Method for bridge t-beam erection process coordination and collision warning considering interference of existing line operation

Abstract

The application discloses a method for bridge T beam erection process coordination and anti-collision early warning considering existing line operation interference, and belongs to the technical field of railway bridge construction safety control. The method aims to solve the problem of reducing collision risk when erecting a bridge T beam under the condition of normal operation of an existing line. The technical solution points are as follows: installing a limit sensor group and a sound-light alarm and connecting a programmable logic controller, simultaneously connecting a bridge erection machine propulsion control system and a hydraulic buffer at the bottom of the bridge T beam; continuously collecting horizontal and vertical measured distances during propulsion; comparing the measured distances with early warning distance ranges containing first and second sub-ranges; when falling into the first sub-range, reducing speed and alarming; when falling into the second sub-range, suspending propulsion and extending a piston rod to a position above the top of a catenary; after exiting the second sub-range, retracting the piston rod and resuming propulsion. The method is used for process coordination and anti-collision control of bridge T beam erection construction across an existing line.

Description

Technical Field

[0001] This invention relates to the field of railway bridge construction safety control technology. More specifically, this invention relates to a method for coordinating and preventing collisions during the erection of T-beams for overpasses, taking into account interference from existing railway lines. Background Technology

[0002] In the construction of T-beams for overpasses crossing existing railway lines, the existing lines are usually in normal operation, resulting in short construction windows and high safety requirements. During hoisting and advancement, the T-beams must strictly avoid collisions with the existing line's overhead contact system and equipment clearances. Currently, this type of construction mainly relies on on-site supervisors visually assessing or using simple measuring tools to determine the horizontal distance between the T-beam's end and the existing line's centerline, and the vertical distance between the T-beam's bottom and the top of the overhead contact system. The bridge erecting machine operator is then notified via walkie-talkie to adjust the advancement speed and direction. This method has the following problems: manual observation is easily affected by factors such as viewing angle, lighting, and weather, resulting in low accuracy in distance judgment, especially during nighttime or foggy weather. There is a delay between manual judgment and voice command transmission; when the T-beam rapidly approaches the clearances, the operator often cannot decelerate or stop in time. During construction, the T-beam may experience slow horizontal drift or vertical sinking due to wind load, bridge erecting machine vibration, or temperature changes, making continuous monitoring and corresponding compensation difficult for humans. When the T-beam has stopped advancing and is within the danger distance range, the distance reading may fluctuate temporarily due to environmental interference or measurement noise. Operators or simple automated judgment systems may mistakenly believe the danger has passed, prematurely retracting temporary protective devices and resuming advancement, increasing the risk of collision. Furthermore, existing construction methods lack an automated process that simultaneously coordinates advancement speed control, audible and visual alarms, physical protective device activation, and disturbance compensation, resulting in poor coordination between various operational stages and significant safety hazards. Therefore, achieving accurate, disturbance-resistant, and automatically coordinated collision avoidance control under the interference of existing railway lines during the erection of overpass T-beams is a technical problem that needs to be solved in practical engineering. Summary of the Invention

[0003] 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.

[0004] To achieve these objectives and other advantages of the present invention, a method for coordinating and collision avoidance warning during the erection of T-beams for overpasses, taking into account interference from existing railway lines, is provided, comprising the following steps: Clearance sensor groups and audible and visual alarms are installed on both sides of the existing line. The clearance sensor groups are connected to a programmable logic controller (PLC). The PLC is also connected to the propulsion control system of the bridge erecting machine and the hydraulic buffer at the bottom of the overpass T-beam. During the process of lifting the overpass T-beam to the bridge erecting machine and starting to advance it above the existing line along the preset path, the horizontal measured distance between the end of the overpass T-beam and the center line of the existing line, as well as the vertical measured distance between the bottom of the overpass T-beam and the top of the contact wire of the existing line, are continuously collected by the clearance sensor group. The programmable logic controller compares the measured horizontal distance with a preset horizontal warning distance range, and simultaneously compares the measured vertical distance with a preset vertical warning distance range. The horizontal warning distance range includes a first horizontal distance sub-range and a second horizontal distance sub-range, and the vertical warning distance range includes a first vertical distance sub-range and a second vertical distance sub-range. The lower limit of the first horizontal distance sub-range is greater than the upper limit of the second horizontal distance sub-range, and the lower limit of the first vertical distance sub-range is greater than the upper limit of the second vertical distance sub-range. When the measured horizontal distance falls into the first horizontal distance sub-range or the measured vertical distance falls into the first vertical distance sub-range, the programmable logic controller sends a deceleration command to the bridge erecting machine's propulsion control system, reducing the propulsion speed of the overpass T-beam to 0.02~0.05m / s, and simultaneously activates the audible and visual alarm to issue a deceleration warning signal. When the measured horizontal distance falls into the second horizontal distance sub-range or the measured vertical distance falls into the second vertical distance sub-range, the programmable logic controller sends a stop command to the propulsion control system of the bridge erecting machine, causing the T-beam of the overpass to stop advancing, and at the same time sends an extension command to the hydraulic buffer, causing the piston rod of the hydraulic buffer to extend downward from the bottom of the T-beam of the overpass to a position 0.05~0.10m above the top of the contact wire. After the measured horizontal distance and the measured vertical distance both exit the second horizontal distance sub-range, the programmable logic controller sends a retraction command to the hydraulic buffer, causing the piston rod to retract to the bottom of the overpass T-beam, and sends a recovery command to the propulsion control system of the bridge erecting machine, so that the overpass T-beam returns to the propulsion speed before the pause.

[0005] Preferably, the clearance sensor group includes four horizontal laser ranging sensors and four vertical laser ranging sensors. The four horizontal laser ranging sensors are symmetrically installed on fixed columns on both sides of the existing line, and the measuring axis is perpendicular to the center line of the existing line. The four vertical laser ranging sensors are installed on the top of the fixed column where each horizontal laser ranging sensor is located, and the measuring axis is vertically upward. The continuous acquisition refers to synchronously reading the output values ​​of eight sensors at a sampling frequency of 10~20Hz, calculating the arithmetic mean after removing the maximum and minimum values ​​from the output values ​​of the four horizontal laser rangefinders to obtain the horizontal measured distance, and calculating the arithmetic mean after removing the maximum and minimum values ​​from the output values ​​of the four vertical laser rangefinders to obtain the vertical measured distance.

[0006] Preferably, the preset horizontal warning distance range is determined based on the fixed horizontal distance D from the centerline of the existing line to the clearance boundary of the existing line equipment and the width W of the overpass T-beam. The first horizontal distance sub-range is [DW / 2-c, DW / 2-d], the second horizontal distance sub-range is [DW / 2-a, DW / 2-b], a, b, c, and d are constant ranges and satisfy a > b > c > d. The value range of a is 0.30~0.50m, the value range of b is 0.05~0.15m, the value range of c is 0.08~0.12m, and the value range of d is 0.02~0.05m. The preset vertical warning distance range is determined based on the fixed vertical distance H from the top of the existing overhead contact line to the top of the existing equipment clearance and the structural height S of the lowest point of the bottom of the overpass T-beam. The first vertical distance sub-range is [HSg, HSh], the second vertical distance sub-range is [HSe, HSf], and e, f, g, and h are constant ranges and satisfy e > f > g > h. The value range of e is 0.25~0.40m, the value range of f is 0.08~0.15m, the value range of g is 0.10~0.15m, and the value range of h is 0.02~0.06m.

[0007] Preferably, the deceleration warning signal emitted by the audible and visual alarm includes a yellow flash and an intermittent buzzing sound. The programmable logic controller adjusts the frequency of the yellow flash and the interval of the intermittent buzzing sound in real time based on the horizontal deviation value when the measured horizontal distance falls into the first horizontal distance sub-range or the vertical deviation value when the measured vertical distance falls into the first vertical distance sub-range. The horizontal deviation value is the upper limit of the first horizontal distance sub-range minus the measured horizontal distance, and the vertical deviation value is the upper limit of the first vertical distance sub-range minus the measured vertical distance. When the horizontal or vertical deviation value is greater than 0.08m, the frequency of the yellow flash is 4~6Hz, and the interval of the intermittent buzzing sound is 0.3~0.6s; when the horizontal or vertical deviation value is greater than 0.04m and less than or equal to 0.08m, the frequency of the yellow flash is 2~4Hz, and the interval of the intermittent buzzing sound is 1~2s; when the horizontal or vertical deviation value is less than or equal to 0.04m, the frequency of the yellow flash is 1~2Hz, and the interval of the intermittent buzzing sound is 3~5s.

[0008] Preferably, the number of hydraulic buffers is four, fixed at the bottom of the overpass T-beam near the four corners. Each hydraulic buffer has a built-in displacement sensor and a proportional throttle valve. While sending a stop command, the programmable logic controller calculates the required target extension length for each hydraulic buffer based on the horizontal and vertical hazard proximity levels. The horizontal hazard proximity level is defined as the lower limit of the second horizontal distance sub-range minus the measured horizontal distance, with the difference being zero when negative. The vertical hazard proximity level is defined as the lower limit of the second vertical distance sub-range minus the measured vertical distance, with the difference being zero when negative. The difference is zero when it is negative; the target extension length is in the range of 0.05~0.10m above the top of the contact wire and is positively correlated with the larger of the horizontal hazard approach degree and the vertical hazard approach degree; the programmable logic controller controls the piston rod of each hydraulic buffer to extend at a first speed of 0.08~0.12m / s to a position 0.02~0.03m away from the target extension length through a proportional throttle valve, and then to extend to the target extension length at a second speed of 0.01~0.02m / s. At the same time, the actual extension length of the piston rod is fed back in real time through the displacement sensor for closed-loop control.

[0009] Preferably, after the programmable logic controller (PLC) detects that the horizontal measured distance has exited the second horizontal distance sub-range and the vertical measured distance has exited the second vertical distance sub-range, it first starts a 0.5s~1.5s delay confirmation timing. If the horizontal or vertical measured distance falls back into the corresponding second sub-range during the delay confirmation timing, the delay confirmation timing is reset and the system remains stopped. After the delay confirmation timing ends, the PLC sends a retraction command to the hydraulic buffers. The retraction command includes staged speed control: at a first retraction speed of 0.06~0.10m / s, all hydraulic buffer piston rods are synchronously retracted to 30%~50% of the total extension length, and then at a second retraction speed of 0.02~0.04m / s, the piston rods are synchronously retracted to the bottom of the overpass T-beam. After the PLC confirms through the displacement sensor built into each hydraulic buffer that the actual position of all piston rods has retracted to a position no more than 0.005m from the bottom of the overpass T-beam, it sends a recovery command to the bridge erecting machine's propulsion control system, causing the overpass T-beam to resume propulsion at the propulsion speed before the pause.

[0010] Preferably, after the piston rod of the hydraulic buffer extends to a position 0.05~0.10m above the top of the contact wire and the overpass T-beam is in a paused advancing state, the programmable logic controller (PLC) enters the drift compensation monitoring mode. It continuously collects the measured horizontal and vertical distances at a sampling frequency of 50~100Hz, and calculates the rate of change of horizontal and vertical distances every 0.2s. When the absolute value of the rate of change of horizontal distance is greater than 0.008m / s and the duration exceeds 0.5s, the PLC sends a dynamic adjustment command to the two hydraulic buffers located in front of the T-beam advancing direction, according to the direction of the rate of change of horizontal distance, causing the piston rods of these two hydraulic buffers to increase by 0.005m / s respectively. The extension length is ~0.015m to counteract horizontal drift; when the absolute value of the vertical distance change rate is greater than 0.005m / s and the duration exceeds 0.5s, the programmable logic controller simultaneously sends a dynamic adjustment command to all four hydraulic buffers, causing the piston rods of the four hydraulic buffers to synchronously increase the extension length by 0.005~0.015m to counteract vertical sinking drift; the total extension length of the piston rod after dynamic adjustment does not exceed 0.12m above the top of the contact wire, and after both the horizontal distance change rate and the vertical distance change rate recover to an absolute value of less than 0.002m / s and remain for 1s, the programmable logic controller gradually pulls back the extension length of the piston rod to the initial position of 0.05~0.10m above the top of the contact wire.

[0011] Preferably, after the programmable logic controller (PLC) sends a stop command to the bridge erecting machine's propulsion control system and suspends the advancement of the overpass T-beam, the PLC enters a boundary locking mode, recording the measured horizontal and vertical distances at the time the stop command was triggered as the horizontal locking reference and vertical locking reference, respectively. During the boundary locking mode activation, the PLC ignores the variability in the measured horizontal distance near the boundary of the second horizontal distance sub-range and exits the judgment condition only if the measured horizontal distance is greater than the horizontal locking reference plus a hysteresis of 0.02 to 0.04 m for 0.5 to 1.0 s consecutively. When incrementing, the measured horizontal distance is determined to have exited the second horizontal distance sub-range. Similarly, the measured vertical distance is determined to have exited the second vertical distance sub-range only when it is greater than the vertical locking reference plus a hysteresis increment of 0.02 to 0.04 m for 0.5 to 1.0 s consecutively. In boundary locking mode, the programmable logic controller (PLC) is prohibited from sending any retraction command to the hydraulic buffer unless both the measured horizontal and vertical distances simultaneously meet the above exit determination conditions. When both exit determination conditions are met, the PLC releases the boundary locking mode and then executes the retraction and recovery commands.

[0012] This invention offers at least the following advantages: Through tiered early warning, phased control, and physical protection with hydraulic buffers, the safe distance to existing railway line equipment can be effectively controlled during the erection of the overpass T-beam. The use of multi-sensor redundant measurement and extreme value elimination improves distance measurement reliability. The introduction of drift compensation and boundary locking modes reduces malfunctions caused by wind loads, vibrations, or noise, making the entire erection process smoother. The entire process is automatically executed by a programmable logic controller, reducing the risk of human error while balancing construction efficiency and the operational safety of existing railway lines.

[0013] 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

[0014] 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.

[0015] This invention provides a method for coordination and collision avoidance early warning during the erection of T-beams for overpasses, taking into account interference from existing railway lines, comprising the following steps: S1. Install clearance sensor groups and audible and visual alarms on both sides of the existing line, and connect the clearance sensor groups to the programmable logic controller. The programmable logic controller is also connected to the propulsion control system of the bridge erecting machine and the hydraulic buffer at the bottom of the overpass T-beam. Specifically, the clearance sensor group can use laser rangefinders or ultrasonic rangefinders. The audible and visual alarm can be an integrated LED flashlight and piezoelectric buzzer. The programmable logic controller (PLC) can be a small modular PLC, such as a model with digital input / output modules and analog input modules. The bridge erecting machine's propulsion control system typically includes a frequency converter and a propulsion motor; the PLC connects to the frequency converter's control terminals via digital output terminals. The hydraulic buffer can be a single-acting hydraulic cylinder with a spring return function, incorporating a displacement sensor and a proportional throttle valve. The clearance sensor group is installed on fixed columns on both sides of the existing track. The columns are typically steel or concrete structures, with the bottom buried below ground level. The sensor installation height is approximately 1.5-2.0 meters above the rail surface. The audible and visual alarm is installed on the upper part of the column, approximately 3-4 meters above the ground, facing the construction area. The PLC is installed in a safe area outside the existing track, usually housed in a dustproof and waterproof control cabinet. The hydraulic buffer is bolted to the four corners of the bottom of the bridge T-beam, with each buffer's mounting surface flush against the bottom surface of the T-beam.

[0016] After the equipment is powered on, the programmable logic controller performs a self-test and reads the initial values ​​of the clearance sensor group to confirm that all equipment is communicating normally. When the bridge erecting machine starts to advance, the programmable logic controller receives sensor signals in real time and executes preset logic judgments.

[0017] S2. During the process of lifting the overpass T-beam to the bridge erecting machine and starting to advance it above the existing line along the preset path, the horizontal measured distance between the end of the overpass T-beam and the center line of the existing line and the vertical measured distance between the bottom of the overpass T-beam and the top of the contact wire of the existing line are continuously collected by the clearance sensor group. Specifically, the horizontal measured distance is defined as the shortest horizontal distance from the outermost point of the overpass T-beam end to the centerline of the existing railway line. The vertical measured distance is defined as the vertical distance from the lowest point of the bottom of the overpass T-beam to the highest point of the top of the existing railway line's contact wire. Continuous data acquisition can be performed at a sampling frequency of 10Hz to 20Hz. The clearance sensor group can include four horizontal laser rangefinders and four vertical laser rangefinders. The four horizontal sensors are symmetrically installed in pairs on fixed columns on both sides of the existing railway line, with the measurement axis perpendicular to the centerline of the existing railway line; the four vertical sensors are installed one-to-one on the top of the fixed column where each horizontal sensor is located, with the measurement axis vertically upward.

[0018] After the bridge erecting machine lifts the overpass T-beam to the predetermined height, it slowly advances horizontally along the preset path towards the existing line. During the advancement process, the sensor group synchronously reads the output value of each sensor at a set sampling frequency, and the programmable logic controller stores the read values ​​into its internal register.

[0019] S3. The programmable logic controller compares the measured horizontal distance with a preset horizontal warning distance range, and simultaneously compares the measured vertical distance with a preset vertical warning distance range. The horizontal warning distance range includes a first horizontal distance sub-range and a second horizontal distance sub-range, and the vertical warning distance range includes a first vertical distance sub-range and a second vertical distance sub-range. The lower limit of the first horizontal distance sub-range is greater than the upper limit of the second horizontal distance sub-range, and the lower limit of the first vertical distance sub-range is greater than the upper limit of the second vertical distance sub-range. Specifically, the horizontal warning distance range is determined based on the fixed horizontal distance D from the centerline of the existing railway line to the equipment clearance boundary of the existing railway line and the width W of the overpass T-beam. The first horizontal distance sub-range is [DW / 2-c, DW / 2-d], where c ranges from 0.08 to 0.12 m and d ranges from 0.02 to 0.05 m. The second horizontal distance sub-range is [DW / 2-a, DW / 2-b], where a ranges from 0.30 to 0.50 m and b ranges from 0.05 to 0.15 m. For example, when D=3.0m and W=1.5m, the first horizontal distance sub-range is [3.0-0.75-0.10, 3.0-0.75-0.03]=[2.15m, 2.22m], and the second horizontal distance sub-range is [3.0-0.75-0.40, 3.0-0.75-0.10]=[1.85m, 2.15m]. The vertical warning distance range is determined based on the fixed vertical distance H from the top of the existing overhead contact line to the top of the existing equipment clearance and the structural height S of the lowest point of the bottom of the overpass T-beam. The first vertical distance sub-range is [HSg, HSh], where the value of g ranges from 0.10 to 0.15m, and the value of h ranges from 0.02 to 0.06m. The second vertical distance sub-range is [HSe, HSf], where the value of e ranges from 0.25 to 0.40 m, and the value of f ranges from 0.08 to 0.15 m. For example, when H = 6.5 m and S = 1.2 m, the first vertical distance sub-range is [6.5-1.2-0.12, 6.5-1.2-0.04] = [5.18 m, 5.26 m], and the second vertical distance sub-range is [6.5-1.2-0.30, 6.5-1.2-0.10] = [5.00 m, 5.20 m].

[0020] The programmable logic controller compares the measured horizontal distance with the two sub-ranges mentioned above, and also compares the measured vertical distance with the two sub-ranges mentioned above.

[0021] During construction, the D and H values ​​are obtained from the design drawings of the existing line, and the W and S values ​​are obtained from the design drawings of the overpass T-beam. Then, these values ​​are written as constants into the preset values ​​of the comparison instruction in the programmable logic controller programming software.

[0022] S4. When the measured horizontal distance falls into the first horizontal distance sub-range or the measured vertical distance falls into the first vertical distance sub-range, the programmable logic controller sends a deceleration command to the bridge erecting machine's propulsion control system, reducing the propulsion speed of the overpass T-beam to 0.02~0.05m / s, and simultaneously activates the audible and visual alarm to issue a deceleration warning signal. Specifically, the propulsion speed can be selected as 0.02 m / s, 0.03 m / s, 0.04 m / s, or 0.05 m / s. The deceleration warning signal may include a yellow flashing light and intermittent beeping sounds. The programmable logic controller (PLC) adjusts the frequency of the yellow flashing light and the interval of the intermittent beeping sounds in real time based on the horizontal deviation value when the measured horizontal distance falls within the first horizontal distance sub-range, or the vertical deviation value when the measured vertical distance falls within the first vertical distance sub-range. The horizontal deviation value is the upper limit of the first horizontal distance sub-range minus the measured horizontal distance, and the vertical deviation value is the upper limit of the first vertical distance sub-range minus the measured vertical distance. When the horizontal or vertical deviation is greater than 0.08m, the frequency of the yellow flash is set to 4~6Hz, and the interval of the intermittent beeping is set to 0.3~0.6s; when the horizontal or vertical deviation is greater than 0.04m and less than or equal to 0.08m, the frequency of the yellow flash is set to 2~4Hz, and the interval of the intermittent beeping is set to 1~2s; when the horizontal or vertical deviation is less than or equal to 0.04m, the frequency of the yellow flash is set to 1~2Hz, and the interval of the intermittent beeping is set to 3~5s.

[0023] When the judgment condition is met, one digital output point of the programmable logic controller outputs a high level to the speed control terminal of the frequency converter of the bridge erecting machine propulsion control system. The frequency converter reduces the motor speed to the corresponding speed according to the preset deceleration ramp time. At the same time, the other two output points of the programmable logic controller control the flashing and buzzer of the audible and visual alarm respectively, and output pulse signals according to the calculated frequency and interval time.

[0024] S5. When the measured horizontal distance falls into the second horizontal distance sub-range or the measured vertical distance falls into the second vertical distance sub-range, the programmable logic controller sends a stop command to the propulsion control system of the bridge erecting machine to stop the advancement of the overpass T-beam, and at the same time sends an extension command to the hydraulic buffer to extend the piston rod of the hydraulic buffer from the bottom of the overpass T-beam downward to a position 0.05~0.10m above the top of the contact wire. Specifically, four hydraulic buffers are installed, fixed at the bottom of the overhead bridge T-beams near the four corners. Each hydraulic buffer has a built-in displacement sensor and a proportional throttle valve. Simultaneously with sending a stop command, the programmable logic controller (PLC) calculates the required target extension length for each hydraulic buffer based on both the horizontal and vertical hazard proximity levels. The horizontal hazard proximity level is defined as the lower limit of a second horizontal distance sub-range minus the measured horizontal distance, with the difference set to zero when negative. The vertical hazard proximity level is defined as the lower limit of a second vertical distance sub-range minus the measured vertical distance, with the difference set to zero when negative. The target extension length is within the range of 0.05~0.10m above the top of the overhead contact line and is positively correlated with the larger of the horizontal and vertical hazard proximity levels.

[0025] Specifically, the target extension length can be determined according to formula L. target = L base The calculation is based on +k×max(horizontal hazard proximity, vertical hazard proximity), where L... base The base extension length corresponds to 0.05m above the top of the contact wire, and k is a proportional coefficient ranging from 0.1 to 0.3. The programmable logic controller (PLC) controls the piston rod of each hydraulic buffer to extend at a first speed of 0.08~0.12m / s to a position 0.02~0.03m away from the target extension length, and then at a second speed of 0.01~0.02m / s to the target extension length. Simultaneously, a displacement sensor provides real-time feedback on the actual extension length of the piston rod for closed-loop control. For example, the first speed can be selected as 0.08m / s, 0.10m / s, or 0.12m / s, and the second speed can be selected as 0.01m / s, 0.015m / s, or 0.02m / s.

[0026] When the judgment condition is met, the programmable logic controller (PLC) sends a stop command to the bridge erecting machine's propulsion control system. This command is typically a disconnection of the propulsion enable signal. Simultaneously, the PLC reads the current values ​​from the four displacement sensors, calculates the required target extension length for each buffer, and then sends the corresponding control voltage or current signal to each proportional throttle valve via the analog output module, causing the piston rod to extend at a two-stage speed. The displacement sensors can be magnetostrictive or resistive, with a measurement accuracy of up to 0.001m.

[0027] S6. After the measured horizontal distance and the measured vertical distance both exit the second horizontal distance sub-range and exit the second vertical distance sub-range, the programmable logic controller sends a retraction command to the hydraulic buffer, causing the piston rod to retract to the bottom of the overpass T-beam, and sends a recovery command to the propulsion control system of the bridge erecting machine, so that the overpass T-beam returns to the propulsion speed before the pause.

[0028] Specifically, after detecting that the horizontal measured distance has exited the second horizontal distance sub-range and the vertical measured distance has exited the second vertical distance sub-range, the programmable logic controller (PLC) can first initiate a 0.5-1.5s delay confirmation timing. If the horizontal or vertical measured distance falls back into the corresponding second sub-range during the delay confirmation timing, the delay confirmation timing is reset and the system remains stopped. After the delay confirmation timing ends, the PLC sends a retraction command to the hydraulic buffers. The retraction command can include staged speed control: at a first retraction speed of 0.06-0.10 m / s, all hydraulic buffer piston rods are synchronously retracted to 30%-50% of their total extension length, and then at a second retraction speed of 0.02-0.04 m / s, the piston rods are synchronously retracted to the bottom of the overpass T-beam. After the PLC confirms, through the displacement sensor built into each hydraulic buffer, that the actual position of all piston rods has retracted to a position no more than 0.005m from the bottom of the overpass T-beam, it sends a recovery command to the bridge erecting machine's propulsion control system, causing the overpass T-beam to resume propulsion at the speed before the pause. For example, the first retraction speed can be selected as 0.06 m / s, 0.08 m / s, or 0.10 m / s, and the second retraction speed can be selected as 0.02 m / s, 0.03 m / s, or 0.04 m / s.

[0029] The programmable logic controller (PLC) continuously reads the measured horizontal and vertical distances. When both distances are greater than the corresponding exit threshold, a delay counter is started. If either distance falls below the threshold again during the delay period, the counter is reset to zero. After the delay, the PLC sends a reverse control signal to the proportional throttle valve, causing the hydraulic oil to flow back from the piston rod side. The piston rod retracts under the action of external load and spring force. The displacement sensor provides real-time position feedback. When the target position of the first retraction stage is reached, the PLC changes the opening of the proportional throttle valve to reduce the retraction speed. When all piston rod positions are less than 0.005m, the PLC restores the enable signal of the bridge erecting machine's propulsion control system.

[0030] The aforementioned technical solution, through a tiered early warning and response mechanism, effectively controls the safe distance between the overpass T-beam and existing railway line equipment during the erection process, reducing the risk of collisions caused by operational errors or environmental factors. The deceleration warning phase provides operators with reaction time, while the stopping and hydraulic buffer extension phases provide physical protection, reducing the likelihood of rigid collisions between the overpass T-beam and the overhead contact line. The entire process is automated by a programmable logic controller, minimizing delays and errors caused by human judgment. The phased extension and retraction of the hydraulic buffer reduces impact and protects equipment and structures.

[0031] Furthermore, the clearance sensor group includes four horizontal laser ranging sensors and four vertical laser ranging sensors. The four horizontal laser ranging sensors are symmetrically installed on fixed columns on both sides of the existing line, and the measuring axis is perpendicular to the center line of the existing line. The four vertical laser ranging sensors are installed one-to-one on the top of the fixed column where each horizontal laser ranging sensor is located, and the measuring axis is vertically upward. The continuous acquisition refers to synchronously reading the output values ​​of eight sensors at a sampling frequency of 10~20Hz, calculating the arithmetic mean after removing the maximum and minimum values ​​from the output values ​​of the four horizontal laser rangefinders to obtain the horizontal measured distance, and calculating the arithmetic mean after removing the maximum and minimum values ​​from the output values ​​of the four vertical laser rangefinders to obtain the vertical measured distance.

[0032] Specifically, the horizontal laser rangefinder can be either a phase-type or pulse-type laser rangefinder, with a measurement range of 0.1~50m and an accuracy of ±1~±3mm. The vertical laser rangefinder can be the same type, with a range of 0.05~30m. The sensor housing can be made of aluminum alloy or stainless steel. All four horizontal and four vertical sensors are independent devices, each with an analog output interface, which can provide either a 4~20mA current output or a 0~10V voltage output. The sensors incorporate a temperature compensation circuit to reduce the impact of ambient temperature on measurement accuracy.

[0033] The fixed columns can be I-shaped steel columns or square steel pipe columns. The column height is determined based on the existing overhead contact line height and the advancement height of the overpass T-beam, typically 4-8m. A concrete foundation can be poured at the base of the column, with a depth of no less than 1m. Four horizontal laser distance measuring sensors are divided into two groups, with two sensors in each group installed on the same side of the existing line. The two sensors on the same side are spaced apart along the existing line direction, with an interval of 2-4m to cover the entire range of movement at the end of the overpass T-beam during advancement. Adjustable angle aluminum alloy brackets can be used for sensor mounting, and the brackets are fixed to the columns with U-bolts. The measuring axis is perpendicular to the centerline of the existing line. During installation, a theodolite or laser line projector is used for calibration to ensure that the laser beam emitted by the sensor is perpendicular to the centerline of the existing line, with an allowable deviation of no more than ±0.5°. The sensor beam height above the rail surface can be 1.5-2.0m; the specific value needs to be determined based on the design elevation of the outermost point at the end of the overpass T-beam.

[0034] The vertical laser rangefinder sensor can be selected from the same series as the horizontal sensor. Each vertical sensor is mounted on the top of the same column, specifically on a bracket extending horizontally from the top of the column. The bracket can be made of angle steel and welded or bolted to the top of the column. The measurement axis of the vertical sensor is vertically upward, meaning the laser beam is emitted vertically upward and projected onto the lower surface of the bottom of the overpass T-beam. During installation, a level or inclinometer is used for calibration to ensure that the angle between the sensor axis and the plumb line does not exceed ±0.3°. The height of the sensor's emission window from the rail surface can be determined based on the column height, typically 4~7m, ensuring that the lowest point of the T-beam's bottom remains within the sensor's effective measurement range throughout the overpass T-beam's advancement process.

[0035] The sampling frequency can be selected as 10Hz, 12Hz, 15Hz, 18Hz, or 20Hz. Synchronous reading refers to the programmable logic controller (PLC) simultaneously reading the current output values ​​of eight sensors within one scan cycle. To achieve synchronization, each sensor can have a synchronization trigger terminal. The PLC sends trigger pulses to all sensors simultaneously through a common digital output point. Upon receiving the trigger pulse, the sensors measure and lock their output values ​​at the same time. Alternatively, RS485 bus communication can be used, with the PLC broadcasting the synchronous reading command. The operation process is as follows: The PLC internally sets a timer interrupt, with the time interval equal to the reciprocal of the sampling period. For example, a sampling frequency of 20Hz corresponds to a 50ms interval. Each time the interrupt service routine is entered, the PLC first outputs a 10μs pulse to the synchronization terminal of all sensors, then delays for 1ms to wait for the sensors to complete the measurement, and then sequentially reads the output voltage or current values ​​of the eight sensors through the analog input module, converts them into distance values, and stores them in an array.

[0036] The method of calculating the arithmetic mean after removing one maximum and one minimum value can reduce the impact of outliers caused by occasional sensor noise or obstruction. The specific process is as follows: The programmable logic controller (PLC) stores the readings from the four horizontal sensors in an array of length 4. It calls a sorting algorithm to sort the array in ascending order of values, then discards the first and last elements. The sum of the two remaining intermediate values ​​is divided by 2 to obtain the measured horizontal distance. If two or more of the four values ​​are identical and happen to be the maximum or minimum value (e.g., three identical maximum values), after removing one maximum value, two maximum values ​​and one minimum value remain. Removing the minimum value leaves two maximum values, and the average value equals the maximum value. The calculation method for the measured vertical distance is similar to that for the horizontal direction. The PLC sorts the readings from the four vertical sensors, removes the maximum and minimum values, and calculates the arithmetic mean of the remaining two values. Since the vertical direction is more susceptible to transient interference from birds, dust, or rain, removing extreme values ​​can effectively improve measurement reliability.

[0037] The above technical solution, by employing four sets of horizontal sensors and four sets of vertical sensors arranged symmetrically, can reduce single-point measurement errors. The averaging method, which removes the maximum and minimum values, filters out instantaneous interference. The sampling frequency of 10~20Hz enables real-time tracking of distance changes during the advancement of the overpass T-beam, providing timely data for subsequent deceleration, stopping, and hydraulic buffer extension. The sensors are mounted on fixed columns, avoiding vibration and positioning errors caused by the movement of the bridge erecting machine.

[0038] Furthermore, the preset horizontal warning distance range is determined based on the fixed horizontal distance D from the centerline of the existing line to the clearance boundary of the existing line equipment and the width W of the overpass T-beam. The first horizontal distance sub-range is [DW / 2-c, DW / 2-d], and the second horizontal distance sub-range is [DW / 2-a, DW / 2-b]. a, b, c, and d are constant ranges and satisfy a > b > c > d. The value range of a is 0.30~0.50m, the value range of b is 0.05~0.15m, the value range of c is 0.08~0.12m, and the value range of d is 0.02~0.05m. The preset vertical warning distance range is determined based on the fixed vertical distance H from the top of the existing overhead contact line to the top of the existing equipment clearance and the structural height S of the lowest point of the bottom of the overpass T-beam. The first vertical distance sub-range is [HSg, HSh], the second vertical distance sub-range is [HSe, HSf], and e, f, g, and h are constant ranges and satisfy e > f > g > h. The value range of e is 0.25~0.40m, the value range of f is 0.08~0.15m, the value range of g is 0.10~0.15m, and the value range of h is 0.02~0.06m.

[0039] The above technical solution presets the horizontal warning distance range based on the fixed horizontal distance D of the existing line equipment clearance and the width W of the overpass T-beam, and further divides it into first and second horizontal distance sub-ranges. Simultaneously, it presets the vertical warning distance range based on the fixed vertical distance H from the top of the contact wire to the top of the equipment clearance and the bottom structural height S of the T-beam, and divides it into first and second vertical distance sub-ranges. This allows the warning threshold to be customized according to the actual dimensions of different projects. The value ranges of a, b, c, d, and e, f, g, h are all selected from engineering experience data, which can reduce unnecessary deceleration and stopping while ensuring safety redundancy, thus improving erection efficiency. The hierarchical setting of the two sub-ranges and the order a > b > c > d and e > f > g > h ensure that deceleration warning occurs before stopping warning, with clear logic, facilitating hierarchical control by the programmable logic controller.

[0040] Furthermore, the deceleration warning signal emitted by the audible and visual alarm includes a yellow flash and intermittent buzzing. The programmable logic controller adjusts the frequency of the yellow flash and the interval of the intermittent buzzing in real time based on the horizontal deviation value when the measured horizontal distance falls into the first horizontal distance sub-range or the vertical deviation value when the measured vertical distance falls into the first vertical distance sub-range. The horizontal deviation value is the upper limit of the first horizontal distance sub-range minus the measured horizontal distance, and the vertical deviation value is the upper limit of the first vertical distance sub-range minus the measured vertical distance. When the horizontal or vertical deviation value is greater than 0.08m, the frequency of the yellow flash is 4~6Hz, and the interval of the intermittent buzzing is 0.3~0.6s; when the horizontal or vertical deviation value is greater than 0.04m and less than or equal to 0.08m, the frequency of the yellow flash is 2~4Hz, and the interval of the intermittent buzzing is 1~2s; when the horizontal or vertical deviation value is less than or equal to 0.04m, the frequency of the yellow flash is 1~2Hz, and the interval of the intermittent buzzing is 3~5s.

[0041] The aforementioned technical solution links the frequency of the yellow flashing lights and the interval of the intermittent buzzing of the audible and visual alarm to the horizontal or vertical deviation values. This allows operators to intuitively judge the degree to which the T-beam of the overpass approaches the clearance limit based on changes in the alarm signal. Larger deviations result in higher alarm frequencies and shorter intervals, indicating a higher level of danger requiring immediate attention; smaller deviations result in lower alarm frequencies and longer intervals, avoiding frequent, loud alarms that might distract operators. This tiered alarm system provides richer information than a single, constant-frequency alarm, helping on-site command and bridge erecting machine operators to take timely adjustments and improving human-machine collaboration efficiency.

[0042] Furthermore, the number of hydraulic buffers is four, fixed at the bottom of the overpass T-beam near the four corners. Each hydraulic buffer has a built-in displacement sensor and a proportional throttle valve. While sending a stop command, the programmable logic controller calculates the required target extension length for each hydraulic buffer based on the horizontal and vertical hazard proximity levels. The horizontal hazard proximity level is defined as the lower limit of the second horizontal distance sub-range minus the measured horizontal distance, with the difference being zero when negative. The vertical hazard proximity level is defined as the lower limit of the second vertical distance sub-range minus the measured vertical distance, with the difference being zero when negative. The difference is zero when it is negative; the target extension length is in the range of 0.05~0.10m above the top of the contact wire and is positively correlated with the larger of the horizontal hazard approach degree and the vertical hazard approach degree; the programmable logic controller controls the piston rod of each hydraulic buffer to extend at a first speed of 0.08~0.12m / s to a position 0.02~0.03m away from the target extension length through a proportional throttle valve, and then to extend to the target extension length at a second speed of 0.01~0.02m / s. At the same time, the actual extension length of the piston rod is fed back in real time through the displacement sensor for closed-loop control.

[0043] The aforementioned technical solution involves installing hydraulic buffers equipped with displacement sensors and proportional throttle valves at the four corners of the bottom of the overpass T-beam. The target extension length of each buffer is independently calculated based on the greater of the horizontal and vertical hazard proximity levels, allowing the buffer's protective position to adapt to the actual attitude deviations of the beam at different stages of its advancement. The two-stage extension control method first extends at a relatively fast speed to near the target position, then at a slower speed to precisely reach the target position. This reduces the inertial impact during the piston rod extension process, avoiding unexpected disturbances to the overhead contact line. The displacement sensors and proportional throttle valves, in conjunction with a programmable logic controller (PLC), form a closed-loop control system, ensuring that the error between the actual extension length and the target value is kept within a small range, thus reliably forming physical isolation above the overhead contact line. Furthermore, the greater the hazard proximity, the longer the target extension length, reflecting the principle of on-demand protection, avoiding excessive extension when unnecessary and minimizing encroachment on existing railway operating space.

[0044] Furthermore, after detecting that the horizontal measured distance has exited the second horizontal distance sub-range and the vertical measured distance has exited the second vertical distance sub-range, the programmable logic controller (PLC) first starts a 0.5s~1.5s delay confirmation timer. If the horizontal or vertical measured distance falls back into the corresponding second sub-range during the delay confirmation timer, the delay confirmation timer is reset and the system remains stopped. After the delay confirmation timer ends, the PLC sends a retraction command to the hydraulic buffers. The retraction command includes staged speed control: at a first retraction speed of 0.06~0.10m / s, all hydraulic buffer piston rods are synchronously retracted to 30%~50% of their total extension length, and then at a second retraction speed of 0.02~0.04m / s, the piston rods are synchronously retracted to the bottom of the overpass T-beam. After the PLC confirms through the displacement sensor built into each hydraulic buffer that the actual position of all piston rods has retracted to a position no more than 0.005m from the bottom of the overpass T-beam, it sends a recovery command to the bridge erecting machine's propulsion control system, causing the overpass T-beam to resume propulsion at the speed before the pause.

[0045] The above technical solution, by introducing a 0.5-1.5s delay confirmation time after exiting the dangerous state, avoids frequent retraction and recovery actions due to short-term fluctuations in distance values, thus improving the stability and reliability of the system. The phased retraction control method first retracts the piston rod to most of its stroke at a relatively fast speed, then completes the final retraction at a slower speed. This reduces the impact during hydraulic system return oil and extends the service life of the buffer seals and cylinder. Simultaneously, the recovery propulsion command is only sent after all piston rods have retracted to within 0.005m of the bottom of the T-beam, ensuring complete buffer reset and preventing accidental contact between the piston rod and the contact wire during subsequent propulsion. This sequential control logic ensures a smooth and orderly exit and recovery process, balancing construction efficiency and equipment safety.

[0046] In another embodiment, after the piston rod of the hydraulic buffer extends to a position 0.05~0.10m above the top of the contact wire and the overpass T-beam is in a paused advancing state, the programmable logic controller (PLC) enters a drift compensation monitoring mode. It continuously collects the measured horizontal and vertical distances at a sampling frequency of 50~100Hz, and calculates the rate of change of horizontal and vertical distances every 0.2s. When the absolute value of the rate of change of horizontal distance is greater than 0.008m / s and the duration exceeds 0.5s, the PLC sends a dynamic adjustment command to the two hydraulic buffers located ahead of the T-beam advancing direction, according to the direction of the rate of change of horizontal distance, causing the piston rods of these two hydraulic buffers to increase by 0.00m / s respectively. An extension length of 5~0.015m is added to counteract horizontal drift. When the absolute value of the vertical distance change rate is greater than 0.005m / s and the duration exceeds 0.5s, the programmable logic controller (PLC) simultaneously sends a dynamic adjustment command to all four hydraulic dampers, causing the piston rods of the four hydraulic dampers to synchronously increase their extension length by 0.005~0.015m to counteract vertical sinking drift. The total extension length of the piston rod after dynamic adjustment does not exceed 0.12m above the top of the contact wire. After both the horizontal and vertical distance change rates recover to an absolute value of less than 0.002m / s and remain so for 1s, the PLC gradually reverts the extension length of the piston rods back to the initial position of 0.05~0.10m above the top of the contact wire.

[0047] Specifically, the drift compensation monitoring mode is a software operating state in which the programmable logic controller (PLC) performs higher-frequency data acquisition and rate-of-change calculation. This mode is automatically activated after the overpass T-beam has paused its advancement and the hydraulic damper has extended to its position. Upon entering this mode, the PLC records the current extension length of each piston rod as an initial reference value. After completing the stop command and the hydraulic damper extension command, the PLC detects that the overpass T-beam's advancement speed is 0 and the actual extension length of all piston rods has reached the target value, and then sets an internal status flag indicating that the drift compensation mode is activated.

[0048] The sampling frequency can be selected as 50Hz, 60Hz, 80Hz, or 100Hz. The programmable logic controller (PLC) continuously reads the measured horizontal and vertical distances at the set sampling frequency. After each value is read, it is stored in a circular buffer. The buffer length corresponds to the number of sampling points within 0.2 seconds; for example, at a sampling frequency of 100Hz, 0.2 seconds corresponds to 20 points. For each new data acquisition, the distance difference between the current time and the time 0.2 seconds ago is calculated, and then divided by 0.2 seconds to obtain the rate of change, in m / s. To avoid noise interference, a moving average filter can be applied to the acquired sequence first, with a filter window length of 5-10 points, before calculating the rate of change. During each sampling interruption, the PLC pushes the new distance value into the buffer, then retrieves the value from 0.2 seconds ago from the head of the buffer, calculates the difference, divides it by 0.2 to obtain the current rate of change, and stores it in the rate of change register.

[0049] A programmable logic controller (PLC) is set to use a timer. The timer starts when the absolute value of the rate of change exceeds a threshold. If the timer reaches 0.5 seconds and the rate of change consistently exceeds the threshold, horizontal drift compensation is triggered. If the rate of change falls below the threshold within 0.5 seconds, the timer is reset. Direction determination: The sign of the rate of change in horizontal distance indicates the drift direction. A positive rate of change indicates an increase in the measured distance, meaning the overpass T-beam is moving away from the existing line's centerline; a negative rate of change indicates a decrease in distance, meaning the distance is moving closer to the existing line's centerline.

[0050] The programmable logic controller (PLC) calculates the sign of the rate of change. If it is negative and the absolute value exceeds the threshold for 0.5 seconds, it outputs an analog signal to the proportional throttle valves of the two front buffers, increasing the piston rod extension length by 0.005~0.015m. The extension length can be selected as 0.005m, 0.008m, 0.010m, 0.012m, or 0.015m. The increase can be positively correlated with the magnitude of the absolute value of the rate of change; for example, the larger the absolute value, the greater the increase. The hydraulic buffers can be supplied with oil from the same hydraulic station, with each buffer controlled by an independent proportional valve. The PLC increases the opening of the proportional throttle valve of the front buffer through the analog output module, allowing more hydraulic oil to enter the rodless chamber, increasing the piston rod extension length. The displacement sensor provides real-time feedback on the length, and the proportional valve closes once the target increment is reached.

[0051] A positive vertical change rate indicates an increased upward distance for the beam, while a negative rate indicates a decreased downward distance. Downward drift, or a negative change rate, indicates the beam is moving downwards towards the contact wire. In this case, all four buffers need to synchronously increase their extension length to lift the beam. The extension length can be selected as 0.005m, 0.008m, 0.010m, 0.012m, or 0.015m. When the absolute value of the vertical change rate is detected to be greater than 0.005m / s and lasts for more than 0.5s, and is in a negative direction, the programmable logic controller simultaneously sends the same incremental command to all four proportional throttle valves, causing the four piston rods to extend synchronously by the same length. Displacement sensors monitor in real time to ensure that the extension of each buffer is consistent, with a deviation not exceeding 0.002m.

[0052] The total extension length of the dynamically adjusted piston rod must not exceed 0.12m above the top of the overhead contact line. This means that the initial extension length is 0.05~0.10m, plus an increase of 0.005~0.015m, and the total must not exceed 0.12m. Before each adjustment, the programmable logic controller (PLC) checks whether the current extension length plus the proposed increase exceeds 0.12m; if it does, it only increases to 0.12m.

[0053] The condition for step-by-step callback is that the absolute values ​​of both the horizontal and vertical rate of change are less than 0.002 m / s and remain so for 1 second. This indicates that both directions are stable. The callback method is step-by-step; for example, the extended length is reduced by 0.002 m every 0.5 seconds until it returns to the initial range of 0.05~0.10 m. It can also be done in two stages: first, a rapid partial retraction, then a slow and precise reset. Here, the length is adjusted back to the normal length after drift compensation, while the overpass T-beam remains in a paused state. Once the stabilization condition is met, the programmable logic controller (PLC) enters the callback phase, setting a target length equal to the initial length, and then decreasing it in steps of 0.001~0.003 m each time, holding each step for 0.2~0.5 seconds, until the difference between the actual length and the target length is less than 0.001 m. If the rate of change exceeds the threshold again during the callback process, the callback is immediately stopped and the drift compensation mode is re-entered. After the callback is completed, the PLC exits the drift compensation monitoring mode but remains in a paused state, waiting for the subsequent exit condition for the second sub-range.

[0054] The aforementioned technical solution, when advancement is paused and the buffers are extended, can promptly detect slow drift of the overpass T-beam caused by wind load, temperature changes, or elastic deformation of the bridge erecting machine by monitoring the distance change rate at high frequency. For horizontal drift, adjusting only the two buffers on the front side of the advancement direction can generate an anti-deflection moment, effectively suppressing lateral approach. For vertical sinking drift, simultaneously adjusting all four buffers can uniformly raise the beam and prevent accidental contact with the contact net. The dynamically adjusted extension length is limited to within 0.12m to avoid overcompensation and new risks. After the drift stops and stabilizes for 1 second, the extension length is gradually adjusted back to restore the initial safe clearance, creating normal conditions for subsequent resumption of advancement. The entire compensation process is completed automatically, reducing the need for manual intervention.

[0055] In another embodiment, after the programmable logic controller (PLC) sends a stop command to the bridge erecting machine's propulsion control system and suspends the advancement of the overpass T-beam, the PLC enters a boundary locking mode. It records the measured horizontal and vertical distances at the time the stop command was triggered as the horizontal locking reference and vertical locking reference, respectively. During the boundary locking mode activation, the PLC ignores the fluctuation-based exit condition for the measured horizontal distance near the boundary of the second horizontal distance sub-range, and only exits when the measured horizontal distance is continuously greater than the horizontal locking reference plus a return of 0.02 to 0.04 meters for 0.5 to 1.0 seconds. The horizontal measured distance is only considered to have exited the second horizontal distance sub-range when the difference increment is large enough. Similarly, the vertical measured distance is only considered to have exited the second vertical distance sub-range when it is greater than the vertical locking reference plus a hysteresis increment of 0.02 to 0.04 m for 0 consecutive 0.5 to 1.0 s. In boundary locking mode, the programmable logic controller (PLC) is prohibited from sending any retraction command to the hydraulic buffer unless both the horizontal and vertical measured distances simultaneously meet the above exit conditions. When both exit conditions are met, the PLC releases the boundary locking mode and then executes the retraction and recovery commands.

[0056] Specifically, boundary locking mode is a software operating state that is automatically activated after the stop command is executed. At the moment the stop command is triggered, the programmable logic controller (PLC) stores the horizontal and vertical measured distances, which are collected and calculated from the sensors, into two holding registers as the horizontal and vertical locking references, respectively. The PLC can use a data storage area with power-off retention to prevent the loss of reference values ​​after an unexpected power outage. When the horizontal measured distance falls into the second horizontal distance sub-range or the vertical measured distance falls into the second vertical distance sub-range, the PLC sends a stop command to the bridge erecting machine's propulsion control system. After the speed of the overpass T-beam drops to zero, the current distance value is immediately latched, and the boundary locking mode flag is set to 1.

[0057] The condition for determining a fluctuating exit is that, without boundary locking, if the measured horizontal distance briefly exceeds the upper limit of the second sub-range due to measurement noise, wind-induced swaying, or elastic vibration of the bridge erecting machine, the original logic might mistakenly determine that a safe exit has been achieved. In boundary locking mode, the programmable logic controller (PLC) will ignore this brief exceedance and will not trigger an exit action. Specifically, the PLC internally sets a boundary locking flag. When this flag is 1, the original direct comparison logic is bypassed, and a delayed hysteresis comparison logic is used instead.

[0058] The continuous time can be selected from 0.5s, 0.6s, 0.7s, 0.8s, 0.9s, or 1.0s. The hysteresis increment can be selected from 0.02m, 0.025m, 0.03m, 0.035m, or 0.04m. The exit condition is that the measured horizontal distance is greater than the horizontal locking reference plus the hysteresis increment, and this state needs to be maintained continuously for the set time. For example, if the horizontal locking reference is 1.85m and the hysteresis increment is 0.03m, then the exit threshold is 1.88m. Exit is determined only if the measured horizontal distance is greater than 1.88m for 0.8s consecutively. The programmable logic controller can be set with a delay timer. The input condition for the timer is that the measured horizontal distance is greater than the sum of the horizontal locking reference and the hysteresis increment. The timer setting is 0.5~1.0s. When the timer expires and the input condition is met, a horizontal exit condition satisfied signal is output. In each scan cycle, the programmable logic controller calculates the current horizontal measured distance and compares it with the exit threshold. If the distance is greater than the threshold, the timer is incremented; if the distance is less than or equal to the threshold, the timer is reset. After the timer reaches the set value, the horizontal exit flag is set.

[0059] The continuous time in the vertical direction can also be selected from 0.5 to 1.0 seconds, and the hysteresis increment can be selected from 0.02 to 0.04 meters. The vertical exit threshold is equal to the vertical lock reference plus the hysteresis increment. For example, if the vertical lock reference is 5.00 meters and the hysteresis increment is 0.03 meters, then the exit threshold is 5.03 meters. The measured vertical distance must be greater than 5.03 meters for 0.6 seconds before exit is determined. The working process is similar to that in the horizontal direction, using an independent delay timer to output a signal indicating that the vertical exit condition is met.

[0060] In boundary lock mode, sending any retraction command to the hydraulic buffer is prohibited. This means that even if either the horizontal or vertical exit condition is met individually, the aforementioned retraction and recovery commands cannot be executed. A retraction command is only allowed when both exit conditions are met simultaneously. The programmable logic controller (PLC) performs a logical AND operation on the horizontal and vertical exit condition fulfillment signals; only when the result is true is the lock released and subsequent actions executed. Simultaneously, a boundary lock mode flag is connected in series in the retraction command output circuit; when boundary lock mode is activated, the retraction command output is forced to 0.

[0061] Once both exit conditions are met, the programmable logic controller (PLC) first releases the boundary locking mode, i.e., clears the boundary locking flag, and then executes the retraction and recovery commands sequentially. Specifically, after detecting that both the horizontal and vertical exit flags are 1, the PLC first sets the boundary locking mode flag to 0, then invokes the retraction process. After all hydraulic buffer piston rods retract to the bottom of the overpass T-beam and the displacement sensors confirm their position, a recovery command is sent to resume the bridge erecting machine's advance.

[0062] The above technical solution introduces a boundary locking mode after a stop, avoiding misjudgments of danger clearance due to brief jumps in distance values ​​caused by measurement noise, wind-induced swaying, or temporary vibrations. This prevents unnecessary frequent retraction and re-extension of the hydraulic buffer. Using a locking reference plus hysteresis increment method, a true exit is only considered if the measured distance is significantly greater than the distance at the trigger stop for a certain period, improving the reliability of the exit determination. Exit conditions must be met simultaneously in both the horizontal and vertical directions, ensuring that the bridge T-beam has returned to a safe position in both the lateral and vertical directions before the buffer can be retracted and advancement can resume, enhancing construction safety. Sending retraction commands in locking mode eliminates the risk of performing actions when the state is uncertain. This method has clear logic, adjustable parameters, and is easy to adapt to the stability conditions of different construction sites.

[0063] 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. A method for collaborative construction and collision avoidance early warning of overpass T-beam erection procedures considering interference from existing railway line operations, characterized in that, Includes the following steps: Clearance sensor groups and audible and visual alarms are installed on both sides of the existing line. The clearance sensor groups are connected to a programmable logic controller (PLC). The PLC is also connected to the propulsion control system of the bridge erecting machine and the hydraulic buffer at the bottom of the overpass T-beam. During the process of lifting the overpass T-beam to the bridge erecting machine and starting to advance it above the existing line along the preset path, the horizontal measured distance between the end of the overpass T-beam and the center line of the existing line, as well as the vertical measured distance between the bottom of the overpass T-beam and the top of the contact wire of the existing line, are continuously collected by the clearance sensor group. The programmable logic controller compares the measured horizontal distance with a preset horizontal warning distance range, and simultaneously compares the measured vertical distance with a preset vertical warning distance range. The horizontal warning distance range includes a first horizontal distance sub-range and a second horizontal distance sub-range, and the vertical warning distance range includes a first vertical distance sub-range and a second vertical distance sub-range. The lower limit of the first horizontal distance sub-range is greater than the upper limit of the second horizontal distance sub-range, and the lower limit of the first vertical distance sub-range is greater than the upper limit of the second vertical distance sub-range. When the measured horizontal distance falls into the first horizontal distance sub-range or the measured vertical distance falls into the first vertical distance sub-range, the programmable logic controller sends a deceleration command to the bridge erecting machine's propulsion control system, reducing the propulsion speed of the overpass T-beam to 0.02~0.05m / s, and simultaneously activates the audible and visual alarm to issue a deceleration warning signal. When the measured horizontal distance falls into the second horizontal distance sub-range or the measured vertical distance falls into the second vertical distance sub-range, the programmable logic controller sends a stop command to the propulsion control system of the bridge erecting machine, causing the T-beam of the overpass to stop advancing, and at the same time sends an extension command to the hydraulic buffer, causing the piston rod of the hydraulic buffer to extend downward from the bottom of the T-beam of the overpass to a position 0.05~0.10m above the top of the contact wire. After the measured horizontal distance and the measured vertical distance both exit the second horizontal distance sub-range, the programmable logic controller sends a retraction command to the hydraulic buffer, causing the piston rod to retract to the bottom of the overpass T-beam, and sends a recovery command to the propulsion control system of the bridge erecting machine, so that the overpass T-beam returns to the propulsion speed before the pause.

2. The method for coordinated construction and collision avoidance early warning of the overpass T-beam erection process as described in claim 1, characterized in that, The clearance sensor group includes four horizontal laser ranging sensors and four vertical laser ranging sensors. The four horizontal laser ranging sensors are symmetrically installed on fixed columns on both sides of the existing line, and the measuring axis is perpendicular to the center line of the existing line. The four vertical laser ranging sensors are installed on the top of the fixed column where each horizontal laser ranging sensor is located, and the measuring axis is vertically upward. The continuous acquisition refers to synchronously reading the output values ​​of eight sensors at a sampling frequency of 10~20Hz, calculating the arithmetic mean after removing the maximum and minimum values ​​from the output values ​​of the four horizontal laser rangefinders to obtain the horizontal measured distance, and calculating the arithmetic mean after removing the maximum and minimum values ​​from the output values ​​of the four vertical laser rangefinders to obtain the vertical measured distance.

3. The method for coordinated construction and collision avoidance early warning of the overpass T-beam erection process as described in claim 1, characterized in that, The preset horizontal warning distance range is determined based on the fixed horizontal distance D from the centerline of the existing line to the clearance boundary of the existing line equipment and the width W of the overpass T-beam. The first horizontal distance sub-range is [DW / 2-c, DW / 2-d], and the second horizontal distance sub-range is [DW / 2-a, DW / 2-b]. a, b, c, and d are constant ranges and satisfy a > b > c > d. The value range of a is 0.30~0.50m, the value range of b is 0.05~0.15m, the value range of c is 0.08~0.12m, and the value range of d is 0.02~0.05m. The preset vertical warning distance range is determined based on the fixed vertical distance H from the top of the existing overhead contact line to the top of the existing equipment clearance and the structural height S of the lowest point of the bottom of the overpass T-beam. The first vertical distance sub-range is [HSg, HSh], the second vertical distance sub-range is [HSe, HSf], and e, f, g, and h are constant ranges and satisfy e > f > g > h. The value range of e is 0.25~0.40m, the value range of f is 0.08~0.15m, the value range of g is 0.10~0.15m, and the value range of h is 0.02~0.06m.

4. The method for coordinated construction and collision avoidance early warning of the overpass T-beam erection process as described in claim 1, characterized in that, The deceleration warning signal emitted by the audible and visual alarm includes a yellow flash and intermittent beeping. The programmable logic controller adjusts the frequency of the yellow flash and the interval of the intermittent beeping in real time based on the horizontal deviation value when the measured horizontal distance falls into the first horizontal distance sub-range or the vertical deviation value when the measured vertical distance falls into the first vertical distance sub-range. The horizontal deviation value is the upper limit of the first horizontal distance sub-range minus the measured horizontal distance, and the vertical deviation value is the upper limit of the first vertical distance sub-range minus the measured vertical distance. When the horizontal or vertical deviation value is greater than 0.08m, the frequency of the yellow flash is 4~6Hz, and the interval of the intermittent beeping is 0.3~0.6s; when the horizontal or vertical deviation value is greater than 0.04m and less than or equal to 0.08m, the frequency of the yellow flash is 2~4Hz, and the interval of the intermittent beeping is 1~2s; when the horizontal or vertical deviation value is less than or equal to 0.04m, the frequency of the yellow flash is 1~2Hz, and the interval of the intermittent beeping is 3~5s.

5. The method for coordinated construction and collision avoidance early warning of the overpass T-beam erection process as described in claim 1, characterized in that, Four hydraulic buffers are fixed at the bottom of the overpass T-beam near the four corners. Each hydraulic buffer has a built-in displacement sensor and a proportional throttle valve. While sending a stop command, the programmable logic controller (PLC) calculates the required target extension length for each hydraulic buffer based on both the horizontal and vertical hazard proximity levels. The horizontal hazard proximity level is defined as the lower limit of the second horizontal distance sub-range minus the measured horizontal distance, with the difference being zero when negative. The vertical hazard proximity level is defined as the lower limit of the second vertical distance sub-range minus the measured vertical distance, with the difference being zero when negative. When negative, it is set to zero; the target extension length is within the range of 0.05~0.10m above the top of the contact wire, and is positively correlated with the larger of the horizontal hazard approach degree and the vertical hazard approach degree; the programmable logic controller controls the piston rod of each hydraulic buffer to extend at a first speed of 0.08~0.12m / s to a position 0.02~0.03m away from the target extension length through a proportional throttle valve, and then to extend to the target extension length at a second speed of 0.01~0.02m / s. At the same time, the actual extension length of the piston rod is fed back in real time through the displacement sensor for closed-loop control.

6. The method for coordinated construction and collision avoidance early warning of the overpass T-beam erection process as described in claim 1, characterized in that, After detecting that the horizontal measured distance has exited the second horizontal distance sub-range and the vertical measured distance has exited the second vertical distance sub-range, the programmable logic controller (PLC) first starts a 0.5s~1.5s delay confirmation timer. If the horizontal or vertical measured distance falls back into the corresponding second sub-range during the delay confirmation timer, the delay confirmation timer is reset and the system remains stopped. After the delay confirmation timer ends, the PLC sends a retraction command to the hydraulic buffers. The retraction command includes staged speed control: at a first retraction speed of 0.06~0.10m / s, all hydraulic buffer piston rods are synchronously retracted to 30%~50% of their total extension length, and then at a second retraction speed of 0.02~0.04m / s, the piston rods are synchronously retracted to the bottom of the overpass T-beam. After the PLC confirms through the displacement sensor built into each hydraulic buffer that the actual position of all piston rods has retracted to a position no more than 0.005m from the bottom of the overpass T-beam, it sends a recovery command to the bridge erecting machine's propulsion control system, causing the overpass T-beam to resume propulsion at the speed before the pause.

7. The method for coordinated construction and collision avoidance early warning of the overpass T-beam erection process as described in claim 5, characterized in that, After the piston rod of the hydraulic buffer extends to a position 0.05~0.10m above the top of the contact wire and the overpass T-beam is in a paused advancing state, the programmable logic controller (PLC) enters the drift compensation monitoring mode. It continuously collects the measured horizontal and vertical distances at a sampling frequency of 50~100Hz and calculates the rate of change of horizontal and vertical distances every 0.2s. When the absolute value of the rate of change of horizontal distance is greater than 0.008m / s and the duration exceeds 0.5s, the PLC sends a dynamic adjustment command to the two hydraulic buffers located in front of the T-beam advancing direction according to the direction of the rate of change of horizontal distance, causing the piston rods of these two hydraulic buffers to increase by 0.005~0.10m respectively. The piston rods extend by 0.005 to 0.015 m to counteract horizontal drift. When the absolute value of the vertical distance change rate is greater than 0.005 m / s and the duration exceeds 0.5 s, the programmable logic controller (PLC) simultaneously sends a dynamic adjustment command to all four hydraulic dampers, causing the piston rods of the four hydraulic dampers to synchronously increase their extension length by 0.005 to 0.015 m to counteract vertical sinking drift. The total extension length of the piston rods after dynamic adjustment does not exceed 0.12 m above the top of the contact wire. After both the horizontal and vertical distance change rates recover to an absolute value of less than 0.002 m / s and remain at that level for 1 s, the PLC gradually reverts the extension length of the piston rods back to the initial position of 0.05 to 0.10 m above the top of the contact wire.

8. The method for coordinated construction and collision avoidance early warning of the overpass T-beam erection process as described in claim 5, characterized in that, After the programmable logic controller (PLC) sends a stop command to the bridge erecting machine's propulsion control system and halts the advancement of the overpass T-beam, the PLC enters boundary locking mode. It records the measured horizontal and vertical distances at the time the stop command was triggered as the horizontal locking reference and vertical locking reference, respectively. During the boundary locking mode activation, the PLC ignores the fluctuation-based exit condition for the measured horizontal distance near the boundary of the second horizontal distance sub-range. Exit only occurs when the measured horizontal distance is continuously greater than the horizontal locking reference plus a hysteresis increment of 0.02 to 0.04 meters for 0.5 to 1.0 seconds. Only when the measured horizontal distance is greater than the vertical locking reference plus a hysteresis increment of 0.02 to 0.04 m for 0.5 to 1.0 s consecutively is the measured vertical distance determined to be outside the second horizontal distance sub-range. Similarly, only when the measured vertical distance is greater than the vertical locking reference plus a hysteresis increment of 0.02 to 0.04 m for 0.5 to 1.0 s consecutively is the measured vertical distance determined to be outside the second vertical distance sub-range is the measured vertical distance determined to be outside the second vertical distance sub-range. In boundary locking mode, the programmable logic controller is prohibited from sending any retraction command to the hydraulic buffer unless the measured horizontal distance and the measured vertical distance simultaneously meet the above exit determination conditions. When both exit determination conditions are met, the programmable logic controller releases the boundary locking mode and then executes the retraction command and the recovery command.