Method and system for accurately locating objects using RFID technology

Abstract

This invention discloses a method and system for precise item positioning using RFID technology, relating to the field of item positioning technology. The system begins by receiving RFID signals emitted from product tags via an antenna array. After obtaining the time difference of the RFID signals arriving at each antenna, the relative position of the product is generated. A reflection path identification algorithm is used to correct the relative position. The incident angle of the signal is estimated based on the phase difference received by each antenna, generating the relative azimuth angle of the product. A fusion algorithm combines the relative position and relative azimuth angle to calculate the actual position coordinates of the product, enabling real-time positioning even when the product is in motion. The positioning system uses a fusion algorithm to calculate the product's position coordinates, effectively reducing the positioning error of a single algorithm, improving positioning accuracy, and dynamically adapting to warehouse structure and environmental characteristics, thus enhancing the spatial adaptability of the positioning system.

Description

Technical Field

[0001] The present invention relates to the technical field of object positioning, and in particular to an object accurate positioning method and system using RFID technology. Background Art

[0002] RFID (Radio-Frequency-Identification) technology is a contactless automatic identification technology that is widely used in object positioning and tracking systems. RFID technology relies on radio frequency signals to identify target objects and obtain their location information through wireless communication between electronic tags (RFID tags) and reading devices (RFID readers). Its application in logistics, retail, warehousing, medical and other fields has significant advantages, especially in real-time object positioning systems.

[0003] The prior art has the following defects:

[0004] 1. The positioning effect of traditional positioning systems will be significantly reduced when facing complex storage structures (such as multi-layer shelves, narrow aisles, etc.), because the signal coverage and algorithm of the positioning system are usually designed for open spaces and have poor adaptability to small or special areas. This leads to the fact that in actual storage environments, the RFID positioning system may have failure areas due to signal interference or incomplete coverage, and cannot accurately locate all areas of the warehouse;

[0005] 2. The antenna layout in traditional RFID positioning systems is usually a fixed structure designed based on human experience, which usually lacks dynamic adaptability and is difficult to optimize according to the actual environmental changes in the warehouse. This fixed layout solution may have signal blind spots when facing different types of storage environments, especially in corners or areas with dense obstacles, where the antenna cannot evenly cover the entire space.

[0006] Based on this, the present invention proposes a method and system for accurately locating items using RFID technology. The positioning system calculates the position coordinates of the product through a fusion algorithm, which effectively reduces the positioning error of a single algorithm and improves the positioning accuracy, making it suitable for high-precision warehouse management. It can also dynamically adapt to the warehouse structure and environmental characteristics, so that the positioning system can achieve good coverage in irregular warehouse environments, thereby enhancing the spatial adaptability of the positioning system. Summary of the invention

[0007] The purpose of the present invention is to provide a method and system for accurately locating an object using RFID technology to address the deficiencies in the background technology.

[0008] In order to achieve the above object, the present invention provides the following technical solution: a method for accurately locating an object using RFID technology, the locating method comprising the following steps:

[0009] After the positioning system obtains warehouse information, it randomly generates several antenna positions in the warehouse through a random generation tool, and after evaluating several antenna positions, selects a corresponding number of antenna positions for arranging antenna arrays;

[0010] When a product is placed on a shelf in any area of ​​the warehouse, the antenna array begins to receive the RFID signal emitted by the product tag, obtains the time difference between the RFID signal reaching each antenna, generates the relative position of the product, and corrects the relative position through the reflection path recognition algorithm. The incident angle of the signal is estimated based on the phase difference received by each antenna, and the relative azimuth of the product is generated.

[0011] The fusion algorithm is used to combine the relative position and relative azimuth of the product to calculate the actual position coordinates of the product and perform real-time positioning when the product is in a moving state.

[0012] In a preferred embodiment, after evaluating a number of antenna positions, a corresponding number of antenna positions are screened out for arranging an antenna array, including the following steps:

[0013] Obtain the product access index, coverage index, and signal interference index of each candidate antenna position, normalize the product access index, coverage index, and signal interference index, map the value ranges of the product access index, coverage index, and signal interference index to [0,1], obtain the normalized value of the product access index, the normalized value of the coverage index, and the normalized value of the signal interference index, and obtain the performance value by adding the normalized value of the product access index to the normalized value of the coverage index and subtracting the normalized value of the signal interference index;

[0014] Sort all candidate antenna positions according to their performance values ​​from large to small, generate a candidate table, obtain the actual number of antenna positions required in the warehouse, and select the candidate antenna positions before the actual number of antenna positions based on the positive order of the candidate table as the actual antenna positions of the warehouse.

[0015] In a preferred embodiment, obtaining the time difference of the RFID signal reaching each antenna to generate the relative position of the product includes the following steps:

[0016] The product tag periodically transmits RFID signals, and each antenna in the antenna array receives the signal and records the precise timestamp of each antenna receiving the signal. The time difference of each pair of antennas receiving the signal is calculated to obtain the time difference of the signal reaching each antenna. The expression is: , where Indicates antenna and antenna The time difference of receiving the signal, , Respectively represent antenna and antenna Timestamp of received signal;

[0017] According to the time difference and signal propagation speed, calculate the antenna and antenna The relative distance difference is expressed as: , where For antenna and antenna The relative distance difference, is the signal propagation speed, Indicates antenna and antenna The time difference of receiving the signal;

[0018] Using the known antenna position coordinates of the warehouse, the relative position of the product tag is determined based on the relative distance difference. The expression is: , where Product tags and antennas Straight-line distance;

[0019] Assume that the distance difference between the antennas is known, that is, , then: , using the least squares method to solve , get the product label position coordinates, the expression is: , where For antenna The location coordinates of is the relative position coordinate of the product label, For antenna The location coordinates of .

[0020] In a preferred embodiment, estimating the incident angle of the signal according to the phase difference received by each antenna to generate the relative azimuth of the product includes the following steps:

[0021] The phase difference of the signal received by the antenna array, for any two antennas in the antenna array, the calculation expression of the phase difference of the received signal relative to a reference point is: , where is the phase difference, is the wavelength of the signal, For antenna and antenna The distance is the relative azimuth, that is, the angle between the product tag signal and the normal direction of the antenna array;

[0022] The incident angle of the signal can be inferred from the known phase difference and the distance between the antennas. The expression is: , where is the relative azimuth.

[0023] In a preferred embodiment, a fusion algorithm is used to combine the relative position and relative azimuth of the product to calculate the actual position coordinates of the product, and real-time positioning is performed when the product is in a moving state, including the following steps:

[0024] Get the corrected relative position coordinates and relative azimuth of the product label, and calculate the actual position coordinates of the product through the fusion algorithm. The fusion algorithm expression is: , where is the actual location of the product label, is the relative position coordinate of the corrected product label, is the relative azimuth.

[0025] In a preferred embodiment, the calculation expression of the product access index is: , where is the product access index, represents the total number of time periods, Indicates the product in the time period The number of accesses within represents the demand frequency of the product, is the time decay factor, is the time decay constant, and .

[0026] In a preferred embodiment, the relative position is corrected by a reflection path recognition algorithm, comprising the following steps:

[0027] Calculate product label to antenna After obtaining the position coordinates of the reflecting object, the propagation time from the reflecting object to the antenna is calculated. The propagation time;

[0028] Based on the reflection object to the antenna The propagation time and product label to the antenna The propagation delay is calculated based on the propagation time, and the distance difference corresponding to the propagation delay is calculated. The relative position coordinates of the corrected product label are: , where is the relative position coordinate of the corrected product label, The relative position coordinates of the product label before correction, is the distance difference, Product tags and antennas The straight-line distance, Indicates antenna The unit vector to the product label.

[0029] In a preferred embodiment, the product tag to antenna is calculated The propagation time is expressed as: , where From product tag to antenna The propagation time, Product tags and antennas Straight-line distance;

[0030] Calculate the propagation time of the reflection path as: , where To reflect the object to the antenna The propagation time, is the straight-line distance from the product label to the reflective object, To reflect the object to the antenna Straight-line distance;

[0031] Based on the reflection object to the antenna The propagation time and product label to the antenna The propagation delay is calculated from the propagation time: , where is the propagation delay;

[0032] Calculate the distance difference corresponding to the propagation delay, the expression is: , where is the distance difference, is the signal propagation speed.

[0033] In a preferred embodiment, the calculation expression of the coverage index is: , where represents the coverage index, Indicates the total number of areas covered, Indicates the number of antennas covered Area of ​​the region, Indicates The distance between the area and the antenna, Indicates the total area of ​​the warehouse;

[0034] The calculation logic of the signal interference index is: obtain the number of areas covered by the candidate antenna position, and detect the electromagnetic interference degree of each area at multiple time points, calculate the electromagnetic interference degree mean and electromagnetic interference degree standard deviation of the area based on the electromagnetic interference degree at multiple time points, divide the electromagnetic interference degree mean by the electromagnetic interference degree standard deviation to obtain the signal impact factor of the area, and sum the signal impact factors of all areas covered by the candidate antenna position to obtain the signal interference index.

[0035] An item precise positioning system using RFID technology, including a location selection module, a location analysis module, an azimuth analysis module, and a positioning tracking module;

[0036] Position selection module: After obtaining warehouse information, a number of antenna positions are randomly generated in the warehouse through a random generation tool. After evaluating a number of antenna positions, a corresponding number of antenna positions are screened out for arranging antenna arrays. The antenna array arrangement information is sent to the position analysis module and the azimuth analysis module.

[0037] Position analysis module: When a product is placed on a shelf in any area of ​​the warehouse, the antenna array starts to receive the RFID signal emitted by the product tag, obtains the time difference between the RFID signal reaching each antenna, generates the relative position of the product, and corrects the relative position through the reflection path recognition algorithm. The corrected relative position information is sent to the positioning tracking module;

[0038] Azimuth analysis module: estimates the incident angle of the signal based on the phase difference received by each antenna, generates the relative azimuth of the product, and sends the relative azimuth information to the positioning tracking module;

[0039] Positioning and tracking module: uses a fusion algorithm to combine the relative position and relative azimuth of the product to calculate the actual position coordinates of the product and perform real-time positioning when the product is in a moving state.

[0040] In the above technical solution, the technical effects and advantages provided by the present invention are:

[0041] 1. The present invention starts to receive the RFID signal sent by the product tag through the antenna array, obtains the time difference of the RFID signal reaching each antenna, generates the relative position of the product, and corrects the relative position through the reflection path recognition algorithm, estimates the incident angle of the signal according to the phase difference received by each antenna, generates the relative azimuth of the product, and uses the fusion algorithm to combine the relative position and relative azimuth of the product to calculate the actual position coordinates of the product, and performs real-time positioning when the product is in a moving state. The positioning system calculates the position coordinates of the product through the fusion algorithm, effectively reducing the positioning error of a single algorithm, improving the positioning accuracy, making it suitable for high-precision warehouse management, and dynamically adapting to the warehouse structure and environmental characteristics, so that the positioning system can also achieve good coverage in irregular warehouse environments, enhancing the spatial adaptability of the positioning system.

[0042] 2. After acquiring warehouse information, the present invention randomly generates several antenna positions in the warehouse through a random generation tool. After evaluating the several antenna positions, a corresponding number of antenna positions are screened out for arranging the antenna array. By evaluating the antenna positions, the arrangement of the antenna array is made more reasonable, thereby increasing the effective use period of the antenna array and further improving the positioning effect of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0044] Figure 1 The figure is a flow chart of the method of the present invention. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] Example 1: Please refer to Figure 1 As shown, the method for accurately locating an object using RFID technology described in this embodiment includes the following steps:

[0047] After the positioning system obtains the warehouse information, it randomly generates several antenna positions in the warehouse through a random generation tool. After evaluating several antenna positions, the corresponding number of antenna positions are screened out for arranging the antenna array. When the product is placed on a shelf in any area of ​​the warehouse, the antenna array begins to receive the RFID signal emitted by the product tag, obtains the time difference when the RFID signal reaches each antenna, generates the relative position of the product, and corrects the relative position through the reflection path recognition algorithm. The incident angle of the signal is estimated according to the phase difference received by each antenna, and the relative azimuth of the product is generated. The fusion algorithm is used to combine the relative position and relative azimuth of the product to calculate the actual position coordinates of the product, and real-time positioning is performed when the product is in a moving state.

[0048] This application starts to receive RFID signals sent by product tags through antenna arrays, obtains the time difference of RFID signals reaching each antenna, generates the relative position of the product, and corrects the relative position through the reflection path recognition algorithm. The incident angle of the signal is estimated according to the phase difference received by each antenna, and the relative azimuth of the product is generated. The fusion algorithm is used to combine the relative position and relative azimuth of the product to calculate the actual position coordinates of the product, and perform real-time positioning when the product is in a moving state. The positioning system calculates the position coordinates of the product through a fusion algorithm, effectively reducing the positioning error of a single algorithm and improving the positioning accuracy, making it suitable for high-precision warehouse management, and dynamically adapting to the warehouse structure and environmental characteristics, so that the positioning system can also achieve good coverage in irregular warehouse environments, enhancing the spatial adaptability of the positioning system.

[0049] After obtaining warehouse information, the present application randomly generates several antenna positions in the warehouse through a random generation tool. After evaluating the several antenna positions, a corresponding number of antenna positions are screened out for arranging the antenna array. By evaluating the antenna positions, the arrangement of the antenna array is made more reasonable, thereby increasing the effective use period of the antenna array and further improving the positioning effect of the product.

[0050] In the present application, a plurality of RFID readers are arranged in the warehouse area, and each reader is connected to a plurality of directional antennas to form an antenna array.

[0051] Embodiment 2: After the positioning system obtains warehouse information, a random generation tool is used to randomly generate a number of antenna positions in the warehouse, and after evaluating the number of antenna positions, a corresponding number of antenna positions are screened out for arranging the antenna array, including the following steps:

[0052] Warehouse information acquisition: The positioning system obtains the structure and layout information of the warehouse, including the warehouse size, shelf location, obstacle distribution, signal attenuation area, etc. This information provides basic data for subsequent antenna layout.

[0053] Randomly generate antenna positions: Based on the warehouse information, a random generation tool is used to randomly generate multiple candidate antenna positions inside the warehouse. These positions cover different areas of the warehouse, ensuring that the candidate points are widely distributed and representative.

[0054] Obtain the product access index, coverage index, and signal interference index of each candidate antenna position, normalize the product access index, coverage index, and signal interference index, map the value ranges of the product access index, coverage index, and signal interference index to [0,1], obtain the normalized value of the product access index, the normalized value of the coverage index, and the normalized value of the signal interference index, and obtain the performance value by adding the normalized value of the coverage index to the normalized value of the product access index and subtracting the normalized value of the signal interference index. The larger the performance value, the better the overall situation of the candidate antenna position is, and the more likely it is to be selected;

[0055] Sort all candidate antenna positions according to their performance values ​​from large to small, generate a candidate table, obtain the actual number of antenna positions required in the warehouse, and select the candidate antenna positions before the actual number of antenna positions based on the positive order of the candidate table as the actual antenna positions of the warehouse.

[0056] The calculation expression of product access index is: , where is the product access index, Indicates the total number of time periods (such as days, weeks), Indicates the product in the time period The number of accesses within represents the demand frequency of the product, is the time decay factor, and its weight is determined by the time distance. The closer the time period, the higher the weight. is the time decay constant, and .

[0057] The product access index reflects the frequency of product access in the area covered by a candidate antenna position. Areas with higher access frequencies usually indicate that there is a higher demand for product flow in the area, and therefore require stronger signal coverage to support data collection and management.

[0058] The larger the product access index, the better the candidate antenna position can meet the needs of frequent product access in the warehouse. Selecting this position can improve the communication quality and real-time data update capabilities in high-mobility areas. Therefore, the larger the product access index, the more preferred the candidate antenna position should be as the actual antenna position to support high-frequency data transmission.

[0059] The calculation expression of the coverage index is: , where represents the coverage index, Indicates the total number of areas covered, Indicates the number of antennas covered Area of ​​the region, Indicates The distance between the area and the antenna, Indicates the total area of ​​the warehouse.

[0060] The coverage index reflects the signal coverage range of the candidate antenna location. The larger the coverage range, the more areas the antenna location can provide signals to, especially in some key areas such as entrances and exits, main passages, etc.

[0061] The larger the coverage index, the larger the warehouse area can be covered by the candidate antenna position, which is conducive to reducing the number of antennas and improving coverage efficiency. Especially in key areas, passages, entrances and exits, antenna positions with large coverage indexes can more effectively meet management needs. Therefore, the larger the coverage index, the more priority should be given to selecting the candidate antenna position as the actual antenna position to ensure the signal coverage integrity of the warehouse.

[0062] The calculation logic of the signal interference index is as follows: obtain the number of areas covered by the candidate antenna position, and detect the electromagnetic interference degree of each area at multiple time points, calculate the mean electromagnetic interference degree and the standard deviation of the electromagnetic interference degree of the area based on the electromagnetic interference degree at multiple time points, divide the mean electromagnetic interference degree by the standard deviation of the electromagnetic interference degree to obtain the signal impact factor of the area, and sum the signal impact factors of all areas covered by the candidate antenna position to obtain the signal interference index.

[0063] The signal interference index indicates the interference of other signal sources or environments at different time points at the candidate antenna location. A higher interference index means that the location may be subject to more signal conflicts, affecting the quality and stability of the signal.

[0064] The smaller the signal interference index, the less likely the antenna position is to be interfered with, and the more stable the signal. Selecting a position with a smaller interference index can ensure signal quality and reduce packet loss and interference rates in data transmission. Therefore, the smaller the signal interference index, the more preferred the candidate antenna position should be as the actual antenna position to ensure the quality and efficiency of data transmission.

[0065] For example, the product access index of location A is 80, the coverage index is 90%, and the signal interference index is 15%. The product access index of location B is 60, the coverage index is 85%, and the signal interference index is 20%. The product access index of location C is 50, the coverage index is 70%, and the signal interference index is 10%. The product access index of location D is 70, the coverage index is 75%, and the signal interference index is 5%. The product access index of location E is 40, the coverage index is 65%, and the signal interference index is 30%;

[0066] Next, in order to make the data of different indicators comparable, the product access index, coverage index and signal interference index are normalized and mapped to [0,1].

[0067] For the product access index, the maximum value is 80 and the minimum value is 40. The normalized value for position A is 1.0, B is 0.5, C is 0.25, D is 0.75, and E is 0.0.

[0068] For the coverage index, the maximum value is 90% and the minimum value is 65%. The normalized value for position A is 1.0, B is 0.8, C is 0.2, D is 0.4, and E is 0.0.

[0069] For the signal interference index, the maximum value is 30% and the minimum value is 5%. The normalized value for position A is 0.6, B is 0.4, C is 0.8, D is 1.0, and E is 0.0.

[0070] We use the formula "Performance value = product access index (normalized value) + coverage index (normalized value) - signal interference index (normalized value)" to calculate the performance value of each location.

[0071] For position A, the performance value is 1.0+1.0-0.6=1.4.

[0072] For position B, the performance value is 0.5+0.8-0.4=0.9.

[0073] For position C, the performance value is 0.25+0.2-0.8=-0.35.

[0074] For position D, the performance value is 0.75+0.4-1.0=0.15.

[0075] For position E, the apparent value is 0.0+0.0-0.0=0.0.

[0076] Sorting and selection: Sort the performance values ​​from high to low. Position A has the highest performance value (1.4), followed by position B (0.9), then position D (0.15), position E (0.0), and finally position C (-0.35). Assuming that the warehouse needs to select two antenna positions, the two positions with the highest performance values, namely position A and position B, are selected as the actual antenna layout positions.

[0077] When a product is placed on a shelf in any area of ​​the warehouse, the antenna array begins to receive the RFID signal emitted by the product tag, obtains the time difference between the RFID signal reaching each antenna, and generates the relative position of the product, including the following steps:

[0078] The product tag periodically transmits RFID signals. Each antenna in the antenna array will receive these signals and record the precise timestamp of each antenna receiving the signal. The time difference of each pair of antennas receiving the signal is calculated to obtain the time difference of the signal reaching each antenna. The expression is: , where Indicates antenna and antenna The time difference of receiving the signal, , Respectively represent antenna and antenna Timestamp of received signal;

[0079] According to the time difference and signal propagation speed, calculate the antenna and antenna The relative distance difference is expressed as: , where For antenna and antenna The relative distance difference, is the signal propagation speed (usually the speed of light 3×10 8 m / s, or adjusted according to environmental conditions), Indicates antenna and antenna The time difference of receiving the signal.

[0080] Using the known antenna position coordinates of the warehouse, the relative position of the product tag is determined based on the relative distance difference. The expression is: , where Product tags and antennas The straight-line distance, is the relative position coordinate of the product label, For antenna The location coordinates of

[0081] Assume that the distance difference between the antennas is known, that is, , then: , where For antenna and antenna The relative distance difference, is the relative position coordinate of the product label, For antenna The location coordinates of For antenna The location coordinates of

[0082] Solve using the least squares method , get the product label position coordinates, the expression is: , where For antenna and antenna The relative distance difference, is the relative position coordinate of the product label, For antenna The location coordinates of For antenna The location coordinates of .

[0083] The relative position is corrected by the reflection path recognition algorithm, including the following steps:

[0084] When the antenna array receives the RFID signal from the product tag, it not only needs to consider the direct path (Line-of-Sight, LOS) signal, but also needs to receive the reflected signal from the reflective surface (such as walls, shelves, equipment, etc.). These signals will affect the positioning of the tag. The signal strength, arrival time and phase information received by the antenna array can record the information of multiple paths.

[0085] By analyzing the signal waveform received by each antenna, identifying whether there are multiple peaks, the presence of reflected signals is determined. If there are multiple peaks where the signal arrives in the signal waveform, it means there is a reflection path.

[0086] According to the warehouse structure and physical environment (such as walls, shelves, antenna positions, etc.), a geometric model of signal propagation is established to simulate the propagation process of RFID signals and consider the time delay of the reflection path. The geometric model can correct the signal propagation time through parameters such as reflection angle and refractive index.

[0087] The preliminary position of the target is corrected by analyzing the reflection path. Based on the detection results of the reflection path, the corrected distance and position are calculated in combination with the time difference. For example, if a reflection path is detected, the additional time delay of the reflection path can be calculated and the preliminary position can be adjusted.

[0088] Calculate product label to antenna The propagation time is expressed as: , where From product tag to antenna The propagation time, Product tags and antennas The straight-line distance, is the signal propagation speed;

[0089] For the reflection path, the signal will first reach an object (such as a shelf, wall, etc.), and then reflect to the antenna. After obtaining the position coordinates of the reflecting object, the propagation time of the reflection path is calculated. The expression is: , where To reflect the object to the antenna The propagation time, is the straight-line distance from the product label to the reflective object, To reflect the object to the antenna The straight-line distance, is the signal propagation speed;

[0090] Based on the reflection object to the antenna The propagation time and product label to the antenna The propagation delay is calculated from the propagation time: , where is the propagation delay, From product tag to antenna The propagation time, To reflect the object to the antenna The propagation time;

[0091] Calculate the distance difference corresponding to the propagation delay, the expression is: , where is the distance difference, is the propagation delay, is the signal propagation speed;

[0092] Then the relative position coordinates of the corrected product label are: , where is the relative position coordinate of the corrected product label, The relative position coordinates of the product label before correction, is the distance difference, Product tags and antennas The straight-line distance, Indicates antenna A unit vector to the product label, indicating the direction of the correction.

[0093] The incident angle of the signal is estimated based on the phase difference received by each antenna to generate the relative azimuth of the product, including the following steps:

[0094] The incident angle of the signal is calculated by the phase difference of the signal received by the antenna array. The relationship between the phase difference and the directional angle of signal propagation is usually determined by the geometric structure of the array antenna and the wavelength of the signal. For any two antennas in the antenna array, the phase difference calculation expression of the received signal relative to a reference point is: , where is the phase difference, is the wavelength of the signal, For antenna and antenna The distance is the relative azimuth, that is, the angle between the product tag signal and the normal direction of the antenna array;

[0095] The incident angle of the signal can be inferred from the known phase difference and the distance between the antennas. The expression is: , where is the relative azimuth.

[0096] The fusion algorithm is used to combine the relative position and relative azimuth of the product to calculate the actual position coordinates of the product, including the following steps:

[0097] Get the corrected relative position coordinates of the product label , and the relative azimuth , the actual position coordinates of the product are calculated through the fusion algorithm, and the fusion algorithm expression is: , where is the actual location of the product label, is the relative position coordinate of the corrected product label, is the relative azimuth.

[0098] Real-time positioning of the product when it is in motion includes the following steps:

[0099] Since the product is in motion, its location will constantly change. In order to track the product's location in real time, it is necessary to use real-time signal reception data for dynamic updates. Whenever the antenna array receives a new signal or the product's motion state changes, the system will calculate and update the product's location information in real time.

[0100] Real-time positioning usually relies on the assistance of sensors (such as accelerometers, gyroscopes, IMUs, etc.). These sensors can detect the motion state of the product (such as acceleration, rotation angle, etc.) and update the actual position coordinates of the product based on signal propagation information.

[0101] During each time period, the actual position of the product can be updated by following these steps:

[0102] Calculate the relative displacement between the current moment and the previous moment, which can be inferred through signal delay, phase difference, accelerometer and other data, and use the previous moment's position and new displacement information to update the current moment's position information. Finally, the system will display the real-time calculated product position on the display or control system, or transmit the data to the management platform for tracking. In this way, the staff or system can understand the precise location of the product in real time, thereby improving warehouse management efficiency.

[0103] Example 3: Please refer to Figure 1 As shown, the object precise positioning system using RFID technology described in this embodiment includes a position selection module, a position analysis module, an azimuth analysis module, and a positioning tracking module;

[0104] Position selection module: After obtaining warehouse information, a number of antenna positions are randomly generated in the warehouse through a random generation tool. After evaluating a number of antenna positions, a corresponding number of antenna positions are screened out for arranging antenna arrays. The antenna array arrangement information is sent to the position analysis module and the azimuth analysis module.

[0105] Position analysis module: When a product is placed on a shelf in any area of ​​the warehouse, the antenna array starts to receive the RFID signal emitted by the product tag, obtains the time difference between the RFID signal reaching each antenna, generates the relative position of the product, and corrects the relative position through the reflection path recognition algorithm. The corrected relative position information is sent to the positioning tracking module;

[0106] Azimuth analysis module: estimates the incident angle of the signal based on the phase difference received by each antenna, generates the relative azimuth of the product, and sends the relative azimuth information to the positioning tracking module;

[0107] Positioning and tracking module: uses a fusion algorithm to combine the relative position and relative azimuth of the product to calculate the actual position coordinates of the product and perform real-time positioning when the product is in a moving state.

[0108] The above formulas are all dimensionless and numerical calculations. The formula is a formula for the most recent real situation obtained by collecting a large amount of data and performing software simulation. The preset parameters in the formula are set by technicians in this field according to actual conditions.

[0109] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0110] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for accurately locating an object using RFID technology, characterized in that: The positioning method includes the following steps: After the positioning system obtains warehouse information, it randomly generates several antenna positions in the warehouse through a random generation tool, and after evaluating several antenna positions, selects a corresponding number of antenna positions for arranging antenna arrays; When a product is placed on a shelf in any area of ​​the warehouse, the antenna array begins to receive the RFID signal emitted by the product tag, obtains the time difference between the RFID signal reaching each antenna, generates the relative position of the product, and corrects the relative position through the reflection path recognition algorithm. The incident angle of the signal is estimated based on the phase difference received by each antenna, and the relative azimuth of the product is generated. The fusion algorithm is used to combine the relative position and relative azimuth of the product to calculate the actual position coordinates of the product and perform real-time positioning when the product is in a moving state; After evaluating a number of antenna positions, a corresponding number of antenna positions are selected for arranging an antenna array, including the following steps: Obtain the product access index, coverage index, and signal interference index of each candidate antenna position, normalize the product access index, coverage index, and signal interference index, map the value ranges of the product access index, coverage index, and signal interference index to [0,1], obtain the normalized value of the product access index, the normalized value of the coverage index, and the normalized value of the signal interference index, and obtain the performance value by adding the normalized value of the product access index to the normalized value of the coverage index and subtracting the normalized value of the signal interference index; Sort all candidate antenna positions according to their performance values ​​from large to small, generate a candidate table, obtain the number of actual antenna positions required in the warehouse, and select the candidate antenna positions before the number of actual antenna positions based on the positive order of the candidate table as the actual antenna positions of the warehouse; The calculation expression of the product access index is: , where is the product access index, represents the total number of time periods, Indicates the product in the time period The number of accesses within represents the demand frequency of the product, is the time decay factor, is the time decay constant, and .

2. The method for accurately locating an object using RFID technology according to claim 1, characterized in that: The relative position of the product is generated by obtaining the time difference of the RFID signal arriving at each antenna, including the following steps: The product tag periodically transmits RFID signals, and each antenna in the antenna array receives the signal and records the precise timestamp of each antenna receiving the signal. The time difference of each pair of antennas receiving the signal is calculated to obtain the time difference of the signal reaching each antenna. The expression is: , where Indicates antenna and antenna The time difference of receiving the signal, , Respectively represent antenna and antenna Timestamp of received signal; According to the time difference and signal propagation speed, calculate the antenna and antenna The relative distance difference is expressed as: , where For antenna and antenna The relative distance difference, is the signal propagation speed, Indicates antenna and antenna The time difference of receiving the signal; Using the known antenna position coordinates of the warehouse, the relative position of the product tag is determined based on the relative distance difference. The expression is: , where Product tags and antennas Straight-line distance; Assume that the distance difference between the antennas is known, that is, , then: , using the least squares method to solve , get the relative position coordinates of the product label, the expression is: , where For antenna The location coordinates of is the relative position coordinate of the product label, For antenna The location coordinates of .

3. The method for accurately locating an object using RFID technology according to claim 2, characterized in that: The incident angle of the signal is estimated based on the phase difference received by each antenna to generate the relative azimuth of the product, including the following steps: The phase difference of the signal received by the antenna array, for any two antennas in the antenna array, the calculation expression of the phase difference of the received signal relative to a reference point is: , where is the phase difference, is the wavelength of the signal, For antenna and antenna The relative distance difference, is the relative azimuth, that is, the angle between the product tag signal and the normal direction of the antenna array; The incident angle of the signal can be inferred from the known phase difference and the distance between the antennas. The expression is: .

4. The method for accurately locating an object using RFID technology according to claim 3, characterized in that: The fusion algorithm is used to combine the relative position and relative azimuth of the product to calculate the actual position coordinates of the product and perform real-time positioning when the product is in a moving state, including the following steps: Get the corrected relative position coordinates and relative azimuth of the product label, and calculate the actual position coordinates of the product through the fusion algorithm. The fusion algorithm expression is: , where is the actual location of the product label, is the relative position coordinate of the corrected product label, is the relative azimuth.

5. The method for accurately locating an object using RFID technology according to claim 4, characterized in that: The relative position is corrected by the reflection path recognition algorithm, including the following steps: Calculate product label to antenna After obtaining the position coordinates of the reflecting object, the propagation time from the reflecting object to the antenna is calculated. The propagation time; Based on the reflection object to the antenna The propagation time and product label to the antenna The propagation delay is calculated based on the propagation time, and the distance difference corresponding to the propagation delay is calculated. The relative position coordinates of the corrected product label are: , where is the relative position coordinate of the corrected product label, To correct the relative position coordinates of the product label before, is the distance difference, Product tags and antennas The straight-line distance, Indicates antenna The unit vector to the product label.

6. The method for accurately locating an object using RFID technology according to claim 5, characterized in that: Calculate product label to antenna The propagation time is expressed as: , where From product tag to antenna The propagation time, Product tags and antennas Straight-line distance; Calculate the propagation time of the reflection path as: , where To reflect the object to the antenna The propagation time, is the straight-line distance from the product label to the reflective object, To reflect the object to the antenna Straight-line distance; Based on the reflection object to the antenna The propagation time and product label to the antenna The propagation delay is calculated from the propagation time: , where is the propagation delay; Calculate the distance difference corresponding to the propagation delay, the expression is: , where is the distance difference, is the signal propagation speed.

7. The method for accurately locating an object using RFID technology according to claim 6, characterized in that: The calculation expression of the coverage index is: , where represents the coverage index, Indicates the total number of areas covered, Indicates the number of antennas covered Area of ​​the region, Indicates The distance between the area and the antenna, Indicates the total area of ​​the warehouse; The calculation logic of the signal interference index is: obtain the number of areas covered by the candidate antenna position, and detect the electromagnetic interference degree of each area at multiple time points, calculate the electromagnetic interference degree mean and electromagnetic interference degree standard deviation of the area based on the electromagnetic interference degree at multiple time points, divide the electromagnetic interference degree mean by the electromagnetic interference degree standard deviation to obtain the signal impact factor of the area, and sum the signal impact factors of all areas covered by the candidate antenna position to obtain the signal interference index.

8. An object precise positioning system using RFID technology, used to implement the positioning method according to any one of claims 1 to 7, characterized in that: It includes a location selection module, a location analysis module, an azimuth analysis module, and a positioning tracking module; Position selection module: After obtaining warehouse information, a number of antenna positions are randomly generated in the warehouse through a random generation tool. After evaluating a number of antenna positions, a corresponding number of antenna positions are screened out for arranging antenna arrays. The antenna array arrangement information is sent to the position analysis module and the azimuth analysis module. Position analysis module: When a product is placed on a shelf in any area of ​​the warehouse, the antenna array starts to receive the RFID signal emitted by the product tag, obtains the time difference between the RFID signal reaching each antenna, generates the relative position of the product, and corrects the relative position through the reflection path recognition algorithm. The corrected relative position information is sent to the positioning tracking module; Azimuth analysis module: estimates the incident angle of the signal based on the phase difference received by each antenna, generates the relative azimuth of the product, and sends the relative azimuth information to the positioning tracking module; Positioning and tracking module: uses a fusion algorithm to combine the relative position and relative azimuth of the product to calculate the actual position coordinates of the product and perform real-time positioning when the product is in a moving state.

Images