Active control system for resonance risk of overpass construction on existing railway line

Abstract

This invention discloses an active control system for resonance risk during cross-extension construction on existing railway lines, belonging to the field of railway construction safety monitoring technology. The system addresses the problem of resonance caused when the excitation frequency of construction machinery approaches the natural frequency of the existing railway line. It includes an array of acceleration sensors installed on the railway line, a variable frequency drive device installed on the construction machinery crossing the line, and a controller. The controller pre-stores a set of natural frequencies of the railway line, reads the frequency command value from the variable frequency drive device as the current excitation frequency, and extracts the real-time dominant vibration frequency from the acceleration signal. When the difference between the current excitation frequency and the natural frequency is less than a preset frequency difference, the controller issues an adjustment command, causing the variable frequency drive device to change its frequency command value. After adjustment, continuous monitoring is performed within a preset time interval. If the difference between the real-time dominant vibration frequency and the natural frequency is again less than the preset frequency difference, the adjustment is repeated. This system is used for active control of resonance risk during cross-extension construction on existing railway lines.

Description

Technical Field

[0001] This invention relates to the field of railway construction safety monitoring technology. More specifically, this invention relates to an active control system for resonance risk during cross-line construction on existing railway lines. Background Technology

[0002] When carrying out overpass construction above existing railway lines, such as erecting bridges, installing overhead contact line supports, or dismantling overpass structures, construction machinery (such as rotary drilling rigs, vibratory hammers, and cranes) often needs to operate above or near the railway line. These machines generate periodic excitation forces during operation, the frequency of which depends on the machine's operating speed or the driving frequency of the vibrating mechanism. Existing railway lines, as continuous elastic structures, possess multiple natural frequencies (such as the bending frequency of the rails, the local frequency of the sleepers, and the resonant frequency of the ballast bed). When the excitation frequency of the construction machinery approaches a certain natural frequency of the railway line, resonance will occur, significantly amplifying the vibration amplitude. This can lead to loosening of rail fasteners, sleeper cracks, ballast bed frost heave, and even exceeding the limits of track geometry, seriously threatening train operation safety.

[0003] Currently, construction sites typically rely on experience to assess resonance risk. This involves estimating the natural frequency range of the railway line before construction using a simple frequency sweep test, and then trying to avoid that range during construction. However, this method has significant shortcomings. First, the natural frequency of the railway line is not constant during construction: temperature changes alter the rail's constraint stiffness, the track bed compaction gradually increases due to construction vibrations, and bridge piers may shift due to adjacent excavation. These factors all cause the natural frequency to drift. The pre-set safe frequency range may no longer be effective in actual construction. Second, the excitation frequency of construction machinery can also deviate from the set value due to load fluctuations (such as drill bits entering different geological layers or changes in boom angle), making it difficult for operators to detect and adjust in a timely manner. Third, judging resonance risk solely based on frequency proximity ignores the actual amplitude of the vibration response, easily misinterpreting environmental background vibrations (such as wind or trains passing near the track) as resonance, leading to unnecessary shutdowns or frequency adjustments and affecting construction progress. Furthermore, existing systems lack continuous monitoring after a single adjustment, and cannot automatically respond if resonance recurs. Currently, there is a lack of compensation methods for the deviation between the output frequency and the actual execution frequency of the variable frequency drive, resulting in insufficient control accuracy. These problems mean that resonance control during cross-pass construction on existing railway lines has long relied on manual experience, lacking a systematic technical solution that can proactively, reliably, and adaptively eliminate resonance risks. Summary of the Invention

[0004] One object of the present invention is to solve at least the above-mentioned problems and to provide at least the advantages that will be described later.

[0005] To achieve these objectives and other advantages of the present invention, an active control system for resonance risk during cross-slope construction on existing railway lines is provided, comprising: An acceleration sensor array, which is installed on an existing railway line, is used to collect vertical vibration signals of the railway line in real time. A variable frequency drive device is installed on the overhead construction machinery to receive frequency commands and adjust the excitation frequency of the overhead construction machinery according to the frequency commands. The controller is electrically connected to both the acceleration sensor array and the frequency converter drive device. The controller compares the absolute value of the difference between the current excitation frequency of the construction machinery and each natural frequency value in the pre-stored natural frequency set in the controller. The current excitation frequency of the construction machinery is obtained by the controller reading the frequency command value currently executed by the frequency converter drive device. The natural frequency set contains the natural frequency values ​​of multiple existing railway lines. When the absolute value of the difference is less than a preset frequency difference value, the controller determines that there is a risk of resonance and outputs an adjustment command to the frequency converter drive device. The preset frequency difference value ranges from 0.5 to 2.0 Hz. The variable frequency drive device responds to the adjustment command by increasing or decreasing its currently executed frequency command value by a preset unit adjustment amount to obtain the adjusted frequency command value. The unit adjustment amount ranges from 1.0 to 3.0 Hz. The controller is also used to continuously extract the real-time dominant vibration frequency from the vertical vibration signal collected by the acceleration sensor array within a preset time interval after outputting the adjustment command. If the absolute value of the difference between the real-time dominant vibration frequency and any natural frequency value in the set of natural frequencies is less than the preset frequency difference again, the controller will repeatedly output the adjustment command to the frequency conversion drive device. The preset time interval is in the range of 0.2~1.0s.

[0006] Preferably, the acceleration sensor array is arranged at equal intervals along the longitudinal direction of the existing railway line, and the distance between two adjacent acceleration sensors ranges from 5 to 15 meters.

[0007] Preferably, while comparing the absolute value of the difference between the current excitation frequency and a certain natural frequency value in the set of natural frequencies, the controller continuously acquires the phase of the real-time dominant vibration frequency and the phase of the current excitation frequency, calculates the phase difference between the two, and calculates the time change rate of the phase difference with a preset sampling time interval, the preset sampling time interval ranging from 0.05 to 0.2 s; when the time change rate of the phase difference is positive and greater than a preset change rate threshold, the controller increases the specified frequency command value in the adjustment command output to the frequency converter by a preset unit adjustment amount, the preset change rate threshold ranging from 10° / s to 30° / s; when the time change rate of the phase difference is negative and the absolute value is greater than the preset change rate threshold, the controller decreases the specified frequency command value by a preset unit adjustment amount.

[0008] Preferably, the controller also stores a vibration amplitude threshold, the value of which ranges from 0.05 to 0.2 m / s. 2 The controller extracts the real-time dominant vibration frequency from the vertical vibration signal collected by the acceleration sensor array, and at the same time extracts the vibration amplitude corresponding to the real-time dominant vibration frequency. The controller only determines that there is a risk of resonance and outputs an adjustment command to the frequency conversion drive device when the absolute value of the difference between the current excitation frequency and a certain natural frequency value in the set of natural frequencies is less than a preset frequency difference value, and the vibration amplitude corresponding to the real-time dominant vibration frequency is greater than the vibration amplitude threshold.

[0009] Preferably, the controller also includes a counter. Each time the controller outputs an adjustment command to the frequency converter drive device, the counter increments by one. When the incremented value of the counter reaches the preset maximum number of adjustments, the controller outputs an alarm signal and stops outputting adjustment commands. The preset maximum number of adjustments ranges from 3 to 10 times.

[0010] Preferably, when the controller extracts the real-time dominant vibration frequency from the vertical vibration signal acquired by the accelerometer array, it first applies a Hanning window to the vertical vibration signal, with the length of the Hanning window ranging from 256 to 1024 sampling points; then, it performs a fast Fourier transform on the windowed signal to obtain a discrete spectrum; finally, it finds the peak frequency point with the largest amplitude in the discrete spectrum, and performs parabolic interpolation between the peak frequency point and one frequency point to its left and right. The extreme point frequency obtained after parabolic interpolation is taken as the real-time dominant vibration frequency, and the extreme point amplitude obtained after parabolic interpolation is taken as the vibration amplitude corresponding to the real-time dominant vibration frequency.

[0011] Preferably, the set of natural frequencies of the existing railway line stored in the controller is obtained through a pulse hammer test before construction. The excitation point of the pulse hammer test is located above the midpoint of the sleeper of the existing railway line, and the pickup point is located above the midpoint of the adjacent sleeper.

[0012] Preferably, the variable frequency drive device integrates a frequency detection circuit for measuring the actual voltage waveform or current waveform output to the overhead construction machinery, and extracting the fundamental frequency from the waveform as the actual output frequency value. After increasing or decreasing the frequency command value by a preset unit adjustment amount, the variable frequency drive device also feeds back the adjusted actual output frequency value to the controller. The controller calculates the absolute value of the difference between the actual output frequency value and the adjusted frequency command value. If the absolute value of the difference is greater than 0.3Hz, the controller sends a compensation command to the variable frequency drive device. When the actual output frequency value is greater than the adjusted frequency command value, the compensation command causes the variable frequency drive device to reduce the compensation amount based on the current actual output frequency value. When the actual output frequency value is less than the adjusted frequency command value, the compensation command causes the variable frequency drive device to increase the compensation amount based on the current actual output frequency value. The compensation amount is equal to the absolute value of the difference multiplied by the feedback gain coefficient, and the value range of the feedback gain coefficient is 0.5~1.0.

[0013] The present invention has at least the following beneficial effects: By collecting vertical vibration signals of the existing railway line in real time using an accelerometer array and combining this with a pre-stored set of natural frequencies in the controller, the system can automatically monitor the proximity of the excitation frequency of the construction machinery to the natural frequency of the railway line during the overpass construction process. When the absolute value of the detected frequency difference is less than the preset frequency difference value, the controller actively outputs an adjustment command to the frequency converter drive device to change the excitation frequency of the construction machinery, thereby preventing excessive vibration of the railway line due to resonance.

[0014] By setting the controller to continuously extract the dominant vibration frequency in real time after adjustment and compare it with the set of natural frequencies, a closed-loop monitoring system is formed. This allows for repeated adjustments even if the resonance risk has not been eliminated, until the frequency difference meets safety requirements. This process requires no manual intervention, has a short response time, and can adapt to frequency drift caused by changes in railway line parameters or fluctuations in mechanical load during construction.

[0015] By introducing a vibration amplitude threshold as an auxiliary criterion, adjustments are only triggered when the frequency is close to the background level and the vibration response amplitude exceeds the background level. This effectively reduces misjudgments and frequent frequency changes caused by environmental noise or non-resonance disturbances, and improves the reliability of the system.

[0016] By arranging the accelerometer array at equal intervals, the vibration mode distribution along the longitudinal direction of the existing railway line can be captured more accurately, avoiding the omission of local resonance nodes due to sparse distribution. At the same time, the reasonable spacing range allows the system to adapt to different line conditions.

[0017] By calculating the rate of change of phase difference and determining its direction, the system can detect the approach trend before the excitation frequency is close enough to the natural frequency, and make early adjustments. It can also determine whether to increase or decrease the frequency adjustment based on the direction of the rate of change, thus avoiding the aggravation of resonance caused by reverse adjustment.

[0018] By setting a counter and a preset maximum number of adjustments, the controller is prevented from issuing adjustment commands without limit when the risk of resonance occurs repeatedly. This prevents the frequency converter and construction machinery from overheating or experiencing mechanical fatigue due to frequent speed adjustments, and issues an alarm signal when the limit is exceeded, prompting on-site personnel to check.

[0019] By employing Hanning window and parabolic interpolation to process vertical vibration signals, the estimation accuracy of peak frequency and amplitude in discrete spectrum is significantly improved. This eliminates the strict limitation of frequency resolution on the frequency domain interval of fast Fourier transform, thereby enabling more accurate judgment of frequency proximity and reducing misjudgment or omission.

[0020] The natural frequency set of existing railway lines is obtained by pulse hammer test. The test method is simple to operate, and all the equipment used are conventional test instruments. The test results are reliable and provide accurate reference data for the control system.

[0021] By integrating a frequency detection circuit into the variable frequency drive device and feeding back the actual output frequency, the controller performs closed-loop compensation for the deviation between the command value and the actual value, which improves the control accuracy of the excitation frequency and makes the actual output frequency follow the controller's set value more accurately, reducing frequency drift caused by load fluctuations or internal errors of the variable frequency drive device.

[0022] The control system of this invention has a simple structure, and all the components used are existing conventional equipment, which makes it easy to implement in cross-pass construction on existing railway lines and can effectively improve the level of construction safety without significantly increasing construction costs.

[0023] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to embodiments, so that those skilled in the art can implement it based on the description.

[0025] This invention provides an active control system for resonance risk during cross-line construction on existing railway lines, comprising: An acceleration sensor array, which is installed on an existing railway line, is used to collect vertical vibration signals of the railway line in real time. The accelerometer array can be composed of piezoelectric accelerometers with piezoelectric ceramic sensing elements. The sensor range can be set to ±5g, and the frequency response range covers 1~100Hz. The accelerometer array is arranged at equal intervals along the longitudinal direction of the existing railway line, with a spacing of 5~15m between adjacent sensors, for example, 10m. Each sensor is fixed to the side of the sleeper or the bottom of the rail using a magnetic base or adhesive, ensuring its sensing axis is perpendicular to the rail top plane. The sensors are connected to the analog input module of the controller via shielded cables.

[0026] A variable frequency drive device is installed on the overhead construction machinery to receive frequency commands and adjust the excitation frequency of the overhead construction machinery according to the frequency commands. The variable frequency drive unit can be a general-purpose AC frequency converter, which integrates a rectifier unit, an inverter unit, and a control circuit. The input of the variable frequency drive unit is connected to a three-phase 380V AC power supply, and the output is connected to the excitation motor of the construction machinery. The variable frequency drive unit is installed in the electrical control cabinet of the construction machinery, and its control terminals are connected to the controller's digital output module and communication interface (such as RS485 or Ethernet) via shielded twisted-pair cables. The variable frequency drive unit receives frequency commands (such as 4-20mA current signals or Modbus messages) from the controller and adjusts the voltage and frequency output to the motor according to these commands, thereby changing the speed of the excitation motor and thus changing the excitation frequency of the construction machinery.

[0027] The controller is electrically connected to both the acceleration sensor array and the frequency converter drive device. The controller compares the absolute value of the difference between the current excitation frequency of the construction machinery and each natural frequency value in the pre-stored natural frequency set in the controller. The current excitation frequency of the construction machinery is obtained by the controller reading the frequency command value currently executed by the frequency converter drive device. The natural frequency set contains the natural frequency values ​​of multiple existing railway lines. When the absolute value of the difference is less than a preset frequency difference value, the controller determines that there is a risk of resonance and outputs an adjustment command to the frequency converter drive device. The preset frequency difference value ranges from 0.5 to 2.0 Hz. The variable frequency drive device responds to the adjustment command by increasing or decreasing its currently executed frequency command value by a preset unit adjustment amount to obtain the adjusted frequency command value. The unit adjustment amount ranges from 1.0 to 3.0 Hz. The controller is also used to continuously extract the real-time dominant vibration frequency from the vertical vibration signal collected by the acceleration sensor array within a preset time interval after outputting the adjustment command. If the absolute value of the difference between the real-time dominant vibration frequency and any natural frequency value in the set of natural frequencies is less than the preset frequency difference again, the controller will repeatedly output the adjustment command to the frequency conversion drive device. The preset time interval is in the range of 0.2~1.0s.

[0028] The controller can be a programmable logic controller (PLC) with an industrial-grade ARM or x86 processor. The controller is housed in an IP65-rated electrical enclosure installed near the operating platform of the construction machinery. The controller acquires voltage signals from the accelerometer array via an analog input module, with a sampling frequency set to 200~1000Hz, for example, 500Hz.

[0029] The controller runs a real-time control program, which includes the following steps: First, the controller reads the currently executed frequency command value from the frequency converter; second, the controller performs a fast Fourier transform on the vertical vibration signal from the accelerometer array, extracting the frequency component with the largest amplitude as the real-time dominant vibration frequency; then, the controller reads a pre-stored set of natural frequencies, obtained through pulse hammer tests on the existing railway line before construction; next, the controller calculates the absolute value of the difference between the current excitation frequency and each natural frequency value, and compares it with a preset frequency difference (e.g., 1.0Hz); if the absolute value of all differences is greater than or equal to 1... If the frequency difference is less than 1.0Hz, no resonance risk is considered, and the controller continues monitoring. If the absolute value of any difference is less than 1.0Hz, a resonance risk is considered, and the controller sends an adjustment command to the frequency converter via the communication interface. The command specifies that the frequency should be increased or decreased by one unit (e.g., 2.0Hz). After sending the adjustment command, the controller waits for a preset time interval (e.g., 0.5s), during which time it continuously acquires vertical vibration signals and extracts the real-time dominant vibration frequency. If, after 0.5s, the absolute value of the difference between the real-time dominant vibration frequency and any natural frequency value is still less than 1.0Hz, the controller sends the adjustment command again, and so on.

[0030] More specifically, the preset frequency difference can be determined as follows: Before construction begins, the construction machinery is run unloaded at different frequencies, and the vertical vibration response of the existing railway line is measured simultaneously. The minimum frequency difference that causes a significant increase in the vibration response amplitude (e.g., exceeding twice the background vibration amplitude) is taken as the preset frequency difference. The unit adjustment amount is set based on: being greater than half of the minimum interval between adjacent natural frequencies in the natural frequency set, to ensure that one adjustment can cross the influence zone of a single natural frequency. The preset time interval is set based on: being greater than 1.5 times the maximum time required for the frequency converter drive to complete one frequency adjustment (including communication delay, frequency converter acceleration / deceleration time, and motor response time).

[0031] When performing cross-line construction above existing railways, the aforementioned technical solution can automatically monitor the proximity of the excitation frequency of the construction machinery to the natural frequency of the railway line. Upon detecting a risk of resonance, it proactively adjusts the excitation frequency to prevent excessive vibration of the railway line due to resonance. After adjustment, the system continuously monitors the vibration response; if the resonance phenomenon persists, further adjustments are made, forming a closed-loop control. This control process requires no manual intervention, has a fast response speed, and can adapt to frequency drift caused by changes in railway line parameters or fluctuations in mechanical load during construction.

[0032] In another embodiment, the acceleration sensor array is arranged at equal intervals along the longitudinal direction of the existing railway line, and the distance between two adjacent acceleration sensors ranges from 5 to 15 meters.

[0033] The specific spacing value can be selected according to the railway line structure type: for ballasted track subgrade sections, the spacing can be 5m or 8m to capture the higher-order modes of local vibration of the track bed; for ballastless track or bridge sections, the spacing can be 10m or 15m to match the wavelength characteristics of the first-order bending mode.

[0034] The method for determining the spacing is as follows: Before construction, environmental pulsation tests are conducted on the existing railway line, the spatial autocorrelation function of the vibration signal is analyzed, and the distance corresponding to the first drop of the autocorrelation coefficient to below 0.5 is taken as the minimum spacing. Then, one-half to one-third of this distance is taken as the sensor spacing.

[0035] When there are obvious uneven sections in the railway line (such as the transition section between the roadbed and the bridge), additional sensors can be added on both sides of the transition section, but the overall spacing principle should still be maintained. Under the equal spacing arrangement, the controller compares the vertical vibration signals collected by adjacent sensors, calculates the amplitude ratio and phase difference of the same frequency component at different locations, and determines that the vibration mode corresponding to the frequency is a standing wave mode when the phase difference between two adjacent sensors is close to 180° and the amplitude is greater than the vibration amplitude threshold. At this time, regardless of whether the current excitation frequency is close to the natural frequency, the controller actively outputs adjustment commands to the frequency converter drive device.

[0036] The above technical solution, by arranging sensor arrays at equal intervals, can more accurately identify the nodal locations of longitudinal vibration modes on existing railway lines, avoiding the risk of misjudging resonance at the nodes. Simultaneously, the reasonable spacing range allows the system to adapt to different track conditions, improving its ability to identify both local vibrations and overall bending vibrations. In another embodiment, while comparing the absolute value of the difference between the current excitation frequency and a certain natural frequency value in the set of natural frequencies, the controller continuously acquires the phase of the real-time dominant vibration frequency and the phase of the current excitation frequency, calculates the phase difference between the two, and calculates the time change rate of the phase difference with a preset sampling time interval, the preset sampling time interval ranging from 0.05 to 0.2 s; when the time change rate of the phase difference is positive and greater than a preset change rate threshold, the controller increases the specified frequency command value in the adjustment command output to the frequency converter by a preset unit adjustment amount, the preset change rate threshold ranging from 10° / s to 30° / s; when the time change rate of the phase difference is negative and the absolute value is greater than the preset change rate threshold, the controller decreases the specified frequency command value by a preset unit adjustment amount.

[0037] The controller may contain a phase detection module, which can be implemented using a digital phase-locked loop or a zero-crossing comparator.

[0038] The phase of the real-time dominant vibration frequency is extracted from the vertical vibration signal acquired by the accelerometer. The extraction method is as follows: the vertical vibration signal is bandpass filtered (the center frequency is set to the current real-time dominant vibration frequency), and then the instantaneous phase is calculated using Hilbert transform.

[0039] The phase of the current excitation frequency can be obtained directly from the frequency command sent by the controller to the variable frequency drive device by generating a reference sine wave of the same frequency through software, or from the actual voltage waveform fed back by the variable frequency drive device by zero-crossing detection.

[0040] The controller acquires both phase values ​​simultaneously in each control cycle (e.g., 20ms), calculates the difference to obtain the instantaneous phase difference, and the phase difference is expressed in degrees.

[0041] To reduce noise interference, the controller can perform a moving average of five consecutive instantaneous phase differences. The preset sampling time interval can be 0.05s, 0.1s, or 0.2s, and the specific value is set according to the response speed of the frequency converter drive. For example, when the frequency adjustment response time of the frequency converter drive (from receiving the command to the actual output frequency stabilization) is 0.5s, the sampling time interval can be selected as 0.1s.

[0042] The formula for calculating the rate of change of phase difference over time is: Rate of change (° / s) = (Current phase difference - Phase difference at the previous sampling moment) / Sampling time interval. When the rate of change is positive, it indicates that the phase of the real-time dominant vibration frequency gradually leads the phase of the excitation frequency; when it is negative, it indicates that it gradually lags behind.

[0043] The preset change rate threshold can be set to 10° / s, 15° / s, 20° / s, 25° / s, or 30° / s. The method for setting this threshold is as follows: before construction, run the construction machinery at a frequency far away from the natural frequency of the existing railway line (e.g., beyond the natural frequency ±5Hz) without load, record the maximum fluctuation value of the phase difference change rate at this time, and take twice the fluctuation value as the change rate threshold.

[0044] When a positive rate of change is detected that is greater than a threshold (e.g., 20° / s), it indicates that the excitation frequency is approaching the low-frequency side of the natural frequency. In this case, the controller explicitly requires the variable frequency drive to increase the frequency command value by one unit adjustment (e.g., 2.0Hz). When a negative rate of change is detected that is greater than a threshold (e.g., 20° / s), it indicates that the excitation frequency is approaching the high-frequency side of the natural frequency. In this case, the adjustment command requires a decrease of one unit adjustment. This judgment process is performed in parallel with the comparison of the absolute value of the frequency difference; that is, the controller simultaneously monitors the rate of change of both the frequency difference and the phase difference, and outputs the adjustment command based on the earlier one that reaches the trigger condition.

[0045] To prevent false triggering caused by transient noise, the controller can be set with a de-jitter counter, requiring that the adjustment is only performed after the rate of change calculated for two or three consecutive times exceeds the threshold.

[0046] The above technical solution introduces the phase difference change rate as a predictive indicator, enabling it to detect the approaching trend before the excitation frequency is sufficiently close to the natural frequency (i.e., the absolute value of the frequency difference is still greater than the preset frequency difference), thus allowing for early adjustment and effectively suppressing the increase in vibration amplitude. Simultaneously, the direction of frequency adjustment (increase or decrease) is determined based on the positive or negative direction of the change rate, avoiding exacerbated resonance caused by reverse adjustment. This method is particularly suitable for scenarios where the excitation frequency drifts slowly, such as speed fluctuations caused by gradual changes in the load on construction machinery.

[0047] In another embodiment, the controller further stores a vibration amplitude threshold, the value of which ranges from 0.05 to 0.2 m / s. 2 The controller extracts the real-time dominant vibration frequency from the vertical vibration signal collected by the acceleration sensor array, and at the same time extracts the vibration amplitude corresponding to the real-time dominant vibration frequency. The controller only determines that there is a risk of resonance and outputs an adjustment command to the frequency conversion drive device when the absolute value of the difference between the current excitation frequency and a certain natural frequency value in the set of natural frequencies is less than a preset frequency difference value, and the vibration amplitude corresponding to the real-time dominant vibration frequency is greater than the vibration amplitude threshold.

[0048] The controller may contain a non-volatile memory for storing a vibration amplitude threshold. This threshold is an acceleration amplitude, the specific value of which can be determined based on the environmental background vibration level of the existing railway line. For example, if a train is passing on a neighboring line but this line is closed, the measured background vibration amplitude might be 0.03 m / s². 2 At this point, the threshold can be selected as 0.08 m / s. 2 When there are no trains running at night and the environment is quiet, the background vibration amplitude may be 0.01 m / s. 2 The threshold can be selected as 0.05 m / s 2 The upper limit of the threshold value is 0.2 m / s. 2 This corresponds to the permissible daily vibration value (approximately 0.3 m / s) recommended in the "Railway Bridge Inspection Specification". 2 Approximately two-thirds of the value is used to allow for a safety margin. The threshold is set as follows: Before construction begins, under conditions of no construction machinery excitation, the vertical vibration signal of the existing railway line is continuously collected for 30 minutes. The root mean square value of the vibration amplitude is calculated, and four times this root mean square value is taken as the vibration amplitude threshold, or the 95th quantile of the probability distribution of the background vibration amplitude is taken.

[0049] The controller extracts the real-time dominant vibration frequency and its corresponding vibration amplitude from the vertical vibration signal acquired by the accelerometer array. The extraction method can be a Fast Fourier Transform (FFT). The time-domain signal is then transformed to the frequency domain by applying a Hanning window (1024 points). The spectral line with the largest amplitude is then searched in the frequency domain; the frequency of this spectral line is the real-time dominant vibration frequency, and its amplitude (in m / s²) is determined. 2 This corresponds to the vibration amplitude. To reduce the impact of spectral leakage on amplitude estimation, parabolic interpolation can be performed between the maximum spectral line and one spectral line to its left and right. The extreme point amplitude obtained after interpolation is taken as the vibration amplitude. The controller completes one extraction in each control cycle (e.g., 0.2s) and compares the extracted amplitude with the stored vibration amplitude threshold.

[0050] When determining resonance risk, the controller performs the following process: First, it compares the absolute value of the difference between the current excitation frequency and each natural frequency value in the set of natural frequencies. If the absolute value of all differences is greater than or equal to a preset frequency difference (e.g., 1.0Hz), it directly determines that there is no resonance risk and does not output an adjustment command. If there exists a natural frequency value such that the absolute value of the difference is less than 1.0Hz, it further determines whether the vibration amplitude corresponding to the real-time dominant vibration frequency extracted from the vertical vibration signal is greater than the vibration amplitude threshold (e.g., 0.08 m / s²). 2If the value is greater than the threshold, a genuine resonance risk is identified, and an adjustment command is output to the frequency converter drive. If the value is less than or equal to the threshold, it is considered that although the frequency is close, the vibration response has not increased significantly (possibly due to large damping or weak coupling), and no adjustment command is output, maintaining the current excitation frequency. The controller can also be configured with a hysteresis comparator: the resonance risk assessment is only lifted when the vibration amplitude drops from above the threshold to below 0.8 times the threshold, avoiding frequent triggering when the amplitude fluctuates near the threshold.

[0051] The above technical solution effectively distinguishes between true resonant amplification response and environmental background vibration or non-resonant disturbance by introducing a vibration amplitude threshold as an auxiliary criterion. When the excitation frequency is close to the natural frequency but the actual vibration amplitude is very small, the system will not misjudge it as a resonance risk and adjust the frequency, thereby reducing unnecessary frequency changes and improving the continuity of construction and the reliability of the control system. This solution is particularly suitable for complex working conditions where there are other vibration sources near the construction site (such as trains passing by on nearby tracks, wind loads, and other construction machinery).

[0052] In another embodiment, the controller further includes a counter. Each time the controller outputs an adjustment command to the frequency converter, the counter increments by one. When the incremented value of the counter reaches a preset maximum number of adjustments, the controller outputs an alarm signal and stops outputting adjustment commands. The preset maximum number of adjustments ranges from 3 to 10 times.

[0053] The controller can contain a software counter, implemented using an integer variable in the PLC program. The counter's initial value is set to 0. Each time the microprocessor in the controller sends an adjustment command to the frequency converter, it executes an increment command, increasing the counter's current value by 1. The preset maximum number of adjustments ranges from 3 to 10, specifically 3, 4, 5, 6, 7, 8, 9, or 10. This value is determined based on the time required for a single adjustment by the frequency converter of the construction machinery and the distribution density of the railway line's natural frequencies. For lines with sparse natural frequencies (intervals between adjacent natural frequencies greater than 5Hz), a smaller preset maximum number of adjustments, such as 3 or 4, can be selected; for lines with dense natural frequencies (intervals between adjacent natural frequencies less than 2Hz), a larger preset maximum number of adjustments, such as 8 or 10, can be selected. Before construction, a vibration exciter can be used to perform a frequency sweep test on the existing railway line. The maximum number of adjustments required to go from the frequency being close to the natural frequency to completely avoiding it is recorded. 1.5 times this number is taken as the preset maximum number of adjustments, and then rounded down to between 3 and 10.

[0054] When the counter's accumulated value reaches the preset maximum number of adjustments (e.g., set to 5 times), the controller performs the following operations: A high-level signal is output from one of the controller's digital output ports, driving an audible and visual alarm. This alarm can be installed on top of the construction machinery's operator's cab or within the safety monitoring area next to the existing railway line. The alarm emits a continuous beeping sound and flashes a red light until the on-site operator manually presses the reset button. Simultaneously, the controller stops sending any subsequent adjustment commands to the frequency converter, but maintains the current frequency command value executed by the frequency converter unchanged, allowing the construction machinery to continue operating at the frequency after the last adjustment. The controller also records the current counter's accumulated value, the alarm occurrence time, and the frequency value after the last adjustment in its internal memory for post-event analysis. To prevent automatic reset, after stopping the output of adjustment commands, the controller will not output any further adjustment commands even if the absolute value of the difference between the subsequently detected real-time dominant vibration frequency and the natural frequency is again less than the preset frequency difference, unless a manual reset signal is received. The reset button can be installed on the controller's panel or on the remote control. Pressing the reset button clears the counter, and the controller resumes normal monitoring and adjustment functions. In addition, the controller can be set with a watchdog timer. When the counter reaches the preset maximum number of adjustments, if the alarm continues for more than the preset time (e.g., 5 minutes) and no one resets it, the controller will automatically cut off the enable signal of the frequency converter drive, forcing the construction machinery to stop and ensuring safety.

[0055] The above technical solution avoids the controller issuing unlimited adjustment commands when resonance risks repeatedly occur, preventing overheating or mechanical fatigue of the frequency converter and construction machinery due to frequent reversals or speed adjustments. By limiting the number of adjustments through a counter and issuing an alarm when the limit is exceeded, operators are prompted to check the railway line condition or adjust construction parameters on-site, enhancing the system's safety redundancy. The function of recording the number of adjustments can also be used to assess the distribution characteristics of the existing railway line's natural frequency and the coupling degree between the construction machinery and the railway line, providing data reference for subsequent construction. In another embodiment, when the controller extracts the real-time dominant vibration frequency from the vertical vibration signal acquired by the accelerometer array, it first applies a Hanning window to the vertical vibration signal, with the length of the Hanning window ranging from 256 to 1024 sampling points; then, it performs a fast Fourier transform on the windowed signal to obtain a discrete spectrum; finally, it finds the peak frequency point with the largest amplitude in the discrete spectrum, and performs parabolic interpolation between the peak frequency point and one frequency point to its left and right. The extreme point frequency obtained after parabolic interpolation is taken as the real-time dominant vibration frequency, and the extreme point amplitude obtained after parabolic interpolation is taken as the vibration amplitude corresponding to the real-time dominant vibration frequency.

[0056] The controller can internally include a digital signal processing module, which can be implemented using software algorithms (such as the FFT library functions integrated in the PLC) or a separate digital signal processor chip. When the controller acquires the vertical vibration signal from the accelerometer array, the sampling frequency can be set to 500Hz or 1000Hz, and the number of sampling points is determined by the length of the Hanning window. The length of the Hanning window can be selected between 256 and 1024, specifically 256, 512, or 1024 sampling points. The selection method is as follows: determine the frequency resolution requirement based on the lowest possible natural frequency (e.g., 5Hz) and the highest frequency of interest (e.g., 50Hz) of the existing railway line. Frequency resolution = sampling frequency / window length. When the sampling frequency is 500Hz and the window length is 256 points, the frequency resolution is approximately 1.95Hz; when the window length is 512 points, the resolution is approximately 0.98Hz; and when the window length is 1024 points, the resolution is approximately 0.49Hz. For applications requiring precise differentiation of adjacent natural frequencies (intervals less than 1 Hz), 1024 points can be selected; for general construction vibration monitoring, 512 points can be selected. Before signal sampling, an anti-aliasing low-pass filter can be applied, with the cutoff frequency set to 0.4 times the sampling frequency.

[0057] The steps for applying the Hanning window are as follows: The controller reads a vertical vibration signal sequence x[i] of length N (N ranges from 256 to 1024), i = 0, 1, ..., N-1. Simultaneously, it generates a Hanning window function sequence w[i] = 0.5•(1-cos(2πi / (N-1))). Multiplying the corresponding points of the two signals yields the windowed signal y[i] = x[i]•w[i]. The windowing process is performed in the controller's memory via cyclic multiplication, executed once per control cycle (e.g., 0.2s). The cosine coefficients used for windowing can be pre-calculated and stored in the controller's read-only memory to avoid real-time calculations consuming processor time.

[0058] A Fast Fourier Transform (FFT) is performed on the windowed signal, using either a radix-2 or radix-4 FFT algorithm. The transformed result yields a discrete spectrum in complex form, with the amplitude spectrum calculated by modulus. The controller's processor needs to support floating-point or fixed-point arithmetic, and the results are stored in an array.

[0059] To find the peak frequency with the largest amplitude in the discrete spectrum: the controller scans from the DC component to the Nyquist frequency (half the sampling frequency) and records the index k corresponding to the spectral line with the largest amplitude. max The frequency of this spectral line is f. peak =k max • Sampling frequency / N.

[0060] When performing parabolic interpolation, take index k. max and its left and right adjacent indices k max-1 and kmax+1 The corresponding amplitudes A0 and A -1 A +1 The parabolic interpolation formula is: extreme point offset δ = (A -1 -A +1 ) / [2•(A -1 +A +1 -2•A0)], extreme point frequency f true =(k max +δ)•Sampling frequency / N, extreme point amplitude A true =A0-(A -1 -A +1 )•δ / 4. When k max When the frequency is at the spectral boundary (i.e., 0 or N / 2), no interpolation is performed, and the original peak frequency and amplitude are used directly. The interpolation process is implemented in the controller using floating-point operations and is executed once per control cycle.

[0061] The above technical solution suppresses spectral leakage through the Hanning window and significantly improves the estimation accuracy of peak frequency and amplitude in the discrete spectrum by combining parabolic interpolation. Frequency resolution is not directly limited by the frequency domain interval (Δf) of the FFT; after interpolation, frequency differences smaller than Δf can be distinguished, thus more accurately determining the proximity of the excitation frequency to the natural frequency and reducing misjudgments or omissions caused by frequency estimation errors. Simultaneously, the interpolated amplitude is closer to the true vibration amplitude, making the determination of the vibration amplitude threshold more reliable.

[0062] In another embodiment, the set of natural frequencies of the existing railway line stored in the controller is obtained by a pulse hammer test before construction. The excitation point of the pulse hammer test is located above the midpoint of the sleeper of the existing railway line, and the pickup point is located above the midpoint of the adjacent sleeper.

[0063] The excitation equipment used for pulse hammer impact testing can be a force hammer. The hammer head can be made of stainless steel or hard plastic, and a piezoelectric force sensor can be installed inside the hammer head to measure the time history of the impact force. The mass range of the force hammer can be selected from 0.5 kg to 5 kg, determined according to the stiffness of the railway line structure: for ballasted track, a 1 kg force hammer can be selected; for ballastless track or bridge sections, a 3-5 kg ​​force hammer can be selected. The hammer head can be equipped with rubber or metal impact pads of different hardness to adjust the excitation frequency bandwidth: rubber pads produce a narrower bandwidth (e.g., below 100 Hz), suitable for low-frequency modes; metal pads produce a wider bandwidth (e.g., above 500 Hz), suitable for high-frequency modes. The specific location of the excitation point is above the midpoint of the sleeper on the existing railway line, that is, directly above the middle section of the sleeper, and can be marked with a marker pen at the center point of the top surface of the sleeper. During excitation, the operator holds the force hammer perpendicular to the top surface of the sleeper and performs transient impacts in a vertically downward direction to ensure that the excitation energy is concentrated in the vertical direction. Each excitation point can be tapped repeatedly 5 to 10 times, and the average value is taken to reduce random errors.

[0064] The vibration pickup device can be an accelerometer, specifically a piezoelectric accelerometer with a sensitivity selectable between 100 and 500 mV / g. The sensor can be mounted using a magnetic base or quick-drying adhesive (such as cyanoacrylate glue). The pickup point is located above the midpoint of the adjacent sleeper, specifically the center point of the top surface of the next sleeper adjacent to the excitation point. For example, if the excitation point is at the midpoint of sleeper A, the pickup point is at the midpoint of sleeper B, and the center-to-center distance between the two sleepers is the sleeper spacing (typically 0.6 m). The sensitive axis of the accelerometer should be perpendicular to the rail top plane, with the direction consistently vertically upwards or downwards. The sensor is connected to a data acquisition unit via a shielded cable. The sampling frequency of the data acquisition unit can be set to 1000–2000 Hz, and the sampling duration can be set to 2–5 seconds to ensure complete recording of the free decay response after impact.

[0065] The pulse hammer test process is as follows: Before construction, a section representing the typical condition of the existing railway line is selected, with a length of no less than 10 sleeper spans. An accelerometer is installed above the midpoint of the selected sleeper as a vibration pickup point, and a force hammer is prepared above the midpoint of the adjacent sleeper as an excitation point. The data acquisition instrument is set to trigger acquisition mode, and the trigger threshold is set to 5% of the force sensor signal range. The operator strikes the excitation point vertically with the force hammer, and the data acquisition instrument simultaneously records the force signal of the force hammer and the response signal of the accelerometer. After each strike, wait at least 5 seconds for the vibration to completely decay before striking again. Each measuring point is struck 5 times. The acquired time-domain signal is windowed (e.g., Hanning window) and subjected to Fast Fourier Transform to calculate the frequency response function: Frequency response function = Fourier transform of response signal / Fourier transform of force signal. Peak values ​​are identified from the amplitude spectrum of the frequency response function, and the frequency corresponding to each peak value is a natural frequency of the existing railway line. The average value of the natural frequencies from multiple measuring points is taken. For multi-mode operation, the first 3 to 5 natural frequencies can be extracted. For example, the first-order bending frequency may be 8 to 15 Hz, the second-order bending frequency may be 20 to 30 Hz, and the local frequency of the track bed may be 40 to 60 Hz. The extracted set of natural frequencies is stored in the controller's non-volatile memory.

[0066] The aforementioned technical solution, through pulse hammer testing, can accurately acquire multiple natural frequencies of the existing railway line in the vertical direction before construction, providing benchmark data for the active control system for resonance risk. The excitation and pickup points are selected above the midpoint of adjacent sleepers, effectively exciting and sensing the bending modes of the railway line and the local modes of the track bed, avoiding interference from local high-frequency vibrations of the rail itself. This method is simple to operate, requires only conventional testing instruments, and yields reliable test results. The natural frequency set is stored in the controller and can be used for real-time comparison and risk assessment during subsequent construction.

[0067] In another embodiment, the frequency conversion drive device integrates a frequency detection circuit for measuring the actual voltage waveform or current waveform output to the overhead construction machinery, and extracting the fundamental frequency from the waveform as the actual output frequency value. After increasing or decreasing the frequency command value by a preset unit adjustment amount, the variable frequency drive device also feeds back the adjusted actual output frequency value to the controller. The controller calculates the absolute value of the difference between the actual output frequency value and the adjusted frequency command value. If the absolute value of the difference is greater than 0.3Hz, the controller sends a compensation command to the variable frequency drive device. When the actual output frequency value is greater than the adjusted frequency command value, the compensation command causes the variable frequency drive device to reduce the compensation amount based on the current actual output frequency value. When the actual output frequency value is less than the adjusted frequency command value, the compensation command causes the variable frequency drive device to increase the compensation amount based on the current actual output frequency value. The compensation amount is equal to the absolute value of the difference multiplied by the feedback gain coefficient, and the value range of the feedback gain coefficient is 0.5~1.0.

[0068] The frequency detection circuit can choose between voltage or current detection. Voltage detection uses a resistor divider network or a Hall effect voltage sensor to acquire the three-phase AC voltage signal at the output terminals of the frequency converter. Current detection uses a Hall effect current sensor or a shunt resistor to acquire the three-phase AC current signal on the output cable. The detected analog signal is low-pass filtered (cutoff frequency can be set to 500Hz), then converted into a digital signal by an analog-to-digital converter and sent to the microcontroller inside the frequency converter. The fundamental frequency can be extracted using the zero-crossing detection method: the microcontroller detects the zero-crossing points of the single-phase voltage or current waveform, calculates the time interval T (in seconds) between two consecutive positive zero-crossing points, and then the fundamental frequency f = 1 / T. To improve anti-interference capability, the arithmetic mean of five consecutive cycles can be taken. The zero-crossing detection method is suitable for situations with small waveform distortion; if the waveform distortion is large, a Fast Fourier Transform (FFT) can be used to perform an FFT on the 256 data points collected in each cycle to find the frequency of the spectral line with the largest amplitude.

[0069] After the variable frequency drive increases or decreases the instruction value in its internal frequency register by a preset unit adjustment (e.g., 2.0Hz) according to the controller's adjustment command, the internal microcontroller reads the actual output frequency value measured by the frequency detection circuit and then sends the actual output frequency value to the controller via a communication interface (RS485, CAN bus, or Ethernet can be selected). The feedback transmission timing can be set to send the feedback within 0.3~0.5s after the adjustment command is executed, after the motor speed has basically stabilized. The feedback data is in floating-point format, in Hz, with one decimal place.

[0070] After receiving the actual output frequency value, the controller calculates the absolute value of the difference between this value and the adjusted frequency command value. The controller internally stores a fixed difference threshold of 0.3Hz. This threshold is set based on the following: the open-loop control accuracy of a typical variable frequency drive is approximately 0.2Hz, and the measurement error of the frequency detection circuit is approximately 0.05Hz, totaling 0.25Hz. Setting it to 0.3Hz avoids frequent compensation triggers due to normal fluctuations while still promptly detecting significant deviations exceeding 0.3Hz. The controller performs a comparison: if the absolute value of the difference is greater than 0.3Hz, a compensation command is generated. The compensation command includes a direction indicator and a compensation amount.

[0071] The compensation direction is determined by the relative magnitude of the actual output frequency value and the adjusted frequency command value. If the actual output frequency value is greater than the adjusted frequency command value, for example, the actual value is 14.0Hz and the command is 13.0Hz, the compensation command requires the frequency converter to reduce the compensation amount by one based on the current actual output frequency value (14.0Hz). If the actual output frequency value is less than the adjusted frequency command value, for example, the actual value is 12.0Hz and the command is 13.0Hz, the compensation amount is increased. The compensation amount is equal to the absolute value of the difference multiplied by the feedback gain coefficient. The feedback gain coefficient can be selected between 0.5 and 1.0, specifically 0.5, 0.6, 0.7, 0.8, 0.9, or 1.0. The method for determining this coefficient is as follows: for large inertial loads (such as large rotary exciters), 0.5 to 0.7 can be selected to avoid overshoot and oscillation; for small inertial loads, 0.8 to 1.0 can be selected for fast convergence. For example, with a coefficient of 0.7 and a difference of 1.0Hz, the compensation amount is 0.7Hz. The controller sends compensation commands (such as "increase by 0.7Hz" or "decrease by 0.7Hz") to the frequency converter. After the frequency converter executes the commands, the new actual output frequency value will theoretically be closer to the original adjusted frequency command value. If the absolute value of the difference is still greater than 0.3Hz after one compensation, the controller can repeatedly send compensation commands until the deviation is less than or equal to 0.3Hz.

[0072] The above technical solution obtains the actual output frequency of the variable frequency drive through a frequency detection circuit and performs closed-loop compensation for the deviation between the command value and the actual value, significantly improving the control accuracy of the excitation frequency. The actual output frequency can more accurately follow the controller's set value, avoiding frequency drift caused by load fluctuations or internal errors of the variable frequency drive, thereby reducing misjudgments and missed judgments of resonance risk. Simultaneously, the compensation amount is adaptively adjusted according to the magnitude of the deviation, and the feedback gain coefficient is adjustable, enabling the system to achieve a balance between response speed and stability, making it suitable for construction machinery with different inertia.

[0073] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. An active control system for resonance risk during cross-pass construction on existing railway lines, characterized in that, include: An acceleration sensor array, which is installed on an existing railway line, is used to collect vertical vibration signals of the railway line in real time. A variable frequency drive device is installed on the overhead construction machinery to receive frequency commands and adjust the excitation frequency of the overhead construction machinery according to the frequency commands. The controller is electrically connected to both the acceleration sensor array and the frequency converter drive device. The controller compares the absolute value of the difference between the current excitation frequency of the construction machinery and each natural frequency value in the pre-stored natural frequency set in the controller. The current excitation frequency of the construction machinery is obtained by the controller reading the frequency command value currently executed by the frequency converter drive device. The natural frequency set contains the natural frequency values ​​of multiple existing railway lines. When the absolute value of the difference is less than a preset frequency difference value, the controller determines that there is a risk of resonance and outputs an adjustment command to the frequency converter drive device. The preset frequency difference value ranges from 0.5 to 2.0 Hz. The variable frequency drive device responds to the adjustment command by increasing or decreasing its currently executed frequency command value by a preset unit adjustment amount to obtain the adjusted frequency command value. The unit adjustment amount ranges from 1.0 to 3.0 Hz. The controller is also used to continuously extract the real-time dominant vibration frequency from the vertical vibration signal collected by the acceleration sensor array within a preset time interval after outputting the adjustment command. If the absolute value of the difference between the real-time dominant vibration frequency and any natural frequency value in the set of natural frequencies is less than the preset frequency difference again, the controller will repeatedly output the adjustment command to the frequency conversion drive device. The preset time interval is in the range of 0.2~1.0s.

2. The active control system for resonance risk during cross-pass construction on existing railway lines as described in claim 1, characterized in that, The acceleration sensor array is arranged at equal intervals along the longitudinal direction of the existing railway line, and the distance between two adjacent acceleration sensors ranges from 5 to 15 meters.

3. The active control system for resonance risk during cross-line construction on existing railway lines as described in claim 1, characterized in that, While comparing the absolute value of the difference between the current excitation frequency and a certain natural frequency value in the set of natural frequencies, the controller continuously acquires the phase of the real-time dominant vibration frequency and the phase of the current excitation frequency, calculates the phase difference between the two, and calculates the time change rate of the phase difference at a preset sampling time interval, the preset sampling time interval ranging from 0.05 to 0.2 s; when the time change rate of the phase difference is positive and greater than the preset change rate threshold, the controller increases the specified frequency command value in the adjustment command output to the frequency converter by a preset unit adjustment amount, the preset change rate threshold ranging from 10° / s to 30° / s; when the time change rate of the phase difference is negative and the absolute value is greater than the preset change rate threshold, the controller decreases the specified frequency command value by a preset unit adjustment amount.

4. The active control system for resonance risk during cross-line construction on existing railway lines as described in claim 1, characterized in that, The controller also stores a vibration amplitude threshold, the value of which ranges from 0.05 to 0.2 m / s. 2 The controller extracts the real-time dominant vibration frequency from the vertical vibration signal collected by the acceleration sensor array, and at the same time extracts the vibration amplitude corresponding to the real-time dominant vibration frequency. The controller only determines that there is a risk of resonance and outputs an adjustment command to the frequency conversion drive device when the absolute value of the difference between the current excitation frequency and a certain natural frequency value in the set of natural frequencies is less than a preset frequency difference value, and the vibration amplitude corresponding to the real-time dominant vibration frequency is greater than the vibration amplitude threshold.

5. The active control system for resonance risk during cross-line construction on existing railway lines as described in claim 1, characterized in that, The controller also includes a counter. Each time the controller outputs an adjustment command to the frequency converter, the counter increments by one. When the incremented value of the counter reaches the preset maximum number of adjustments, the controller outputs an alarm signal and stops outputting adjustment commands. The preset maximum number of adjustments ranges from 3 to 10 times.

6. The active control system for resonance risk during cross-line construction on existing railway lines as described in claim 4, characterized in that, When the controller extracts the real-time dominant vibration frequency from the vertical vibration signal acquired by the accelerometer array, it first applies a Hanning window to the vertical vibration signal, with the length of the Hanning window ranging from 256 to 1024 sampling points. Then, it performs a fast Fourier transform on the windowed signal to obtain a discrete spectrum. Finally, it finds the peak frequency with the largest amplitude in the discrete spectrum and performs parabolic interpolation between the peak frequency and one frequency to its left and right. The extreme point frequency obtained after parabolic interpolation is taken as the real-time dominant vibration frequency, and the extreme point amplitude obtained after parabolic interpolation is taken as the vibration amplitude corresponding to the real-time dominant vibration frequency.

7. The active control system for resonance risk during cross-line construction on existing railway lines as described in claim 1, characterized in that, The set of natural frequencies of the existing railway line stored in the controller is obtained through pulse hammer test before construction. The excitation point of the pulse hammer test is located above the midpoint of the sleeper of the existing railway line, and the pickup point is located above the midpoint of the adjacent sleeper.

8. The active control system for resonance risk during cross-line construction on existing railway lines as described in claim 1, characterized in that, The variable frequency drive device integrates a frequency detection circuit, which is used to measure the actual voltage waveform or current waveform output to the overhead construction machinery, and extract the fundamental frequency from the waveform as the actual output frequency value. After increasing or decreasing the frequency command value by a preset unit adjustment amount, the variable frequency drive device also feeds back the adjusted actual output frequency value to the controller. The controller calculates the absolute value of the difference between the actual output frequency value and the adjusted frequency command value. If the absolute value of the difference is greater than 0.3Hz, the controller sends a compensation command to the variable frequency drive device. When the actual output frequency value is greater than the adjusted frequency command value, the compensation command causes the variable frequency drive device to reduce the compensation amount based on the current actual output frequency value. When the actual output frequency value is less than the adjusted frequency command value, the compensation command causes the frequency converter to increase the compensation amount based on the current actual output frequency value. The compensation amount is equal to the absolute value of the difference multiplied by the feedback gain coefficient, and the feedback gain coefficient ranges from 0.5 to 1.0.