Differential type pipeline inspection robot and control method

Abstract

According to the differential type pipeline inspection robot and the control method, the front driving motor and the rear driving motor drive the connecting rod assemblies on the bases at the two ends of the shell to rotate correspondingly, and then the hemispherical wheels on the connecting rod assemblies abut against the inner wall of a pipeline, so that the hemispherical wheels rotate; as the wheel shafts sleeved with the semispherical wheels deviate outwards to form torsion angles, in the process that the robot rotates close to the inner wall of the pipeline, a front-back motion component is decomposed in the axis direction of the shell, and meanwhile a circular motion component is decomposed in the circumferential direction of the pipeline; the robot can move in the axis direction of the shell, so that the robot moves forwards or backwards in the rotating process; the position and posture of the robot in the pipeline can be accurately controlled, so that the robot can walk on the target track, the quality and efficiency of pipeline inspection operation are improved, and meanwhile, the control flexibility is good.

Description

Technical Field

[0001] The present invention relates to the technical field of robots, and in particular to a differential pipeline inspection robot and a control method thereof. Background Art

[0002] The pipeline inspection robot is a special robot that is often used in narrow pipelines that are inaccessible to humans. It replaces humans in performing inspection operations such as pipeline detection and repair in harsh environments. Since the pipeline inspection robot works within the inner diameter of the pipeline, it is required to walk within the inner cylindrical surface so that the pipeline inspection robot can perform inspection operations.

[0003] For example, the patent document with Chinese patent application number 201910864921.5 and announcement date 2023.12.26 discloses a pipeline crawling robot with relative position navigation function, including an image acquisition part, a robot body, an arm mechanism and a relative positioning system; the image acquisition part realizes the recognition of targets and obstacles during the robot's walking process, the robot body serves as the robot's bearing structure and is used to connect other structures, and the arm mechanism drives the robot to move in the pipeline.

[0004] The pipeline crawling robot of the above-mentioned document realizes the inspection and repair of special spaces such as pipelines, and has a positioning system for relative position navigation. The large arm driving mechanism of the pipeline crawling robot only uses one crank to drive four large arms to move simultaneously, which increases the compactness of the mechanism, ensures the coordination of the robot's large arm movement, and helps the robot maintain the stability and balance of the center of gravity in the slippery pipe wall; when the pipeline crawling robot faces different pipe diameters inside the pipeline, it changes the bending amount of the small arm so that the robot can pass through pipes with different diameters.

[0005] However, it mainly moves in the pipeline by swinging its arms. Since it only relies on swinging to move forward, the reliability of movement cannot be ensured when encountering greater resistance. In addition, there may be various complex environments in the pipeline, which require the robot to be individually controlled front and back and cooperate with each other to complete the work requirements. The four arms of the pipeline crawling robot are driven simultaneously by a crank, so the front and back control of the pipeline crawling robot is synchronized, and it is impossible to achieve individual front and back control and cooperation, so as to accurately control the position and posture of the robot. Summary of the invention

[0006] The object of the present invention is to provide a differential pipeline inspection robot and a control method, which can control the robot to walk reliably in the pipeline, thereby improving the quality and efficiency of pipeline inspection operations, while having good control flexibility.

[0007] To achieve the above-mentioned purpose, on one hand, the present invention provides a differential pipeline inspection robot, comprising a shell and a cover arranged at both ends of the shell, a driving device is arranged in the shell, a base is arranged on the cover, an output end of the driving device passes through the cover and is fixedly connected to the base, a boss is arranged on the base, and two or more connecting rod assemblies arranged in a circle are arranged on the outer side of the boss, the bottom end of the connecting rod assembly is hinged to the boss, the top end of the connecting rod assembly is hinged to a hemispherical wheel seat, the connecting rod assembly is connected to the base through an elastic member, a wheel axle is fixedly provided on the hemispherical wheel seat, the wheel axle is outwardly deviated and forms a torsion angle with a vertical plane passing through the connecting rod assembly and the axis of the shell, a hemispherical wheel is sleeved on the wheel axle, the connecting rod assembly comprises a front connecting rod assembly and a rear connecting rod assembly, the front connecting rod assembly and the rear connecting rod assembly are respectively arranged on both sides of the shell, and the torsion angle on the front connecting rod assembly and the torsion angle on the rear connecting rod assembly are oppositely arranged.

[0008] The above arrangement can drive the base to rotate on the outside of the cover through the driving device. Since the hemispherical wheel is sleeved on the hemispherical wheel seat, and the hemispherical wheel seat is fixedly connected to the connecting rod assembly, and the connecting rod assembly is hinged to the boss, the hemispherical wheel, the hemispherical wheel seat, the connecting rod assembly and the boss are connected to form a whole. In this way, during the rotation of the base, the hemispherical wheel, the hemispherical wheel seat and the connecting rod assembly can be driven to rotate synchronously. Since the hemispherical wheel abuts against the inner wall of the pipe to generate friction, the hemispherical wheel rotates around the wheel axle in the opposite direction to the base. At the same time, since the wheel axle deviates outward to form a torsion angle, the robot will rotate along the outer wall during the process of close contact with the inner wall of the pipe. The axial direction of the shell is decomposed into a forward and backward motion component, and since the circumferential component makes the robot move forward or backward during the rotation process, friction will be generated during the robot's forward or backward process. The friction will cause the hemispherical wheel to rotate in the opposite direction of the circumferential direction on the wheel axle, so that the robot can move along the axial direction of the shell, thereby realizing the forward or backward movement of the robot, thereby ensuring the reliability of the robot's movement in the pipeline, and by setting the torsion angles oppositely on the front connecting assembly and the rear connecting assembly, the rotation direction of the front connecting rod assembly and the rear connecting rod assembly can be controlled to achieve control of the robot's moving position.

[0009] Furthermore, a control compartment is provided in the shell, and a central control module, a battery, a drive device and an inspection instrument compartment are provided in the control compartment. The drive device includes a front drive motor and a rear drive motor, and the front drive motor and the rear drive motor are relatively arranged in the control compartment. The output ends of the front drive motor and the rear drive motor are respectively fixedly connected to the center of the base through the covers at both ends of the shell.

[0010] The above arrangement makes it easy for the front drive motor and the rear drive motor to drive the base to rotate.

[0011] Furthermore, the boss is arranged to protrude outward along the axial direction of the base, and more than two hinge seats are arranged in a circle on the base and located on the outside of the boss. The connecting rod assembly includes connecting rod one and connecting rod two. One end of connecting rod one is hinged to the boss through a pin, one end of connecting rod two is hinged to the hinge seat through a pin, and the other ends of connecting rod one and connecting rod two are hinged to the hemispherical wheel seat through a pin. After the hemispherical wheel seat, connecting rod one, connecting rod two and the base are connected, a four-bar linkage is formed.

[0012] The above arrangement enables the hemispherical wheel seat, connecting rod one and connecting rod two to form an integrated four-bar linkage after being connected to the base. In this way, during the rotation of the base, the connecting rod assembly and the hemispherical wheel seat can be driven to rotate synchronously. At the same time, it is convenient for the connecting rod assembly to rotate around the base without interfering with the angle of contact between the hemispherical wheel and the inner wall of the pipe, thereby enabling the robot to rotate in the pipe.

[0013] Furthermore, one end of the elastic member is fixedly connected to the second connecting rod, and the other end of the elastic member is fixedly connected to the base.

[0014] The above arrangement can pull the connecting rod assembly to rotate around the base through the elastic member, and adjust the connecting rod assembly to expand outward to adapt to pipes of different diameters, so that the robot can perform inspection operations in pipes of different diameters.

[0015] Furthermore, the wheel axle on the four-bar linkage connected to the front drive motor and the wheel axle on the four-bar linkage connected to the rear drive motor are arranged in opposite directions and deviate outwards.

[0016] The above settings ensure that the robot can move forward or backward after rotating the hemispherical wheels.

[0017] Another aspect of the present invention provides a control method for a differential pipeline inspection robot, comprising the following steps: S1 presets the target inspection trajectory of the robot as follows: , For the trajectory Middle Position points, is the displacement of the robot in the direction of the pipeline axis, is the rotation angle of the robot in the pipeline, S2 robot finds track The closest pose point to the pose at time t Then, the time required for the robot to reach the nearest position point is calculated by presetting the moving distance and moving speed in the target pipeline axis direction. , and then calculate the target angular velocity of the robot body to reach the nearest posture point, and finally calculate the target angular velocity required by the front drive motor and the rear drive motor to reach the nearest posture point according to the relationship between the target angular velocity and the required angular velocity of the front drive motor and the rear drive motor, the target moving speed and the torsion angle, and set the angular velocity of the front drive motor and the rear drive motor of the robot at time t to the target angular velocity, so that the robot reaches the nearest posture point at the target angular velocity and the target moving speed; S3 repeats step S2 until the robot reaches the trajectory The last posture point in the inspection is completed.

[0018] The above method, when it is known that the trajectory is reached at a certain moving speed When the target posture point in the trajectory is reached, the angular velocity of the front drive motor and the rear drive motor is determined according to the relationship between the target angular velocity and the required angular velocity of the front drive motor and the rear drive motor, the target moving speed and the torsion angle. By controlling the angular velocity of the front drive motor and the rear drive motor, the robot can accurately reach the trajectory. The target posture point in the pipeline can be determined, and the translation and rotation changes in the control process are flexible, stable and smooth, so that the robot has good control performance in the pipeline, thereby improving the quality and efficiency of pipeline inspection operations.

[0019] Further, S1 includes S11-S13; S11 determines the relationship between the rotational angular velocities of the fuselage, the front drive motor, and the rear drive motor; S12 determines the relationship between the moving speed of the robot along the pipeline axis and the body angle; S13 determines the moving distance of the robot along the pipeline axis at time t And the body rotation angle , thus forming the robot's position point at time t .

[0020] The above method determines the relationship between angular velocities through kinematic relationships, and then determines the preset trajectory of the posture points through multiple records to facilitate subsequent calculations.

[0021] Furthermore, the relationship between the rotational angular velocities of the fuselage, the front drive motor and the rear drive motor in step S11 is as follows: (1) In formula (1), is the fuselage angular velocity, is the angular velocity of the front drive motor, is the angular velocity of the rear drive motor.

[0022] The above settings can control the angular velocity of the front drive motor and the angular velocity of the rear drive motor. When the angular velocity of the front drive motor is opposite to the angular velocity of the rear drive motor and the difference between the two is 0, the robot only moves along the axial direction of the pipeline without rotational motion. When the difference between the two is not 0, the robot moves forward or backward in a spiral in the pipeline, thereby enabling the robot to move in the pipeline with different postures, thereby meeting the inspection operation requirements.

[0023] Further, S12 includes: calculating the moving speed of the robot along the axial direction of the pipeline based on the contact point A between the hemispherical wheel and the inner wall of the pipeline, taking the axial direction of the pipeline as the x-axis, the horizontal direction of the pipeline cross section as the y-axis, and the vertical direction of the pipeline cross section as the z-axis, establishing a spatial coordinate system, and setting the direction of the wheel axis as OQ, (7); is the fuselage angular velocity, is the angular velocity of the front drive motor, is the angular velocity of the rear drive motor; r is the radius of the pipeline; Angle is the torsion angle; v is the moving speed of the robot in the direction of the pipeline axis.

[0024] With the above settings, we can first use formula (7) to conveniently calculate the moving speed of the robot along the pipeline axis.

[0025] Furthermore, S13 also includes the v , Integrate over time to obtain the movement distance of the robot along the pipeline axis at time t And the body rotation angle , make , (8).

[0026] With the above settings, the position and posture of the robot at time t can be obtained by integration.

[0027] Furthermore, the time in step S2 for: (9) Target angular velocity for: (10) Set the robot's moving speed in the pipe axis direction v and target angular velocity Substituting into formula (7) we get (11) Then the robot can move to the nearest position point The angular velocity required by the front drive motor and the rear drive motor can be updated by the central control module to the angular velocity of the front drive motor and the rear drive motor of the robot at time t when the robot moves to the nearest position point. The angular velocity required for the front and rear drive motors.

[0028] The above settings can accurately control the robot to move at a certain speed. v and target angular velocity Arrival track The pose points in . BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a structural schematic diagram of the present invention.

[0030] Figure 2 It is a side view of the present invention.

[0031] Figure 3 It is a cross-sectional schematic diagram of the present invention.

[0032] Figure 4 It is a schematic diagram of the front drive motor in the present invention rotating in reverse and moving forward.

[0033] Figure 5 It is a schematic diagram of the rear drive motor in the present invention rotating forward and moving backward, and reverse and moving forward.

[0034] Figure 6 It is a structural schematic diagram of another viewing angle of the present invention.

[0035] Figure 7 It is the front view of the present invention.

[0036] Figure 8 It is a schematic diagram of the hemispherical wheel in the present invention.

[0037] Fig. 9 It is a schematic structural diagram of the upper hemispherical wheels of the front connecting rod assembly and the rear connecting rod assembly in the present invention. DETAILED DESCRIPTION

[0038] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] like Figure 1-9As shown, a differential pipeline inspection robot comprises a shell 1 and covers 2 arranged at both ends of the shell 1, the covers 2 are detachably connected to the shell 1, a control compartment is arranged in the shell 1, a central control module 11, a battery 12, a drive device and an inspection instrument compartment 14 are arranged in the control compartment, a base 3 is arranged on the cover 2, an output end of the drive device passes through the cover 2 and is fixedly connected to the base 3, the drive device comprises a front drive motor 13 and a rear drive motor 10, the battery 12 is respectively connected to the central control module 11, the front drive motor 13 and the rear drive motor 10, plays a role in providing power, a pipeline inspection instrument is carried in the inspection instrument compartment 14, the central control module 11 is respectively connected to the pipeline inspection instrument, the front drive motor 13 and the rear drive motor 10, the front drive motor 13 and the rear drive motor 10 are relatively arranged in the control compartment, and the output ends of the front drive motor 13 and the rear drive motor 10 are respectively fixedly connected to the center of the base 3 through the covers 2 at both ends of the shell 1, so that it is convenient for the front drive motor 13 and the rear drive motor 10 to drive the base 3 to rotate.

[0040] The base 3 is provided with a boss 4, which is protruding outward along the axial direction of the base 3. More than two hinge seats 5 are provided on the base 3 and located on the outer side of the boss 4 and are arranged in a circumference. More than two connecting rod assemblies are provided on the outer side of the boss 4 and are arranged in a circumference. The number of the hinge seats 5 matches the number of the connecting rod assemblies. In this embodiment, the number of connecting rod assemblies is set to twelve, and six are set on each of the bases 3 of the covers 2 at both ends of the shell 1. The bottom end of the connecting rod assembly is hinged to the boss 4, and the top end of the connecting rod assembly is hinged with a hemispherical wheel seat 6. The connecting rod assembly is connected to the base 3 through an elastic member 7. The connecting rod assembly includes a connecting rod 1 21 and a connecting rod 2 22. The connecting rod 1 21 is One end is hinged to the boss 4 through a pin, one end of the connecting rod 22 is hinged to the hinge seat 5 through a pin, and the other ends of the connecting rod 1 21 and the connecting rod 2 22 are hinged to the bottom of the hemispherical wheel seat 6 through a pin. The hemispherical wheel seat 6, the connecting rod 1 21, the connecting rod 2 22 are connected to the base 3 to form a four-bar linkage, so that the hemispherical wheel seat 6, the connecting rod 1 21 and the connecting rod 2 22 are connected to the hinge seat 5 to form an integrated four-bar linkage. In this way, during the rotation of the base 2, the connecting rod assembly and the hemispherical wheel seat 6 can be driven to rotate synchronously, and at the same time, it is convenient for the connecting rod assembly to rotate around the base 3 without interfering with the angle of contact between the hemispherical wheel 6 and the inner wall of the pipe, thereby enabling the robot to rotate in the pipe.

[0041] In this embodiment, one end of the elastic member 7 is fixedly connected to the connecting rod 22, and the other end of the elastic member 7 is fixedly connected to the base 3. The elastic member 7 is a spring, so that the connecting rod assembly can be pulled by the elastic member 7 to rotate around the base 3, and the connecting rod assembly can be adjusted to expand outward to adapt to pipes of different diameters, so that the robot can perform inspection operations in pipes of different diameters.

[0042] The hemispherical wheel seat 6 is fixed with a wheel axle 8, which is set to deviate outward and form a torsion angle with the vertical plane passing through the axis of the connecting rod assembly and the housing 1. In this embodiment, the torsion angle formed by the wheel axle 8 on the four-bar linkage connected to the front drive motor 13 is set in the opposite direction to the torsion angle of the wheel axle 8 on the four-bar linkage connected to the rear drive motor 10. Fig. 9 As shown, the hemispherical wheel 9 on the front connecting rod assembly 601 is tilted to one side, and the hemispherical wheel 9 on the rear connecting rod assembly 602 is tilted to the other side, thereby forming a reverse outward deviation setting, so that the torsion angles at both ends of the robot are reversely deviated outward, and the hemispherical wheel 9 is sleeved on the wheel axle 8, thereby ensuring that the robot can move forward or backward after the hemispherical wheel 9 rotates.

[0043] In this embodiment, a limit block 61 is provided on the top of the hemispherical wheel seat 6, one end of the wheel axle 8 is fixedly connected to the limit block 61, the hemispherical wheel 9 is sleeved on the wheel axle 6, and a limit piece (not marked in the figure) is provided at the other end of the wheel axle 6. The limit piece is spirally connected to the wheel axle 8. In this way, when the hemispherical wheel 9 is sleeved on the wheel axle 8 and rotates around the wheel axle 8, the limit piece can prevent the hemispherical wheel 9 from separating from the wheel axle 8. A thread is provided at the other end of the wheel axle 8, and the limit piece is a nut.

[0044] In this embodiment, the robot includes the following 12 kinematic features.

[0045]

[0046] Table 1 Robot kinematic characteristics Combination Figure 4 and Figure 5 As shown, the positive direction of the rotation angle is when looking at the robot from the rear, the clockwise direction is positive, and the counterclockwise direction is negative. The rear drive speed and the front drive speed are the rotation speeds of the rear drive motor and the front drive motor respectively. It can be concluded from the above table and the figure that when the front drive motor and the rear drive motor rotate in opposite directions, if the rear drive motor rotates faster than the front drive motor, the robot will rotate forward and spiral backward, so that the moving position can be controlled by the angular velocities of the two motors.

[0047] A control method for a differential pipeline inspection robot, the specific steps are as follows: S1 presets the robot's target inspection trajectory as P. For the trajectory Middle Position points, is the displacement of the robot in the direction of the pipeline axis, is the rotation angle of the robot in the pipeline; S1 includes S11-S13; S11 determines the relationship between the rotational angular velocities of the fuselage, the front drive motor 13 and the rear drive motor 10: (1) In formula (1), is the fuselage angular velocity, is the angular velocity of the front drive motor, is the angular velocity of the rear drive motor, such as Figure 6 As shown, when the angular velocity of the front drive motor 13 is opposite to the angular velocity of the rear drive motor 10, and the difference between the two is 0, the robot only moves along the axial direction of the pipeline without rotational motion. When the difference between the two is not 0, the robot moves forward or backward in a spiral manner in the pipeline.

[0048] S12 determines the relationship between the robot's moving speed along the pipeline axis and the body angle, such as Figure 7-8 As shown, The robot's moving speed along the pipeline axis is calculated based on the contact point A between the hemispherical wheel and the inner wall of the pipeline. The pipeline axis is the x-axis, the horizontal direction of the pipeline section is the y-axis, and the vertical direction of the pipeline section is the z-axis. A spatial coordinate system is established, and the direction of the wheel axis is OQ. The direction of the OQ vector is the pipeline axis x-axis rotating around the y-axis first. Angle, then rotate around the z axis The direction perpendicular to the wheel axle is AB, the direction from the contact point A to the pipeline axis is AC, and the direction through the contact point A and parallel to the x-axis is AD. The radial velocity at the contact point A pointing to the pipeline axis is calculated using the following formula: (2) In formula (2), v AC is the radial velocity pointing to the pipeline axis at the contact point A, r is the pipeline radius, is the angular velocity of the fuselage relative to the pipe, (3) The projection of the vector OQ in the direction of the wheel axle on the xy plane is , where c represents cosine and s represents sin, Angle is the tilt working angle of the hemispherical wheel seat maintained by the four-bar linkage. Angle is the torsion angle, and the projection of vector OQ on the xyz plane is calculated as follows:

[0049] Further we get:

[0050] According to the synthetic relationship of velocity loss, we can get: (4) From formula (4), we can get: (5) In formula (5) is the moving speed of the robot in the pipeline axis direction, make (6) Combining equations (1), (2), (3), (5) and (6) yields: (7).

[0051] The real-time speed of the drive motor rotor can be obtained by equipping the drive motor with a Hall sensor or encoder. The central control module can obtain the real-time speed of the front and rear drive motors by reading the Hall sensor or encoder. and , and then we can find the corresponding time point v , .

[0052] S13 determines the moving distance of the robot along the pipeline axis at time t And the body rotation angle , for the formula (7) v , Integrate over time to obtain the movement distance of the robot along the pipeline axis at time t And the body rotation angle , make , Then we get: (8) The robot's position at time t is ; and eventually form For the trajectory Middle Position points.

[0053] S4 robot finds track The closest pose point to the pose at time t , determine the moving distance and moving speed in the direction of the pipeline axis, and calculate the time required for the robot to reach the nearest posture point based on the moving distance and moving speed in the direction of the pipeline axis , (9) Then calculate the target angular velocity of the body to reach the nearest pose point , (10) After calculating the target angular velocity required for the front and rear drive motors to reach the nearest position, the robot's moving speed in the pipe axis direction is set to v and target angular velocity Substituting into formula (7) we get (11) Then the robot can move to the nearest position point The angular velocity required by the front drive motor and the rear drive motor can be updated by the central control module to the angular velocity of the front drive motor and the rear drive motor of the robot at time t when the robot moves to the nearest position point. The angular velocity required by the front and rear drive motors enables the robot to be precisely controlled to move at a speed v and target angular velocity Arrival track The closest pose point in ; S3 repeats step S2 until the robot reaches the trajectory The last posture point in the inspection is completed.

[0054] The working principle of the present invention is as follows: the front drive motor and the rear drive motor are used to respectively drive the connecting rod assemblies on the bases at both ends of the shell to rotate, thereby causing the hemispherical wheels on the connecting rod assemblies to abut against the inner wall of the pipe, causing the hemispherical wheels to rotate. Since the wheel shaft of the hemispherical wheels is set outwardly to form a torsion angle, the robot rotates close to the inner wall of the pipe, and at the same time, a forward and backward motion component is decomposed along the axial direction of the shell, and a circular motion component is decomposed in the circumferential direction of the pipe, so that the robot can move along the axial direction of the shell, thereby enabling the robot to simultaneously realize forward or backward movements during the rotation process.

Claims

1. A differential pipeline inspection robot, comprising a housing and covers arranged at both ends of the housing, characterized in that: A driving device is provided in the shell, and a base is provided on the cover. The output end of the driving device passes through the cover and is fixedly connected to the base. A boss is provided on the base, and more than two connecting rod assemblies are arranged in a circumference on the outer side of the boss. The bottom end of the connecting rod assembly is hinged to the boss, and the top end of the connecting rod assembly is hinged to a hemispherical wheel seat. The connecting rod assembly is connected to the base through an elastic member. A wheel axle is fixedly provided on the hemispherical wheel seat. The wheel axle is deviated outwardly and forms a torsion angle with a vertical plane passing through the connecting rod assembly and the axis of the shell. A hemispherical wheel is sleeved on the wheel axle. The connecting rod assembly includes a front connecting rod assembly and a rear connecting rod assembly. The front connecting rod assembly and the rear connecting rod assembly are respectively arranged on both sides of the shell, and the torsion angle on the front connecting rod assembly and the torsion angle on the rear connecting rod assembly are arranged oppositely.

2. A differential pipeline inspection robot and control method according to claim 1, characterized in that: A control compartment is provided in the shell, and a central control module, a battery, a drive device and an inspection instrument compartment are provided in the control compartment. The drive device includes a front drive motor and a rear drive motor, which are relatively arranged in the control compartment. The output ends of the front drive motor and the rear drive motor pass through the covers at both ends of the shell and are fixedly connected to the center of the base.

3. The differential pipeline inspection robot and control method according to claim 1, characterized in that: The boss is protruding outward along the axial direction of the base, and more than two hinge seats are arranged in a circle on the base and located on the outside of the boss. The connecting rod assembly includes connecting rod one and connecting rod two. One end of connecting rod one is hinged to the boss through a pin, one end of connecting rod two is hinged to the hinge seat through a pin, and the other ends of connecting rod one and connecting rod two are hinged to the hemispherical wheel seat through a pin. The hemispherical wheel seat, connecting rod one, connecting rod two and the base are connected to form a four-bar linkage.

4. The differential pipeline inspection robot and control method according to claim 1, characterized in that: One end of the elastic member is fixedly connected to the second connecting rod, and the other end of the elastic member is fixedly connected to the base.

5. The differential pipeline inspection robot and control method according to claim 2, characterized in that: The wheel axle on the four-bar linkage connected to the front drive motor and the wheel axle on the four-bar linkage connected to the rear drive motor are arranged in opposite directions and deviate outwards.

6. A control method for a differential pipeline inspection robot, characterized in that: The following steps are involved: S1 presets the robot's target inspection trajectory as P. For the trajectory Middle Position points, is the displacement of the robot in the direction of the pipeline axis, is the rotation angle of the robot in the pipeline; S2 robot finds track The closest pose point to the pose at time t Then, the time required for the robot to reach the nearest position is calculated by the moving distance and moving speed in the pipeline axis direction. , and then calculate the target angular velocity of the robot body when it reaches the nearest posture point; finally, according to the relationship between the target angular velocity and the required angular velocity of the front drive motor and the rear drive motor, the target moving speed and the torsion angle, calculate the target angular velocity required by the front drive motor and the rear drive motor when the robot body reaches the nearest posture point, and set the angular velocity of the front drive motor and the rear drive motor of the robot at time t to the target angular velocity, so that the robot reaches the nearest posture point at the target angular velocity and the moving speed in step (2); S3 repeats step S2 until the robot reaches the trajectory The last posture point in the inspection is completed.

7. The control method of a differential pipeline inspection robot according to claim 6, characterized in that: S1 includes S11-S13; S11 determines the relationship between the rotational angular velocities of the fuselage, the front drive motor, and the rear drive motor; S12 determines the relationship between the moving speed of the robot along the pipeline axis and the body angle; S13 determines the moving distance of the robot along the pipeline axis at time t And the body rotation angle , thus forming the robot's position point at time t .

8. The control method of a differential pipeline inspection robot according to claim 7, characterized in that: The relationship between the rotational angular velocities of the fuselage, the front drive motor and the rear drive motor in step S11 is as follows: （1）； In formula (1), is the fuselage angular velocity, is the angular velocity of the front drive motor, is the angular velocity of the rear drive motor. When the angular velocity of the front drive motor is opposite to that of the rear drive motor and the difference between them is 0, the robot only moves along the axis of the pipeline without rotation. When the difference between them is not 0, the robot moves forward or backward in a spiral in the pipeline. S12 includes: calculating the moving speed of the robot along the axial direction of the pipeline based on the contact point A between the hemispherical wheel and the inner wall of the pipeline, taking the axial direction of the pipeline as the x-axis, the horizontal direction of the pipeline cross section as the y-axis, and the vertical direction of the pipeline cross section as the z-axis, establishing a spatial coordinate system, and setting the direction of the wheel axis as OQ: （7）； is the fuselage angular velocity, is the angular velocity of the front drive motor, is the angular velocity of the rear drive motor; r is the radius of the pipeline; Angle is the torsion angle; v is the moving speed of the robot in the direction of the pipeline axis.

9. The control method of a differential pipeline inspection robot according to claim 7, characterized in that: S13 also includes the v , Integrate over time to obtain the movement distance of the robot along the pipeline axis at time t And the body rotation angle , make , （8）。 10. The control method of a differential pipeline inspection robot according to claim 6, characterized in that: time for: （9） Target angular velocity for: （10） Set the robot's moving speed in the pipe axis direction v and target angular velocity Substituting into formula (7) we get （11） Then the robot can move to the nearest position point The angular velocity required by the front drive motor and the rear drive motor can be updated by the central control module to the angular velocity of the front drive motor and the rear drive motor of the robot at time t when the robot moves to the nearest position point. The angular velocity required for the front and rear drive motors.

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