accurate downhole positioning based on UWB. Background Technology

[0002] Coal mining is a highly hazardous and complex industry, making real-time and accurate location tracking of miners and equipment underground crucial for safety management. Underground positioning technology helps monitor personnel positions, prevent accidents, and improve rescue efficiency. Underground micro-wave (UWB) technology, as an emerging underground positioning technology, offers many advantages for coal mine applications. First, UWB provides highly accurate positioning information, achieving centimeter-level precision, enabling accurate acquisition of miners' and equipment's location information. Second, UWB technology exhibits good robustness and stability in the complex coal mine environment, resisting the effects of multipath propagation and signal attenuation, ensuring reliable positioning performance. Furthermore, UWB technology has low power consumption, making it suitable for long-term use in underground environments. However, traditional Time-of-Flight (TOF) positioning methods have relatively complex processes and slow positioning speeds, increasing the probability of collisions during ranging.

[0003] To streamline the UWB ranging process, increase system concurrency, and reduce collision probability, a fast and accurate underground positioning method is proposed. This method starts from the basic principle of Time-of-Flight (TOF) ranging, optimizes the ranging process, integrates transmitted information, shortens the TOF ranging time, and increases system concurrency to meet the increasingly high concurrency requirements of accurate positioning systems in coal mines. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a rapid and accurate underground positioning method based on UWB. The identification card in this invention uses randomly spaced broadcast network access request frames to join the network. After successful network access, the identification card enters a dormant state, waiting for the ranging timing to arrive before automatically waking up. Upon waking, it listens for ranging request frames initiated by the reader and replies with ranging response frames to complete unilateral ranging. Finally, it combines the timestamps of the network access request frame or the previous ranging response frame to achieve bilateral ranging. Unilateral ranging between the identification card and the reader can achieve bilateral ranging positioning accuracy, optimizing the identification card positioning timing and shortening the TOF ranging time, increasing system concurrency, and reducing the probability of wireless signal collisions, thus meeting the needs of rapid positioning and high-concurrency applications in coal mines.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A rapid and accurate downhole positioning method based on UWB, comprising the following steps:

[0007] S1: Design for identification card network entry, initial distance measurement, and normal distance measurement;

[0008] S2: Design communication protocols for the network access phase and the ranging phase;

[0009] S3: Perform downhole positioning.

[0010] Optionally, S1 includes the following steps:

[0011] S11: Identification card registration;

[0012] The identification card sends network access request frames at fixed and random intervals to join the network. Random sending reduces conflicts caused by multiple cards simultaneously initiating network access requests. The identification card uses a delayed transmission method when initiating the request frame, adding the card number, the network access request frame transmission timestamp TA1, and other information to the frame for broadcast. After receiving the network access request frame, the card reader's left and right antennas save the card number, transmission timestamp, and other information, as well as the reception timestamps TB1 and TC1. The reader assigns ranging timing to the identification card and sends the assigned timing and current timing along with a network access response frame to the identification card number as the destination address. The network access response frame only needs to be replied to by the antenna with the stronger receiving signal. After receiving the network access response frame, the identification card calibrates its own timing according to the current timing and enters a timed sleep state according to the assigned timing.

[0013] S12: Initial distance measurement using the identification card;

[0014] After the identification card wakes up from its timed sleep, it enters a receiving state and waits for the reader to initiate a ranging request. The reader, according to the timing allocated to the identification card, sends ranging request frames sequentially to the identification card via its left and right antennas. Each ranging request frame includes the current timing and additional information, and simultaneously saves the ranging request frame sending timestamps TB2 and TC2. Upon receiving the ranging request frame, the identification card saves the transmitted information and corrects the current timing, saving the ranging request frame receiving timestamps TA2B and TA2C. After processing the transmitted information, the identification card sends the ranging response frame along with TA2B, TA2C, and the ranging response frame sending timestamp TA3 to the reader. The reader's left and right antennas receive the ranging response frame and save the ranging response frame receiving timestamps TB3 and TC3. Then, combining these with the three timestamps TA1, TB1, and TC1 generated from the network access request frame, the left and right antennas use the DS-TWR algorithm to measure the distance to the identification card. Based on the ranging distance and the received signal strength, the reader determines whether the identification card is located to the left or right of the reader, achieving one-dimensional positioning in the well.

[0015] S13: The identification card is measuring distance normally;

[0016] After the initial ranging, the identification card goes into sleep mode according to the allocated timing sequence. After waking up, it waits for the reader to initiate a ranging request frame. Under normal ranging procedures, the reader also initiates a ranging request frame and waits for a ranging response frame. It uses the same method as the initial ranging to obtain all the transmission and reception timestamps in this process. Combined with the timestamps TA3, TB3, and TC3 generated in the previous ranging round, the DS-TWR algorithm is used to calculate the ranging distance between the identification card and the left and right antennas in this round.

[0017] Optionally, S2 includes the following steps:

[0018] S21: Network Access Phase

[0019] The identification card randomly initiates a network access request frame and broadcasts it with the broadcast address as the destination address. All card readers can receive the network access request frame and then identify the frame as a network access request frame through the command number of the command control bit, and save the attached information and the network access request frame sending timestamp.

[0020] After receiving the network access request frame, the card reader saves the network access request frame reception timestamp, queries the timing allocation table to allocate ranging timing for the new network access identification card, and sends it back to the identification card along with the current timing, the total number of timings in the system, and the attached information through the network access response frame. The identification card will only receive the network access response frame that arrives first, and subsequent network access response frames from other card readers will be discarded.

[0021] S22: Distance Measurement Phase

[0022] After the identification card wakes up from its timed sleep, it enters the receiving state. The card reader sends ranging request frames according to the allocated timing and saves the sending timestamp of the ranging request frame. The ranging request frame includes the current timing, channel, and additional information. After receiving the ranging request frame, the identification card performs timing calibration using the current timing, and the identification card will perform timing correction for each subsequent ranging measurement. The left and right antennas of the card reader initiate ranging request frames respectively. The identification card determines whether the ranging request frame is sent by the left or right channel based on the information attached to the ranging request frame, and saves the receiving timestamp of the ranging request frame sent by the left or right channel respectively.

[0023] After receiving the ranging request frame, the identification card attaches the receiving timestamp of the ranging request frame, the sending timestamp of the ranging response frame, and the accompanying information to the ranging response frame and transmits them back using a delayed transmission method. After receiving the ranging response frame, the card reader saves the receiving timestamp of the ranging response frame for both the left and right channels, and also saves the timestamp information attached to the ranging response frame. Finally, the card reader combines all the timestamps and uses the DS-TWR algorithm to solve for the distance between the identification card and the left and right antennas of the card reader. That is, the card reader only needs to perform one SS-TWR ranging measurement, and then combine the timestamp of the network access request frame or the ranging response frame to use the DS-TWR algorithm to solve for a more accurate distance.

[0024] Optionally, the communication protocol of the network access request frame is:

[0025] The sequence number is 1 to 2, and the data is XX. This is defined as the header, representing the UWB communication header.

[0026] The serial number is 3 to 4, the data is XX, and it is defined as PANID, representing the region ID;

[0027] The sequence number is 5-6, the data is XX, defined as the destination address, representing the broadcast address;

[0028] The serial numbers are 7 to 8, the data is XX, and it is defined as the source address, representing the address of the identification card;

[0029] The sequence number is 9, the data is XX, and it is defined as command control, representing the command number of the network access request frame;

[0030] The serial number is 10, the data is XX, and it is defined as the device type, representing the device type number;

[0031] The serial number is 11, the data is XX, which is defined as the software version and represents the current identification card software version number;

[0032] The sequence number is 12, the data is XX, and it is defined as attached information, representing attached transmission information;

[0033] The sequence number is 13 to 17, the data is XX, and it is defined as a timestamp, representing the timestamp when the network access request frame was sent.

[0034] Optionally, the communication protocol of the network access response frame is:

[0035] The sequence number is 1 to 2, and the data is XX. This is defined as the header, representing the UWB communication header.

[0036] The serial number is 3 to 4, the data is XX, and it is defined as PANID, representing the region ID;

[0037] The serial number is 5-6, the data is XX, and it is defined as the destination address, representing the address of the identification card;

[0038] The serial numbers are 7 to 8, the data is XX, and it is defined as the source address, representing the card reader address;

[0039] The sequence number is 9, the data is XX, and it is defined as command control, representing the command number of the network access request frame;

[0040] The sequence number is 10 to 11, the data is XX, and it is defined as the allocation sequence, representing the allocation sequence of the identification card.

[0041] The serial number is 12-13, the data is XX, which is defined as the current timing sequence and represents the current timing sequence of the card reader;

[0042] The sequence number is 14, the data is XX, and it is defined as the total number of timing sequences, representing the total number of timing sequences in the system;

[0043] The sequence number is 15, the data is XX, and it is defined as attached information, representing attached transmission information.

[0044] Optionally, the communication protocol of the ranging request frame is:

[0045] The sequence number is 1 to 2, and the data is XX. This is defined as the header, representing the UWB communication header.

[0046] The serial number is 3 to 4, the data is XX, and it is defined as PANID, representing the region ID;

[0047] The serial number is 5-6, the data is XX, and it is defined as the destination address, representing the address of the identification card;

[0048] The serial numbers are 7 to 8, the data is XX, and it is defined as the source address, representing the card reader address;

[0049] The sequence number is 9, the data is XX, and it is defined as command control, representing the ranging request frame command number;

[0050] The serial number is 10-11, the data is XX, and it is defined as the current timing sequence, representing the current timing sequence of the card reader;

[0051] The sequence number is 12, the data is XX, and it is defined as a channel, representing the left channel or the right channel;

[0052] The sequence number is 13, the data is XX, and it is defined as attached information, representing attached transmission information.

[0053] Optionally, the communication protocol of the ranging response frame is:

[0054] The sequence number is 1 to 2, and the data is XX. This is defined as the header, representing the UWB communication header.

[0055] The serial number is 3 to 4, the data is XX, and it is defined as PANID, representing the region ID;

[0056] The serial number is 5-6, the data is XX, and it is defined as the destination address, representing the card reader address;

[0057] The serial numbers are 7 to 8, the data is XX, and it is defined as the source address, representing the address of the identification card;

[0058] The sequence number is 9, the data is XX, and it is defined as command control, representing the ranging response frame command number;

[0059] The sequence number is 10 to 14, the data is XX, and it is defined as timestamp 1, representing the timestamp of the left channel ranging request frame reception;

[0060] The sequence number is 15-19, the data is XX, and it is defined as timestamp 2, representing the timestamp of the right channel ranging request frame reception;

[0061] The sequence number is 20-24, the data is XX, and it is defined as timestamp 3, representing the timestamp of the ranging response frame transmission.

[0062] The sequence number is 25, the data is XX, and it is defined as attached information, representing attached transmission information.

[0063] Optionally, S3 specifically includes:

[0064] The identification card sends network access request frames at random intervals to join the network. These frames are broadcast and include the identification card information and a sending timestamp. Upon receiving the network access request frame, the card reader saves the identification card information and the receiving timestamp, allocates a ranging time sequence to the identification card, and sends back the current and allocated timestamps via a network access response frame. Upon receiving the network access response frame, the identification card saves the network access information and enters a timed sleep state according to the allocated timestamp. After waking from sleep, the identification card enters a receiving state, waiting for the card reader to initiate a ranging request frame. The card reader initiates a ranging request frame according to the allocated timestamp and saves the sending timestamp. Upon receiving the ranging request frame, the identification card saves the transmission information and the receiving timestamp, and attaches the receiving timestamp and the ranging response frame's sending timestamp together. The ranging response frame is transmitted back. After receiving the ranging response frame, the card reader saves the receiving timestamp of the ranging response frame and reads the receiving timestamp of the ranging request frame and the sending timestamp of the ranging response frame. Then, it combines the sending timestamp of the network access request frame, the receiving timestamp of the network access request frame, and the sending timestamp of the ranging request frame with the DS-TWR positioning algorithm to calculate the ranging distance. After the ranging is completed, the identification card enters sleep mode again to wait for the next ranging. During the next ranging, the card reader will introduce the sending and receiving timestamps of the ranging response frame from the previous ranging round, and combine them with the timestamp of the current ranging round to form six timestamps for DS-TWR ranging. That is, the card reader performs one SS-TWR ranging and then combines the timestamps of the network access request frame or the previous ranging response frame with the DS-TWR algorithm to solve for the distance between the identification card and the left and right antennas.

[0065] The beneficial effects of this invention are as follows:

[0066] (1) The identification card makes network access requests by randomly broadcasting network access request frames. Because it uses a random interval for broadcasting and listens to whether the channel is idle before broadcasting, the probability of collision with other signals when broadcasting network access request frames can be reduced.

[0067] (2) After the identification card successfully enters the network and is assigned a timing sequence, it enters a sleep state. When the ranging timing sequence arrives, it will automatically wake up and listen for the ranging request frame initiated by the card reader. After listening for the ranging request frame, it will reply with a ranging response frame to complete the single-sided ranging. The single-sided ranging process is simple and has the advantages of short ranging time and high concurrency.

[0068] (3) After the card reader and the identification card perform single-sided ranging, the card reader can achieve double-sided ranging by combining the sending and receiving timestamps of the identification card’s network access request frame or the previous ranging response frame. That is, the identification card and the card reader can achieve double-sided ranging positioning accuracy by performing single-sided ranging, which can meet the high-precision positioning application scenarios in coal mines.

[0069] (4) During the TOF ranging process between the card reader and the identification card, the left and right antennas will send ranging request frames to the card reader in sequence. After receiving the ranging request frames, the identification card will reply with a ranging response frame in a unified manner. Thus, the identification card can achieve simultaneous ranging with the dual antennas of the card reader, optimize the ranging process and improve ranging efficiency.

[0070] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0071] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0072] Figure 1 This identifies the network access sequence of the identification card;

[0073] Figure 2 For the initial distance measurement process of the identification card;

[0074] Figure 3 This is the normal distance measurement procedure for the identification card. Detailed Implementation

[0075] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0076] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures, and should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0077] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0078] System Design

[0079] 1. Identification Card Network Access Process

[0080] The identification card sends network access request frames at fixed and random intervals to join the network. Random sending reduces conflicts caused by multiple cards simultaneously initiating network access requests. The identification card uses a delayed transmission method when initiating the request frame, adding the card number, the timestamp TA1, and other information to the broadcast frame. After receiving the network access request frame, the reader's left and right antennas save the card number, timestamp, and other information, as well as the timestamps TB1 and TC1. The reader assigns ranging timing to the identification card and sends the assigned timing and current timing along with a network access response frame to the card number as the destination address. The network access response frame only needs to be replied to by the antenna with the stronger receiving signal. Upon receiving the network access response frame, the identification card calibrates its own timing according to the current timing and enters a periodic sleep state according to the assigned timing.

[0081] (See Figure 1 )

[0082] 2. Initial Distance Measurement Procedure for Identification Cards

[0083] After the identification card wakes up from its timed sleep state, it enters a receiving state and waits for the reader to initiate a ranging request. The reader, according to the timing allocated to the identification card, sends ranging request frames sequentially to the identification card via its left and right antennas. Each ranging request frame includes the current timing and additional information, and simultaneously saves the ranging request frame transmission timestamps TB2 and TC2. Upon receiving the ranging request frame, the identification card saves the transmitted information and corrects the current timing, saving the ranging request frame reception timestamps TA2B and TA2C. After processing the transmitted information, the identification card sends the ranging response frame along with TA2B, TA2C, and the ranging response frame transmission timestamp TA3 to the reader. The reader's left and right antennas receive the ranging response frame respectively and save the ranging response frame reception timestamps TB3 and TC3. Combining these with the three timestamps TA1, TB1, and TC1 generated from the network access request frame transmission, the left and right antennas can respectively use the DS-TWR algorithm to measure the distance to the identification card. Based on the ranging distance and the received signal strength, it can determine whether the identification card is located to the left or right of the reader, achieving one-dimensional positioning in the well. (See...) Figure 2 )

[0084] 3. Normal Distance Measurement Procedure for Identification Cards

[0085] After the initial ranging measurement, the identification card enters a timed sleep state according to the allocated timing sequence. Upon waking, it waits for the reader to initiate a ranging request frame. In the normal ranging process, the reader also initiates a ranging request frame and waits for a ranging response frame. Using the same method as the initial ranging measurement, it obtains all transmission and reception timestamps during this process and combines them with the timestamps TA3, TB3, and TC3 generated in the previous ranging round. The DS-TWR algorithm is then used to calculate the ranging distance between the identification card and the left and right antennas in this round. This method requires only one SS-TWR ranging measurement by the reader, combined with the timestamps of the network access request frame or the previous ranging response frame, to calculate the ranging distance in this round using the DS-TWR algorithm. It has advantages such as a simple ranging process, high ranging accuracy, and high system concurrency. (See...) Figure 3 )

[0086] II. Communication Protocol Design

[0087] 1. Network access phase

[0088] The identification card randomly initiates a network access request frame and broadcasts it with the broadcast address as the destination address. All card readers can receive the network access request frame and then identify the frame as a network access request frame through the command number of the command control bit. The attached information and the network access request frame sending timestamp are saved. The network access request frame communication protocol is shown in Table 1.

[0089] Table 1

[0090] 1～2 XX head UWB Communication Header 3～4 XX PANID Region ID 5～6 XX Destination address Broadcast address 7～8 XX Source address Identification card address 9 XX Command and Control Network access request frame command number 10 XX Equipment type Device type number 11 XX Software version Current identification card software version number 12 XX Additional Information Attached transmission information 13～17 XX Timestamp Network access request frame transmission timestamp

[0091] After receiving the network access request frame, the card reader saves the timestamp of the network access request frame reception, queries the timing allocation table to allocate ranging timing for the new network access identification card, and sends it back to the identification card along with the current timing, the total number of timings in the system, and the attached information through the network access response frame. The identification card will only receive the network access response frame that arrives first, and subsequent network access response frames from other card readers will be discarded. The network access response frame communication protocol is shown in Table 2.

[0092] Table 2

[0093] 1～2 XX head UWB Communication Header 3～4 XX PANID Region ID 5～6 XX Destination address Identification card address 7～8 XX Source address Card reader address 9 XX Command and Control Network access response frame command number 10～11 XX Time allocation Assign timing to the identification card 12～13 XX Current time series Current timing of card reader 14 XX Total number of time series Total system timings 15 XX Additional Information Attached transmission information

[0094] 2. Distance Measurement Phase

[0095] After the identification card wakes up from its timed sleep state, it enters the receiving state. The card reader sends ranging request frames according to the allocated timing sequence and saves the sending timestamp of the ranging request frame. The ranging request frame includes the current timing, channel, and additional information. After receiving the ranging request frame, the identification card performs timing calibration using the current timing sequence, and the identification card will perform timing calibration for each subsequent ranging measurement. The left and right antennas of the card reader initiate ranging request frames respectively. The identification card determines whether the ranging request frame was sent by the left or right channel based on the channel information attached to the ranging request frame, and saves the receiving timestamp of the ranging request frame sent by the left or right channel respectively. The ranging request frame communication protocol is shown in Table 3.

[0096] Table 3

[0097] 1～2 XX head UWB Communication Header 3～4 XX PANID Region ID 5～6 XX Destination address Identification card address 7～8 XX Source address Card reader address 9 XX Command and Control Ranging Request Frame Command Number 10～11 XX Current time series Current timing of card reader 12 XX aisle Left Channel / Right Channel 13 XX Additional Information Attached transmission information

[0098] After receiving the ranging request frame, the identification card attaches the receiving timestamp of the ranging request frame, the sending timestamp of the ranging response frame, and the accompanying information to the ranging response frame and transmits them back using a delayed transmission method. After receiving the ranging response frame, the card reader saves the receiving timestamp of the ranging response frame for both the left and right channels, and also saves the timestamp information attached to the ranging response frame. Finally, the card reader combines all the timestamps to use the DS-TWR algorithm to calculate the distance between the identification card and the left and right antennas of the card reader. That is, the card reader only needs to perform one SS-TWR ranging measurement, and then combine the timestamps of the network access request frame or the ranging response frame to use the DS-TWR algorithm to calculate a more accurate distance. The ranging response frame communication protocol is shown in Table 4.

[0099] Table 4

[0100] 1～2 XX head UWB Communication Header 3～4 XX PANID Region ID 5～6 XX Destination address Card reader address 7～8 XX Source address Identification card address 9 XX Command and Control Ranging response frame command number 10～14 XX Timestamp 1 Left channel ranging request frame reception timestamp 15～19 XX Timestamp 2 Right Channel Ranging Request Frame Receive Timestamp 20～24 XX Timestamp 3 Ranging response frame transmission timestamp 25 XX Additional Information Attached transmission information

[0101] 3. Process

[0102] This positioning method involves the identification card sending network access request frames at random intervals to join the network. These frames are broadcast and include the identification card information and a sending timestamp. Upon receiving the network access request frame, the card reader saves the identification card information and the receiving timestamp, allocates a ranging time sequence to the identification card, and transmits the current and allocated time sequences back via a network access response frame. Upon receiving the network access response frame, the identification card saves the network access information and enters a timed sleep state according to the allocated time sequence. After waking from sleep, the identification card enters a receiving state, waiting for the card reader to initiate a ranging request frame. The card reader initiates a ranging request frame according to the timing allocated to the identification card and saves the transmission timestamp. After receiving the ranging request frame, the identification card saves the transmission information and the reception timestamp, and attaches the reception timestamp and the ranging response frame transmission timestamp together to the ranging response frame for transmission. After receiving the ranging response frame, the card reader saves the ranging response frame reception timestamp, and reads the ranging request frame reception timestamp and the ranging response frame transmission timestamp. Combining these with the network access request frame transmission timestamp, network access request frame reception timestamp, and ranging request frame transmission timestamp, the DS-TWR positioning algorithm is used to calculate the ranging distance. After ranging is completed, the identification card enters sleep mode again to wait for the next ranging measurement. During the next ranging measurement, the card reader will incorporate the transmission and reception timestamps of the ranging response frame from the previous ranging measurement, and combine them with the current ranging timestamp to form six timestamps for DS-TWR ranging. In other words, the card reader performs one SS-TWR ranging measurement, and by combining the network access request frame or the previous ranging response frame timestamp, the distance between the identification card and the left and right antennas can be calculated using the DS-TWR algorithm. This positioning method allows the identification card to quickly measure distances with the antennas on both sides of the card reader, increasing the concurrent ranging capacity.

[0103] The innovative aspects of this invention are as follows:

[0104] (1) The card reader initiates a ranging request, and the identification card receives the ranging request.

[0105] (2) Combine the timestamp of the previous ranging test with the timestamp of the current ranging test to perform ranging.

[0106] (3) Only one SS-TWR distance measurement is needed to calculate the distance value using the DS-TWR algorithm.

[0107] (4) The identification card simultaneously measures the distance with the left and right antennas of the card reader.

[0108] (5) The positioning accuracy within the positioning area is less than 30cm.

[0109] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A rapid and accurate downhole positioning method based on UWB, characterized in that, Includes the following steps: S1. Identification Card Network Entry: Before broadcasting the network entry request frame, the identification card listens to whether the channel is idle and sends a network entry request frame at a fixed time plus a random time to enter the network. The network entry request frame is sent in broadcast form and includes the identification card number, the network entry request frame transmission timestamp TA1, and additional information. After receiving the network entry request frame, the left and right antennas of the card reader save the identification card number, the network entry request frame transmission timestamp TA1, and the additional information in the network entry request frame, and save the network entry request frame reception timestamps TB1 and TC1, respectively. The card reader allocates a ranging timing sequence for the identification card and attaches the ranging timing sequence and the current timing sequence to the network entry response frame, and performs directional backhaul with the identification card number as the destination address. After receiving the network access response frame, the identification card calibrates its own timing according to the current timing and performs timed sleep according to the ranging timing. S2. Initial Ranging of Identifier Card: After the identifier card wakes up from its timed sleep state, it enters a receiving state and waits for the reader to initiate a ranging request frame. The reader, according to the ranging timing sequence, causes the left and right antennas to sequentially send ranging request frames to the identifier card, and saves the timestamps TB2 and TC2 for the left and right antennas respectively. The ranging request frame includes the current timing sequence, channel, and additional information. After receiving the ranging request frame, the identifier card saves the transmission information and corrects it according to the current timing sequence, saving the timestamps TA2B and TA2C for the left and right channel ranging request frames respectively. The identifier card then transmits the timestamps TA2B and TA2C of the left and right channel ranging request frames, along with the ranging response frame. The reader sends a ranging response frame along with a timestamp TA3 and sends the ranging response frame to the card reader. The left and right antennas of the card reader receive the ranging response frame and save the receiving timestamps TB3 and TC3 respectively. The left antenna of the card reader uses the DS-TWR algorithm in combination with TA1, TB1, TB2, TA2B, TA3 and TB3 to measure the distance of the identification card. The right antenna of the card reader uses the DS-TWR algorithm in combination with TA1, TC1, TC2, TA2C, TA3 and TC3 to measure the distance of the identification card. Based on the ranging distance between the identification card and the left and right antennas of the card reader, as well as the received signal strength when the left and right antennas of the card reader receive the ranging response frame, the side with the smaller ranging distance and stronger received signal strength is determined as the side where the identification card is located, thus achieving one-dimensional positioning in the well. S3. Normal ranging of the identification card: After the first ranging measurement, the identification card goes into sleep mode according to the ranging timing sequence. After waking up, it waits for the card reader to initiate the next round of ranging request frames. The card reader sends the current round of ranging request frames to the identification card in sequence by the left and right antennas according to the ranging timing sequence, and waits for the identification card to send back the current round of ranging response frames. The card reader obtains the sending timestamp and receiving timestamp during the current round of ranging, and combines them with the sending timestamp TA3 of the ranging response frame generated in the previous round of ranging, the receiving timestamp TB3 of the ranging response frame of the left antenna, and the receiving timestamp TC3 of the ranging response frame of the right antenna. The card reader uses the DS-TWR algorithm to calculate the ranging distance between the identification card and the left and right antennas of the card reader in this round, so that the card reader can achieve DS-TWR ranging by performing one SS-TWR ranging measurement and combining the timestamps of the network access request frame or the previous round of ranging response frames.

2. The method for rapid and accurate downhole positioning based on UWB according to claim 1, characterized in that, During the network access process of the identification card, the identification card randomly initiates a network access request frame and broadcasts it with the broadcast address as the destination address. After receiving the network access request frame, all card readers identify the network access request frame through the command number in the command control field. After receiving the network access request frame, the card reader queries the timing allocation table to allocate ranging timing for the newly accessing identification card, and sends it back to the identification card along with the current timing, the total number of system timings, and additional information through a network access response frame. The identification card only receives the network access response frame that arrives at the first moment.

3. The method for rapid and accurate downhole positioning based on UWB according to claim 1, characterized in that, During the initial ranging measurement and normal ranging measurement of the identification card, the identification card enters the receiving state after a timed sleep wake-up. The card reader sends a ranging request frame according to the ranging timing and saves the sending timestamp of the ranging request frame. The ranging request frame includes the current timing, channel, and additional information. After receiving the ranging request frame, the identification card performs timing calibration using the current timing. The identification card performs timing correction every time ranging is measured. The left and right antennas of the card reader initiate ranging request frames respectively. The identification card determines whether the ranging request frame is sent by the left channel or the right channel according to the channel in the ranging request frame, and saves the receiving timestamps of the ranging request frames sent by the left channel and the right channel respectively.

4. The method for rapid and accurate downhole positioning based on UWB according to claim 3, characterized in that, The communication protocol of the network access request frame includes the following fields arranged in sequence: Numbers 1 to 2 correspond to header fields, which are used to represent the UWB communication header; Numbers 3 and 4 correspond to the PANID field, which is used to represent the region ID; Numbers 5 and 6 correspond to the destination address field, which is used to represent the broadcast address; Serial numbers 7 and 8 correspond to the source address field, which is used to represent the identification card address; Serial number 9 corresponds to the command control field, which is used to represent the network access request frame command number; Serial number 10 corresponds to the device type field, which is used to represent the device type number; Serial number 11 corresponds to the software version field, which is used to represent the current identification card software version number; Serial number 12 corresponds to the attached information field, which is used to represent the attached transmission information; Numbers 13 to 17 correspond to timestamp fields, which are used to represent the timestamp of the network access request frame being sent.

5. The method for rapid and accurate downhole positioning based on UWB according to claim 4, characterized in that, The communication protocol of the network access response frame includes the following fields arranged in sequence: Numbers 1 to 2 correspond to header fields, which are used to represent the UWB communication header; Numbers 3 and 4 correspond to the PANID field, which is used to represent the region ID; Serial numbers 5 and 6 correspond to the destination address field, which is used to represent the identification card address; Numbers 7 and 8 correspond to the source address field, which is used to represent the card reader address; Serial number 9 corresponds to the command control field, which is used to represent the network access response frame command number; Serial numbers 10 to 11 correspond to the allocation timing field, which is used to represent the ranging timing allocated to the identification card; Serial numbers 12-13 correspond to the current timing field, which is used to represent the current timing of the card reader; Serial number 14 corresponds to the total number of timing sequences field, which is used to represent the total number of timing sequences in the system. Serial number 15 corresponds to the attached information field, which is used to represent the attached transmission information.

6. The method for rapid and accurate downhole positioning based on UWB according to claim 5, characterized in that, The communication protocol of the ranging request frame includes the following fields arranged in sequence: Numbers 1 to 2 correspond to header fields, which are used to represent the UWB communication header; Numbers 3 and 4 correspond to the PANID field, which is used to represent the region ID; Serial numbers 5 and 6 correspond to the destination address field, which is used to represent the identification card address; Numbers 7 and 8 correspond to the source address field, which is used to represent the card reader address; Sequence number 9 corresponds to the command control field, which is used to represent the ranging request frame command number; Serial numbers 10-11 correspond to the current timing field, which is used to represent the current timing of the card reader; Serial number 12 corresponds to the channel field, which is used to represent the left channel or the right channel; Serial number 13 corresponds to the attached information field, which is used to represent the attached transmission information.

7. The method for rapid and accurate downhole positioning based on UWB according to claim 6, characterized in that, The communication protocol of the ranging response frame includes the following fields arranged in sequence: Numbers 1 to 2 correspond to header fields, which are used to represent the UWB communication header; Numbers 3 and 4 correspond to the PANID field, which is used to represent the region ID; Numbers 5 and 6 correspond to the destination address field, which is used to represent the card reader address; Serial numbers 7 and 8 correspond to the source address field, which is used to represent the identification card address; Serial number 9 corresponds to the command control field, which is used to represent the ranging response frame command number; Serial numbers 10 to 14 correspond to the timestamp 1 field, which is used to represent the timestamp of the left channel ranging request frame reception. Serial numbers 15-19 correspond to the timestamp 2 field, which is used to represent the timestamp of the right channel ranging request frame reception. Serial numbers 20-24 correspond to the timestamp 3 field, which is used to represent the time stamp of the ranging response frame transmission. Serial number 25 corresponds to the attached information field, which is used to represent the attached transmission information.

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