Concrete bridge reinforcement protection layer thickness detection system and method based on unmanned aerial vehicle

Abstract

The invention discloses a concrete bridge reinforcement protection layer thickness detection system and method based on an unmanned aerial vehicle, and the system comprises a computer device, an unmanned aerial vehicle remote controller, and a flying mechanical arm device. The flying mechanical arm equipment at least comprises an unmanned aerial vehicle, a mechanical arm, a working platform, a depth camera, a steering engine, a wireless transmission module, a telescopic mechanism and a flying mechanical arm controller. The flying mechanical arm equipment takes an unmanned aerial vehicle as a mobile platform and is used for carrying a mechanical arm and a working platform to complete thickness detection of a bridge reinforcement protection layer; a wireless transmission module and a steering engine are fixedly mounted at the top of the unmanned aerial vehicle; a turntable of the steering engine is fixedly mounted at one end of the mechanical arm; a depth camera is mounted in the middle of the mechanical arm; and the telescopic mechanism is fixedly mounted on the lower panel of the unmanned aerial vehicle through the mounting base. According to the system and the method, the detection cost is saved, high-altitude operation of detection personnel is avoided, the working efficiency and the safety are improved, and the system is an integrated detection system which replaces manual detection operation and is flexible.

Description

Technical Field

[0001] The present invention belongs to the technical field of flying mechanical arms, and mainly relates to a system and method for detecting the thickness of a steel bar protective layer of a concrete bridge based on an unmanned aerial vehicle. Background Art

[0002] Concrete bridges need to bear multiple loads such as the bridge's own weight and traffic loads, and need to have a certain degree of stability and strength. In the concrete bridge steel bar protection layer thickness inspection project, the most important inspection parts are bridge beams and piers. The steel bar protection layer has the functions of protecting the steel bars from corrosion and wear, bearing external impact forces and preventing water seepage. The deviation between the thickness of the protection layer and the design is mainly caused by the displacement of the steel bars during the construction of the concrete structure. If the thickness of the protection layer is too small, it will cause steel bar corrosion and concrete carbonization. If the thickness of the protection layer is too large, it will affect the stiffness and bearing capacity of the bridge's bending members.

[0003] At present, there are two methods for detecting the thickness of the steel bar protective layer: the local damage method and the non-destructive testing method. The local damage method requires chiseling the concrete protective layer until the steel bar is exposed. This method is the most direct and accurate, but it is easy to damage the steel bar. Non-destructive testing is non-destructive to the structure and is the current mainstream testing method. It is divided into electromagnetic induction method and radar method. However, the thickness detection of the steel bar protective layer under the concrete bridge mainly relies on manual non-destructive testing equipment to detect the target area. The existing bridge beam and pier detection devices have problems such as low detection safety, low efficiency, and traffic obstruction: (1) The height of the bridge beam is relatively high, and the risk factor of manual operation is high; (2) The bridge is built above the river, which makes it difficult to implement manual operations; (3) The inspection vehicle is large in size and weight, and needs to occupy the road for operation and travel slowly, which poses a traffic safety hazard. Summary of the invention

[0004] The present invention is aimed at the problems existing in the existing detection methods, and provides a system and method for detecting the thickness of the steel bar protective layer of a concrete bridge based on an unmanned aerial vehicle, including a computer device, an unmanned aerial vehicle remote controller and a flying mechanical arm device, wherein the flying mechanical arm device at least includes an unmanned aerial vehicle, a mechanical arm, a working platform, a depth camera, a steering gear, a wireless transmission module, a telescopic mechanism and a flying mechanical arm controller; the flying mechanical arm device uses an unmanned aerial vehicle as a mobile platform, which is used to carry the mechanical arm and the working platform to complete the thickness detection of the bridge steel bar protective layer; the wireless transmission module and the steering gear are fixedly installed on the top of the unmanned aerial vehicle; the turntable of the steering gear is fixedly installed at one end of the mechanical arm; a depth camera is installed in the middle of the mechanical arm, and a working platform is fixedly installed at the other end; the telescopic mechanism is fixedly installed on the lower panel of the unmanned aerial vehicle through a mounting base. The system and method of the present invention save detection costs, avoid high-altitude operations of detection personnel, and improve work efficiency and safety. It is an integrated detection system that replaces manual detection operations and is flexible and maneuverable.

[0005] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a concrete bridge steel bar protective layer thickness detection system based on a drone, including a computer device, a drone remote controller and a flight mechanical arm device, wherein the flight mechanical arm device at least includes a drone, a mechanical arm, a working platform, a depth camera, a steering gear, a wireless transmission module, a telescopic mechanism and a flight mechanical arm controller;

[0006] The flying robotic arm device uses a drone as a mobile platform, which is used to carry a robotic arm and a working platform to complete the thickness detection of the bridge steel bar protective layer; a wireless transmission module and a steering gear are fixedly installed on the top of the drone; the turntable of the steering gear is fixedly installed at one end of the robotic arm; a depth camera is installed in the middle of the robotic arm, and a working platform is fixedly installed at the other end; the telescopic mechanism is fixedly installed on the lower panel of the drone through a mounting base.

[0007] As an improvement of the present invention, the working platform is composed of a reduction motor, a slide base, a slide, a spring and a pressure sensor; the slide base includes a belt and a pulley, and a pulley is installed in the middle of the slide base; a driven pulley is installed on both sides of the pulley, and the driven pulley is located inside the belt. The reduction motor drives the pulley to rotate, and the belt drives the slide to move; a spring is placed on one side of each of the two driven pulleys; one end of the spring is fixedly connected to the pressure sensor; and a thickness gauge is fixedly installed on the slide.

[0008] As another improvement of the present invention, the telescopic mechanism consists of a mounting base, an electric push rod, a moving part and a battery; the electric push rod is installed on the lower panel of the drone through the mounting base; a moving part is installed on the other end of the electric push rod; the moving part is installed on the surface of the battery and is used to push the battery to move on the surface of the battery carrier.

[0009] In order to achieve the above purpose, the present invention also adopts a technical solution: a method for detecting the thickness of the steel bar protective layer of a concrete bridge based on an unmanned aerial vehicle, comprising the following steps:

[0010] S1: Preheat the measuring equipment and fly the flying robot arm equipment under the concrete bridge through the UAV remote control;

[0011] S2: The depth camera on the robotic arm transmits the image under the concrete bridge through the wireless transmission module. After the operator selects the inspection location, he controls the flying robotic arm device to approach the inspection location.

[0012] S3: The working platform at the end of the flying robot arm equipment is 10 cm close to the detection plane. The flying robot arm controller controls the drone to approach the detection plane. According to the position of the steel bar layout, the direction perpendicular to the axis of the inspected steel bar is determined as the detection direction. The steering gear angle at one end of the robot arm is adjusted by the flying robot arm controller to keep the thickness gauge parallel to the detection plane.

[0013] S4: The flying robot arm device detects each grid in turn according to the trajectory planning. After the thickness gauge contacts the detection plane, the reduction motor starts to work, driving the thickness gauge to move slowly along the detection direction on the detection plane until the instrument protective layer thickness indication is minimum. At this time, the center line of the thickness gauge probe coincides with the axis of the steel bar, the reduction motor stops rotating, the thickness gauge and the steel bar are relatively still, the value is recorded and the depth camera is used to record the stop position of the thickness gauge each time. After completing the detection of one steel bar, the reduction motor starts to work, driving the thickness gauge to move to the next steel bar until all the steel bars arranged in the corresponding grid of the work platform are detected. The steel bar detection image, steel bar position and protective layer thickness data are transmitted to the computer equipment through the wireless transmission module, and the thickness gauge returns to its position for the second measurement.

[0014] S5: After obtaining the steel bar protective layer thickness data, the detection is completed and the flying robotic arm equipment is controlled to return.

[0015] As an improvement of the present invention, after the first detection in step S4 is completed, the slide on the working platform is returned to its position, and step S4 is repeated. The same steel bar and the same location are detected at least twice, and the average value of the detection data is taken.

[0016] As another improvement of the present invention, in step S2, after the operator selects the detection part, the flight robot arm controller performs grid map modeling on the plane to be detected based on the image obtained by the depth camera, and plans the path to complete the detection of each grid one by one; the direction of the grid map modeling is perpendicular to the axis direction of the steel bar distribution, and the side length of each grid does not exceed the effective detection range of the working platform. As another improvement of the present invention, in steps S3 and S4, after the thickness gauge contacts the detection plane, the pitch angle of the drone is adjusted to ensure the contact force, the spring contracts, and the pressure sensor values ​​on both sides are kept consistent, and the position error caused by external disturbances is compensated by the design position and angle controller of the pressure sensors on both sides of the detection platform.

[0017] As another improvement of the present invention, the method for calculating the position and angle deviation caused by the disturbance is:

[0018] When the pressure sensor remains in contact with the detection surface:

[0019] F1=kx1,F2=kx2

[0020] Where F1 and F2 are the pressure values ​​detected by the pressure sensors at both ends of the working platform, k is the spring elastic coefficient, and x1 and x2 are the contraction lengths of the springs at both sides;

[0021]

[0022] Where θ is the deflection angle of the flight manipulator device around the contact surface, and L is the distance between the centers of the two pressure sensors on the working platform;

[0023] Δx=l(1-cosθ)

[0024] Δy=-l·sin(θ)

[0025] Where Δx, Δy are position deviations, and l is the distance between the servo and the detection plane.

[0026] Compared with the prior art, the present invention has the following beneficial effects: the present invention discloses a system and method for detecting the thickness of the steel bar protective layer of a concrete bridge based on an unmanned aerial vehicle, which realizes the integrated detection of the steel bar protective layer at the bridge beam and pier of the lower part of the concrete bridge. The flying mechanical arm of the present invention does not require manual handheld detection equipment to reach the lower part of the bridge to complete the detection operation, fully utilizes the flexibility and maneuverability of the unmanned aerial vehicle and does not require road occupation, effectively improving the safety and work efficiency of the steel bar protective layer thickness detection operation of the lower structure of the concrete bridge. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of a steel bar protective layer thickness detection system of the present invention;

[0028] Figure 2 It is a schematic diagram of the mechanical structure of the working platform in the flying mechanical arm device of the present invention;

[0029] Figure 3 It is a schematic diagram of the mechanical structure of the telescopic mechanism in the flying mechanical arm device of the present invention;

[0030] Figure 4 This is a schematic diagram of an operation scene of the flying mechanical arm device of the present invention;

[0031] Figure 5 A schematic diagram of modeling and path planning of the detection plane grid by the flying manipulator device of the present invention;

[0032] Figure 6 This is a schematic diagram of the position angle deviation caused by the rotation of the flight manipulator device of the present invention due to disturbance;

[0033] Figure 7 Schematic diagram of the position and angle controller designed for disturbance compensation of the present invention;

[0034] Figure 8 It is a schematic diagram of the steps of the method for detecting the thickness of the steel bar protective layer of the present invention;

[0035] Fig. 9 A schematic diagram of the workflow of the working platform in the flying mechanical arm device of the present invention detecting the thickness of the steel bar protective layer;

[0036] In the figure: 1. Computer equipment; 2. UAV remote control; 3. Flying robot arm equipment; 31. UAV; 32. Robotic arm; 33. Working platform; 331. Reduction motor; 332. Slide base; 333. Belt; 334. Pulley; 335. Driven pulley; 336. Spring; 337. Pressure sensor; 338. Slide; 339. Thickness gauge; 34. Depth camera; 35. Servo; 36. Wireless transmission module; 37. Telescopic mechanism; 371. Mounting base; 372. Electric push rod; 373. Moving part; 374. Battery; 375. Battery carrier board; 38. Flying robot arm controller; 4. Pier; 5. Bridge beam and slab; 6. Steel bars. DETAILED DESCRIPTION

[0037] The present invention will be further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0038] Example 1

[0039] A concrete bridge steel bar cover thickness detection system based on drone, such as Figure 1 As shown, it includes a computer device 1, a drone remote controller 2 and a flying robotic arm device 3, and the flying robotic arm device 3 at least includes a drone 31, a robotic arm 32, a working platform 33, a depth camera 34, a steering gear 35, a wireless transmission module 36, a telescopic mechanism 37 and a flying robotic arm controller 38; the flying robotic arm device 3 uses the drone 31 as a mobile platform, which can be used to carry the robotic arm 32 and the working platform 33 to complete the thickness detection of the steel bar protective layer under the bridge; the wireless transmission module 36 and the steering gear 35 are fixedly installed on the top of the drone 31; the turntable of the steering gear 35 is fixedly installed at one end of the robotic arm 32; the depth camera 34 is installed in the middle of the robotic arm 32, and the working platform 33 is fixedly installed at the other end; the telescopic mechanism 37 is fixedly installed on the lower panel of the drone 31 through a mounting base.

[0040] like Figure 2 As shown, Figure 23 is a schematic diagram of the mechanical structure of the working platform 33 in the flight manipulator device 3. The working platform 33 is composed of a reduction motor 331, a slide base 332, a spring 336, a pressure sensor 337 and a slide 338. The slide base 332 includes a belt 333 and a pulley 334. A pulley 334 is installed in the middle of the slide base 332. A driven pulley 335 is installed on both sides of the pulley 334 and inside the belt 333. The reduction motor 331 drives the pulley 334 to rotate, and the belt 333 drives the slide 338 to move. A spring 336 is placed on one side of each of the two driven pulleys 335. One end of the spring 336 is fixedly connected to the pressure sensor 337. A thickness gauge 339 is fixedly installed on the slide 336.

[0041] Figure 3 FIG. 3 is a schematic diagram of the mechanical structure of the telescopic mechanism 37 in the flight robot arm device 3. Figure 3 As shown, the telescopic mechanism 37 is composed of a mounting base 371, an electric push rod 372, a moving part 373 and a battery 374. The electric push rod 372 is installed on the lower panel of the drone 31 through the mounting base 371. The other end of the electric push rod 372 is installed with a moving part 373. The moving part 373 is installed on the surface of the battery 374 and is used to push the battery 374 to move on the surface of the battery carrier 375 so as to adjust the center of gravity of the flight robotic arm device 3.

[0042] The system of the present invention solves the problem of detecting the thickness of the steel bar protective layer at the bottom of a concrete bridge, saves detection costs compared with manual detection, avoids high-altitude operation of detection personnel, and improves work efficiency and safety.

[0043] Example 2

[0044] The UAV-based concrete bridge steel bar protection layer thickness detection method is suitable for the steel bar protection layer thickness detection at 4 locations on the pier and 5 locations on the bridge beam and slab. Figure 4 This is a schematic diagram of the operation scene of the flying robotic arm equipment. Figure 5 This is a schematic diagram of the modeling and path planning of the detection plane grid for the flying robot arm equipment. Figure 6 This is a schematic diagram of the position angle deviation caused by the rotation of the flight robot arm equipment due to disturbance. Figure 8 The following is a schematic diagram of the specific steps of the detection, which specifically includes the following steps:

[0045] S1. The operator sets up a workbench on the shore, preheats and zeroes the thickness gauge 339, and after the instrument is successfully started, the flying robot arm device 3 is flown to the pier 4 under the concrete bridge through the UAV remote controller 2;

[0046] S2, the depth camera 34 transmits 36 the image of the bridge pier 4 or bridge beam 5 to be inspected through the wireless transmission module, and the operator selects the inspection location, which is required to be flat and smooth, while avoiding the joints of the steel bars 6, the binding wires and the metal embedded parts, and then manipulates the flying robot arm 3 to approach the inspection location;

[0047] After the operator selects the inspection location, the flight robot controller 38 performs grid map modeling on the plane to be inspected based on the image obtained by the depth camera 34, and plans a path to complete the inspection of each grid one by one; the direction of the grid map modeling is perpendicular to the distribution axis of the steel bar 6, and the side length of each grid does not exceed the effective inspection range of the working platform 33, ensuring that the thickness gauge 339 on the working platform 33 can measure each steel bar 6 in the grid, such as Figure 5 shown.

[0048] S3, the working platform 33 at the end of the flying robot arm device 3 is close to the detection plane at 10 cm. When it is close to the detection part, the flying robot arm controller 38 controls the drone 31 to slowly approach the detection plane. According to the arrangement of the steel bars 6, the direction perpendicular to the axis of the steel bars 6 to be detected is determined as the detection direction. The flying robot arm controller 38 can adjust the angle of the servo 35 at one end of the robot arm 32 to keep the thickness gauge 339 parallel to the detection plane. At the same time, the electric push rod 373 is controlled to extend and retract to push the battery 374 to move on the surface of the battery carrier 375 to balance the change of the center of gravity of the flying robot arm device 3 caused by the change of the lifting angle of the robot arm 32;

[0049] S4. The flying robot arm device 3 detects each grid in turn according to the trajectory planning. After the thickness gauge 339 contacts the detection plane, the reduction motor 331 starts working, driving the thickness gauge 339 to move slowly along the detection direction on the detection plane until the instrument protective layer thickness indication is minimum. At this time, the center line of the thickness gauge 339 probe should coincide with the axis of the steel bar 6. The reduction motor 331 stops working, the thickness gauge 339 and the steel bar 6 are relatively still, and the values ​​are recorded and the depth camera 34 is used to record each stop position of the thickness gauge 339. After completing the detection of one steel bar, the reduction motor 331 starts working, driving the thickness gauge 339 to move to the next steel bar 6. Until all the steel bars 6 arranged under the corresponding grid of the working platform 33 are detected, the steel bar 6 detection image, the steel bar 6 position and the protective layer thickness data are transmitted to the computer device 1 through the wireless transmission module 36, and the thickness gauge 339 returns to its position for the second measurement. The working process of the working platform 33 in the flying robot arm device 3 to detect the steel bar protective layer thickness is as follows. Fig. 9 shown.

[0050] After the thickness gauge 339 contacts the detection plane, the pitch angle of the drone 31 can be adjusted to ensure a certain contact force, the spring 336 contracts, and the values ​​of the pressure sensors 337 on both sides remain consistent. External disturbances will cause the flying mechanical arm device 3 to rotate around the contact surface, and the thickness gauge 339 cannot remain parallel to the detection plane, which will affect the thickness measurement test results, such as Figure 6 As shown; the step is to design a position and angle controller by detecting the pressure sensors 337 on both sides of the platform to compensate for the position error caused by external disturbances; Figure 7 shown.

[0051] The position and angle deviation calculation method caused by the disturbance is as follows: Assuming that the flight manipulator device 3 does not deflect at a large angle around the contact surface, and the pressure sensor 337 remains in contact with the detection plane:

[0052] F1=kx1,F2=kx2

[0053] Where F1 and F2 are the pressure values ​​detected by the pressure sensors at both ends of the working platform, k is the spring elastic coefficient, and x1 and x2 are the contraction lengths of the springs at both sides;

[0054]

[0055] Where θ is the deflection angle of the flight manipulator device around the contact surface, and L is the distance between the centers of the two pressure sensors on the working platform;

[0056]

[0057] Where Δx, Δy are position deviations, and l is the distance between the servo and the detection plane;

[0058] S5. After the first detection is completed, the upper slide 338 of the working platform 33 is returned to its original position, and step S4 is repeated to detect the same part of the same steel bar 6 twice;

[0059] S6. After the inspection of the bridge pier 4 is completed, the flight manipulator controller 38 is used to adjust the steering gear angle 35 degrees to make the working platform 33 face upwards, and at the same time, the telescopic mechanism 37 is controlled to work, and the center of gravity of the flight manipulator device 3 is adjusted to keep the posture of the drone 31 stable; the drone 31 is controlled to fly upward to the bottom of the concrete bridge beam 5, and the depth camera 34 transmits the image of the lower surface of the bridge through the wireless transmission module 36, and the operator selects the inspection area;

[0060] S7, repeat steps S2, S3, S4, S5. After completing the thickness detection of the steel bar protective layer of the lower bridge pier 4 and the bridge beam slab 5 of the concrete bridge, control the flying robot arm device 3 to return.

[0061] It should be noted that the above content only illustrates the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications all fall within the protection scope of the claims of the present invention.

Claims

1. The UAV-based concrete bridge steel bar protective layer thickness detection system is characterized by : including computer equipment, UAV remote control and flight mechanical arm equipment, the flight mechanical arm equipment at least includes UAV, mechanical arm, working platform, depth camera, steering gear, wireless transmission module, telescopic mechanism and flight mechanical arm controller; The flying robotic arm device uses a drone as a mobile platform, which is used to carry a robotic arm and a working platform to complete the thickness detection of the bridge steel bar protective layer; a wireless transmission module and a servo are fixedly installed on the top of the drone; the turntable of the servo is fixedly installed at one end of the robotic arm; a depth camera is installed in the middle of the robotic arm, and a working platform is fixedly installed at the other end; the telescopic mechanism is fixedly installed on the lower panel of the drone through a mounting base.

2. The concrete bridge steel bar protective layer thickness detection system based on drone as claimed in claim 1 is characterized by: The working platform is composed of a reduction motor, a slide base, a slide, a spring and a pressure sensor; the slide base includes a belt and a pulley, and a pulley is installed in the middle of the slide base; a driven pulley is installed on both sides of the pulley, and the driven pulley is located inside the belt. The reduction motor drives the pulley to rotate, and the belt drives the slide to move; a spring is placed on one side of each of the two driven pulleys; one end of the spring is fixedly connected to the pressure sensor; a thickness gauge is fixedly installed on the slide.

3. The concrete bridge steel bar protective layer thickness detection system based on drone as claimed in claim 2 is characterized by: The telescopic mechanism consists of a mounting base, an electric push rod, a moving part and a battery; the electric push rod is installed on the lower panel of the drone through the mounting base; the other end of the electric push rod is installed with a moving part; the moving part is installed on the surface of the battery and is used to push the battery to move on the surface of the battery carrier.

4. A method for detecting the thickness of the steel bar protective layer of a concrete bridge based on an unmanned aerial vehicle using the system as claimed in claim 1, characterized in that: The following steps are involved: S1: Preheat the measuring equipment and fly the flying robot arm equipment under the concrete bridge through the UAV remote control; S2: The depth camera on the robotic arm transmits the image under the concrete bridge through the wireless transmission module. After the operator selects the inspection location, he controls the flying robotic arm device to approach the inspection location. S3: The working platform at the end of the flying robot arm equipment is 10 cm close to the detection plane. The flying robot arm controller controls the drone to approach the detection plane. According to the position of the steel bar layout, the direction perpendicular to the axis of the steel bar to be detected is determined as the detection direction. The flying robot arm controller adjusts the servo angle at one end of the robot arm to keep the thickness gauge parallel to the detection plane. At the same time, the telescopic rod is adjusted to adjust the center of gravity of the flying robot arm equipment. S4: The flying robot arm device detects each grid in turn according to the trajectory planning. After the thickness gauge contacts the detection plane, the reduction motor starts to work, driving the thickness gauge to move slowly along the detection direction on the detection plane until the instrument protective layer thickness indication is the smallest. At this time, the center line of the thickness gauge probe coincides with the axis of the steel bar, the reduction motor stops rotating, records the value and uses the depth camera to record each stop position of the thickness gauge. After completing the detection of one steel bar, the reduction motor continues to work, driving the thickness gauge to move to the next steel bar until all the steel bars arranged under the corresponding grid of the working platform are detected. The steel bar detection image, steel bar position and protective layer thickness data are transmitted to the computer device through the wireless transmission module, and the thickness gauge returns to its position for the second measurement; S5: After obtaining the steel bar protective layer thickness data, the detection is completed and the flying robotic arm equipment is controlled to return.

5. The method for detecting the thickness of the steel bar protective layer of a concrete bridge based on an unmanned aerial vehicle as claimed in claim 4, characterized in that: After the first detection in step S4 is completed, the slide on the working platform is returned to its position, and step S4 is repeated. The same steel bar and the same location are detected at least twice, and the average value of the detection data is taken.

6. The method for detecting the thickness of the steel bar protective layer of a concrete bridge based on an unmanned aerial vehicle as claimed in claim 4, characterized in that: In step S2, after the operator selects the inspection location, the flight robot arm controller performs grid map modeling on the plane to be inspected based on the image acquired by the depth camera, and plans a path to complete the inspection of each grid one by one; the direction of the grid map modeling is perpendicular to the axis direction of the steel bar distribution, and the side length of each grid does not exceed the effective detection range of the working platform.

7. The method for detecting the thickness of the steel bar protective layer of a concrete bridge based on an unmanned aerial vehicle as claimed in claim 4, characterized in that: In step S3 and step S4, after the thickness gauge contacts the detection plane, the pitch angle of the drone is adjusted to ensure the contact force, the spring contracts, and the pressure sensor values ​​on both sides remain consistent. The position error caused by external disturbance is compensated by the designed position and angle controller of the pressure sensors on both sides of the detection platform.

8. The method for detecting the thickness of the steel bar protective layer of a concrete bridge based on an unmanned aerial vehicle according to claim 7, characterized in that: The position and angle deviation calculation method caused by the disturbance is: While the pressure sensor remains in contact with the detection surface: F1=kx1,F2=kx2 Where F1 and F2 are the pressure values ​​detected by the pressure sensors at both ends of the working platform, k is the spring elastic coefficient, and x1 and x2 are the contraction lengths of the springs at both sides; Where θ is the deflection angle of the flight manipulator device around the contact surface, and L is the distance between the centers of the two pressure sensors on the working platform; Δx=l(1-cosθ) Δy=-l·sin(θ) Where Δx, Δy are position deviations, and l is the distance between the servo and the detection plane.

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