A device for quantifying the depth of defects on the surface of underwater bridges

Abstract

This invention provides a device for quantitatively measuring the depth of surface defects on underwater bridges. In this device, a brushless DC motor drives a probe rod for axial movement. A first and second bearing housing improve the motion accuracy and stability of the probe rod. The control unit acquires the operating parameters of the brushless DC motor through a current sensor, a speed sensor, and an absolute angle encoder, thus obtaining the motion state of the probe rod. The moving auxiliary components include a handheld part for moving the device to the detection point on the bridge surface. A ring arm assembly and a curved auxiliary wheel assembly enable a reference detection distance between the device and the bridge surface, facilitating movement of the device on the bridge surface for multi-point detection. This device utilizes the principle of mechanical tactile sensing, allowing for high-precision blind measurement of crack depth on bridge pier surfaces without the need for light or clear water. Its compact structure makes it suitable for narrow spaces such as inside bridge caissons and between pile groups, providing crucial data support for bridge maintenance decisions.

Description

Technical Field

[0001] This invention belongs to the field of underwater engineering inspection technology, specifically relating to a device for quantitatively measuring the depth of surface defects on underwater bridges. Background Technology

[0002] Underwater bridge foundations are constantly exposed to complex hydrological environments, making them highly susceptible to erosion from water flow, sediment abrasion, ship impacts, and chemical corrosion. This can lead to defects such as concrete spalling, surface depressions, and even voids. If these defects are not detected and addressed promptly, they will seriously threaten the overall structural safety of the bridge.

[0003] Currently, underwater surface inspection mainly relies on the following methods: diver exploration, underwater optical photography, and sonar scanning. However, these technologies have significant limitations:

[0004] Significant impact from water quality: In some high-turbidity waters, visibility is extremely low, underwater optical equipment is almost rendered ineffective, and it is impossible to obtain clear images;

[0005] Measurement blind zone and insufficient accuracy: Although multibeam sonar or side-scan sonar has a wide detection range, when performing fine measurements at close range (a few centimeters to tens of centimeters), it has a large measurement blind zone due to multipath effect and surface scattering, making it difficult to accurately quantify the depth of tiny depressions.

[0006] Therefore, this application anticipates a contact measurement method that can automatically counteract water flow resistance interference, adapt to different water depth environments, and quantify the depth of depressions with high precision. Summary of the Invention

[0007] To address the problems in existing underwater bridge surface inspection methods, such as optical photography being severely affected by water turbidity, sonar equipment having measurement blind spots in the near field, and traditional contact measurements having a high false alarm rate due to water flow resistance interference, this invention provides a device for quantitatively measuring the depth of defects on the surface of underwater bridges.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] In a first aspect, embodiments of this disclosure provide a device for quantitatively measuring the depth of surface defects on an underwater bridge, comprising a base and a control unit. The base is provided with a detection element and a moving auxiliary element. The detection element includes a first bearing seat and a second bearing seat spaced apart on the base, and a DC brushless motor. The first and second bearing seats are connected through a common detection rod, and the output end of the DC brushless motor is drively connected to the detection rod. The moving auxiliary element includes ring arm wheel assemblies disposed on both sides of the base, a curved auxiliary wheel assembly disposed on the base, and a handheld part.

[0010] The brushless DC motor is equipped with a current sensor, a speed sensor, and an absolute angle encoder that are electrically connected to the control unit.

[0011] Furthermore, a motor bracket is provided between the first bearing housing and the second bearing housing, and a DC brushless motor is provided on the motor bracket. The output end of the DC brushless motor is sequentially connected to the motor conversion shaft and the transmission gear, and the transmission gear is meshed with the detection rod gear.

[0012] Furthermore, the ring arm wheel assembly includes a first connecting rod and a bending rod. One end of the first connecting rod is fixedly connected to the base, and the other end is hinged to one end of the bending rod via a locking hinge. A pulley is provided at the other end of the bending rod, and the bending rod bends toward the detection rod's touch end.

[0013] The curved auxiliary wheel assembly includes a support frame, and three second links are provided on the side of the support frame near the touch end of the probe rod. The three second links are arranged in an isosceles triangle along the height direction, with the taller second link being horizontally positioned and the two shorter second links being inclined towards the probe rod. Each of the second links is provided with a pulley at its end.

[0014] The handheld part is vertically mounted on the top surface of the support frame.

[0015] Furthermore, the control unit is configured to perform the following steps:

[0016] Step S1: Control the DC brushless motor to drive the probe rod to move axially until the probe rod reaches the preset zero position, and establish a relative measurement coordinate system;

[0017] Step S2: In the zero position, control the DC brushless motor to drive the probe rod to move axially. The axial movement moves at a constant speed towards the flat side wall of the bridge above the water surface, or towards the side wall of the bridge to be tested below the water surface.

[0018] Step S3: During the axial movement of the probe rod, within the learning window, current sample data and velocity sample data are collected in real time based on the current sensor and velocity sensor, and baseline current and baseline velocity are established based on the current sample data and velocity sample data, and a current learning threshold is constructed based on the baseline current.

[0019] Step S4: During the axial movement of the probe rod, outside the learning window, real-time current and real-time velocity values ​​are collected based on the current sensor and velocity sensor, and the real-time current change and real-time velocity change are obtained.

[0020] Step S5: Preset current change threshold and speed change threshold. During the axial movement of the probe rod, if the bottoming judgment condition is met at the same time, it is determined that the probe rod has bottomed out, and the DC brushless motor is controlled to stop. Based on the absolute angle encoder and the measurement coordinate system, the actual extension amount of the probe rod is obtained.

[0021] Step S6: Repeat steps S2-S5 to obtain multiple sets of actual protrusions when the bridge flat sidewall moves. The reference distance is obtained by averaging. The difference between the reference distance and the actual protrusion when the bridge sidewall to be inspected moves is taken as the bridge defect depth.

[0022] Furthermore, the control unit is also configured to obtain the baseline current within the learning window. and baseline speed Baseline current include:

[0023] ;

[0024] In the formula, The data collection period; For current sample data, current sample dataset ;

[0025] The current learning threshold include:

[0026] ;

[0027] In the formula, The coefficient of the learning current;

[0028] The baseline speed include:

[0029] ;

[0030] In the formula, For speed sample data, speed sample dataset .

[0031] Furthermore, the control unit is also configured to obtain real-time current changes outside the learning window. and real-time velocity change Real-time current change include:

[0032] ;

[0033] In the formula, This is the real-time current value; Baseline current;

[0034] The real-time speed change include:

[0035]

[0036] In the formula, To preset the average real-time velocity within the data acquisition sliding window, the data acquisition sliding window adopts a first-in-first-out (FIFO) mechanism and has a length of [missing information]. A circular array; This is the baseline speed.

[0037] Furthermore, the control unit is also configured to, when performing a bottoming-out judgment, include a current amplitude judgment condition, a speed change judgment condition, and a current change judgment condition. The current amplitude judgment condition includes: a preset current abnormality flag number threshold; if the real-time current value is greater than the current learning threshold, it is counted as a current abnormality flag, and the current abnormality flag number is accumulated; if the real-time current value is less than the current learning threshold, the current abnormality flag number is cleared to zero, until the continuously accumulated current abnormality flag number reaches the current abnormality flag number threshold.

[0038] The speed change determination criteria include: a preset threshold for the number of speed anomaly flags; if the absolute value of the real-time speed change is greater than the preset speed change threshold... If the absolute value of the real-time speed change is less than the preset speed change threshold, then this will be counted as a single speed anomaly flag. If the speed anomaly flag is not cleared, the count will be reset to zero until the cumulative speed anomaly flag count reaches the speed anomaly flag count threshold; and,

[0039] The criteria for determining current change include: the absolute value of the real-time current change is greater than a preset current change threshold. .

[0040] Furthermore, the control unit is also configured to set the target current of the input brushless DC motor to 0 and mark the bottoming state if it is determined that the bottom has been reached.

[0041] If bottoming out is detected, the control unit stops the absolute angle encoder from counting and calculates the actual extension of the probe rod. :

[0042] ;

[0043] In the formula, This refers to the number of revolutions of the brushless DC motor. When the control unit detects that the value of the absolute angle encoder changes from 0 to 359 and then back to 0, Add one; This is the value in the absolute angle encoder when the brushless DC motor is stopped; The displacement of the probe rod driven by one revolution of the DC brushless motor.

[0044] Furthermore, the control unit is also configured to obtain a reference distance based on the actual extension of group L during the movement of the bridge's leveling sidewalls. Baseline distance include:

[0045] ;

[0046] In the formula, The actual amount of extension when the bridge's sidewalls are moved during leveling.

[0047] Furthermore, the control unit is also configured to obtain the bridge defect depth. At that time, including:

[0048] ;

[0049] In the formula, This represents the actual extension of the bridge sidewall under inspection during movement. This is the baseline distance.

[0050] Compared with the prior art, the present invention has the following beneficial technical effects:

[0051] This invention provides a device for quantitatively measuring the depth of surface defects on underwater bridges. In this device, a brushless DC motor drives a probe rod for axial movement. A first and second bearing housing improve the motion accuracy and stability of the probe rod. The control unit acquires the operating parameters of the brushless DC motor through a current sensor, a speed sensor, and an absolute angle encoder, thus obtaining the motion state of the probe rod. The moving auxiliary components include a handheld part for moving the device to the detection point on the bridge surface. A ring arm assembly and a curved auxiliary wheel assembly allow the device to establish a reference detection distance with the bridge surface, facilitating movement of the device on the bridge surface for multi-point detection. This device utilizes the principle of mechanical tactile sensing, enabling high-precision blind measurement of crack depth on bridge pier surfaces without the need for light or clear water. Its compact structure makes it suitable for narrow spaces such as inside bridge caissons and between pile groups, providing centimeter-level depth data and crucial data support for bridge maintenance decisions.

[0052] Furthermore, within the learning window, the control unit establishes baseline current and baseline velocity by collecting current sample data and velocity sample data in real time. This automatically filters out background resistance fluctuations caused by changes in water flow velocity, water depth, and pressure, effectively preventing false alarms caused by water flow impact and significantly improving the detection reliability in dynamic water areas.

[0053] Furthermore, the bottom-touching determination conditions include current amplitude determination conditions, velocity change determination conditions, and current change determination conditions. The current amplitude determination conditions and velocity change determination conditions are each set with corresponding abnormal flag number thresholds, which can overcome the problem of slight disturbances in the acquired signal caused by the variability of underwater fluid flow velocity and fluid density, making the bottom-touching determination more accurate. Attached Figure Description

[0054] Figure 1 A schematic diagram of the device structure for quantifying the depth of surface defects on an underwater bridge, according to an embodiment of the present disclosure, is shown.

[0055] Figure 2 A schematic diagram of a measurement performed using this device in an embodiment of this disclosure is shown;

[0056] Figure 3 A schematic diagram of the structure of the detection element according to an embodiment of this disclosure is shown;

[0057] Figure 4 A flowchart illustrating the quantitative determination of the depth of surface defects on an underwater bridge by a control unit according to an embodiment of the present disclosure is shown.

[0058] In the diagram: 1-base; 2-first bearing seat; 3-probe rod; 20-second bearing seat; 4-DC brushless motor; 5-handheld part; 7-motor bracket; 8-motor conversion shaft; 9-transmission gear; 10-first connecting rod; 11-bending rod; 12-pulley; 13-support frame; 14-second connecting rod. Detailed Implementation

[0059] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0060] This disclosure provides an apparatus for quantitatively measuring the depth of surface defects on underwater bridges, such as... Figure 1 and Figure 3 As shown, the device includes a base 1 and a control unit. The base 1 is equipped with a detection component and a moving auxiliary component. The detection component includes a first bearing seat 2 and a second bearing seat 20 spaced apart on the base 1, and a DC brushless motor 4. The first bearing seat 2 and the second bearing seat 20 are connected through the same detection rod 3. The output end of the DC brushless motor 4 is connected to the detection rod 3. The moving auxiliary component includes a ring arm wheel assembly on both sides of the base 1, a curved auxiliary wheel assembly on the base 1, and a handheld part 5.

[0061] The brushless DC motor 4 is equipped with a current sensor, a speed sensor, and an absolute angle encoder that are electrically connected to the control unit. The control unit uses CAN communication to control the brushless DC motor 4 to drive the probe rod 3 to extend and retract in a gear and rack transmission manner, and to process data to obtain the defect depth. At the same time, the control unit also communicates with the host computer via Ethernet to obtain instructions.

[0062] It should be noted that the first bearing housing 2 and the second bearing housing 20 form a double-point support structure. This double-point support structure can effectively limit the radial runout of the probe rod 3, ensuring that the probe rod 3 moves in a straight line during its extension. The probe rod 3 is a rigid rod with a high-precision rack structure machined on its surface, and its front end is machined flat, directly serving as the contact end for the surface to be measured.

[0063] In this embodiment, a motor bracket 7 is provided between the first bearing housing 2 and the second bearing housing 20. A DC brushless motor 4 is provided on the motor bracket 7. The output end of the DC brushless motor 4 is sequentially connected to the motor conversion shaft 8 and the transmission gear 9. The transmission gear 9 is meshed with the detection rod 3.

[0064] In this embodiment, the ring arm wheel assembly includes a first connecting rod 10 and a bending rod 11. One end of the first connecting rod 10 is fixedly connected to the base 1, and the other end is hinged to one end of the bending rod 11 through a locking hinge. The other end of the bending rod 11 is provided with a pulley 12, and the bending rod 11 bends toward the detection end of the probe rod 3.

[0065] The curved auxiliary wheel assembly includes a support frame 13. Three second links 14 are provided on the side of the support frame 13 near the touch end of the probe rod 3. The three second links 14 are arranged in an isosceles triangle along the height direction. The higher second link 14 is set horizontally, and the two lower second links 14 are both set inclined towards the probe rod 3. Each of the ends of the second links 14 is provided with a pulley 12.

[0066] The handheld part 5 is vertically mounted on the top surface of the support frame 13, which is a frame structure and is vertically mounted on the base 1.

[0067] It should be noted that both the ring arm wheel assembly and the curved auxiliary wheel assembly are used to assist the device in moving up and down on the bridge surface. The bending angle of the bending rod 11 and the first connecting rod 10 can be controlled by the locking hinge, forming a ring structure around the bridge. The pulley 12 at the end of the bending rod 11 is used to assist the movement. The arrangement of the three second connecting rods 14 in the curved auxiliary wheel assembly can generate an inward automatic correction force, improving the stability of the movement.

[0068] like Figure 4As shown, in this embodiment, the control unit is configured to perform the following steps when quantifying the depth of surface defects on an underwater bridge:

[0069] Step S1: The control unit controls the DC brushless motor 4 to drive the probe rod 3 to move axially until the probe rod 3 reaches the preset zero position, and then establishes a relative measurement coordinate system.

[0070] Step S2: In the zero position, control the DC brushless motor 4 to drive the probe rod 3 to move axially. The axial movement moves at a constant speed towards the flat sidewall of the bridge above the water surface, or towards the sidewall of the bridge to be inspected below the water surface. It should be noted that the inspection of the flat sidewall of the bridge is mainly used to obtain the reference distance of the healthy sidewall of the bridge, which is convenient for calculating the depth of the defect.

[0071] Step S3: During the axial movement of the probe rod 3, within the learning window, current sample data and velocity sample data are collected in real time based on the current sensor and velocity sensor. Baseline current and baseline velocity are established based on the current sample data and velocity sample data, and a current learning threshold is constructed based on the baseline current. It should be noted that the learning window refers to the baseline current and baseline velocity applicable to the underwater fluid parameters within the current time period, under the premise that the probe rod 3 does not contact the bridge surface, through the actual collected current sample data and velocity sample data, in order to overcome the interference of environmental factors and eliminate the influence of environmental impedance. Fluid parameters include factors that affect the movement of the probe rod 3, such as fluid velocity, fluid pressure, and underwater pressure.

[0072] Specifically, the control unit is configured to obtain the baseline current within the learning window. and baseline speed Baseline current include:

[0073] ;

[0074] In the formula, The data collection period; For current sample data, current sample dataset ;

[0075] The current learning threshold include:

[0076] ;

[0077] In the formula, The coefficient of the learning current;

[0078] The baseline speed include:

[0079] ;

[0080] In the formula, For speed sample data, speed sample dataset .

[0081] Step S4: During the axial movement of the probe rod 3, outside the learning window, real-time current and real-time velocity values ​​are collected based on the current sensor and velocity sensor, and the real-time current change and real-time velocity change are obtained.

[0082] Specifically, the control unit is also configured to obtain real-time current changes outside the learning window. and real-time velocity change Real-time current change include:

[0083] ;

[0084] In the formula, This is the real-time current value; Baseline current;

[0085] The real-time speed change include:

[0086]

[0087] In the formula, To preset the average real-time velocity within the data acquisition sliding window, the data acquisition sliding window adopts a first-in-first-out (FIFO) mechanism and has a length of [missing information]. A circular array; This is the baseline speed.

[0088] Step S5: Preset current change threshold and speed change threshold. During the axial movement of the probe rod 3, if the bottoming judgment condition is met at the same time, the probe rod 3 is judged to have bottomed out, and the DC brushless motor 4 is controlled to stop. Based on the absolute angle encoder and the measurement coordinate system, the actual extension amount of the probe rod 3 is obtained.

[0089] Specifically, the control unit is further configured to, when performing a bottoming-out judgment, include a current amplitude judgment condition, a speed change judgment condition, and a current change judgment condition. The current amplitude judgment condition includes: a preset current abnormality flag number threshold; if the real-time current value is greater than the current learning threshold, it is counted as a current abnormality flag and the current abnormality flag number is accumulated; if the real-time current value is less than the current learning threshold, the current abnormality flag number is cleared to zero until the continuously accumulated current abnormality flag number reaches the current abnormality flag number threshold.

[0090] The speed change determination criteria include: a preset threshold for the number of speed anomaly flags; if the absolute value of the real-time speed change is greater than the preset speed change threshold... If the absolute value of the real-time speed change is less than the preset speed change threshold, then this will be counted as one speed anomaly flag. If the speed anomaly flag is not cleared, the count will be reset to zero until the cumulative speed anomaly flag count reaches the speed anomaly flag count threshold; and,

[0091] The criteria for determining current change include: the absolute value of the real-time current change is greater than a preset current change threshold. .

[0092] It should be noted that the preset speed change threshold The value is a constant, obtained based on the rotational speed characteristics of the brushless DC motor 4, and serves as the criterion for judging abnormal speed changes in the brushless DC motor 4. In this embodiment, the speed change threshold is used. The value is set to 70 RPM. The current change threshold is... The constant value is obtained based on the load characteristics of the brushless DC motor 4 and serves as the criterion for judging abnormal current changes in the brushless DC motor 4. In this embodiment, the current change threshold value is used. The value is 1.5A.

[0093] In underwater bridge inspection, the probe will face water flow impact, eddies, underwater attachments such as weeds and silt, as well as electrical noise interference from the motor itself. In this embodiment, the current amplitude determination condition can filter out transient interference. Only when the resistance is not only large but also persists for a period of time, where the resistance is reflected in the current level of the DC brushless motor 4, will it be considered a true physical obstruction, eliminating the illusion caused by the instantaneous impact of the water flow. For example, if the probe 3 is located in a position with water flow or weeds, the current will continue to rise and reach the threshold due to the influence of resistance. However, in reality, the contact end of the probe 3 does not touch the bottom, thus causing a false judgment.

[0094] The speed change judgment condition represents the kinematic response of the probe rod 3. A significant change in motor speed that continues to reach the abnormal flag threshold means that the probe rod 3 can no longer move forward in physical space. However, in some cases, although the current of the DC brushless motor 4 increases, the probe rod 3 may only be affected by resistance, such as the presence of water flow or aquatic plants, and the speed may not decrease drastically. In this case, it should not be judged as reaching the actual concrete surface of the bridge.

[0095] The current change condition represents the instantaneous impact force on the probe rod 3. Due to the special characteristics of the underwater environment, such as the different distribution areas of aquatic plants or water currents, it is possible that even when both the current amplitude judgment condition and the velocity change judgment condition are met, the contact end of the probe rod 3 may still be in the area of ​​aquatic plants or water currents and has not touched the bottom. This is when the current change threshold is reached. It can determine whether the DC brushless motor 4 can continue to operate and perform measurements to avoid misjudgment.

[0096] Furthermore, the control unit is configured to set the target current of the input brushless DC motor 4 to 0 if bottoming is detected, causing the brushless DC motor 4 to stop abruptly and marking the bottoming state. The brushless DC motor 4 employs dual closed-loop PID control, with the speed loop PID as the outer loop and the current loop PID as the inner loop. The system uses a set rotational speed as the target speed, calculates the difference between the real-time detected rotational speed and the target speed, and outputs a target current command after calculation by the speed loop PID. This command corresponds to the electromagnetic torque, which is then tracked by the current loop to achieve rapid and stable torque control, thereby ensuring that the probe extends towards the bridge surface at a constant, smooth, and impact-free speed.

[0097] If bottoming is detected, the control unit controls the absolute angle encoder to stop counting and calculates the actual extension of the probe rod 3. :

[0098] ;

[0099] In the formula, This refers to the number of revolutions of the brushless DC motor. When the control unit detects that the value of the absolute angle encoder changes from 0 to 359 and then back to 0, Add one; This is the value in the absolute angle encoder when the brushless DC motor is stopped; The displacement of the probe rod driven by one revolution of the DC brushless motor.

[0100] Step S6: Repeat steps S2-S5 to obtain multiple sets of actual protrusions when the bridge flat sidewall moves. The reference distance is obtained by averaging. The difference between the reference distance and the actual protrusion when the bridge sidewall to be inspected moves is taken as the bridge defect depth.

[0101] Specifically, the control unit is also configured to be based on The reference distance is obtained by measuring the actual extension of the group during the movement of the bridge's leveling sidewalls. Baseline distance include:

[0102] ;

[0103] In the formula, The actual amount of extension when the bridge's sidewalls are moved during leveling.

[0104] After obtaining the depth of bridge defects At that time, including:

[0105] ;

[0106] In the formula, This represents the actual extension of the bridge sidewall under inspection during movement. This is the baseline distance.

[0107] When using this device, if Figure 2 As shown, a bridge surface detection point is preset. The moving auxiliary part is pressed against the side wall of the bridge by the hand-held part 5. The relative angle of the first connecting rod 10 and the bending rod 11 is adjusted so that the moving auxiliary part surrounds the bridge and the three pulleys 12 of the curved auxiliary wheel assembly press against the bridge surface at the same time. At the same time, it is ensured that the touch end of the probe rod 3 can contact the area to be detected.

[0108] The control unit controls the start of the brushless DC motor 4, which is driven by the motor conversion shaft 8 and the transmission gear 9 to drive the probe rod 3 to move axially and reach the preset zero position.

[0109] In the zero position, the DC brushless motor 4 is controlled to drive the probe rod 3 to move axially. The axial movement moves at a constant speed toward the flat side wall of the bridge above the water surface, or toward the side wall of the bridge to be tested below the water surface.

[0110] During the axial movement of the probe rod 3, within the learning window, current sample data and velocity sample data are collected in real time based on the current sensor and velocity sensor, and baseline current and baseline velocity are established based on the current sample data and velocity sample data, and a current learning threshold is constructed based on the baseline current.

[0111] During the axial movement of the probe rod 3, outside the learning window, real-time current and real-time velocity values ​​are collected based on the current sensor and velocity sensor, and the real-time current change and real-time velocity change are obtained.

[0112] With preset current change thresholds and speed change thresholds, if the bottoming-out determination condition is met simultaneously during the axial movement of the probe rod 3, it is determined that the probe rod 3 has bottomed out, and the DC brushless motor 4 is controlled to stop. Based on the absolute angle encoder and the measurement coordinate system, the actual extension amount of the probe rod 3 is obtained.

[0113] Repeat the above steps multiple times to obtain multiple sets of actual protrusions when the bridge's flat sidewall moves. The reference distance is obtained by averaging. The difference between the reference distance and the actual protrusion when the bridge's sidewall to be inspected moves is taken as the bridge defect depth.

Claims

1. A device for quantitatively determining the depth of surface defects on underwater bridges, characterized in that, The device includes a base (1) and a control unit. The base (1) is provided with a detection component and a moving auxiliary component. The detection component includes a first bearing seat (2) and a second bearing seat (20) spaced apart on the base (1), and a DC brushless motor (4). The first bearing seat (2) and the second bearing seat (20) are connected through the same detection rod (3). The output end of the DC brushless motor (4) is connected to the detection rod (3). The moving auxiliary component includes a ring arm wheel assembly on both sides of the base (1), a curved auxiliary wheel assembly on the base (1), and a handheld part (5). The brushless DC motor (4) is equipped with a current sensor, a speed sensor, and an absolute angle encoder that are electrically connected to the control unit.

2. The device for quantitatively determining the depth of surface defects on underwater bridges according to claim 1, characterized in that, A motor bracket (7) is provided between the first bearing housing (2) and the second bearing housing (20). A DC brushless motor (4) is provided on the motor bracket (7). The output end of the DC brushless motor (4) is sequentially connected to the motor conversion shaft (8) and the transmission gear (9). The transmission gear (9) meshes with the gear of the probe rod (3).

3. The device for quantitatively determining the depth of surface defects on underwater bridges according to claim 1, characterized in that, The ring arm wheel assembly includes a first connecting rod (10) and a bending rod (11). One end of the first connecting rod (10) is fixedly connected to the base (1), and the other end is hinged to one end of the bending rod (11) through a locking hinge. The other end of the bending rod (11) is provided with a pulley (12), and the bending rod (11) bends toward the detection end of the probe (3). The curved auxiliary wheel assembly includes a support frame (13). Three second links (14) are provided on the side of the support frame (13) near the touch end of the probe rod (3). The three second links (14) are arranged in an isosceles triangle along the height direction. The second link (14) with the higher height is set horizontally, and the two second links (14) with the lower height are both set inclined towards the probe rod (3). Each of the ends of the second links (14) is provided with a pulley (12). The handheld part (5) is vertically mounted on the top surface of the support frame (13).

4. The device for quantitatively determining the depth of surface defects on underwater bridges according to claim 1, characterized in that, The control unit is configured to perform the following steps: Step S1: Control the DC brushless motor (4) to drive the probe rod (3) to move axially until the probe rod (3) reaches the preset zero position, and establish a relative measurement coordinate system; Step S2: At the zero position, control the DC brushless motor (4) to drive the probe rod (3) to move axially. The axial movement moves at a constant speed towards the flat side wall of the bridge above the water surface, or towards the side wall of the bridge to be tested below the water surface. Step S3: During the axial movement of the probe rod (3), within the learning window, current sample data and velocity sample data are collected in real time based on the current sensor and velocity sensor, and baseline current and baseline velocity are established based on the current sample data and velocity sample data, and a current learning threshold is constructed based on the baseline current. Step S4: During the axial movement of the probe rod (3), outside the learning window, real-time current value and real-time speed value are collected based on the current sensor and speed sensor, and the real-time current change and real-time speed change are obtained. Step S5: Preset current change threshold and speed change threshold. During the axial movement of the probe rod (3), if the bottoming judgment condition is met at the same time, the probe rod (3) is judged to have bottomed out, and the DC brushless motor (4) is controlled to stop. Based on the absolute angle encoder and the measurement coordinate system, the actual extension amount of the probe rod (3) is obtained. Step S6: Repeat steps S2-S5 to obtain multiple sets of actual protrusions when the bridge flat sidewall moves. The reference distance is obtained by averaging. The difference between the reference distance and the actual protrusion when the bridge sidewall to be inspected moves is taken as the bridge defect depth.

5. The device for quantitatively determining the depth of surface defects on underwater bridges according to claim 4, characterized in that, The control unit is also configured to obtain the baseline current within the learning window. and baseline speed Baseline current include: ； In the formula, The data collection period; For current sample data, current sample dataset ; The current learning threshold include: ； In the formula, The coefficient for the learning current; The baseline speed include: ； In the formula, For speed sample data, speed sample dataset .

6. The device for quantitatively determining the depth of surface defects on underwater bridges according to claim 4, characterized in that, The control unit is also configured to obtain real-time current changes outside the learning window. and real-time velocity change Real-time current change include: ； In the formula, This is the real-time current value; Baseline current; The real-time speed change include: In the formula, To preset the average real-time velocity within the data acquisition sliding window, the data acquisition sliding window adopts a first-in-first-out (FIFO) mechanism and has a length of [missing information]. A circular array; This is the baseline speed.

7. The device for quantitatively determining the depth of surface defects on underwater bridges according to claim 4, characterized in that, The control unit is further configured to, when performing a bottoming-out judgment, include a current amplitude judgment condition, a speed change judgment condition, and a current change judgment condition. The current amplitude judgment condition includes: a preset current abnormality flag number threshold; if the real-time current value is greater than the current learning threshold, it is counted as a current abnormality flag and the current abnormality flag number is accumulated; if the real-time current value is less than the current learning threshold, the current abnormality flag number is cleared to zero until the continuously accumulated current abnormality flag number reaches the current abnormality flag number threshold. The speed change determination criteria include: a preset threshold for the number of speed anomaly flags; if the absolute value of the real-time speed change is greater than the preset speed change threshold... If the absolute value of the real-time speed change is less than the preset speed change threshold, then this will be counted as a single speed anomaly flag. If the speed anomaly flag count is zeroed, the count will continue to accumulate until it reaches the speed anomaly flag count threshold. The criteria for determining current change include: the absolute value of the real-time current change is greater than a preset current change threshold. .

8. The device for quantitatively determining the depth of surface defects on underwater bridges according to claim 4, characterized in that, The control unit is also configured to set the target current of the input brushless DC motor (4) to 0 and mark the bottoming state if it is determined that the bottom has been reached. If bottoming is detected, the control unit controls the absolute angle encoder to stop counting and calculates the actual extension of the probe rod (3). : ； In the formula, This refers to the number of revolutions of the brushless DC motor. When the control unit detects that the value of the absolute angle encoder changes from 0 to 359 and then back to 0, Add one; This is the value in the absolute angle encoder when the brushless DC motor is stopped; The displacement of the probe rod driven by one revolution of the DC brushless motor.

9. The device for quantitatively determining the depth of surface defects on underwater bridges according to claim 4, characterized in that, The control unit is also configured to obtain a reference distance based on the actual extension of group L during the movement of the bridge's leveling sidewall. Baseline distance include: ； In the formula, The actual amount of extension when the bridge's sidewalls are moved during leveling.

10. The device for quantitatively determining the depth of surface defects on underwater bridges according to claim 4, characterized in that, The control unit is also configured to obtain the bridge defect depth. At that time, including: ； In the formula, This represents the actual extension of the bridge sidewall under inspection during movement. This is the baseline distance.

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