Multi-station IMU batch calibration system and method based on distributed acquisition and wireless transmission

Abstract

The application discloses a kind of multi-station IMU batch calibration system and method based on distributed acquisition and wireless transmission, including IMU calibration array being set in rotary table rotating end, SPI distributed data collector, synchronous trigger signal source, rotating end converging device and rotating end wireless sending device, and fixed end wireless receiving device and fixed end computer being set in rotary table fixed end.Synchronous trigger signal source drives SPI distributed data collector to collect the data of IMU to be calibrated in the same sampling period, writes the same sampling batch number and is packaged into acquisition data frame in combination with identification information;After the data frame is converged in rotating end, it is sent to fixed end wireless receiving device by wireless link;Fixed end computer completes the merging and rearrangement of same period data according to sampling batch number and identification information.The application overcomes the defects that cross-border transmission channel is limited and multiple nodes are difficult to align, realizes near-end high-speed acquisition of massive calibration data, strict space-time synchronization and boundaryless transmission.

Description

Technical Field

[0001] This invention belongs to the field of batch calibration technology of inertial measurement units, specifically relating to a multi-station IMU batch calibration system and method based on distributed acquisition and wireless transmission. Background Technology

[0002] Inertial Measurement Units (IMUs) typically include components such as gyroscopes, accelerometers, and temperature sensors, and are widely used in navigation, attitude measurement, motion control, and automated equipment. To obtain key parameters of the IMU, such as zero bias, scaling factor, installation error, and temperature drift, rigorous calibration tests are usually performed using a precision turntable.

[0003] In existing batch calibration schemes, the turntable movement is typically controlled by a fixed-end computer or main controller, and data from multiple acquisition front-ends is read via RS485 bus, USB interface, Ethernet cable, or slip ring circuit. This method can meet testing requirements when calibrating a small number of IMUs. However, with the emergence of high-capacity batch calibration needs, when the number of IMUs to be calibrated expands to hundreds, and continuous acquisition of multi-axis data at high sampling frequencies of 200Hz or even 500Hz is required, existing technologies have the following problems: First, the data from multi-station IMUs must cross the motion boundary between the rotating end and the fixed end of the turntable. If a large number of cables or multi-channel slip rings are used for transmission, not only is the cable arrangement complex and the number of slip ring channels has a physical limit, but the signal integrity of long-distance wired transmission is also difficult to guarantee, increasing the system maintenance difficulty and failure rate, and making it difficult to balance the large-capacity data transmission with the simplicity of wiring. Second, high-precision IMU calibration requires that the data sampling of multiple IMUs must be strictly aligned with the same turntable motion state (such as turntable angle, angular velocity, etc.). In the existing models where data is read sequentially from a fixed terminal or uploaded in a distributed manner from multiple independent acquisition terminals, problems such as inconsistent sampling batches and misaligned timestamps are prone to occur at each node, leading to confusion in the workstation correspondence and making it difficult for the fixed-end computer to rearrange data and calculate calibration parameters. Third, IMU devices typically use short-distance, high-speed interfaces such as SPI to output multi-axis data. To accommodate long-distance wired transmission across turntables, existing solutions have to convert SPI signals to long-distance serial bus signals (such as RS485), which not only increases the cost of interface conversion circuits and electrical isolation but also increases the complexity of overall synchronous control.

[0004] In summary, existing multi-station IMU calibration systems are constrained by inherent defects such as slip ring channel limitations, poor data synchronization, and complex communication protocol conversion when dealing with high-frequency batch calibration of hundreds of IMUs. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a multi-station IMU batch calibration system and method based on distributed acquisition and wireless transmission. Its purpose is to overcome the shortcomings of existing large-capacity IMU calibration schemes, such as limited cross-border transmission channels, poor data synchronization among multiple nodes, and complex long-distance protocol conversion.

[0006] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution: In a first aspect, the present invention provides a multi-station IMU batch calibration system based on distributed acquisition and wireless transmission, comprising: An IMU calibration array, located at the rotating end of the turntable, is used to install multiple IMUs to be calibrated. At least one SPI distributed data acquisition unit is set at the rotating end of the turntable and connected to the plurality of IMUs to be calibrated via an SPI interface; A synchronous trigger signal source is communicatively connected to the SPI distributed data acquisition unit and is used to output a synchronous trigger signal; The SPI distributed data acquisition unit responds to the synchronization trigger signal, acquires data from the IMU to be calibrated within the same sampling period and writes the same sampling batch number, and encapsulates and generates an acquisition data frame by combining the identification information of the IMU to be calibrated. A rotating end aggregation device is disposed at the rotating end of the turntable and connected to the SPI distributed data acquisition unit for aggregating the acquired data frames; A rotating end wireless transmitting device is disposed at the rotating end of the turntable and connected to the rotating end aggregation device, and is used to transmit the aggregated data frames through a wireless link. A fixed-end wireless receiving device, mounted on the fixed end of the turntable, is used to receive the aggregated data frames; and A fixed-end computer, located at the fixed end of the turntable and connected to the fixed-end wireless receiving device, is used to merge data from the same sampling period according to the sampling batch number in the acquired data frame, and to rearrange the data of the IMU to be calibrated according to the identification information to generate a batch calibration dataset.

[0007] In one possible implementation of the first aspect, the SPI distributed data acquisition device includes a control unit, a multi-channel SPI host interface, a chip select control unit, a direct memory access receiving unit, and a local cache unit; the control unit is used to control the multi-channel SPI host interface to read data from the IMU to be calibrated, the chip select control unit is used to select the corresponding IMU to be calibrated, and the acquired data is written to the local cache unit through the direct memory access receiving unit.

[0008] In one possible implementation of the first aspect, multiple IMUs to be calibrated connected to the same SPI host interface share the SPI clock signal line and master output / slave input signal line, and are respectively connected to the chip select terminal of the corresponding IMU to be calibrated through the independent chip select signal line output by the chip select control unit.

[0009] In one possible implementation of the first aspect, the identification information includes a workstation number and a collector number when there are multiple SPI distributed data collectors.

[0010] In one possible implementation of the first aspect, the acquired data frame further includes turntable status information, which includes at least one of turntable angle, turntable angular velocity, turntable motion stage, and timestamp, so that the fixed-end computer can align the data of the IMU to be calibrated with the corresponding turntable motion state after rearrangement.

[0011] In one possible implementation of the first aspect, the rotating end aggregation device is an Ethernet switch or an Ethernet aggregation controller; multiple SPI distributed data acquisition units are connected to the rotating end aggregation device via Ethernet wired interfaces to perform high-speed data aggregation inside the rotating end of the turntable, and the Ethernet wired interfaces are not used as transmission channels across the rotating boundary of the turntable.

[0012] In one possible implementation of the first aspect, the acquired data frame further includes a frame sequence number and a checksum, and the rotating end wireless transmitting device retains a local buffer; when the fixed end computer detects that the received acquired data frame has missing frames, out-of-order frames, or a checksum failure based on the checksum and frame sequence number, it generates a retransmission request containing the missing frame sequence number and sends it back to the rotating end wireless transmitting device via the wireless link; the rotating end wireless transmitting device reads the corresponding acquired data frame from the local buffer according to the retransmission request and retransmits it.

[0013] Secondly, this invention provides a multi-station IMU batch calibration method based on distributed acquisition and wireless transmission, applied to the multi-station IMU batch calibration system described in the first aspect, the method comprising: Multiple IMUs to be calibrated are installed in the IMU calibration array at the rotating end of the turntable; A synchronous trigger signal is output to the SPI distributed data acquisition unit located at the rotating end of the turntable through a synchronous trigger signal source; The SPI distributed data acquisition unit responds to the synchronization trigger signal, acquires data from the IMU to be calibrated through the SPI interface within the same sampling period, writes the same sampling batch number, and encapsulates and generates a data acquisition frame by combining the identification information of the IMU to be calibrated. The rotating end gathering device gathers the collected data frames and transmits them to the fixed end wireless receiving device at the fixed end of the turntable via a wireless link through the rotating end wireless transmitting device. The fixed-end computer located at the fixed end of the turntable acquires the data frames received by the fixed-end wireless receiving device, merges data from the same sampling period according to the sampling batch number in the data frames, and rearranges the data of the IMU to be calibrated according to the identification information to generate a batch calibration dataset.

[0014] In one possible implementation of the second aspect, the SPI distributed data acquisition unit includes a control unit, a multi-channel SPI host interface, a chip select control unit, a direct memory access receiver unit, and a local cache unit; The methods for collecting data from the IMU to be calibrated include: For multiple IMUs to be calibrated connected to the same SPI host interface, the chip select signal output by the chip select control unit is used to select them sequentially within one sampling period and read them in a time-division multiplexing manner. For IMUs to be calibrated connected to different SPI host interfaces, the control unit controls multiple SPI host interfaces to perform parallel readings. Furthermore, the collected data is written into the local cache unit through the direct memory access receiving unit.

[0015] In one possible implementation of the second aspect, the acquired data frame further includes a frame sequence number and a checksum; After the fixed-end computer acquires the collected data frame, the method further includes: The fixed-end computer performs verification and frame sequence number continuity detection on the acquired data frames based on the verification code and frame sequence number. If a missing frame or verification failure is detected, the fixed-end computer generates a retransmission request containing the sequence number of the missing frame and feeds it back to the rotating end wireless transmission device of the turntable via a wireless link. The rotating end wireless transmitting device reads the acquisition data frame with the corresponding frame number from the local buffer according to the retransmission request and retransmits it.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects: The multi-station IMU batch calibration system based on distributed acquisition and wireless transmission provided by this invention effectively overcomes the inherent defects of traditional large-capacity calibration schemes, such as limited physical channels, difficulty in synchronous reordering, and complex protocol conversion, through the coordination of hardware architecture and data links. This invention deploys an SPI distributed data acquisition unit directly on the rotating end of the turntable, utilizing the SPI interface to acquire data from the IMU to be calibrated nearby, eliminating the cost of long-distance serial bus protocol conversion and isolation circuits from the source. Simultaneously, under the global drive of a synchronous trigger signal source, the acquisition end achieves concurrent acquisition of multiple nodes with the same sampling period, and also assigns the same sampling batch number and IMU identification information to the underlying data, solving the problem of spatiotemporal synchronization and identity binding of massive, dispersed data at the hardware level. The aforementioned high-frequency acquired data is rapidly integrated by a convergence device inside the rotating end, and then transmitted wirelessly across the turntable's movement boundary to the fixed end via a wireless link. This overcomes the physical limitations of the number of traditional slip ring channels and the wiring constraints and signal attenuation risks caused by dense cabling, improving the system's hardware scalability and ensuring reliable operation. Finally, the fixed-end computer only needs to parse the batch number and identification information inherent in the data frame to complete the periodic merging and source rearrangement of massive data from multiple workstations. These features are interconnected and progressive, meeting the concurrent calibration requirements of hundreds of IMU nodes under ultra-high frequency sampling conditions. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the specific embodiments of the present invention, the drawings used in the description of the specific embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the overall architecture of a multi-station IMU batch calibration system based on distributed acquisition and wireless transmission according to the present invention.

[0019] Figure 2 This is a schematic diagram of the internal structure of an SPI distributed data acquisition unit.

[0020] Figure 3 This is a schematic diagram of a rotating end data aggregation and wireless cross-border transmission architecture.

[0021] Figure 4 This is a schematic diagram of the wireless reliable transmission and data rearrangement process.

[0022] In the diagram: Ⅰ. Rotating end of the turntable; Ⅱ. Fixed end of the turntable; 1. Three-axis turntable body; 2. IMU calibration array; 3. Fixed end wireless receiver; 4. Fixed end computer. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] like Figure 1 As shown, this embodiment provides a multi-station IMU batch calibration system based on distributed acquisition and wireless transmission. The system is divided into two parts: a rotating turntable end I and a fixed turntable end II. The rotating turntable end I moves synchronously with the three-axis turntable body 1, and the fixed turntable end II is set in a stationary position outside the turntable.

[0025] IMU calibration array 2 is located at the rotating end I of the turntable and is used to install multiple IMUs to be calibrated. IMU calibration array 2 is mounted on the table surface of the three-axis turntable body 1 or on a dedicated calibration fixture. Multiple IMUs to be calibrated can be arranged in matrix, group, ring, or multi-layer array in each station. Each station is equipped with a positioning reference, locking structure, and electrical connection terminals to ensure that the installation posture of each IMU to be calibrated is consistent and the electrical connection is reliable.

[0026] At least one Serial Peripheral Interface (SPI) distributed data acquisition unit is located at the rotating end I of the turntable. Each IMU to be calibrated is connected to the nearest SPI distributed data acquisition unit via a short-distance SPI cable. The SPI distributed data acquisition unit rotates with the rotating end I of the turntable, completing the acquisition of IMU data at the nearest point on the rotating end, thus avoiding the transmission of SPI signals across the rotation boundary.

[0027] The synchronous trigger signal source communicates with the SPI distributed data acquisition unit and is used to output synchronous trigger signals. The synchronous trigger signal source can trigger based on the sampling period, or it can combine the turntable controller's position signal, angle trigger signal, or timer period signal to generate a synchronization command, providing a unified sampling time reference for the entire system; the synchronous trigger signal can be in the form of a SYNC synchronous signal or a Trigger trigger signal, and is synchronously distributed to each SPI distributed data acquisition unit by the synchronous trigger signal source.

[0028] The SPI distributed data acquisition unit responds to the synchronization trigger signal, acquiring data from the IMU to be calibrated within the same sampling period and writing it to the same sampling batch number. This data is then combined with the identification information of the IMU to be calibrated to encapsulate and generate a data acquisition frame. The sampling batch number is used to mark all acquired data at the same sampling time; it can be an incrementing integer or a combination of task number and sampling sequence number. The identification information is used to distinguish different IMUs to be calibrated, achieving a one-to-one correspondence between data and workstation.

[0029] The rotary end aggregation device is located at the rotary end I of the turntable and connected to the SPI distributed data acquisition unit to aggregate acquired data frames. When multiple SPI distributed data acquisition units are configured, the rotary end aggregation device completes the centralized integration of multiple acquired data inside the rotary end, eliminating the need to directly transmit the dispersed acquired signals to the outside.

[0030] The rotating end wireless transmitter is located at the rotating end I of the turntable and connected to the rotating end aggregation device. It is used to transmit the aggregated acquired data frames via a wireless link. The rotating end wireless transmitter rotates with the turntable, transmitting data wirelessly across the motion boundary between the rotating end and the fixed end.

[0031] The fixed-end wireless receiver 3 is installed at the fixed end II of the turntable and is used to receive the aggregated data frames. The fixed-end wireless receiver 3 is arranged on a stationary support, equipment cabinet or near the fixed-end computer around the turntable, and establishes a two-way wireless communication link with the rotating-end wireless transmitter; the fixed-end wireless receiver 3 can be connected to the fixed-end computer 4 via Ethernet, USB or PCIe interface.

[0032] The fixed-end computer 4 is set at the fixed end II of the turntable and connected to the fixed-end wireless receiver 3. The fixed-end computer 4 runs receiving and rearranging software to merge data from the same sampling period according to the sampling batch number in the acquired data frame, and rearranges the data of the IMU to be calibrated according to the identification information to generate a batch calibration dataset.

[0033] Specifically, during system operation, all IMUs to be calibrated are first installed at their corresponding stations in IMU calibration array 2, completing physical connections and parameter configurations. A synchronization trigger signal source outputs a synchronization trigger signal to the SPI distributed data acquisition unit according to the set sampling period. Upon receiving the synchronization trigger signal, each SPI distributed data acquisition unit starts data acquisition for the current sampling period, reads the angular velocity, acceleration, temperature, and status register data of the IMU to be calibrated at the corresponding station, writes a unified sampling batch number to all data within that period, binds the identification information of the corresponding IMU to be calibrated, and encapsulates it into a data acquisition frame. The data acquisition frames output by each SPI distributed data acquisition unit are transmitted to the rotating end aggregation device, where data aggregation is completed inside the rotating end I of the turntable. The aggregated data acquisition frames are sent to the rotating end wireless transmitter, which transmits them outwards via a wireless link. The fixed end wireless receiver 3 captures the data acquisition frames in the wireless link and forwards them to the fixed end computer 4. The fixed-end computer 4 first parses the sampling batch number in the acquired data frame and merges all data belonging to the same sampling period; then, based on the identification information in the acquired data frame, it allocates the data to the data queue of the corresponding IMU to be calibrated, and completes the rearrangement of multi-station data; finally, it generates a complete batch calibration dataset according to the preset format.

[0034] This solution decentralizes the data acquisition process to the rotating end I of the turntable, utilizing the SPI interface to read IMU data locally. This eliminates the need to transmit large amounts of raw SPI signals across the rotation boundary, reducing the requirements for cables and slip rings for cross-boundary transmission. Through a unified synchronization trigger signal and sampling batch number mechanism, IMU data from multiple acquisition units and workstations are collected under the same sampling reference, ensuring time synchronization of batch data and facilitating subsequent alignment with the turntable's motion state. Data is aggregated internally at the rotating end before being transmitted outward via a single wireless link, simplifying the cross-rotation boundary transmission architecture, reducing the cost and maintenance complexity of multi-channel slip rings and long-distance cables, and supporting simultaneous batch calibration of hundreds of IMUs.

[0035] Optionally, as a preferred configuration, the system can be configured with 16 SPI distributed data acquisition units, each corresponding to 32 IMU acquisition channels, for a total of 512 acquisition channels. Of these, 500 channels are used to connect to the IMUs to be calibrated, and the remaining 12 channels are reserved as backup or diagnostic channels. The system's sampling frequency is configured to 200Hz by default, and can be configured to 500Hz depending on the IMU data length, SPI clock frequency, and system redundancy. The fixed-end computer 4 can store the rearranged batch calibration data in HDF5, BIN, or CSV format.

[0036] Optionally, the rotating end wireless transmitter and the fixed end wireless receiver 3 can use at least one of Wi-Fi, Wi-Fi 6, industrial wireless bridge, ultra-wideband (UWB), dedicated radio frequency communication, or 5G industrial cellular communication to establish a data upload link from the rotating end to the fixed end and an acknowledgment and retransmission control link from the fixed end to the rotating end. The rotating end wireless transmitter can operate in transparent bridge mode to transmit Ethernet data frames, or it can use User Datagram Protocol (UDP) datagrams to send encapsulated acquisition data frames.

[0037] In one alternative implementation, such as Figure 2 As shown, the SPI distributed data acquisition unit includes a control unit, a multi-channel SPI master interface, a chip select control unit, a Direct Memory Access (DMA) receiver unit, and a local cache unit. The control unit, implemented using a microcontroller unit (MCU) or a field-programmable gate array (FPGA), serves as the core control entity of the acquisition unit, providing functions such as SPI parallel control, DMA acquisition scheduling, unified timestamp generation, sampling batch number generation, frame sequence number generation, cyclic redundancy check (CRC) code generation, and device status detection. The multi-channel SPI master interface is the physical communication interface between the acquisition unit and the IMUs to be calibrated. The chip select control unit is connected to the chip select pin of each IMU to be calibrated, used to select the specified IMU device. The DMA receiver unit is used for high-speed data transfer. The local cache unit uses static random-access memory (SRAM) to temporarily store the acquired IMU data. The acquisition unit also has a synchronization trigger input port and an Ethernet output interface. The synchronization trigger signal is connected to the control unit via the synchronization trigger input port, and the acquired data is sent to the rotating end aggregation device via the Ethernet output interface.

[0038] The control unit is used to control the multi-channel SPI host interface to read data from the IMU to be calibrated. The chip select control unit is used to select the corresponding IMU to be calibrated and write the collected data into the local buffer unit through the DMA receiving unit.

[0039] When the synchronization trigger signal arrives at the synchronization trigger input port, the control unit initiates the acquisition process, sending a strobe command to the chip select control unit, which then selects the corresponding IMU to be calibrated. Under the control unit's scheduling, the SPI host interface reads raw data such as angular velocity, acceleration, temperature, and status registers from the selected IMU via SPI burst read. The acquired data bypasses the control unit's core processing link and is directly transferred to the local buffer unit via the DMA receiving unit for temporary storage, completing the multi-IMU data acquisition within one sampling cycle.

[0040] This implementation uses a multi-channel SPI host interface combined with chip select control architecture, which can expand multiple IMU acquisition channels on a single data acquisition unit, increasing the access capacity of a single device. The introduction of a DMA receiver unit enables direct data transfer, reducing the computational load on the control unit and improving the data acquisition and buffering rate, supporting multi-channel acquisition requirements at higher sampling frequencies. The local buffer unit provides temporary storage for data, accommodating the rate difference between aggregation and wireless transmission, and also providing storage for subsequent data retransmission.

[0041] In one optional implementation, multiple IMUs to be calibrated connected to the same SPI master interface share the SPI clock signal line (Serial Clock, SCLK) and the Master Out Slave In (MOSI) signal line. The SPI clock signal line provides a unified communication clock reference for all IMUs to be calibrated connected to this bus; the Master Out Slave In signal line is used to send control commands and read commands from the data acquisition side, and all IMUs on the same channel share this signal line.

[0042] Each IMU to be calibrated is connected to its respective chip select terminal via an independent chip select (CS) signal line output by the chip select control unit. The chip select control unit outputs multiple independent chip select signals, each corresponding to one IMU to be calibrated. The IMU only responds to communication commands on the SPI bus when the corresponding chip select signal is valid. The Master In Slave Out (MISO) signal line can use an independent feedback method, with each IMU corresponding to an independent master in slave out signal line; alternatively, provided that electrical isolation and timing requirements are met, it can be connected to a shared signal line via time-division multiplexing of the chip select signal.

[0043] Within a single sampling period, the control unit controls the chip select control unit to sequentially switch the level states of each chip select signal line in a preset order, selecting the IMUs to be calibrated under the same SPI master interface one by one. For each selected IMU, the SPI master interface sends a read command through a shared master-slave input signal line, and the corresponding IMU returns the acquired data via the SPI bus. After completing the data reading for that IMU, the chip select signal is switched to select the next IMU to be calibrated and execute the read operation; that is, the single SPI bus uses a high-speed time-division multiplexing acquisition method with chip select. During this process, the SPI clock signal line continuously provides a synchronization clock to ensure the timing consistency of each read operation. For different SPI master interfaces, the control unit can schedule them to execute read operations simultaneously, realizing multi-bus parallel acquisition; therefore, the parallel acquisition of this system includes two forms: multi-SPI bus parallel acquisition and single SPI bus high-speed time-division multiplexing acquisition with chip select.

[0044] By configuring the SPI clock frequency and DMA receiving mode, a single data acquisition unit with 4 SPI host interfaces and 8 IMUs to be calibrated can complete the data reading of all 32 channels at the default sampling frequency of 200Hz. The sampling frequency can be increased to 500Hz according to the IMU data length, SPI clock frequency and system redundancy configuration.

[0045] By sharing the SPI clock signal line and master-slave input / output signal line, the number of wires on a single SPI bus is significantly reduced, lowering the complexity of cable routing inside the rotating end. Using independent chip select signals to individually select each IMU enables single-bus multi-node expansion while ensuring communication reliability. This enhances the IMU access capability of a single SPI interface and facilitates expanding the number of batch calibration stations with limited data acquisition hardware resources.

[0046] In one optional implementation, the identification information includes a workstation number, which corresponds one-to-one with a physical workstation on the IMU calibration array 2, used to mark the installation position of the IMU to be calibrated in the calibration fixture. When there are multiple SPI distributed data acquisition units, the identification information also includes an acquisition unit number, which is used to distinguish different SPI distributed data acquisition unit devices.

[0047] During the system initialization phase, the SPI distributed data acquisition unit establishes a mapping relationship between the workstation number, IMU number, acquisition unit number, SPI channel number, chip select number, and local buffer for each IMU to be calibrated, so that each piece of acquired data can be traced back to the corresponding physical workstation, product identity, and acquisition device through identification information.

[0048] When encapsulating the acquisition data frame, the SPI distributed data acquisition unit writes the station number corresponding to the IMU to be calibrated into the identifier field of the data frame. In a multi-acquisition unit configuration, it also writes its own acquisition unit number, corresponding SPI channel number, and chip select number into the corresponding fields. After receiving the acquisition data frame, the fixed-end computer 4 parses the acquisition unit number, SPI channel number, chip select number, and station number, and allocates the data to the IMU data sequence of the corresponding station according to the preset mapping relationship, thus completing the rearrangement of multi-station data.

[0049] This implementation establishes a unique mapping between collected data and physical workstations by combining multi-dimensional identifiers such as workstation numbers and data acquisition unit numbers. This ensures that the fixed end can accurately reproduce the corresponding data for each IMU, avoiding data confusion across multiple workstations. This identifier mechanism, in conjunction with the sampling batch number, can differentiate data from multiple workstations within the same batch and supports continuous traceability of single-workstation data across batches.

[0050] In one optional implementation, the acquired data frame also includes turntable status information, which includes at least one of turntable angle, turntable angular velocity, turntable motion stage, and timestamp. The turntable status information can be synchronously sent to each SPI distributed data acquisition unit by a synchronous trigger signal source, or it can be pushed in real time by the turntable controller to the acquisition system at the rotating end, and encapsulated together with the acquired data.

[0051] Specifically, while the synchronous trigger signal initiates data acquisition, the turntable status information corresponding to the current moment is simultaneously transmitted to each SPI distributed data acquisition unit. The SPI distributed data acquisition unit binds the turntable status information with the IMU data from the same sampling batch, encapsulating them together in the acquisition data frame. After the fixed-end computer 4 completes data rearrangement, it uses the turntable status information in the acquisition data frame to map the IMU output data of each sampling batch to the turntable angle, angular velocity, or motion stage at the corresponding moment, achieving time alignment between the IMU measurement data and the turntable's reference motion state.

[0052] This implementation binds turntable status information and IMU-acquired data into the same data frame for transmission, avoiding the errors associated with separate time alignment of turntable status data acquired by the fixed end, and improving the correspondence accuracy between IMU data and turntable reference status. This design allows calibration data to be directly associated with the corresponding turntable motion conditions, simplifying the data matching process during subsequent calibration parameter calculation.

[0053] In one alternative implementation, such as Figure 3As shown, the rotating end aggregation device is a gigabit Ethernet switch or Ethernet aggregation controller, equipped with multiple Ethernet access ports and at least one uplink port. Multiple SPI distributed data acquisition units are each equipped with gigabit Ethernet wired interfaces, connected to the access ports of the rotating end aggregation device via short-distance Ethernet cables, completing high-speed data aggregation inside the rotating end I of the turntable.

[0054] This wired Ethernet connection is confined to the interior of the rotating end I of the turntable and moves with it. It is a short-distance, high-speed aggregation link within the rotating end and does not cross the movement boundary between the rotating and fixed ends, nor does it serve as a transmission channel across the rotating boundary of the turntable. Data transmission between the rotating and fixed ends is entirely handled by the wireless link between the wireless transmitter at the rotating end and the wireless receiver at the fixed end. Even if the system retains a power supply slip ring or rotating power supply connector, it is only used for powering the rotating end equipment or transmitting low-frequency control signals and is not used as the main cross-boundary transmission channel for multi-station IMU calibration data.

[0055] After each SPI distributed data acquisition unit completes data acquisition and encapsulation, it sends the acquired data frames to the rotating end aggregation device via its own Ethernet wired interface. The rotating end aggregation device exchanges and aggregates multiple Ethernet data streams within the rotating end, integrating all acquired data frames into a single uplink and sending it to the rotating end wireless transmitter. The entire aggregation process is completed within the rotating motion system, and the Ethernet cable does not pass through the motion interface between the rotating end and the fixed end.

[0056] In one alternative implementation, such as Figure 4 As shown, the acquired data frame includes a frame header, task number, collector number, SPI channel number, chip select number, workstation number, IMU number, sampling batch number, frame sequence number, timestamp, turntable status information, IMU raw data length, IMU raw data, and Cyclic Redundancy Check (CRC) checksum. The specific definitions of each field are shown in Table 1 below:

[0057] The data acquisition unit number, SPI channel number, and chip select number directly restore the IMU's physical location in the acquisition network; the workstation number and IMU number restore the IMU's workstation location and product identity in the calibration fixture; the sampling batch number is used to group data from different data acquisition units into the same sampling period; and the frame sequence number is used for detecting missing frames, out-of-order data, and duplicate data during wireless transmission. The frame sequence number is an incrementing sequence number based on the transmission order, and the CRC checksum is used to verify data integrity. The rotating end wireless transmitter maintains a local circular buffer to temporarily store transmitted but unacknowledged acquisition data frames.

[0058] A bidirectional wireless link is established between the fixed-end wireless receiver 3 and the rotating-end wireless transmitter, which supports both data uploading from the rotating end to the fixed end and the transmission of control commands and retransmission requests from the fixed end to the rotating end.

[0059] When the rotating wireless transmitter sends data frames, it assigns a continuously increasing frame number to each frame and calculates the corresponding CRC checksum. Simultaneously, it stores a copy of the frame in its local circular buffer. Upon receiving the data frame, the fixed wireless receiver 3 forwards it to the fixed computer 4. The fixed computer 4 first parses the frame header and verifies data integrity using the CRC checksum. Then, it uses the frame number to determine if the frame sequence is continuous, identifying missing, out-of-order, or duplicate frames.

[0060] If the verification passes and the frame sequence is continuous, the fixed-end computer 4 generates an ACK confirmation signal and feeds it back to the rotating end via the wireless link. Upon receiving the confirmation, the rotating end wireless transmitter deletes the corresponding confirmed buffer and continues sending the next frame. If a missing frame, out-of-order frame, duplicate frame, or CRC check failure is detected, the fixed-end computer 4 sends a NACK or missing frame request, generating a retransmission request containing the task number, collector number, and missing frame sequence number. This request is fed back to the rotating end wireless transmitter via the wireless link through the fixed-end wireless receiver 3. Upon receiving the retransmission request, the rotating end wireless transmitter queries its local circular buffer and retrieves the corresponding frame sequence number of the collected data frame, retransmitting it. The fixed-end computer 4 verifies the retransmitted data frame again; if the verification passes, it is written to the corresponding data queue or sent to the host computer for processing. If all IMU data that should be included under the same sampling batch number is not completely received, the fixed-end computer 4 can generate a corresponding retransmission request based on the missing collector number, SPI channel number, chip select number, or frame sequence number.

[0061] When the wireless link quality degrades, the rotating end wireless transmitter can implement strategies such as channel switching, transmission power adjustment, packet transmission, reducing upload frequency, or activating a backup link to ensure stable data transmission. These strategies do not alter the core architecture of multi-station IMU data being aggregated at the rotating end and transmitted wirelessly to the fixed end.

[0062] This implementation uses a dual verification mechanism of frame sequence number and CRC checksum to accurately identify data loss, corruption, and other issues that occur during wireless transmission. Combined with a local ring buffer and directional retransmission mechanism at the rotating end, it can proactively recover abnormal data when wireless link quality fluctuates, improving the integrity and reliability of batch calibration data in wireless transmission scenarios and preventing data packet loss from affecting the validity of calibration results. The bidirectional wireless link design achieves closed-loop feedback of transmission status without adding a wired cross-border channel, ensuring stable transmission of high-capacity batch calibration data.

[0063] This embodiment provides a multi-station IMU batch calibration method based on distributed data acquisition and wireless transmission, applicable to the multi-station IMU batch calibration system described in any of the foregoing embodiments. The specific process of the method is as follows: S1. Install multiple IMUs to be calibrated in the corresponding positions of the IMU calibration array 2 on the rotating end I of the turntable, and complete the positioning, locking, and electrical connection of the SPI interface; the fixed end computer 4 reads or enters the mapping table between the position number and the IMU number, configures the mapping relationship between the position number, IMU number, data acquisition unit number, SPI channel number, and chip select number in the system, and completes the power-on self-test and parameter configuration of each device. The fixed end computer 4 issues calibration task parameters, including at least one of the following: sampling frequency, sampling duration, task number, turntable motion program, and wireless transmission parameters. The turntable prepares to execute position, speed, or swinging motion according to the calibration program.

[0064] S2. The synchronization trigger signal source outputs a synchronization trigger signal to all SPI distributed data acquisition units synchronously according to a preset sampling frequency. Each SPI distributed data acquisition unit responds to the synchronization trigger signal and starts data acquisition within the same sampling period: For IMUs to be calibrated under different SPI host interfaces, the control unit schedules multiple SPI host interfaces to perform reading in parallel; for multiple IMUs to be calibrated under the same SPI host interface, the chip select signal output by the chip select control unit sequentially selects each IMU within one sampling period, and reads angular velocity, acceleration, temperature, and status register data in a time-division multiplexing manner through SPI burst reading; the acquired data is directly written to the local buffer unit for temporary storage through the DMA receiving unit.

[0065] The S3 and SPI distributed data acquisition units write a unified sampling batch number to all IMU data acquired within the same sampling period. At the same time, they bind the corresponding IMU's workstation number, acquisition unit number, SPI channel number, chip select number, IMU number and other identification information, and add timestamp, turntable status information, frame sequence number and CRC check code to encapsulate and form a standard acquisition data frame.

[0066] S4. Each SPI distributed data acquisition unit sends the encapsulated acquisition data frames to the rotating end aggregation device via the Ethernet interface, completing high-speed aggregation of multiple data streams within the rotating end I of the turntable. All aggregated acquisition data frames are then sent to the rotating end wireless transmission device, which transmits them across the rotation boundary via a wireless link to the fixed end wireless receiving device 3 at the fixed end II of the turntable. During transmission, the rotating end wireless transmission device stores the transmitted frames in a local circular buffer, awaiting confirmation from the fixed end.

[0067] S5. The fixed-end wireless receiving device 3 receives the data frames transmitted via the wireless link and forwards them to the fixed-end computer 4. The fixed-end computer 4 first parses the frame header and performs a CRC check to verify data integrity; then, it performs continuity detection based on the frame sequence number to identify missing frames, out-of-order frames, and duplicate frames.

[0068] S6. If a missing frame, out-of-order data, or verification failure is detected, the fixed-end computer 4 generates a retransmission request containing the task number, collector number, and corresponding frame sequence number, and sends it to the rotating end via the wireless reverse link through the fixed-end wireless receiving device 3. After receiving the retransmission request, the rotating-end wireless transmitting device extracts the acquisition data frame with the corresponding frame sequence number from its local circular buffer and retransmits it. The fixed-end computer 4 verifies the retransmitted data again until successful reception is confirmed.

[0069] S7. If the verification passes and the frame sequence is complete, the fixed-end computer 4 merges all data within the same sampling period according to the sampling batch number, and then allocates the data of each IMU to the corresponding data queue according to the mapping relationship between the collector number, SPI channel number, chip select number and station number, thus completing the rearrangement of multi-station data; at the same time, according to the turntable status information in the data frame, the IMU acquisition data is aligned with the corresponding turntable motion status.

[0070] S8 and the fixed-end computer 4 organize the rearranged and aligned multi-station IMU data into a structured batch calibration dataset, and output calibration data files organized by IMU number or station number, stored in HDF5, BIN or CSV format for subsequent IMU calibration parameter calculation.

[0071] In this invention, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0072] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0073] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit them. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the scope of the technology disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention.

Claims

1. A multi-station IMU batch calibration system based on distributed acquisition and wireless transmission, characterized in that, include: An IMU calibration array, located at the rotating end of the turntable, is used to install multiple IMUs to be calibrated. At least one SPI distributed data acquisition unit is set at the rotating end of the turntable and connected to the plurality of IMUs to be calibrated via an SPI interface; A synchronous trigger signal source is communicatively connected to the SPI distributed data acquisition unit and is used to output a synchronous trigger signal; The SPI distributed data acquisition unit responds to the synchronization trigger signal, acquires data from the IMU to be calibrated within the same sampling period and writes the same sampling batch number, and encapsulates and generates an acquisition data frame by combining the identification information of the IMU to be calibrated. A rotating end aggregation device is disposed at the rotating end of the turntable and connected to the SPI distributed data acquisition unit for aggregating the acquired data frames; A rotating end wireless transmitting device is disposed at the rotating end of the turntable and connected to the rotating end aggregation device, and is used to transmit the aggregated data frames through a wireless link. A fixed-end wireless receiving device is installed at the fixed end of the turntable to receive the aggregated data frames. as well as A fixed-end computer, located at the fixed end of the turntable and connected to the fixed-end wireless receiving device, is used to merge data from the same sampling period according to the sampling batch number in the acquired data frame, and to rearrange the data of the IMU to be calibrated according to the identification information to generate a batch calibration dataset.

2. The multi-station IMU batch calibration system based on distributed acquisition and wireless transmission according to claim 1, characterized in that, The SPI distributed data acquisition unit includes a control unit, a multi-channel SPI host interface, a chip select control unit, a direct memory access receiving unit, and a local cache unit. The control unit is used to control the multi-channel SPI host interface to read the data of the IMU to be calibrated, the chip select control unit is used to select the corresponding IMU to be calibrated, and the collected data is written to the local cache unit through the direct memory access receiving unit.

3. The multi-station IMU batch calibration system based on distributed acquisition and wireless transmission according to claim 2, characterized in that, Multiple IMUs to be calibrated connected to the same SPI host interface share the SPI clock signal line and master output / slave input signal line, and are respectively connected to the chip select terminal of the corresponding IMU to be calibrated through the independent chip select signal line output by the chip select control unit.

4. The multi-station IMU batch calibration system based on distributed acquisition and wireless transmission according to claim 1, characterized in that, The identification information includes the workstation number and the collector number when there are multiple SPI distributed data collectors.

5. The multi-station IMU batch calibration system based on distributed acquisition and wireless transmission according to claim 1, characterized in that, The acquired data frame also includes turntable status information, which includes at least one of turntable angle, turntable angular velocity, turntable motion stage, and timestamp, so that the fixed-end computer can align the data of the IMU to be calibrated with the corresponding turntable motion state after rearrangement.

6. The multi-station IMU batch calibration system based on distributed acquisition and wireless transmission according to claim 1, characterized in that, The rotating end aggregation device is an Ethernet switch or an Ethernet aggregation controller; multiple SPI distributed data acquisition units are connected to the rotating end aggregation device via Ethernet wired interfaces to perform high-speed data aggregation inside the rotating end of the turntable. The Ethernet wired interfaces are not used as transmission channels across the rotating boundary of the turntable.

7. The multi-station IMU batch calibration system based on distributed acquisition and wireless transmission according to claim 1, characterized in that, The acquired data frame also includes a frame sequence number and a checksum, and the rotating end wireless transmitter maintains a local buffer. When the fixed end computer detects that the received acquired data frame has missing frames, out-of-order frames, or a checksum failure based on the checksum and frame sequence number, it generates a retransmission request containing the missing frame sequence number and sends it back to the rotating end wireless transmitter via the wireless link. The rotating end wireless transmitter reads the corresponding acquired data frame from the local buffer according to the retransmission request and retransmits it.

8. A batch calibration method for multi-station IMUs based on distributed acquisition and wireless transmission, characterized in that, Applied to the multi-station IMU batch calibration system as described in any one of claims 1 to 7, the method comprises: Multiple IMUs to be calibrated are installed in the IMU calibration array at the rotating end of the turntable; A synchronous trigger signal is output to the SPI distributed data acquisition unit located at the rotating end of the turntable through a synchronous trigger signal source; The SPI distributed data acquisition unit responds to the synchronization trigger signal, acquires data from the IMU to be calibrated through the SPI interface within the same sampling period, writes the same sampling batch number, and encapsulates and generates a data acquisition frame by combining the identification information of the IMU to be calibrated. The rotating end gathering device gathers the collected data frames and transmits them to the fixed end wireless receiving device at the fixed end of the turntable via a wireless link through the rotating end wireless transmitting device. The fixed-end computer located at the fixed end of the turntable acquires the data frames received by the fixed-end wireless receiving device, merges data from the same sampling period according to the sampling batch number in the data frames, and rearranges the data of the IMU to be calibrated according to the identification information to generate a batch calibration dataset.

9. The multi-station IMU batch calibration method based on distributed acquisition and wireless transmission according to claim 8, characterized in that, The SPI distributed data acquisition unit includes a control unit, a multi-channel SPI host interface, a chip select control unit, a direct memory access receiver unit, and a local cache unit. The methods for collecting data from the IMU to be calibrated include: For multiple IMUs to be calibrated connected to the same SPI host interface, the chip select signal output by the chip select control unit is used to select them sequentially within one sampling period and read them in a time-division multiplexing manner. For IMUs to be calibrated connected to different SPI host interfaces, the control unit controls multiple SPI host interfaces to perform parallel readings. Furthermore, the collected data is written into the local cache unit through the direct memory access receiving unit.

10. The multi-station IMU batch calibration method based on distributed acquisition and wireless transmission according to claim 8, characterized in that, The acquired data frame also includes a frame sequence number and a checksum; After the fixed-end computer acquires the collected data frame, the method further includes: The fixed-end computer performs verification and frame sequence number continuity detection on the acquired data frames based on the verification code and frame sequence number. If a missing frame or verification failure is detected, the fixed-end computer generates a retransmission request containing the sequence number of the missing frame and feeds it back to the rotating end wireless transmission device of the turntable via a wireless link. The rotating end wireless transmitting device reads the acquisition data frame with the corresponding frame number from the local buffer according to the retransmission request and retransmits it.

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