A small pipeline defect detection robot

Abstract

The present invention discloses a small pipeline defect detection robot, comprising: a main controller, with an axial support module one and an axial support module two respectively connected to two ends of the main controller. The axial support module one and the axial support module two are connected to a power supply module. A camera module is connected to the main controller. Omnidirectional wheels and universal balls are installed on the main controller, the axial support module one, the axial support module two and the power supply module. The universal balls are used as driven wheels and the omnidirectional wheels are used as driving wheels. The omnidirectional wheels are driven to work by a motor and a coupling; the CCD camera of this device can capture clear and distinctively featured images in an environment with sufficient light; at the same time, it can still clearly capture images in the dark. For the details, due to the effect of the infrared supplementary light, they will be slightly blurred compared to the images feedback under the condition of sufficient light, but their features can still be distinguished. When actually photographing a pipeline, the pipeline defect features are obvious and clear, and the noise is small.

Description

Technical Field

[0001] The present invention relates to the field of robot motion control, and particularly to a small pipeline defect detection robot. Background Art

[0002] Many types of pipelines, such as gas pipelines, are exposed to the outside all year round. The pipeline wall will be corroded by the internal transported substances and the external natural environment. Therefore, many defects will occur, such as a reduction in the pipeline wall thickness (mainly surface depressions, dot-like corrosion or pipe wall perforations, etc.), pipe wall cracks, etc., which will lead to problems such as resource loss and various hazards to the ecological environment.

[0003] Pipelines can be classified into steel pipes (alloy material pipes, high-carbon material pipes, stainless steel material pipes, surface galvanized material pipes, ordinary carbon material pipes, etc.), copper pipes (alloy material pipes, copper pipes, etc.), plastic pipes (polypropylene, polyvinyl chloride material pipes, etc.), rubber-lined pipes, cast iron pipes, composite pipes, rubber pipes, cement pipes, etc. According to different uses, the pipe diameters generally range from 15 mm to 3000 mm. The traditional detection method for small pipelines is mainly manual inspection. By combining the line inspection method with positioning technology and using an alternating current ground potential difference measuring device, the defect location of the pipeline can be accurately detected. However, this method is inefficient, has a large workload, and is limited by factors such as terrain, environment, and safety.

[0004] In contrast, the detection technology based on robots is more efficient and convenient. Advanced integrated chips are implanted into the robot body, and a variety of sensors and devices are carried, enabling it to have good mechanical performance and efficient and comprehensive flaw detection capabilities. Workers only need to operate the upper computer to obtain the detailed information of pipeline defects, which greatly shortens the time required for pipeline inspection work and also greatly improves the quality of inspection work.

[0005] Currently, most inspection robots are AGV-type robots used inside large pipelines to detect internal pipeline defects. Obviously, this method is not applicable to small pipelines. At the same time, only considering internal pipeline defects and ignoring the safety detection of the outer wall also reflects the incompleteness of the detection technology. Summary of the Invention

[0006] According to the problems existing in the prior art, the present invention discloses a small pipeline defect detection robot, including: a main controller, with an axial support module one and an axial support module two respectively connected to both ends of the main controller. The axial support module one and the axial support module two are connected to a power supply module. A camera module is connected to the main controller. Omnidirectional wheels and universal balls are installed on the main controller, the axial support module one, the axial support module two, and the power supply module. The universal ball is used as a driven wheel, and the omnidirectional wheel is used as a driving wheel. The omnidirectional wheel is driven by a motor and a coupling.

[0007] The main controller uses an incremental PID control algorithm to correct the speed of the pipeline robot: taking the real-time speed of the motor as the input quantity, obtaining the speed error of the motor through the PID control algorithm, calculating the correction amount for the next adjustment through the proportional P, integral I, and differential D of the speed error e, and then obtaining the adjusted voltage value by signal feedback to the motor.

[0008] When the sampling period is T, and the voltage error is set as w, the incremental PID control algorithm is:

[0009]

[0010] K i = K p T / T i

[0011] K d = K p T d / T

[0012] Its transfer function is:

[0013]

[0014] Setting the initial values of the robot control system, the transfer function then becomes:

[0015]

[0016] Where K p is the proportionality coefficient, T I is the integral time constant, and T D is the differential time constant.

[0017] The main controller, the first axial support module, the second axial support module, and the power supply module are connected by an electric screw telescopic rod to form a closed-loop device.

[0018] The camera module is set on the Raspberry Pi. A CCD camera and a communication module are also installed on the Raspberry Pi. Infrared devices and radio frequency devices are arranged on both sides of the CCD camera.

[0019] A mobile battery and a motor drive board are installed on the power supply module. The motor drive board receives the command signal transmitted by the Raspberry Pi and drives the omnidirectional wheels to move.

[0020] The electric screw telescopic rod includes a sub-rod and a mother-rod. The outer surface of the sub-rod is threadedly connected to the inner surface of the mother-rod. A motor is installed on the mother-rod. The Raspberry Pi drives the motor to work according to the actual diameter of the working pipeline to control the forward and reverse rotation of the sub-rod and the mother-rod, thereby adjusting the telescopic length of the electric screw telescopic rod.

[0021] Due to the adoption of the above technical solution, a small pipeline defect detection robot provided by the present invention can adjust its running speed by changing the value assigned to PWM in the program during the speed regulation process, and test the moving speed of the robot when it is loaded. After testing, when PWM is set to 100%, the average rotational speed of the motor can reach 90 rpm / m, so the average speed of the robot for pipeline inspection is 0.27 m / s. The adaptive mechanism can adjust the length of the telescopic rod according to the change rate of the current moving speed of the robot. Due to the addition of the PID algorithm, when the friction on the wheel suddenly increases, the robot can still approach the set speed. It can be concluded that the motion control system of the robot can meet the functional requirements and has certain feedback speed regulation and adaptive functions. During the experiment, the robot moved smoothly without jamming.

[0022] In addition, the CCD camera can capture clear and distinct images in an environment with sufficient light; at the same time, it can still clearly capture the picture in the dark. For the details, due to the effect of the infrared supplementary light, compared with the images feedback under the condition of sufficient light, they will be slightly blurred, but their features can still be distinguished. When actually shooting the pipeline, the pipeline defect features are obvious and clear, and the noise is small. The distortion of the image is small when changing the focal length, meeting the requirements of actual inspection.

[0023] In summary, this design can quickly and accurately move along the outer wall of the pipeline, and can capture clear pictures, meeting the requirements of small external pipeline inspection work. At the same time, after comparing with relevant literature, it can be obtained that the detection speed is slightly faster than that of the internal pipeline inspection robot. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings described below are only some embodiments recorded in the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0025] Figure 1 It is a schematic structural diagram of the small pipeline defect detection robot of the present invention;

[0026] Figure 2 It is a schematic structural diagram of the small pipeline defect detection robot of the present invention;

[0027] Figure 3 It is a partial connection diagram of the omnidirectional wheels in the present invention;

[0028] Figure 4 It is a partial connection diagram of the CCD camera in the present invention;

[0029] Figure 5 Connection diagram of the electric screw telescopic rod in the present invention;

[0030] Figure 6 Structural diagram of the small pipeline defect detection robot system in the present invention;

[0031] Figure 7 Electrical connection diagram of the present invention;

[0032] Figure 8 Schematic diagram of the robot speed regulation control loop in the present invention;

[0033] Figure 9 Schematic diagram of the incremental PID control algorithm in the present invention;

[0034] Figure 10 PID speed regulation experiment results in the present invention. Specific implementation manners

[0035] To make the technical solutions and advantages of the present invention clearer, the following clearly and completely describes the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention:

[0036] As Figures 1 to 3 shown, a small pipeline defect detection robot includes a main controller 3. An axial support module one 1 and an axial support module two 2 are respectively connected to both ends of the main controller 3. Among them, the axial support module one 1 and the axial support module two 2 are connected to a power supply module 4. A camera module 32 is connected to the main controller 3. Omnidirectional wheels 5 and universal balls 6 are installed on the main controller 3, the axial support module one 1, the axial support module two 2 and the power supply module 4. The omnidirectional wheels 5 are used as driving wheels and are driven by a motor 37 and a coupling 38, and the universal balls 6 are used as driven wheels. Among them, the omnidirectional wheels 5, the universal balls 6 and the connected motor 37 and coupling 38 form a power system, and the rotation speed of each motor can be independently adjusted. The Raspberry Pi 36 controls the movement of the robot by sending control signals to the motors in different modules. When the power systems of the axial support module one 1 and the axial support module two 2 start to work, the omnidirectional wheels and universal balls in the main controller 3 and the power supply module 4 perform passive movements, and the robot can realize the overall clockwise and counterclockwise movements in the axial direction. When the power systems of the main controller 3 and the power supply module 4 start, the omnidirectional wheels and universal balls of the axial support module one 1 and the axial support module two 2 perform passive movements, and the robot can realize the overall forward and backward movements in the radial direction. When the robot needs to turn, according to the current position, the omnidirectional wheels in the inner module are locked, and the omnidirectional wheels in the outer module move, and the turning can be completed.

[0037] Furthermore, Figure 2 and Figure 4As shown in the figure, the camera module 32 is set on the Raspberry Pi 36 and consists of a CCD camera 33, an infrared device 34 and a radio frequency device 35. A communication module with Bluetooth and wireless network functions is also installed on the Raspberry Pi 36.

[0038] Further, the main controller 3, the axial support module 1, the axial support module 2 and the power supply module 4 are connected by an electric screw telescopic rod 7 to form a closed-loop device.

[0039] Further, a mobile battery and a motor drive board are installed on the power supply module 4, and the motor drive board receives the command signal transmitted by the Raspberry Pi and drives the omnidirectional wheels 5 to move.

[0040] Further, as Figure 5 shown, the electric screw telescopic rod 7 includes a sub-rod 71 and a mother-rod 72. The outer surface of the sub-rod 71 is threadedly connected to the inner surface of the mother-rod 72. A motor 73 is installed on the mother-rod 72. The Raspberry Pi drives the motor 73 to work according to the actual working pipeline diameter to control the forward and reverse rotation of the sub-rod 71 and the mother-rod 72, thereby adjusting the length of the electric screw telescopic rod 7. During actual work, the robot adjusts the telescopic rod size in real time according to the pipe diameter change, ensuring the running stability of the robot while minimizing the frictional energy loss as much as possible.

[0041] The small external pipeline inspection robot needs to carry various devices into the working environment and complete the inspection task through the operation terminal. By adopting the method of single-module design, the camera module 32, the Raspberry Pi 36, the communication module are installed in the main controller 3; the mobile battery and the motor drive board are installed in the power supply module 4. Add 2 to 4 support modules and use the electric screw telescopic rod 7 to combine, and the communication between different modules can be completed by docking the interfaces of different modules. If equipment with other functions is needed in some occasions, such as the infrared device 34, the radio frequency device 35, etc., they can be installed in the support module to make it a functional module. Such a design is conducive to the inspection work in different environments and the secondary development of researchers.

[0042] Since the small pipeline defect detection robot needs to have movements in both the axial and radial directions, and in the mechanical design part, an installation mode of two pairs of single units installed horizontally and two pairs of single units installed vertically is adopted. Therefore, for the control principle of the robot movement, it can be transformed into the following method:

[0043] (1) Axial movement: Control the forward and reverse rotation of the DC motor installed on the vertically installed single unit. At this time, the horizontally installed omnidirectional wheels are pushed as driven wheels, and the robot can move clockwise and counterclockwise axially as a whole.

[0044] (2) Radial movement: Control the forward and reverse rotation of the DC motor installed on the horizontally installed single unit. At this time, the vertically installed omnidirectional wheels are pushed as driven wheels, and the robot can move forward and backward radially as a whole.

[0045] As Figure 7 shown, set the Raspberry Pi 3B+ with the connected dual L298N motor driver board as the client, and place it and the operating end under the same WIFI. Define the GPIO ports on the Raspberry Pi in the control program, and write the power-on modes with different high and low levels of the interfaces for pressing different buttons. Connect the Raspberry Pi 36, the driver board, and the motor 37 as shown in the figure. When the single-chip microcomputer receives a signal, it outputs a signal at the corresponding pin, and after being amplified by the driver board, it drives the corresponding motor 37 to move.

[0046] During operation, after installing and clamping the robot to the pipeline, connect it remotely to the operating end such as a computer through the communication module in the Raspberry Pi 36, remotely log in to the operating system of the Raspberry Pi 36 through the network or Bluetooth, and call the program saved in advance in the Raspberry Pi 36 to operate the robot. The built-in programs include (1) motion control program (2) status monitoring program (3) adaptive adjustment program (4) image operation program. Among them, calling program (1) can remotely control the axial, radial or turning motion of the robot through the buttons on the operating end; calling program (2) can determine the current position, posture and speed of the robot according to the number and frequency of pulses sent by each pin of the Raspberry Pi. Calling program (3) can calculate the optimal spacing of the module according to the current speed of the robot through the PID algorithm and the adaptive control algorithm, convert it into a signal and send it to the electric screw telescopic rod 7 to adapt to the change of the pipe diameter. Calling program (4) can turn on / off the CCD camera 33, the infrared device 34, and the radio frequency device 35, and transmit the real-time picture to the operating end.

[0047] When the pipeline inspection robot is affected by uncontrollable factors from the inside and outside (such as insufficient battery voltage, static friction on the pipe surface, or sudden increase in pipe diameter, etc.), it may affect the driving force and running stability of the power system, and then cause the actual movement speed of the robot to be inconsistent with the input speed. At this time, a closed-loop circuit is needed to correct the speed of the pipeline robot. In the closed-loop control, this paper introduces the PID algorithm to design the motion control program, which is pre-set in the Raspberry Pi 36. When working, after the operating end remotely logs in to the Raspberry Pi 36, it calls the motion control program. While performing axial and radial motions, the real-time rotation speed of the motor 37 is used as the input of this PID control algorithm, and the adjusted voltage is used as the output. The control principle block diagram is as Figure 8 .

[0048] The adjustment process is as Figure 8As shown in the figure, where v is the input speed received by the robot, e is the speed error measured by the encoder on the motor 37 and then adjusted through the PID control algorithm, s is the pulse width modulation signal sent to the motor 37, and u is the output speed. First, the operating end inputs a speed value, and the motor 37 starts to work. At the same time, its actual speed is fed back to the PID control algorithm. The correction amount for the next adjustment is calculated through the three parameters of proportional P, integral I, and differential D of the speed error e. Finally, it is fed back to the motor 37 through a signal to achieve the speed regulation function.

[0049] In the PID algorithm, the continuous closed-loop control law is as follows:

[0050]

[0051] Among them, K p is the proportional coefficient, T I is the integral time constant, T D is the differential time constant. From this, its transfer function can be deduced as:

[0052]

[0053] According to the analysis, it can be obtained that the incremental PID control needs to be used in this design. When the sampling period is T, assuming the voltage error amount is w, the formula (3-5) then becomes:

[0054]

[0055] Among them

[0056] K i = K p T / T i

[0057] K d = K p T d / T

[0058] Its transfer function is:

[0059]

[0060] Set the initial value of the robot control system, and the transfer function then becomes:

[0061]

[0062] Perform system correction, that is, add a PID control algorithm to the original system, as Figure 9 shown. Design four groups of PID adjustment experiments, and the experimental results are as Figure 10As shown, in the figure, ZPK1 represents the original system without the (gain) motor power drive part. ZPK3 has a relatively large overshoot, and the line ZPK4 balances the overshoot and the rise time. ZPK2 is close to the optimal state, enabling fast, stable, and accurate PID regulation. Through experimental debugging, it is determined that it is relatively good in this state. Although there is a moderate overshoot, the peak time is reduced, and the system response characteristics are optimized.

[0063] As mentioned above, the above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes should be covered within the protection scope of the present invention.

Claims

1. A small pipeline defect detection robot, characterized in that Including: A main controller (3), with an axial support module one (1) and an axial support module two (2) respectively connected to both ends of the main controller (3). The axial support module one (1) and the axial support module two (2) are connected to a power supply module (4). A camera module (32) is connected to the main controller (3). Omnidirectional wheels (5) and universal balls (6) are installed on the main controller (3), the axial support module one (1), the axial support module two (2) and the power supply module (4). Taking the universal ball (6) as a driven wheel and the omnidirectional wheel (5) as a driving wheel, the omnidirectional wheel (5) is driven to work by a motor (37) and a coupling (38); the main controller (3) uses an incremental PID control algorithm to correct the speed of the pipeline robot: taking the real-time rotation speed of the motor (37) as an input quantity, obtaining the speed error of the motor through the PID control algorithm, calculating the correction quantity for the next adjustment through the proportional P, integral I and differential D of the speed error e, and then obtaining the adjusted voltage value by signal feedback to the motor (37). When the sampling period is T, assuming the voltage error quantity is w, the incremental PID control algorithm is: K i = K p T / T I K d = K p T d / T Its transfer function is: Setting the initial value of the robot control system, the transfer function then becomes: where K p is the proportionality coefficient, T I is the integral time constant, T D is the derivative time constant.

2. The small pipeline defect detection robot according to claim 1, wherein: The main controller (3), the axial support module one (1), the axial support module two (2) and the power supply module (4) are connected by an electric screw telescopic rod (7) to form a closed-loop device.

3. The small pipeline defect detection robot according to claim 2, wherein: The camera module (32) is arranged on a Raspberry Pi (36). A CCD camera (33) and a communication module are also installed on the Raspberry Pi (36). Infrared devices (34) and radio frequency devices (35) are arranged on both sides of the CCD camera (33).

4. The small pipeline defect detection robot according to claim 3, characterized in that: A mobile battery and a motor drive board are installed on the power supply module (4). The motor drive board receives the command signal transmitted by the Raspberry Pi (36) and drives the omnidirectional wheel (5) to move.

5. The small pipeline defect detection robot according to claim 3, characterized in that: The electric screw telescopic rod (7) includes a sub-rod (71) and a mother-rod (72). The outer surface of the sub-rod (71) and the inner surface of the mother-rod (72) are connected by threads. A motor (73) is installed on the mother-rod (72). The Raspberry Pi (36) drives the motor (73) to work according to the actual working pipeline diameter to control the forward and reverse rotation of the sub-rod (71) and the mother-rod (72), thereby adjusting the telescopic length of the electric screw telescopic rod (7).

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