A method for cable retraction and extension control of a submersible robot

Abstract

A cable retraction and deployment control method for a submersible oil operation robot belongs to the field of oil tank operation technology. Its features include the following steps: Step a, system initialization; Step b, the controller calculates the iteration time; Step c, the controller corrects the time-varying function l(θ) and the correction value e; Step d, the compensation value c is calculated; Step e, the controller determines whether the force F obtained by the force sensor reaches the set cable safety connection limit force Ft; Steps f to g, the controller determines whether the position radius r is greater than the function k(L) or less than -k(L); Steps h to i, the cable retraction and deployment device (1) performs the cable retraction or deployment operation. This cable retraction and deployment control method for a submersible oil operation robot can prevent the cable from getting tangled with the floating roof tank support or ground obstacles, thereby ensuring smooth robot operation and protecting the cable.

Description

Technical Field

[0001] A method for controlling the cable retraction and deployment of a submersible oil operation robot, belonging to the field of oil storage tank operation technology. Background Technology

[0002] Crude oil storage tanks are complex, enclosed environments containing oil, such as... Figure 6 As shown, when robot 6 is working inside crude oil storage tank 4, since the status of robot 6 cannot be directly observed, it is easy for the robot's cable 5 to become entangled with the floating roof support 2 or the bottom obstacle 17 (such as ground anode block). This will seriously affect the use of the equipment and may even lead to the robot being unable to move or the cable being damaged.

[0003] Traditional methods for preventing cable tangling typically only consider one aspect: hardware or the control of cable reeling devices. Structurally, this usually involves changing the cable material; however, for large, enclosed oil tanks, this cannot prevent cables from tangling with obstacles. In terms of cable reeling device control, it generally only considers the cable's follow-up design and does not take into account the possibility of cables tangling with obstacles in enclosed submersible oil environments.

[0004] Currently, in addition to traditional methods for preventing cable tangling, some improved methods for preventing cable tangling have also emerged:

[0005] (1) Chinese invention patent with application number 201710548014.0 and application date of September 22, 2017, entitled “Wired control robot cable rewinding device and cable rewinding method”, discloses a technical solution. In this technical solution, the number of rotations of the cable rewinding motor encoder is obtained to calculate the length of the cable released, and the length of the robot travels is compared with the distance traveled by the robot, thereby controlling the cable to rewind and release. However, there are errors in the calculation of the cable release length and the distance traveled by the robot in this method. This method does not correct the errors, and does not consider the applicability of this cable rewinding method in a closed oil-sealed environment.

[0006] (2) Chinese invention patent application number 201810963374.1, filed on August 22, 2018, entitled "An Automatic Matching System for Cable Retraction and Deployment Speed," discloses a technical solution. In this solution, the speed of the cable and the vehicle body is obtained through speed sensors and displacement sensors, and the speed of the cable and the vehicle body is controlled to be consistent through a cable retraction and deployment speed comparison device. However, in the actual control process, these measured data and the cable retraction and deployment speed comparison device all have errors, which the patent does not correct. Moreover, although the purpose of this method is to eliminate the risk of cable breakage and to provide cable redundancy, the cable retraction and deployment device in this method moves with the vehicle body, and the application of the cable retraction and deployment system when the cable retraction and deployment device is fixed is not considered. Furthermore, since its cable retraction and deployment device is fixed to the vehicle body, its technical solution is difficult to apply to the control of robot cables in crude oil storage tanks.

[0007] (3) Chinese invention patent application number 202110651483.1, filed on June 10, 2021, entitled "Cable winding and unwinding device, cable winding and unwinding method and mobile robot", discloses a technical solution. In this technical solution, the drive mechanism can rotate forward to drive the winding drum to rotate forward, and the drive mechanism can also be reversed by the pulling action of the cable to release the cable. However, this design only mentions a cable winding and unwinding method, and does not analyze how to prevent the cable from getting tangled with obstacles in a closed oil-sealed environment.

[0008] (4) Chinese invention patent application number 202210686709.6, filed on June 16, 2022, entitled "An Adaptive Cable Retrieval Control Method for Tethered Unmanned Aerial Vehicles," discloses a technical solution. In this technical solution, the catenary principle is used to analyze the force on the tethered cable, and the critical catenary coefficient is determined using Newton's iteration method, thereby calculating the cable profile and length, and determining whether it can pass through obstacles. However, this method only calculates the shorter length of cable that needs to be retrieved or deployed when crossing obstacles, and this technical solution, applied to unmanned aerial vehicles, is also difficult to directly apply to the control of robot cables in crude oil storage tanks. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a cable retraction and deployment control method for submersible oil operation robots that can prevent cables from getting tangled with floating roof tank supports or ground obstacles, thereby ensuring smooth operation of the robot and protecting the cables.

[0010] The technical solution adopted by this invention to solve its technical problem is: a cable retraction and deployment control method for a submersible oil operation robot, comprising a robot placed inside a crude oil storage tank and a cable retraction and deployment device located outside the crude oil storage tank, wherein the robot and the cable retraction and deployment device are connected by a cable, characterized by comprising the following steps:

[0011] Step a: Install an anti-tangle pipe at the manhole of the crude oil storage tank, and pass the cable through the anti-tangle pipe; define the origin of the robot inside the crude oil storage tank as the position where the robot is lowered from the manhole of the crude oil storage tank, and perform system initialization;

[0012] Step b: Define the iteration time. The controller determines whether the iteration time has been reached. If the iteration time has been reached, proceed to step c; otherwise, the controller continues to determine the iteration time.

[0013] Step c: After the iteration time is reached, the controller corrects the time-varying function l(θ) of the cable radius of the winding roller and the correction value e of the cable length error.

[0014] Step d: Based on the time-varying function l(θ) and correction value e from step c, calculate the compensation value c of the cable winding and unwinding device;

[0015] Step e: Install a tension sensor at the connection point between the cable and the robot. The signal output terminal of the tension sensor is connected to the controller. The controller determines whether the force F obtained by the force sensor reaches the set cable safety connection limit force Ft. If it does, proceed to step f; otherwise, return to step b.

[0016] Step f: The controller determines whether the position radius r of the robot between two adjacent iteration times is greater than the function k(L). If it is greater than k(L), step h is executed; otherwise, step g is executed. k(L) is a single-valued function of the robot length.

[0017] Step g: The controller determines whether the position radius r of the robot in two adjacent iteration times is less than the function -k(L). If it is less than -k(L), proceed to step i; otherwise, return to step b.

[0018] Step h: The controller determines that the cable take-up and take-up device performs a take-up operation on the cable to bring the cable to the target length.

[0019] Step i: The controller determines that the cable take-up and release device performs the cable release operation to make the cable reach the target length.

[0020] Preferably, in steps h and i, the target length is X+c, where c is the compensation value of the cable winding device and X is the calculated value of the cable output by the cable winding device.

[0021] Preferably, step c includes the following steps:

[0022] Given the total length of the cable It is a function of l(θ) and e, therefore another .

[0023] Suppose we are at a certain time T = k * 0.5 (k = 0, 1, 2, ..., n), where e is considered a constant. Using gradient descent, we correct l(θ) as follows:

[0024]

[0025] Now, treating the corrected l(θ) as a constant, we can use gradient descent to correct e as follows:

[0026] .

[0027] Preferably, in step d, the compensation value c is:

[0028] Where X is the calculated value of the cable output by the cable winding and unwinding device calculated by the positioning device, and X' is the total length of cable unwound by the cable winding and unwinding device calculated by l(θ):

[0029] θ is the rotation angle of the winding roller in the cable take-up and unwinding device, r 卷 The radius of the winding roller.

[0030] Preferably, the calculated value X of the cable output by the cable take-up and take-down device is:

[0031]

[0032] Where h1 is the distance between the bottom of the anti-winding pipe and the top surface of the crude oil storage tank, h3 is the vertical distance between the robot's cable connection and the bottom of the anti-winding pipe, r is the position radius, l is the length between the output end of the cable winding device and the manhole, and e is the correction value for the cable length error.

[0033] Preferably, in step c, the method for determining the time-varying function l(θ) is as follows:

[0034] Step c-1: Measure the radius r of the winding roller in the cable take-up and unwinding device. 卷 ;

[0035] Step c-2: Divide the cable delivery section of the cable take-up and delivery device into segments and record the cable length X' corresponding to each segment point;

[0036] Step c-3: According to the order of the segmentation points, make the cable delivery device extend the cable to the length corresponding to the segmentation point, and record the rotation angle θ measured by the encoder at that cable length.

[0037] Step c-4: Repeat step c-3 multiple times and take the average of the recorded θ values;

[0038] Step c-5, using the least squares fitting method to... By performing a polynomial fit with θ, we obtain l(θ).

[0039] Preferably, the anti-winding pipe includes an upper pipe body and a lower pipe body fixed by a connecting flange. A sealing plate is provided at the top of the upper pipe body, and a positioning ring for engaging with a manhole is provided around the lower surface of the sealing plate. An arc-shaped expansion opening is formed at the bottom of the lower pipe body.

[0040] Preferably, the upper and lower pipes are both separate structures, and the connecting seams of the fixed upper and lower pipes are staggered.

[0041] Preferably, the cable take-up and untake-down device includes a drive mechanism and a winding roller. The output shaft of the drive mechanism is connected to the input shaft of the winding roller via a conveyor belt. An encoder is also installed on the rotating shaft of the winding roller, and the signal output terminal of the encoder is connected to a controller.

[0042] Compared with the prior art, the beneficial effects of this invention are:

[0043] The cable retraction and deployment control method of this submersible robot can prevent the cable from getting tangled with the floating roof support or ground obstacles, thereby ensuring smooth operation of the robot and protecting the cable.

[0044] In this submersible robot cable retraction and deployment control method, a customized rigid tube structure design and a cable retraction and deployment control scheme are proposed to address the two potential cable entanglement scenarios. The application of the customized rigid tube structure effectively solves the problem of cable entanglement with the floating roof support. The cable retraction and deployment control scheme analyzes the relationship between the cable retraction and deployment device and the positional information changes during the submersible robot's movement to control the cable retraction and deployment, ensuring that the cable remains relatively taut and does not entangle with ground obstacles. Attached Figure Description

[0045] Figure 1 This is a flowchart illustrating the cable retraction and deployment control method for submersible oil operation robots.

[0046] Figure 2 This is a schematic diagram of the cable retraction and deployment control method for submersible oil operation robots, showing the layout inside the tank.

[0047] Figure 3 Isometric drawing of anti-tangling pipe for cable retraction and deployment control method of submersible oil operation robot.

[0048] Figure 4A front view of the anti-tangling tube for the cable retraction and deployment control method of a submersible oil operation robot.

[0049] Figure 5 This is a schematic diagram of a cable retraction and deployment device for a submersible oil operation robot cable retraction and deployment control method.

[0050] Figure 6 This is a schematic diagram of the layout inside an existing crude oil storage tank.

[0051] The components include: 1. Cable winding and unwinding device; 2. Floating roof support; 3. Anti-winding pipe; 4. Crude oil storage tank; 5. Cable; 6. Robot; 7. Sealing plate; 8. Upper pipe body; 9. Connecting flange; 10. Lower pipe body; 11. Horn mouth; 12. Handle; 13. Drive mechanism; 14. Conveyor belt; 15. Winding roller; 16. Encoder; 17. Bottom surface obstacle. Detailed Implementation

[0052] Figures 1-5 This is the preferred embodiment of the present invention, which is described below in conjunction with the accompanying drawings. Figures 1-6 The present invention will be further described below.

[0053] like Figure 1 As shown, a method for controlling the cable retraction and extension of a submersible robot (hereinafter referred to as the control method) includes the following steps:

[0054] Step 1001, Begin;

[0055] Combination Figure 2 First, connect robot 6 to cable 5 at the output end of cable take-up device 1. Then, insert robot 6 into crude oil storage tank 4 through the manhole at the top of crude oil storage tank 4. Next, after fitting anti-winding tube 3 onto the outside of cable 5, insert and secure anti-winding tube 3 through the manhole at the top of crude oil storage tank 4. Inside crude oil storage tank 4, the bottom of anti-winding tube 3 is lower than or flush with the bottom of floating roof support 2.

[0056] like Figures 3-4 As shown, the anti-winding tube 3 includes an upper tube body 8 and a lower tube body 10, which are fixed at their joint by a connecting flange 9. A sealing plate 7 is provided at the top of the upper tube body 8, a handle 12 is provided in the middle of the upper surface of the sealing plate 7, and a positioning ring for engaging with a manhole is provided around the lower surface of the sealing plate 7. The lower tube body 10 expands outward at its bottom to form a flared opening 11.

[0057] The upper pipe body 8 (including the sealing plate 7) and the lower pipe body 10 are both separate structures. The upper pipe body 8 and the lower pipe body 10 are divided into two parts along their axial direction. After the upper pipe body 8 and the lower pipe body 10 are connected as one unit by the connecting flange 9, the connecting seams of the upper pipe body 8 and the lower pipe body 10 are staggered.

[0058] like Figure 5 As shown, the cable winding device 1 includes a drive mechanism 3 and a winding roller 15. The drive mechanism 13 and the winding roller 15 are respectively supported by their respective brackets. The drive mechanism 13 includes a drive motor and a reducer. The output shaft of the reducer in the drive mechanism 13 is connected to the input shaft of the winding roller 15 via a conveyor belt 14. The cable is wound on the winding roller 15. An encoder 16 is also installed on the rotating shaft of the winding roller 15 for detecting the rotation angle of the winding roller 15.

[0059] A controller is also provided, with the signal output of encoder 16 connected to it. The controller acquires the rotation angle of the winding roller 15 collected by encoder 16 and the position information of robot 6 acquired by positioning device. After calculation, it sends a command to frequency converter to drive drive mechanism 13, which in turn drives winding roller 15 to rotate via conveyor belt 14, thereby achieving precise control of cable 5 winding and unwinding. A tension sensor is also installed at the connection point of cable 5 at the tail end of robot 6, and the output of the tension sensor is also connected to the controller.

[0060] After robot 6 is placed into crude oil storage tank 4, the vertical projection position of anti-winding pipe 3 is used as the origin of robot 6, and the positioning device and tension sensor are initialized first. The positioning device is installed on robot 6 and is implemented using technology known in the art, which will not be described in detail here.

[0061] Combination Figure 2 Let h1 be the distance between the bottom of the anti-winding pipe 3 and the top surface of the crude oil storage tank 4; h2 be the vertical distance between the tail cable connection of the robot 6 and the bottom surface of the crude oil storage tank 4; h3 be the vertical distance between the tail cable connection of the robot 6 and the bottom of the anti-winding pipe 3; r be the horizontal distance between the tail cable connection of the robot 6 and the origin (hereinafter referred to as the position radius); l be the length between the output end of the cable roller 15 and the manhole; D be the diameter of the crude oil storage tank 4; and H be the height of the crude oil storage tank 4. Therefore, the cable length X between the output end of the cable roller 15 and the tail cable connection of the robot 6 is:

[0062] (1)

[0063] Where e is the correction value for the error in calculating the cable length based on the position radius r.

[0064] Step 1002: The controller determines whether the iteration time has been reached;

[0065] In this control method, the iteration time is defined as 0.5s. The controller determines whether the preset iteration time has been reached. If the iteration time has been reached, step 1003 is executed; otherwise, the controller continues to determine the iteration time.

[0066] Step 1003: Correct the time-varying function of the cable radius of the winding roller and the correction value of the cable length error;

[0067] The system acquires the robot's position radius r, the winding roller rotation angle θ, and the force F from the force sensor in real time, calculates the cable winding and unwinding length X, and updates l(θ) and e. l(θ) is a single-valued function of θ introduced by the time-varying radius of the cable stock on the roller, used to calculate the unwinding length of the cable winding and unwinding device. It is introduced experimentally, and its specific steps are as follows:

[0068] Step 1003-1: Measure the radius r of the winding roller 15 in the cable winding device 1. 卷 ;

[0069] Step 1003-2: Divide the cable laying section of the cable laying device 1 into segments and record the cable length X' corresponding to each segment point;

[0070] Step 1003-3: According to the order of the segmentation points, make the cable delivery device 1 deliver the cable to the length of the cable corresponding to the segmentation point, and record the rotation angle θ measured by the encoder at that cable length.

[0071] Step 1003-4: Repeat step 1003-3 multiple times and take the average of the recorded θ values;

[0072] Step 1003-5, use the least squares fitting method to... By performing a polynomial fit with θ, we obtain l(θ).

[0073] The steps to update l(θ) and e are as follows:

[0074] Given the total length of the cable It is a function of l(θ) and e, therefore another .

[0075] Assuming we are at a certain moment T = k * 0.5 (k = 0, 1, 2, ..., n), where e is considered a constant, meaning the cable length correction value calculated using the position radius r is accurate, then the correction of l(θ) using the gradient descent method is as follows:

[0076] (2)

[0077] In the formula: α is the learning rate, which takes a value of 0.08~0.2, preferably 0.1.

[0078] At this point, if we consider the corrected l(θ) in equation (2) as a constant, meaning the roller's calculation of the cable length is accurate, then the gradient descent method can be used to correct e as follows:

[0079] (3)

[0080] In the formula: α is the learning rate, which takes a value of 0.08~0.2, preferably 0.1.

[0081] The above correction process is performed in each iteration T=k*0.5 (k=0, 1, 2, ..., n).

[0082] Step 1004: Calculate the compensation value of the cable reel-in / out device;

[0083] The controller obtains the position radius r and uses the encoder to obtain the rotation angle θ of the winding roller 15 to calculate the cable length. There are two error factors in this process: (1) the error e caused by the positioning device; (2) the error l(θ) introduced by the time-varying radius of the cable stock on the roller. Therefore, in step 1003 of the above process, after correcting l(θ) and e, a compensation value c needs to be added to the total cable length. The steps to determine the compensation value c are as follows:

[0084] After updating l(θ) and e, the corrected value l(θ) is used to calculate the total cable length as follows:

[0085] (4)

[0086] Where: X' is the total length of cable laid out by the cable reeling device calculated by l(θ), r 卷 The radius of the winding roller is 15.

[0087] Therefore, to calculate the compensation value c, we can substitute the collaboratively updated corrected l(θ) and e into equations (1) and (4) respectively. The absolute value of the difference between X' and X' is:

[0088] (5)

[0089] Step 1005: The controller determines whether the force on the tension sensor has reached its limit value;

[0090] The controller determines whether the force F obtained by the force sensor reaches the set cable safety connection limit force Ft. If it does, it executes step 1006; otherwise, it returns to step 1002.

[0091] Step 1006: The controller determines whether the robot position is greater than the single-valued function k(L) with respect to the robot length;

[0092] The controller determines whether the current position radius r of robot 6 is greater than the position radius r of the previous moment. If it is greater than k(L), step 1008 is executed; otherwise, step 1007 is executed.

[0093] Step 1007: The controller determines whether the robot position is less than the inverse of the single-valued function k(L) of the robot length;

[0094] The controller determines whether the current position radius r of robot 6 is less than the position radius r of the previous moment. If it is less than the function -k(L), proceed to step 1009; otherwise, return to step 1002.

[0095] In the above working steps, k(L) is a single-valued function of the robot length. Its purpose is to increase the system's elasticity and prevent the cable winding device from causing the winding roller 15 to continuously rotate forward and backward due to the frequent changes of Δr near the origin. This protects the cable winding device 1. k(L) = 0.2L, where L is the length of the robot 6.

[0096] Step 1008: Determine the take-up length of the cable take-up device 1;

[0097] The controller controls the drive mechanism 13 in the cable winding and unwinding device 1 to operate, causing the winding roller 15 in the cable winding and unwinding device 1 to perform a winding operation so that the cable length reaches X+c, and then executes step 1010.

[0098] Step 1009: Determine the cable length of the cable reeling / unwinding device 1;

[0099] The controller controls the drive mechanism 13 in the cable winding and unwinding device 1 to operate, causing the winding roller 15 in the cable winding and unwinding device 1 to perform a cable unwinding operation so that the cable length reaches X+c, and then executes step 1010.

[0100] Step 1010: Determine whether robot 6 is at the origin.

[0101] The controller determines whether the current position of robot 6 is at the origin. If it is at the origin, it executes step 1011; otherwise, it returns to step 1002.

[0102] Step 1011, End.

[0103] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for controlling the cable retraction and deployment of a submersible oil operation robot, comprising a robot (6) placed inside a crude oil storage tank (4) and a cable retraction and deployment device (1) located outside the crude oil storage tank (4), wherein the robot (6) and the cable retraction and deployment device (1) are connected by a cable (5), characterized in that: Includes the following steps: Step a, install an anti-tangle pipe (3) at the manhole of the crude oil storage tank (4), and pass the cable (5) through the anti-tangle pipe (3); define the origin of the robot (6) in the crude oil storage tank (4) as the position where the robot is lowered from the manhole of the crude oil storage tank (4), and perform system initialization; Step b: Define the iteration time. The controller determines whether the iteration time has been reached. If the iteration time has been reached, proceed to step c; otherwise, the controller continues to determine the iteration time. Step c, after the iteration time is reached, the controller corrects the time-varying function l(θ) of the cable radius of the winding roller and the correction value e of the cable length error, where θ is the rotation angle of the winding roller (15); Step d: Based on the time-varying function l(θ) and correction value e in step c, calculate the compensation value c of the cable winding and unwinding device (1); Step e: Set a tension sensor at the connection between cable (5) and robot (6). The signal output terminal of the tension sensor is connected to the controller. The controller determines whether the force F obtained by the force sensor reaches the set cable safety connection limit force Ft. If it does, execute step f. If it does not, return to step b. Step f: The controller determines whether the position radius r of the robot (6) between two adjacent iteration times is greater than the function k(L). If it is greater than k(L), step h is executed; otherwise, step g is executed. k(L) is a single-valued function of the length of the robot (6), and L is the length of the robot (6). Step g: The controller determines whether the position radius r of the robot (6) between two adjacent iteration times is less than the function -k(L). If it is less than -k(L), step i is executed; otherwise, step b is returned. Step h, the controller determines that the cable take-up and take-up device (1) performs a take-up operation on the cable (5) so that the cable (5) reaches the target length; Step i, the controller determines that the cable take-up and release device (1) performs the cable (5) release operation so that the cable (5) reaches the target length.

2. The cable retraction and extension control method for submersible oil operation robots according to claim 1, characterized in that: In steps h and i, the target length is X+c, where c is the compensation value of the cable winding device (1) and X is the calculated value of the cable (5) output by the cable winding device (1).

3. The cable retraction and extension control method for submersible oil operation robots according to claim 1, characterized in that: Step c includes the following steps: The calculated value of the cable (5) output by the cable take-up and take-down device (1) is known. It is a function of l(θ) and e, therefore another X' is the total length of cable laid out by the cable winding and unwinding device calculated by l(θ); Suppose we are at a certain time T = k * 0.5 (k = 0, 1, 2, ..., n), where e is considered a constant. Using gradient descent, we correct l(θ) as follows: Now, treating the corrected l(θ) as a constant, we can use gradient descent to correct e as follows: α is the learning rate.

4. The cable retraction and extension control method for submersible oil operation robots according to claim 3, characterized in that: In step d, the compensation value c is: Where X is the calculated value of the cable (5) output by the cable winding and unwinding device (1) calculated by the positioning device, and X' is the total length of cable unwound by the cable winding and unwinding device calculated by l(θ): θ is the angle of rotation of the winding drum (15) in the cable take-up device (1), r 卷 is the radius of the winding drum (15).

5. The cable retraction and extension control method for a submersible robot according to claim 3 or 4, characterized in that: The calculated value X of the cable (5) output by the cable take-up and take-down device (1) is: Where h1 is the distance between the bottom of the anti-winding pipe (3) and the top surface of the crude oil storage tank (4), h3 is the vertical distance between the cable connection of the robot (6) and the bottom of the anti-winding pipe (3), r is the position radius, l is the length between the output end of the cable winding device (1) and the manhole, and e is the correction value for the cable length error.

6. The cable retraction and deployment control method for a submersible robot according to claim 1, characterized in that: In step c, the method for determining the time-varying function l(θ) is as follows: Step c-1, measure the radius r of the winding roller (15) in the cable winding device (1). 卷 ; Step c-2, the cable laying section of the cable laying device (1) is segmented, and the total cable laying length X' of the cable laying device calculated by l(θ) is recorded for each segment point; Step c-3: According to the order of the segmentation points, make the cable winding and unwinding device (1) unwind the cable to the length of the cable corresponding to the segmentation point, and record the angle θ measured by the encoder at the length of the cable. Step c-4: Repeat step c-3 multiple times and take the average of the recorded θ values; Step c-5, using the least squares fitting method to... By performing a polynomial fit with θ, we obtain l(θ).

7. The cable retraction and extension control method for a submersible robot according to claim 1, characterized in that: The anti-winding tube (3) includes an upper tube body (8) and a lower tube body (10) fixed by a connecting flange (9). A sealing plate (7) is provided on the top of the upper tube body (8), and a positioning ring for engaging with a manhole is provided around the lower surface of the sealing plate (7). An arc-shaped expansion opening is formed at the bottom of the lower tube body (10).

8. The cable retraction and extension control method for a submersible robot according to claim 7, characterized in that: The upper tube (8) and the lower tube (10) are both separate structures, and the connecting seams of the fixed upper tube (8) and the lower tube (10) are staggered.

9. The cable retraction and extension control method for a submersible robot according to claim 1, characterized in that: The cable winding and unwinding device (1) includes a drive mechanism (13) and a winding roller (15). The output shaft of the drive mechanism (13) is connected to the input shaft of the winding roller (15) via a conveyor belt (14). An encoder (16) is also installed on the rotating shaft of the winding roller (15). The signal output terminal of the encoder (16) is connected to the controller.

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