Radio frequency synchronization method of intelligent book detection device based on CAN bus

Abstract

This invention relates to the field of radio frequency identification (RFID) technology, specifically to a radio frequency synchronization method for an intelligent book detection device based on a CAN bus. The intelligent book detection device, based on a CAN bus, comprises several cabinets, each cabinet corresponding to a column controller. Each cabinet has multiple layers of space. The column controllers communicate with an external host computer via a network. Each layer of space corresponds to a layer reader / writer. The layer panels use layer-type antennas, each composed of two or more radio frequency antenna coils that partially overlap. The layer readers / writers communicate with the column controllers via a CAN bus. When a layer reader / writer activates radio frequency detection, it performs a time synchronization check with the column controller within a time interval T1. If the check is not performed within T1, it is considered a synchronization timeout, and all radio frequency operations are stopped to avoid interference with adjacent layers. Compared to ordinary tag detection, this significantly improves detection efficiency.

Description

Technical fields:

[0001] This invention relates to the field of radio frequency identification (RFID) technology, specifically to a radio frequency synchronization method for a CAN bus-based intelligent book detection device that can effectively solve the problem of mutual interference of radio frequency signals and improve the success rate and efficiency of detection. Background technology:

[0002] In the current field of RFID smart bookshelf technology, radio frequency identification (RFID) systems generally consist of a reader, an antenna, and RFID tags affixed to the books. During operation, the reader transmits radio frequency signals through the antenna to read the RFID tags. The tag's UID is fed back to the reader via the antenna for detection and amplification. The reader binarizes the received signal to detect the tag's UID and match it with the book to which the tag is affixed. In this system, the reader is a crucial component, responsible for signal transmission, reception, encoding, and decoding control throughout the RFID detection process. Traditional smart bookshelves are equipped with one reader per section and multiple vertical antennas per layer. However, this architecture results in a large number of vertical antennas and high costs, making it difficult to widely adopt in libraries.

[0003] One of the recent upgrade directions for smart bookshelves is the shelf-type smart bookshelf. The earliest generation of shelf-type smart bookshelves still used a reader-writer combined with an antenna, but the antenna was upgraded to a large shelf-type antenna for each shelf. By eliminating the need for a vertical antenna, costs were effectively reduced, and the book capacity of the bookshelf was increased. However, this also brought new problems. Due to the increased area of ​​the bookshelf antenna coil, it became more sensitive to the coupling of weak radio frequency signals. This led to severe mutual interference when multiple smart bookshelves simultaneously activated radio frequency detection. To ensure detection accuracy, a time-division detection method had to be used, resulting in reduced detection efficiency.

[0004] To address this issue, the new generation of shelf-type smart bookshelves has undergone some optimizations. Since most interference occurs between radio frequency (RF) transmission and reception, controlling the RF transmission and reception at different time intervals can effectively prevent RF interference. This method is called RF synchronization. Previously, attempts were made to achieve RF synchronization by adding a separate 485 synchronization line, but this could not be successfully implemented due to difficulties in on-site wiring and complex synchronization logic.

[0005] To better realize the application of the radio frequency synchronization mechanism in smart bookshelf products, the existing bookshelf products and technologies have been further upgraded. While reducing the layer antenna design, an architecture combining column controllers and layer readers / writers is adopted, which communicate with each other via a CAN bus. At the same time, the CAN bus is also compatible with the function of radio frequency synchronization, which solves the problem of radio frequency interference, controls costs, and reduces product complexity. Summary of the Invention:

[0006] This invention addresses the shortcomings and deficiencies of existing products and technologies by proposing a radio frequency synchronization method for an intelligent book detection device based on the CAN bus.

[0007] This invention achieves its purpose through the following measures:

[0008] A radio frequency synchronization method for a CAN bus-based intelligent book detection device is characterized in that the CAN bus-based intelligent book detection device includes several cabinets, each cabinet is equipped with a corresponding column controller, each cabinet has multiple layers of space, the column controller communicates with an external host computer via a network, each layer of space is equipped with a corresponding layer reader / writer, the layer plate adopts a layer plate antenna, the layer plate antenna is composed of two or more radio frequency antenna coils, and the two or more radio frequency antenna coils partially overlap each other; the layer reader / writer communicates with the column controller via a CAN bus.

[0009] When the layer reader enables radio frequency detection, it is set to perform time synchronization with the column controller within a time period of T1. If the synchronization is not performed within T1 time, it will be judged as a synchronization timeout, and all radio frequency operations will be stopped to avoid interference to adjacent layers.

[0010] When performing radio frequency (RF) detection, the layer reader divides each round of RF transmission and reception into a fixed-length time slot T2. Each time slot T2 performs only one RF transmission or reception operation. Each time slot is fixedly numbered based on the last synchronization time with the column controller. The reserved communication time slot is used only for communication with the column controller to avoid interference between communication and RF operations. To ensure that the tag's response accurately falls within time slot T2, the frame ends of the control reader's transmitted commands are strictly synchronized; that is, each reader ensures that the RF command transmission ends at the same time. Assume the length of the command to be transmitted is T. cmd Readers with shorter transmission commands need to increase the transmission delay. The command delay time is calculated as: T = T² - T cmd T cmd The length varies depending on the inventory command mask, and the calculation method is T. cmd =T SOF +T flg +T code +T mask +T crc +T EOF，其中 TSOF This is the frame header time, with a value of 75.52µs; T flg This is the time flag, with a value of 302.08µs; T code This is the command code time, with a value of 302.08us; T mask This is the mask time, and its value is related to the mask length, being a multiple of 302.08µs, with a range of 0 to 2416.64µs; T crc The check bit time is set to 302.08 µs; T EOF This is the frame end time, with a value of 37.76us.

[0011] The layer reader also features guidance and misalignment indicator lights.

[0012] In the multi-RF antenna coils of the layered antenna of the present invention, each antenna has a 10% to 20% overlap area in the lateral direction to avoid RF dead zones, and adjacent antennas are distributed on different layers of the PCB board of the layered antenna.

[0013] The mid-layer plate antenna of this invention can be equipped with a human proximity sensor, and the layer reader can be connected to the human proximity sensor signal to detect whether someone is approaching in real time. When no one is around, detection can be stopped to reduce power consumption.

[0014] In this invention, the column controller achieves microsecond-level synchronization between layer readers via CAN remote frames. The column controller communicates with the layer readers via CAN data frames and controls the readers to be in different detection modes through protocols. The detection modes include inventory mode, active monitoring mode, and passive mode. When the layer reader is in inventory mode, it will actively perform one round of radio frequency detection and then stop, recording all detected tag UIDs and waiting for the column controller to query and report.

[0015] In this invention, when the layer reader is in active monitoring mode, it determines whether detection needs to be activated based on the human body sensor signal. When someone approaches or leaves, it actively performs radio frequency detection. When it detects an increase or decrease in the number of books on the layer, it actively reports to the column controller. When the layer reader is in passive mode, it can receive and execute special instructions from the column controller, including instructions for reader tag AFI, block data, and tag indicator light control.

[0016] In order to reduce the antenna size, each layer reader is equipped with multiple antennas and operates by time-division switching. The magnetic field is not turned off during antenna switching to keep the tag in a stationary state by the previous antenna, thereby improving the tag detection efficiency.

[0017] In order to further improve the tag detection efficiency, the reader of each layer can establish a buffer and refer to the detection results of the previous round in the new round of tag detection to prioritize the search and separation of previously detected tags. After actual testing, this method can significantly improve the detection efficiency compared with ordinary tag detection. Attached image description:

[0018] Appendix Figure 1 This is a block diagram of the architecture of the present invention.

[0019] Appendix Figure 2 This is a schematic diagram of the radio frequency antenna distribution in this invention.

[0020] Appendix Figure 3 This is a schematic diagram of the radio frequency synchronization mechanism in this invention.

[0021] Figure labels: 1. Library management platform, 2. Column controller, 3. Layer reader / writer, 4. RF antenna, 5. Layer indicator light, 6. Human proximity sensor, 7. Synchronization time slot, 8. Transmit time slot, 9. Receive time slot, 10. Communication time slot. Detailed implementation method:

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0023] like Figure 1 As shown, this invention proposes an intelligent book detection device, which includes: a book management platform 1, a column controller 2, a layer reader / writer 3, an RF antenna 4, layer indicator lights 5, and a human proximity sensor 6. The book management platform 1 communicates with the column controller 2 via a network, issuing control commands, including but not limited to commands for reading / writing AFI, block data, guiding indicator light flashing, switching detection modes, and querying books on the shelf. The column controller 2 is connected to the layer reader / writer 3 via a CAN bus, and synchronizes and communicates strictly according to fixed time slots. Figure 3 As shown, synchronization is initiated by the column controller, most control command communications are also initiated by the column controller, and active reporting communications are initiated by the reader / writer. Communications from different initiators are distributed across different time slots to avoid time slot timeouts due to communication congestion. The reader / writer 3 is connected to the RF antenna 4, the shelf indicator light 5, and the human proximity sensor 6. The shelf indicator light 5 can provide guidance by flashing or indicating misplaced shelves, and the human proximity sensor 6 is used to detect if anyone is approaching the bookshelf. Figure 2 As shown, there is a certain overlap area between each layer of RF antennas to prevent readout blind spots.

[0024] Example 1:

[0025] This example provides a radio frequency synchronization method for an intelligent book detection device in inventory mode:

[0026] Step 1: The book management platform 1 sends a command to the column controller 2 to start a round of inventory counting. The column controller sends a synchronization command to the layer readers 3 and confirms that all layer readers 3 are online.

[0027] Step 2: The column controller 2 sends a message to the layer reader 3 to start a round of book inventory. The layer reader 3 switches to the first antenna, turns on the radio frequency and starts to send and receive tag responses in time slots. The layer reader 3 needs to calculate the delay time after the time slot is turned on and start sending the command based on the length of the transmission command. Theoretically, the shorter the command, the longer the delay time, to ensure that all layers finish radio frequency transmission at the same time.

[0028] Step 3: Since the RFID tags will respond at a fixed time after receiving the query command, all the response commands will fall into the same time slot. The layer reader 3 adjusts the mask length according to the response and continues to send the count command or the set-to-still command in the next time slot until all tags in this antenna are detected or the antenna timeout time is reached.

[0029] Step 4: The layer that has completed the detection of the first antenna will automatically switch to the next antenna. The intermediate magnetic field will not be turned off. The tags that were detected and put to rest during the detection of the previous antenna will not be reset, thus affecting the detection of the next antenna and shortening the detection time.

[0030] Step 5: After all antennas in this layer have been detected, the layer reader 3 will turn off the radio frequency and wait for the column controller 2 to query the detection results. Since the complete book UID data is large, in order to avoid CAN bus congestion caused by simultaneous uploading, the column controller 2 will query the detection status of the layer reader 3 and obtain the detection results layer by layer during the detection period. In order to improve efficiency, the layer reader 3 that has finished detection first will start this process first.

[0031] Step 6: After the column controller 2 obtains the detection results of all layer readers 3, it reports the complete book UID information of this round of inventory to the book management platform 1 to complete this round of inventory.

[0032] Example 2:

[0033] This example provides a radio frequency synchronization method for an intelligent book detection device in active monitoring mode:

[0034] Step 1: The book management platform 1 sends a command to the column controller 2 to enable the active monitoring mode. The column controller sends a synchronization command to the layer readers 3 and confirms that all layer readers 3 are online.

[0035] Step 2: The column controller 2 sends a command to the layer reader 3 to enable the active monitoring mode. If the layer reader 3 determines that it does not have the book UID data of this layer, it will first start a round of inventory, the process is as in Example 1, but no data is reported.

[0036] Step 3: The layer reader 3 determines the status of the human proximity sensor. If someone approaches or leaves, it actively starts a new round of tag detection. Based on the UID data of the books in this layer stored in its own memory, if a tag change is detected during the detection process, it actively sends the change information to the column controller 2.

[0037] Step 4: After receiving the actively reported data from the layer reader 3, the column controller 2 re-encapsulates the protocol and reports it to the book management platform 1.

[0038] Example 3:

[0039] This example provides a radio frequency synchronization method for an intelligent book detection device in passive command mode:

[0040] Step 1: The book management platform 1 sends instructions such as tag AFI, block data, and tag indicator light control to the column controller 2;

[0041] Step 2: The column controller first turns off the active monitoring mode of the layer reader 3 and resynchronizes it, and the layer reader 3 enters the passive command mode;

[0042] Step 3: The column controller sends tag AFI, block data and tag indicator control instructions to the designated layer reader 3. Layers that do not receive control instructions remain silent until all designated layers complete the instructions.

[0043] Step 4: The column controller reports the instruction execution result to the book management platform 1. If it is an AFI or block data read instruction, the corresponding AFI or block data is reported.

[0044] Compared with the prior art, the present invention has the following advantages: (1) Higher detection efficiency: Due to the reduction in antenna size, the range of mutual influence between radio frequency antennas is reduced to adjacent antennas. Due to the adoption of radio frequency synchronization mechanism, all layer readers can work synchronously, and the response time for changes in books can be within 10 seconds. (2) Lower cost: Due to the continuation of the layered antenna design, the product cost is greatly reduced compared with the traditional vertical antenna. (3) Wide range of applications: It can be applied in many fields such as intelligent management of books, archives, and dense items.

Claims

1. A radio frequency synchronization method for an intelligent book detection device based on a CAN bus, characterized in that, The CAN bus-based intelligent book detection device includes several cabinets, each cabinet is equipped with a corresponding column controller, each cabinet has multiple layers of space, the column controller communicates with an external host computer via a network, each layer of space is equipped with a corresponding layer reader / writer, the layer plate adopts a layer plate antenna, the layer plate antenna is composed of two or more radio frequency antenna coils, the two or more radio frequency antenna coils partially overlap each other; the layer reader / writer communicates with the column controller via a CAN bus. When the layer reader enables radio frequency detection, it is set to perform time synchronization with the column controller within a time period of T1. If the synchronization is not performed within T1 time, it will be judged as a synchronization timeout, and all radio frequency operations will be stopped to avoid interference to adjacent layers. When performing radio frequency detection, the layer reader divides each round of radio frequency transmission and reception into a fixed-length time slot T2. Each time slot T2 performs only one radio frequency transmission or reception operation. Each time slot is fixedly numbered according to the last synchronization time with the column controller. The reserved communication time slot is only used for communication with the column controller to avoid mutual interference between communication and radio frequency operation. To ensure that the tag's response falls accurately within time slot T2, the frame ends of the control reader's command transmission are kept strictly synchronized. This means that each reader must finish transmitting the radio frequency command at the same time. Assume the length of the command to be transmitted is T. cmd Readers with shorter transmission commands need to increase the transmission delay. The command delay time is calculated as: T = T² - T cmd T cmd The length varies depending on the inventory command mask, and the calculation method is T. cmd =T SOF +T flg +T code +T mask +T crc +T EOF , among which, T SOF It is the frame header time; T flg It is the flag time; T code It is the command code time; T mask It is the mask time; T crc For check bit time; T EOF For frame end time, the layer reader also has guidance and misalignment indicator lights.

2. The radio frequency synchronization method for a CAN bus-based intelligent book detection device according to claim 1, characterized in that, In the multi-RF antenna coils of the layered antenna, each antenna has a 10% to 20% overlap area in the lateral direction to avoid RF dead zones. Adjacent antennas are distributed on different layers of the PCB board of the layered antenna.

3. The radio frequency synchronization method for a CAN bus-based intelligent book detection device according to claim 1, characterized in that, The layered antenna is equipped with a human proximity sensor, and the layer reader connects to the human proximity sensor signal to detect whether someone is approaching in real time. When no one is around, detection is not required to reduce power consumption.

4. The radio frequency synchronization method for a CAN bus-based intelligent book detection device according to claim 1, characterized in that, The column controller achieves microsecond-level synchronization between layer readers via CAN remote frames. The column controller communicates with the layer readers via CAN data frames and controls the readers to be in different detection modes through protocols. The detection modes include inventory mode, active monitoring mode, and passive mode. When the layer reader is in inventory mode, it will actively perform one round of radio frequency detection and then stop, recording all detected tag UIDs and waiting for the column controller to query and report. When in active monitoring mode, the library management platform sends a command to the column controller to enable active monitoring mode. The column controller sends a synchronization command to the layer readers and confirms that all layer readers are online. The column controller sends a command to the layer readers to enable active monitoring mode. If a layer reader determines that it does not have the UID data of the book in its layer, it will first start a round of inventory, but will not report the data. The layer reader checks the status of the human proximity sensor. If someone approaches or leaves, it will actively start a new round of tag detection. Based on its stored UID data of the book in its layer, if a tag change is detected during the detection process, it will actively send the change information to the column controller. After receiving the actively reported data from the layer readers, the column controller re-encapsulates the protocol and reports it to the library management platform. In passive command mode: The library management platform sends tag AFI, block data, and tag indicator light control commands to the column controller; the column controller first disables the active monitoring mode of the layer reader and resynchronizes, and the layer reader enters passive command mode; the column controller sends tag AFI, block data, and tag indicator light control commands to the designated layer readers, and layers that do not receive control commands remain silent until all designated layers complete the commands; the column controller reports the command execution results to the library management platform, and if it is an AFI or block data read command, it reports the corresponding AFI or block data.

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