Railway mobile equipment ranging control method based on millimeter wave secondary radar

Abstract

The millimeter wave secondary radar-based track mobile device ranging control method comprises five steps: S1: a vehicle-mounted interrogator generates a coded interrogation signal in a millimeter wave frequency band and transmits the coded interrogation signal to a transponder arranged along a track; S2: after receiving the coded interrogation signal conforming to a predefined coding format, the transponder generates a millimeter wave response signal carrying a unique identity; S3: a vehicle-mounted receiver extracts identity and carrier phase information in the millimeter wave response signal, and forms an accurate distance measurement value resistant to multipath interference; S4: a control unit fuses the accurate distance measurement value with vehicle-mounted sensor data, and generates real-time pose information with millimeter-level precision; and S5: an actuator adjusts a running state of a mobile device according to a dynamic control instruction, and realizes cooperative running or accurate parking control of the track mobile device. The millimeter wave secondary radar-based track mobile device ranging control method can solve the problems of high-precision continuous ranging and anti-interference control of the track mobile device.

Description

Technical Field

[0001] The present invention relates to the technical field of rail transit ranging control, and in particular to a ranging control method for rail transit mobile equipment based on millimeter-wave secondary radar. Background Art

[0002] Current distance measurement and control for mobile rail equipment (such as trains and locomotives) primarily relies on satellite positioning, track circuits, point transponders, and traditional radar. Satellite positioning fails in obstructed environments like tunnels and elevated areas, and its meter-level accuracy is insufficient. Track circuits can only provide occupancy information for sections within a hundred meters, failing to meet continuous positioning requirements. Point transponders must be densely deployed, and the distance between two points relies on mileage calculations, resulting in cumulative errors. Traditional millimeter-wave primary radar is susceptible to multipath interference in metal-dense rail environments, making it difficult to distinguish between multiple targets and small, slow-moving objects.

[0003] Furthermore, existing technologies suffer from three major flaws: First, positioning accuracy and continuity are difficult to reconcile. For example, the error of a combined satellite and inertial navigation solution rapidly increases after signal loss. Second, the control closed-loop response lags because ranging data is not deeply embedded in the real-time control algorithm. Third, anti-interference capabilities are weak, resulting in a high false alarm rate in complex electromagnetic environments. In recent years, millimeter-wave radar has been introduced into rail transit due to its weather resistance and high resolution. However, primary radar mode suffers from a degraded signal-to-noise ratio in the presence of strong rail reflections and is unable to identify specific targets.

[0004] While secondary radar has mature applications in aviation, its direct application to rail applications presents new challenges: high transponder power and maintenance costs, significant Doppler shift due to high-speed movement, and severe signal attenuation in metallic environments. Existing patented technologies focus on improving single ranging methods or general radar algorithms. They lack systematic solutions to address the pain points of rail mobile equipment, such as metal multipath interference, multi-target identification, and real-time control. Furthermore, there are no solutions that fully integrate millimeter-wave secondary radar ranging with dynamic control loops. Summary of the Invention

[0005] In view of the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a ranging control method for mobile equipment on rails based on millimeter-wave secondary radar, which is used to solve the problems of high-precision continuous ranging and anti-interference control of mobile equipment on rails. The present invention uses a vehicle-mounted millimeter-wave interrogator to transmit a coded signal to trigger transponders along the route. The directionally returned response signal carrying an identity identifier is combined with carrier phase and Doppler shift detection to resist multipath interference. After time-division multiple access is used to separate multiple targets, millimeter-level distance measurements are generated. The vehicle-mounted sensor data is integrated to construct real-time posture information, and control instructions are dynamically calculated based on its deviation from the preset trajectory. The equipment status is adjusted through a closed-loop actuator to achieve coordinated operation or millimeter-level precision parking.

[0006] The present invention provides a ranging control method for a track mobile device based on a millimeter-wave secondary radar, comprising:

[0007] S1: The onboard interrogator generates a coded interrogation signal in the millimeter wave band and transmits it to the transponders deployed along the track;

[0008] S2: After receiving the interrogation signal in a predefined coding format, the transponder generates a millimeter-wave response signal carrying a unique identity and transmits it directionally;

[0009] S3: The on-board receiver extracts the ID and carrier phase information from the millimeter-wave reply signal, combines it with the Doppler shift detection results, and uses the time-division multiple access protocol to separate multi-target interference, forming an accurate distance measurement value that is resistant to multipath interference.

[0010] S4: The control unit fuses the precise distance measurement with the vehicle's sensor data to generate real-time position information with sub-meter accuracy. It then calculates dynamic control instructions based on the deviation between this position information and the preset trajectory.

[0011] S5: The actuator adjusts the operating status of the mobile equipment according to the dynamic control instructions, and at the same time inputs the equipment status feedback data into the control unit to form a closed-loop control, thereby realizing the coordinated operation or precise parking control of the track mobile equipment.

[0012] In one embodiment of the present invention, the process of generating a coded interrogation signal includes: generating a dynamically changing pseudo-random sequence based on a preset encryption algorithm as the basis for signal encoding, modulating the coded information onto multiple mutually orthogonal subcarriers through orthogonal frequency division multiplexing technology to form a broadband millimeter wave signal with anti-interception characteristics; the predefined coding format includes a device type identification segment and a geographic location identification segment, and the transponder decides whether to respond by verifying the matching degree between the device type identification segment and its own registration information, and writes the absolute coordinate information of the corresponding track into the geographic location identification segment of the millimeter wave response signal; in step S3, the on-board receiver realizes centimeter-level positioning of the mobile device relative to the track coordinate system by analyzing the absolute coordinate information and the carrier phase difference.

[0013] In one embodiment of the present invention, the implementation of directional transmission includes: the transponder uses a phased array antenna array to receive the interrogation signal and determines the azimuth of the vehicle-mounted interrogator by calculating the signal arrival angle; when generating the millimeter wave response signal, the beam pointing angle of the phased array antenna array is controlled to align with the azimuth for directional beamforming transmission; the vehicle-mounted receiver synchronously starts the receiving beam scanning in step S3, locks the beam pointing when the response signal from the target azimuth is detected, and suppresses the reflection interference from the non-target direction by dynamically adjusting the receiving beam width.

[0014] In one embodiment of the present invention, the formation of an accurate distance measurement value that is resistant to multipath interference includes: performing multi-cycle continuous sampling of carrier phase information, using the least squares method to fit the phase change curve to eliminate jump errors; converting the Doppler frequency shift detection result into a radial velocity component, and calculating the dynamic distance compensation amount in combination with the carrier wavelength; allocating an independent time window to each transponder in the time division multiple access protocol, and when the response signals of different transponders overlap within the time window, using an iterative interference elimination algorithm to gradually remove the interference signal components.

[0015] In one embodiment of the present invention, the on-board sensor data fusion process includes: obtaining displacement pulse counts from the odometer and obtaining three-axis angular velocity and acceleration information from the inertial measurement unit; constructing a Kalman filter with precise distance measurement values ​​as observation quantities, and correcting the odometer cumulative error and the inertial measurement unit drift error as state variables in real time; and outputting position information including the displacement of the mobile device in the tangential direction of the track, the offset in the normal direction, and the heading deflection angle.

[0016] In one embodiment of the present invention, the calculation of dynamic control instructions includes: when achieving coordinated operation, constructing a relative motion model based on the precise distance measurement values ​​of adjacent mobile devices, and generating speed coordination instructions with the goal of maintaining a fixed spacing; when achieving precise parking, inputting the preset parking point coordinates and real-time posture information into a sliding mode variable structure controller to generate a deceleration instruction that is adaptive to the braking curve; the deviation amount includes a weighted comprehensive evaluation value of the displacement deviation, speed deviation, and heading angle deviation.

[0017] In one embodiment of the present invention, the dynamic change of the pseudo-random sequence follows the following rules: a periodic seed update signal is generated based on the precise clock of the satellite timing module, and a nonlinear shift register is used to regenerate the sequence during each update; a sequence version identification field is set in the interrogation signal frame structure, and the transponder synchronously switches the local decoding sequence library based on this field; and the on-board receiver rejects disguised signals from unauthorized devices by verifying the synchronization between the sequence version identification field and the local sequence.

[0018] In one embodiment of the present invention, the beam control of the phased array antenna array also includes: establishing a track equipment signal feature database at the transponder end to store the radio frequency fingerprint information of authorized on-board interrogators; extracting its carrier frequency offset and modulation error rate characteristics when receiving the interrogation signal, and matching and verifying them with the database; and initiating the directional response mechanism only when the radio frequency fingerprint match is successful and the signal strength exceeds the threshold.

[0019] In one embodiment of the present invention, the execution of the iterative interference cancellation algorithm includes: sorting the overlapping response signals in descending order of signal strength, and preferentially demodulating the coding information of the strongest signal; reconstructing the waveform of the demodulated signal based on its coding parameters, and subtracting the reconstructed waveform from the original mixed signal; and repeatedly performing the sorting demodulation and waveform cancellation operations on the remaining signals until all target signals are separated.

[0020] In one embodiment of the present invention, the design of the Kalman filter includes: establishing a functional relationship model between the track curvature radius and the speed of the mobile device as a constraint condition for the angular velocity measurement of the inertial measurement unit; when the precise distance measurement value is lost continuously for more than a set period, enabling the tightly coupled solution mode of the odometer and the inertial measurement unit; when passing through the track switch area, introducing the track topology information provided by the transponder as the filter topology constraint matrix.

[0021] The present invention provides a ranging control method for track mobile equipment based on millimeter-wave secondary radar. The method triggers transponders along the line by transmitting coded signals through a vehicle-mounted millimeter-wave interrogator, utilizes the directionally returned response signal carrying an identity identifier, combines carrier phase and Doppler frequency shift detection to resist multipath interference, and generates centimeter-level distance measurement values ​​after multiple targets are separated by time division multiple access. The method also integrates vehicle-mounted sensor data to construct real-time posture information, dynamically calculates control instructions based on its deviation from a preset trajectory, and adjusts the equipment status through a closed-loop actuator to achieve coordinated operation or millimeter-level precise parking. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 The present invention is a flow chart of a method for ranging control of a track mobile equipment based on millimeter-wave secondary radar. DETAILED DESCRIPTION

[0024] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. The details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other unless they conflict.

[0025] It should be noted that the illustrations provided in the following embodiments are merely schematic illustrations of the basic concept of the present invention. Therefore, the illustrations only show components related to the present invention and are not drawn according to the number, shape, and size of components in actual implementation. In actual implementation, the type, quantity, and proportion of each component may be changed arbitrarily, and the component layout may also be more complex.

[0026] In the following description, numerous details are discussed to provide a more thorough explanation of the embodiments of the present invention. However, it will be apparent to those skilled in the art that the embodiments of the present invention may be practiced without these specific details. In other embodiments, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring the embodiments of the present invention.

[0027] See Figure 1 , shown is the distance measurement control method for a track mobile device based on a millimeter-wave secondary radar of the present invention. The distance measurement control method for a track mobile device based on a millimeter-wave secondary radar of the present invention includes five steps: S1: the on-board interrogator generates a coded interrogation signal in the millimeter-wave frequency band and transmits it to the transponder deployed along the track; S2: after receiving the interrogation signal in accordance with the predefined coding format, the transponder generates a millimeter-wave response signal carrying a unique identity and transmits it in a directionally direction; S3: the on-board receiver extracts the identity and carrier phase information from the millimeter-wave response signal, combines it with the Doppler frequency shift detection result, separates multi-target interference through the time division multiple access protocol, and forms an accurate distance measurement value that is resistant to multipath interference; S4: the control unit fuses the accurate distance measurement value with the on-board sensor data to generate real-time posture information with sub-meter accuracy, and calculates dynamic control instructions based on the deviation between the posture information and the preset running trajectory; S5: the actuator adjusts the running state of the mobile device according to the dynamic control instruction, and at the same time inputs the device status feedback data into the control unit to form a closed-loop control, thereby realizing the coordinated operation or precise parking control of the track mobile device.

[0028] like Figure 1As shown in the figure, the core framework of a ranging control method for mobile track equipment based on millimeter-wave secondary radar is constructed. Its technical implementation begins with an onboard interrogator generating a millimeter-wave coded signal in a specific frequency band. This signal generation relies on a millimeter-wave RF chipset. The baseband processor modulates a preset binary code sequence (such as a cyclic redundancy check code) onto a 60-81 GHz carrier, forming a highly directional electromagnetic beam that radiates along the track. Passive or active transponders deployed along the track detect the signal at the receiving end via a millimeter-wave receiver link. When the received signal's coding format matches a reference template pre-stored in local memory, the transponder control unit generates a unique feedback signal. This feedback signal is remodulated to the millimeter-wave frequency band and transmitted using a directional antenna array (such as a microstrip patch array) for spatial beam focusing. This ensures that the signal energy is concentrated in the direction of the interrogator to reduce environmental scattering interference. After the onboard receiver captures the response signal, it is first down-converted to an intermediate frequency (IF) using a mixer and then sampled by an analog-to-digital converter to produce a digital signal stream. The signal processing unit extracts the identity field from it to complete target authentication, and uses phase-locked loop technology to demodulate the carrier phase information. The analysis of phase information needs to be combined with the Doppler frequency shift effect caused by high-speed movement: the frequency deviation of the signal spectrum is analyzed by fast Fourier transform, and the radial velocity component is calculated. In order to overcome the multipath reflection interference caused by metal structures such as rails, the system uses a time division multiple access protocol to divide the communication time slots - the control center allocates an independent response time window to each transponder, and the on-board interrogator polls transponders in different areas according to a predetermined sequence. When multiple response signals overlap in the time domain, the digital signal processor separates them based on the signal arrival time difference and coding orthogonality, and finally calculates the distance measurement value with centimeter-level accuracy through the relationship between phase difference and wavelength (Δφ=4πd / λ).

[0029] Furthermore, after receiving the distance values, the control unit simultaneously collects pulse counts from the onboard odometer and three-axis angular velocity data from the inertial measurement unit. An extended Kalman filter is used for multi-source fusion: distance measurements are used as observations to correct for accumulated odometer errors, while inertial data is used to compensate for posture estimation during periods of missing ranging signals. The fused output includes the mobile device's real-time position (longitudinal displacement s), lateral offset δ, and heading angle θ in the track coordinate system. This posture information is compared with a preset trajectory (such as a train operation plan). If the longitudinal displacement deviation exceeds a threshold, a proportional-integral-derivative controller generates an acceleration adjustment command; if the lateral offset exceeds the limit, a steering compensation command is output. The traction motor controller or hydraulic brake system in the actuator dynamically adjusts the device's motion based on these commands, while simultaneously feeding back actual speed and position information to the control unit to form a closed loop. When applied to multi-device collaborative scenarios, the system constructs a dynamic safety spacing model by exchanging posture information between devices in real time, enabling automated platooning. In precision parking scenarios, an exponentially decaying braking curve is generated based on the remaining displacement from the target point, ultimately achieving millimeter-level parking accuracy.

[0030] like Figure 1 As shown, after receiving the distance values, the control unit simultaneously collects pulse counts from the onboard odometer and three-axis angular velocity data from the inertial measurement unit. An extended Kalman filter is used for multi-source fusion: distance measurements are used as observations to correct for accumulated odometer errors, while inertial data is used to compensate for posture estimation during periods of missing ranging signals. The fused output includes the mobile device's real-time position (longitudinal displacement s), lateral offset δ, and heading angle θ in the track coordinate system. This posture information is compared with a preset trajectory (such as a train operation plan). If the longitudinal displacement deviation exceeds a threshold, a proportional-integral-derivative controller generates an acceleration adjustment command; if the lateral offset exceeds the limit, a steering compensation command is output. The traction motor controller or hydraulic brake system in the actuator dynamically adjusts the device's motion based on these commands, while simultaneously feeding back actual speed and position information to the control unit to form a closed loop. When applied to multi-device collaborative scenarios, the system constructs a dynamic safety spacing model by exchanging posture information between each device in real time, enabling automated platooning. In precision parking scenarios, an exponentially decaying braking curve is generated based on the remaining displacement from the target point, ultimately achieving millimeter-level parking accuracy.

[0031] In an embodiment of the application, the generation mechanism of the focused coded interrogation signal is integrated with the responder's geographic information set. The core innovation lies in the dynamic encryption coding and absolute coordinate binding. At the signal generation layer, a non-linear feedback shift register is built in the baseband processor, whose initial seed is updated by the precise clock of the vehicle-mounted timing module (such as the Beidou second pulse). At each update, the register generates a new pseudo-random sequence through a chaotic mapping algorithm, and the sequence length matches the millimeter wave signal bandwidth to ensure the spread spectrum gain. The modulation process adopts the orthogonal frequency division multiplexing technology: the pseudo-random sequence is divided into multiple sub-segments, which are modulated onto subcarriers with a spacing of Δf to form a wideband signal resistant to frequency-selective fading. The signal frame structure is designed in three segments: the preamble contains the synchronization header and sequence version identification, the payload segment writes the dynamic encryption code and device type code, and the check segment uses the Reed-Solomon error correction coding. After receiving the signal, the responder first identifies the synchronization header through the matched filter, and then retrieves the local stored decoding key library according to the sequence version identification. After the device type code and the pre-registered information (such as the rail segment number to which the responder belongs) are compared and consistent, the response mechanism is activated. At this time, the responder reads the pre-stored absolute geographic coordinates (such as the longitude and latitude in the WGS-84 coordinate system) from the non-volatile memory, and encodes them with the identity to generate the response signal. The geographic position identification segment uses differential encoding compression technology: only the coordinate offset relative to the rail reference point is transmitted, reducing the data transmission load. When the vehicle-mounted receiver analyzes the response signal, it first verifies the data integrity through the cyclic redundancy check, and then extracts the absolute coordinate information. The positioning solution adopts a two-stage fusion strategy: in the first stage, the carrier phase interference principle is used to calculate the signal incidence angle through the phase difference measured by two receiving antennas, and the responder coordinate is used to solve the rough position; in the second stage, the carrier phase integer ambiguity resolution algorithm is introduced, and the over-determined equation set is constructed through multi-frequency point observation values, and the LAMBDA method is used to search for the optimal ambiguity combination, and finally the centimeter-level positioning result of the mobile device in the track coordinate system is obtained. This process needs to compensate for the coordinate drift caused by the thermal expansion and contraction of the steel rail: the control center periodically broadcasts the rail deformation correction parameters to the responder through the optical fiber network, and the responder updates the stored absolute coordinate values accordingly.

[0032] Furthermore, the core technology for anti-interference mechanisms for directional transmission and reception lies in dynamic phased array beam control. The transponder's phased array antenna array consists of M×N microstrip antenna elements, each connected to a programmable phase shifter. When the array detects an incoming interrogation signal, the digital signal processor calculates the signal's angle of arrival using a multiple signal classification algorithm. First, the received signal's covariance matrix is ​​calculated, then its eigenvalue decomposition is performed. The spatial spectrum function is constructed using the orthogonality between the noise subspace and the steering vector. The angle corresponding to the spectrum peak is the estimated direction of arrival. This angle information is input into the beam control module, which drives the phase shifters to adjust the phase offset of each antenna element so that the main lobe of the transmitted beam is aligned with the incoming signal. Beamforming uses Taylor weighting to suppress sidelobe levels and prevent signal energy leakage into adjacent track areas. The onboard receiver simultaneously initiates the adaptive beamforming process. The receiving array utilizes a dimensionality reduction processing architecture: the antenna elements are divided into multiple subarrays. The output signals of each subarray are synthesized through analog beamforming and then fed into the digital processing unit. During the initial scanning phase, the receiver iteratively optimizes the beam weight vector using a gradient descent algorithm to maximize the array gain in the target direction. Once the reply signal is locked onto, the system monitors the rate of change of the signal's arrival angle in real time. If the rate of change exceeds a threshold (indicating a sharp turn), it switches to predictive tracking mode. This mode uses the angular velocity data from the inertial measurement unit (IMU) as input to a Kalman filter to predict the next direction of arrival and pre-adjust the beam pointing direction.

[0033] like Figure 1As shown, to combat strong reflection interference caused by metal structures, the system implements three-dimensional spatial filtering. In the elevation dimension, a zero-point formation technique is employed, using a constrained optimization algorithm to generate a radiation null in the direction of rail reflection. In the azimuth dimension, a time-division multiple access protocol is incorporated to enable the receive beam only within the theoretical azimuth range of the transponder. A dynamic beamwidth adjustment strategy is implemented based on the signal-to-noise ratio. When an increase in interference power is detected, the beamwidth is automatically narrowed to 0.8 times the theoretical value to improve spatial resolution, while the transmit power is increased to compensate for gain loss. All beamsteering parameters are hardware-accelerated using a field-programmable gate array (FPGA), ensuring microsecond-level response latency to meet the requirements of high-speed mobility scenarios. The core technologies for precise distance measurement, which is robust against multipath interference, lie in dynamic carrier phase compensation and a multi-target separation algorithm. The onboard receiver continuously samples carrier phase information, using oversampling to capture instantaneous phase values ​​at a rate four times the signal bandwidth to construct a phase-time series dataset. To eliminate phase jumps caused by signal obstruction, the system uses a sliding window least squares fit: within a window of length N (N is adaptively adjusted by the speed of the mobile device), a cubic polynomial is used to fit the phase variation curve, and outliers that deviate from the fitted curve by more than three standard deviations are removed. The slope of the phase curve is used to calculate the integer multiple ambiguity of the carrier wavelength, which is resolved through a dual-frequency measurement method—simultaneously receiving reply signals in the 60GHz and 81GHz bands and using the wavelength difference between the two frequencies to construct an ambiguity-free equivalent wavelength. Doppler shift detection uses complex signal quadrature demodulation technology: the received signal is divided into in-phase and quadrature paths, and the instantaneous phase difference is calculated using an inverse tangent operation. The differential result is the instantaneous Doppler shift. This frequency shift is multiplied by the carrier wavelength and divided by four to obtain the radial velocity compensation term, which is used to correct the periodic ranging error caused by the high-speed movement of the device.

[0034] Furthermore, the implementation of the time-division multiple access protocol relies on high-precision time synchronization: the onboard interrogator obtains a nanosecond clock from a satellite timing module and embeds a timestamp in the interrogation signal header. Upon receiving the interrogation signal, the transponder records the local response time and encodes the time difference in the response signal. The control center assigns each transponder a dynamically adjustable time slot length, adjusted based on historical communication quality indices—longer slots are allocated to tunnel sections with severe signal attenuation. When the response signals from different transponders overlap in the time domain, an iterative interference cancellation algorithm is initiated: first, a discrete Fourier transform is performed on the mixed signal to obtain a spectrum, and the dominant frequency corresponding to the amplitude peak is detected. The strongest signal source is identified based on a preset frequency-to-transponder mapping table, and its encoded information is demodulated using the Viterbi algorithm. The time domain waveform of this signal is reconstructed and subtracted from the original signal, with the remaining signal fed into the next processing loop. This process is repeated until all identifiable signals are separated, ultimately outputting a clean signal for each target for phase ranging. Rail multipath effects are additionally mitigated using spatial filtering: reflection paths are predicted based on an electronic track map, creating suppression notches in the receive beam pattern.

[0035] The present invention discloses a ranging control method for track mobile equipment based on millimeter-wave secondary radar. The method triggers transponders along the line by transmitting coded signals via a vehicle-mounted millimeter-wave interrogator, utilizes the directionally returned response signal carrying an identity identifier, combines carrier phase and Doppler shift detection to resist multipath interference, and generates centimeter-level distance measurement values ​​after multiple targets are separated by time-division multiple access. The method also integrates vehicle-mounted sensor data to construct real-time posture information, dynamically calculates control instructions based on its deviation from a preset trajectory, and adjusts the equipment status through a closed-loop actuator to achieve coordinated operation or millimeter-level precise parking.

[0036] Therefore, the millimeter-wave secondary radar-based ranging control method for a track mobile device of the present invention can solve the problems of high-precision continuous ranging and anti-interference control of a track mobile device.

[0037] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A ranging control method for a track mobile device based on millimeter wave secondary radar, characterized in that: include: S1: The onboard interrogator generates a coded interrogation signal in the millimeter wave band and transmits it to the transponders deployed along the track; The generation process of the coded interrogation signal includes: generating a dynamically changing pseudo-random sequence as a signal encoding basis based on a preset encryption algorithm, modulating the coded information onto multiple mutually orthogonal subcarriers through orthogonal frequency division multiplexing technology to form a broadband millimeter wave signal with anti-interception characteristics; the predefined coding format includes a device type identification segment and a geographic location identification segment, the transponder determines whether to respond by verifying the match between the device type identification segment and its own registration information, and writes the absolute coordinate information of the corresponding track into the geographic location identification segment of the millimeter wave response signal; in step S3, the on-board receiver realizes centimeter-level positioning of the mobile device relative to the track coordinate system by analyzing the absolute coordinate information and the carrier phase difference. S2: After receiving the interrogation signal in a predefined coding format, the transponder generates a millimeter-wave response signal carrying a unique identity and transmits it directionally; S3: The on-board receiver extracts the identity identifier and carrier phase information from the millimeter wave response signal, combines the Doppler frequency shift detection result, and separates multi-target interference through a time division multiple access protocol to form an accurate distance measurement value that is resistant to multipath interference. The formation of the accurate distance measurement value resistant to multipath interference includes: performing multi-cycle continuous sampling of the carrier phase information, fitting the phase change curve using the least squares method to eliminate jump errors; converting the Doppler frequency shift detection result into a radial velocity component, and calculating a dynamic distance compensation amount in combination with the carrier wavelength; in the time division multiple access protocol, allocating an independent time window to each transponder. When the response signals of different transponders overlap within the time window, an iterative interference cancellation algorithm is used to gradually remove the interference signal components. S4: The control unit fuses the precise distance measurement value with the vehicle-mounted sensor data to generate real-time posture information with sub-meter accuracy, and calculates dynamic control instructions based on the deviation between the posture information and the preset running trajectory; S5: The actuator adjusts the operating state of the mobile device according to the dynamic control instruction, and inputs the device status feedback data into the control unit to form a closed-loop control, thereby realizing the coordinated operation or precise parking control of the track mobile device.

2. The method for controlling ranging of a track mobile device based on millimeter-wave secondary radar according to claim 1, characterized in that: The implementation of the directional transmission includes: the transponder uses a phased array antenna array to receive the interrogation signal and determines the azimuth of the on-board interrogator by calculating the signal arrival angle; when generating the millimeter wave response signal, the beam pointing angle of the phased array antenna array is controlled to align with the azimuth to perform directional beamforming transmission; the on-board receiver synchronously starts the receiving beam scanning in step S3, locks the beam pointing when the response signal from the target azimuth is detected, and suppresses the reflection interference from the non-target direction by dynamically adjusting the receiving beam width.

3. The method for controlling ranging of a track mobile device based on millimeter-wave secondary radar according to claim 1, characterized in that: The on-board sensor data fusion includes: obtaining displacement pulse counts from the odometer and obtaining three-axis angular velocity and acceleration information from the inertial measurement unit; constructing a Kalman filter with precise distance measurements as observations, and using the odometer cumulative error and the inertial measurement unit drift error as state variables for real-time correction; and outputting position information including the mobile device's displacement in the track tangent direction, offset in the normal direction, and heading deflection angle.

4. The method for ranging control of a track mobile device based on millimeter-wave secondary radar according to claim 1, characterized in that: The calculation of the dynamic control instructions includes: when achieving coordinated operation, constructing a relative motion model based on the precise distance measurement values ​​of adjacent mobile devices, and generating speed coordination instructions with the goal of maintaining a fixed spacing; when achieving precise parking, inputting the preset parking point coordinates and real-time posture information into the sliding mode variable structure controller to generate a deceleration instruction that is adaptive to the braking curve; the deviation amount includes a weighted comprehensive evaluation value of displacement deviation, speed deviation and heading angle deviation.

5. The method for ranging control of a track mobile device based on millimeter-wave secondary radar according to claim 1, characterized in that: The dynamic change of the pseudo-random sequence follows the following rules: a periodic seed update signal is generated based on the precise clock of the satellite timing module, and a nonlinear shift register is used to regenerate the sequence each time it is updated; a sequence version identification field is set in the interrogation signal frame structure, and the transponder synchronously switches the local decoding sequence library based on this field; the on-board receiver rejects disguised signals from unauthorized devices by verifying the synchronization between the sequence version identification field and the local sequence.

6. The method for ranging control of a track mobile device based on millimeter-wave secondary radar according to claim 2, characterized in that: The beam control of the phased array antenna array also includes: establishing a track equipment signal feature database at the transponder end to store the radio frequency fingerprint information of authorized on-board interrogators; extracting its carrier frequency offset and modulation error rate characteristics when receiving the interrogation signal, and matching and verifying them with the database; and initiating a directional response mechanism only when the radio frequency fingerprint match is successful and the signal strength exceeds a threshold.

7. The method for ranging control of a track mobile device based on millimeter-wave secondary radar according to claim 1, characterized in that: The execution of the iterative interference cancellation algorithm includes: sorting overlapping response signals in descending order of signal strength, preferentially demodulating the coded information of the strongest signal; reconstructing the waveform of the demodulated signal based on its coding parameters, and subtracting the reconstructed waveform from the original mixed signal; and repeating the sorting, demodulation and waveform cancellation operations on the remaining signals until all target signals are separated.

8. The method for ranging control of a track mobile device based on millimeter-wave secondary radar according to claim 3, characterized in that: The design of the Kalman filter includes: establishing a functional relationship model between the track curvature radius and the speed of the mobile device as a constraint condition for the angular velocity measurement of the inertial measurement unit; enabling the tightly coupled solution mode of the odometer and the inertial measurement unit when the precise distance measurement value is lost continuously for more than a set period; and introducing the track topology information provided by the transponder as the filter topology constraint matrix when passing through the track switch area.

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