A serpentine robotic arm for passing through internal through-holes of a cabin and a passing-through method

Abstract

The present invention relates to a serpentine robotic arm for passing through internal through-holes of a cabin and a passing-through method, including: obtaining the starting point of the entrance hole and the target point of the exit hole of a path planning task; making a plane passing through the starting point and the target point, and judging whether there are obstacles in the plane; when there are no obstacles, perform the following steps: respectively calculating the maximum turning angles from the starting point and the target point to obtain the intersection distance of the serpentine robotic arm from entering the cabin to leaving the cabin under the maximum turning angles, where the intersection distance is the distance between the intersection point of the axis and the inner surface of the entrance hole of the entrance hole when the rod deflects to the limit position in the entrance hole and the intersection point of the axis and the inner surface of the exit hole of the exit hole when the rod deflects to the limit position; according to the projection relationship of the vectors of the rods of the serpentine robotic arm on the intersection distance, taking the ratio ki of the actual turning angle and the stroke of the rod of the serpentine robotic arm as the motion coefficient; and planning the path of the serpentine robotic arm by adjusting the motion coefficient of the rod.

Description

Technical Field

[0001] The present invention relates to the fields of internal installation, testing, and maintenance of complex cabins, and particularly to a serpentine robotic arm for passing through holes inside a cabin and a passing method. Background Art

[0002] As a highly flexible bionic mechanism, a serpentine robotic arm can enter environments that are difficult or impossible for conventional robotic arms to enter, bypass obstacles, reach the target position, and deliver payloads to narrow spaces. It is very suitable for working in confined and dangerous areas. For example, it can be used for disaster rescue in natural disasters or earthquake ruins, assembly and repair work in narrow spaces, etc. Therefore, the structural size of the serpentine robotic arm must be significantly reduced.

[0003] The configuration of a serpentine robotic arm is an open-loop mechanism in which each rod is connected in sequence. The rods are connected by spherical pairs, Hooke's joints, or revolute joints. By the movement of each rod, the positions of the rods of the serpentine robotic arm are changed to complete various movements such as winding forward. A spherical pair has 3 degrees of freedom, and the degree of freedom of rotation around the axis of the rod belongs to a local degree of freedom, which does not affect the degree of freedom of the robotic arm and will cause uncertainty in the joint driving amount. Therefore, spherical pairs are usually not used as the kinematic pairs of serpentine robotic arms. A revolute joint has only one degree of freedom, which limits the movement range of each rod and affects the flexibility of the serpentine robotic arm. Revolute joints are usually not used as the kinematic pairs of serpentine robotic arms either. Therefore, Hooke's joints are the most common kinematic pairs of serpentine robotic arms.

[0004] The main function of the commonly used Hooke's joints in engineering is to transmit power, and it does not concern whether the rotation center of the cross shaft coincides with the geometric center of the Hooke's joint. However, the rotation center of each joint cross shaft in a serpentine robotic arm is the starting point for calculating the positions of subsequent joints, and the rotation center of the cross shaft needs to be accurately grasped. To make the rotation center of the cross shaft coincide with the geometric center of the Hooke's joint as much as possible, the dimensions of the axial positioning parts need to be accurately adjusted. Due to factors such as machining errors, assembly errors, and stress deformation of related parts, the rotation center of the cross shaft after assembly may still deviate from the geometric center position of the Hooke's joint.

[0005] Common Hooke's joints often act as passive joints, without angle sensors installed and without interfaces for adding angle sensors, resulting in the inability to measure the rotation angle of the Hooke's joint and thus the inability to achieve closed-loop control. In addition, since the rods of the serpentine robotic arm are not modularized, it also affects the rapid response of the serpentine robotic arm to different working requirements.

[0006] In engineering applications in multiple fields, it is required that a serpentine robotic arm pass through many holes inside a complex cabin in sequence and enter the cabin to complete various operations. Currently, there is still a lack of a fast and simple method for planning the optimal path of a serpentine robotic arm that can meet various constraint conditions. Summary of the Invention

[0007] The present invention mainly aims at the above problems and proposes a serpentine robotic arm for passing through internal holes in a cabin and a passing-through method. The purpose is to establish modular rod units, improve the rapid response ability of the serpentine robotic arm to different requirements, and quickly find an optimized path that meets various requirements according to the structural and motion characteristics of the serpentine robotic arm.

[0008] To achieve the above object, the present invention provides a method for passing through internal holes in a cabin, including the following steps:

[0009] S100: Obtain the starting point of the entrance hole and the target point of the exit hole for the path planning task;

[0010] S200: Make a plane passing through the starting point and the target point, and determine whether there are obstacles in the plane;

[0011] S300: When there are no obstacles, perform the following obtaining steps:

[0012] S301: Calculate the maximum turning angles respectively from the starting point and the target point to obtain the intersection distance of the serpentine robotic arm from entering the cabin to leaving the cabin under the maximum turning angle. Wherein, the intersection distance is the distance between the intersection point of the axis and the inner surface of the entrance hole of the cabin when the rod deflects to the limit position in the entrance hole, and the intersection point of the axis and the inner surface of the exit hole of the cabin when the rod deflects to the limit position;

[0013] S302: According to the projection relationship of the vectors of each rod of the serpentine robotic arm on the intersection distance, take the ratio k i of the actual turning angle and stroke of the rod of the serpentine robotic arm as the motion coefficient;

[0014] S303: Plan the path of the serpentine robotic arm by adjusting the rod motion coefficient.

[0015] Furthermore, it also includes step S400: When there are obstacles, perform the following obtaining steps:

[0016] S401: Re-find a plane without obstacles passing through the starting point and the target point;

[0017] S402: If there is a plane that meets the obstacle-free plane, continue with the steps of S301 - S303;

[0018] S403: If there is no plane that meets the obstacle-free plane, intersect the plane passing through the starting point and the target point with the obstacle, and set path intermediate points on each path by setting an obstacle avoidance threshold to segment and plan the path of the serpentine robotic arm.

[0019] Further, in the step S200, the step of making a plane passing through the starting point and the target point includes:

[0020] S201: According to the known starting point O s coordinates (x s , y s , z s ) and the target point O e coordinates (x e , y e , z e ), obtain the projection coordinate point O s of the starting point O sXY on the plane XOY with coordinates (x s , y s , 0) and the projection coordinate point O e of the target point O eXY on the plane XOY with coordinates (x e , y e , 0);

[0021] S202: According to the coordinates (x sXY , y s , 0) of the projection coordinate point O s and the coordinates (x eXY , y e , 0) of the projection coordinate point O e , obtain the vector O s from the starting point O e to the target point O s O e =(x e -x s y e -y s z e -z s ) T and the vector O sXY from the projection coordinate point O eXY to the projection coordinate point O sXY O eXY =(x e -x s y e -y s 0) T ;

[0022] S203: Cross-multiply the vector O s O e with the vector O sXY O eXY to obtain the vector O s O e and the vector OsXY O eXY The normal vector p of the plane formed se = (-y e +y s x e -x s 0) T ;

[0023] S204: Cross-multiply the vector O s O e with the normal vector p se to obtain the vector n se ,

[0024] where

[0025] S205: Normalize the vector n se to obtain the unit vector n of the plane, where

[0026] Furthermore, the formula for the maximum rotation angle θ imax of the rod of the i-th serpentine robotic arm in the inlet hole is:

[0027]

[0028] In the formula, D i is the aperture of the inlet hole, d i is the diameter of the rod of the i-th serpentine robotic arm, and h s is the depth of the inlet hole.

[0029] Furthermore, the formula for the maximum rotation angle θ emax of the rod of the n-th serpentine robotic arm in the outlet hole is:

[0030]

[0031] In the formula, D n is the aperture of the outlet hole, d n is the diameter of the rod of the n-th serpentine robotic arm, and h e is the depth of the outlet hole.

[0032] Furthermore, in step S302, the projection relationship of the vectors of each rod of the serpentine robotic arm on the intersection distance is: the sum of the lengths of the projections of the vectors of each rod on O' si O' en is equal to ||O' si O' en ||, where:

[0033]

[0034] wherein, ||O′ si O′ en || is the intersection distance, and θ s is the total angle that the serpentine robotic arm needs to turn, L′ i is the length of the i-th rod, and L′ n is the length of the n-th rod.

[0035] To achieve the above object, the present invention provides a serpentine robotic arm for passing through a through-hole inside a cabin, comprising:

[0036] A serpentine arm body, which includes a plurality of rod assemblies coupledly arranged, and Hooke hinge assemblies orthogonally arranged therebetween. Among them, the Hooke hinge assembly includes a cross shaft, a driving fork and a driven fork respectively connected to both ends of the cross shaft. Installation holes are provided at both ends of each rotating shaft of the cross shaft;

[0037] A driving assembly, which is connected to the serpentine arm body and is used to drive the rod assemblies of the serpentine arm body to rotate around the cross shaft; and,

[0038] A measuring assembly, which includes a laser tracker target seat, a laser tracker target ball, a laser tracker and an angle sensor. Among them, a laser tracker target seat is installed in each of the installation holes at both ends of each rotating shaft of the cross shaft, and the laser tracker target ball is arranged inside the laser tracker target seat; the laser tracker is installed at the central position between the two laser tracker target balls at both ends of the same rotating shaft of the cross shaft; angle sensors are respectively installed on the driving fork and the driven fork for measuring the rotation angles of the two rotating shafts of the cross shaft relative to the driving fork and the driven fork.

[0039] Further, the rod assembly includes a rod front section assembly, and the rod front section assembly includes a rod front section base, a rope perforation bushing, and a rod front section outer base. A plurality of outer semi-circular arc grooves for installing the rope perforation bushing are distributed on the edge of the rod front section base, and a plurality of inner semi-circular arc grooves for installing the rope perforation bushing are correspondingly distributed on the inner edge of the rod front section outer base. An installation area for installing the rope perforation bushing is formed between the outer semi-circular arc groove and the inner semi-circular arc groove; the rod front section outer base is composed of two semi-ring parts, and the two semi-ring parts are detachably arranged on the rod front section base.

[0040] Further, the rope locking bushing includes a left half bushing and a right half bushing. The outer parts of the left half bushing and the right half bushing are frustum-shaped, and an engaging surface is provided inside, and an engaging groove for allowing a rope to pass through is provided on the engaging surface.

[0041] Further, the Hooke's joint assembly further includes a cross shaft bushing. The cross shaft bushing is mounted on the shaft diameters at both ends of each rotating shaft of the cross shaft. The inner diameter of the cross shaft bushing is sleeved outside each rotating shaft of the cross shaft. Each rotating shaft of the cross shaft is rotatably arranged relative to the cross shaft bushing. The driving fork and the driven fork are provided with holes for mounting the outer diameter of the cross shaft bushing, and the holes for mounting the outer diameter of the cross shaft bushing are open structures for placing each rotating shaft of the cross shaft.

[0042] The above technical solution of the present invention has the following advantages: By installing an angle sensor in the Hooke's joint assembly, the rotation angle can be accurately measured, closed-loop feedback can be achieved, and the motion control accuracy can be improved; By installing a laser tracker target seat, a laser tracker target ball, and a laser tracker in the Hooke's joint assembly, the rotation center of the cross shaft can be determined, the structural parameter error of the snake-like robotic arm can be reduced, and the motion accuracy can be improved. In addition, a simple and fast via-hole traversal path planning method is proposed, which can quickly obtain an optimized path and improve work efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 FIG. is a schematic assembly structure diagram of a snake-like robotic arm provided by an embodiment of the present application.

[0044] Figure 2 FIG. is a partial structure diagram of a snake-like robotic arm provided by an embodiment of the present application.

[0045] Figure 3 FIG. is a schematic structure diagram of a rod assembly provided by an embodiment of the present application.

[0046] Figure 4 FIG. is a schematic structure diagram of a front rod assembly provided by an embodiment of the present application.

[0047] Figure 5 FIG. is a schematic structure diagram of a middle rod provided by an embodiment of the present application.

[0048] Figure 6 FIG. is a schematic structure diagram of a rear rod assembly provided by an embodiment of the present application.

[0049] Figure 7 FIG. is a schematic structure diagram of a rope locking bushing assembly provided by an embodiment of the present application.

[0050] Figure 8 FIG. is a schematic structure diagram of a cross shaft assembly provided by an embodiment of the present application.

[0051] Figure 9 FIG. is a schematic structure diagram of a Hooke's joint assembly provided by an embodiment of the present application.

[0052] Figure 10This is a schematic diagram of the installation position of a measurement component for measuring the position of the Hooke joint axis in an embodiment of the present application.

[0053] Figure 11 This is a schematic diagram of a measurement method for the cross-axis axis in an embodiment of the present application.

[0054] Figure 12 This is a schematic diagram of a measuring device structure for the Hooke joint rotation angle in an embodiment of the present application.

[0055] Figure 13 This is a sectional view of the working environment of passing through the through-hole in the cabin in an embodiment of the present application.

[0056] Figure 14 This is a schematic diagram of the path of a snake-shaped robotic arm starting from the cabin entrance and passing through the cabin exit in an embodiment of the present application.

[0057] Figure 15 This is a schematic diagram of the movement modes of each rod in an embodiment of the present application.

[0058] Figure 16 This is a schematic diagram of the relative postures between each rod in an embodiment of the present application.

[0059] Figure 17 This is a schematic diagram of the maximum rotation angle of the i-th rod in the hole in an embodiment of the present application.

[0060] Figure 18 This is a schematic diagram of the shortest distance for entering and leaving the cabin in an embodiment of the present application.

[0061] Figure 19 This is a schematic diagram of the rotation angle distribution of each rod in an embodiment of the present application.

[0062] Figure 20 This is a schematic diagram of the segmented obstacle avoidance path planning in an embodiment of the present application.

[0063] In the figure: 1. Driving component; 2. Rod component; 3. Cross shaft component; 4. Rope component; 5. Measuring component; 21. Front section of rod component; 22. Middle section of rod; 23. Rear section of rod component; 24. Front section connecting screw; 25. Front section positioning pin; 26. Rear section connecting screw; 27. Rear section positioning pin; 211. Front section base of rod; 212. Rope perforation bushing; 213. Outer base of front section of rod; 214. Driven fork; 215. Driven fork connecting screw; 216. Driven fork positioning pin; 217. Locking screw for outer base of front section of rod; 231. Rear section base of rod; 232. Rope perforation bushing; 233. Rope locking bushing; 234. Outer base of rear section of rod; 235. Driving fork; 236. Driving fork connecting screw; 237. Driving fork positioning pin; 238. Locking screw for outer base of rear section of rod; 2331. Left half bushing; 2332. Right half bushing; 31. Cross shaft; 32. Cross shaft bushing; 51. Laser tracker target seat; 52. Laser tracker target ball. Detailed implementation mode

[0064] The following combines the drawings and embodiments to further describe in detail the specific implementation mode of the present invention. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0065] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, so it cannot be understood as a limitation to the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0066] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installation", "connection", and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0067] Please refer to Figure 1 As shown, it is a schematic structural diagram of a serpentine robotic arm assembly for passing through an internal through-hole of a cabin body provided by a preferred embodiment of the present application.

[0068] The cabin internal via traversal method disclosed herein is applied to a serpentine robotic arm, which can establish a communication connection with at least one server via a network. The network can be a wired network or a wireless network, such as radio, Wireless Fidelity (WIFI), cellular, satellite, or broadcast. The cellular network can be a 4G network or a 5G network.

[0069] See also Figure 1 Figure 2 , Figure 1 、 Figure 2 This is a hardware structure diagram of a serpentine robotic arm that passes through a hole inside a cabin according to one embodiment of the present invention. Figure 1 In the embodiment shown, the serpentine robot arm includes a serpentine arm body, a drive assembly 1, and a measurement assembly 5, wherein the serpentine arm body includes a rod assembly 2, a cross-axis assembly 3, a rope assembly 4, etc. It can be understood by those skilled in the art that Figure 1 、 Figure 2 The specific structure of the serpentine robotic arm shown in the figure does not constitute a limitation of the serpentine robotic arm. The serpentine robotic arm may include more or fewer components than shown in the figure. Some components are not necessary components of the serpentine robotic arm and can be omitted or combined as needed without changing the essence of the invention.

[0070] The technical solution of the present disclosure will be described below by taking a serpentine robotic arm that passes through a hole inside a cabin disclosed in this application as an example.

[0071] According to an example of the present disclosure, Figures 1 - 12 As shown in the three-dimensional diagram of the serpentine robot arm passing through the hole inside the cabin, the serpentine robot arm is a series mechanism composed of multiple rod components 2 connected together. Hooke's hinges are used as kinematic pairs between each rod component 2, and a combination of multiple ropes is used to drive each joint. The structural form of the serpentine robot arm (the ropes between the rods are omitted to show the joint structure) is as follows: Figure 1 shown.

[0072] Rod assemblies 2 are mounted on drive assembly 1, each connected in sequence via a cross-axis assembly 3. Drive assembly 1 drives a specific combination of ropes in rope assembly 4. By varying the rope lengths, the rod assemblies 2 rotate around adjacent cross-axis assemblies 3, creating a serpentine motion. Measurement assembly 5, mounted on cross-axis assembly 3, measures the position and rotation angle of each axis of cross-axis assembly 3.

[0073] like Figure 2As shown, the cross shaft assembly 3 is installed between two adjacent rod assemblies 2, connecting the two adjacent rod assemblies 2 to form a Hooke joint, enabling each rod assembly 2 to rotate relative to the adjacent rod assembly 2 about two orthogonal axes. Thus, each rod assembly 2 has two rotational degrees of freedom. Each rod assembly 2 requires at least three ropes in the rope assembly 4 for traction. The ropes used for traction are usually evenly distributed on the circumference to balance the forces on each rope. The driving rope in the rope assembly 3 passes through the rod assembly 2 that does not need to be driven and is connected to the driven rod assembly 2. The measuring assembly 5 is installed on the cross shaft assembly 3 to measure the positions and rotation angles of the rotating shafts of the cross shaft assembly 3.

[0074] As Figure 3 As shown, the rod assembly 2 consists of a front rod assembly 21, a middle rod 22, a rear rod assembly 23, front section connecting screws 24, front section positioning pins 25, rear section connecting screws 26, and rear section positioning pins 27. The lower end face of the front rod assembly 21 is connected to the upper end face of the middle rod 22. The cylindrical boss on the lower end face of the front rod assembly 21 fits precisely with the round hole on the upper end face of the middle rod 22 to determine the radial relative position relationship between the front rod assembly 21 and the middle rod 22. The front rod assembly 21 is connected to the middle rod 22 by evenly distributed front section connecting screws 24, and then, using the front section positioning pins 25, a "one plane and two holes" positioning method is formed to prevent the front rod assembly 21 from having a slight rotation relative to the middle rod 22, thereby accurately determining the relative position relationship between the front rod assembly 21 and the middle rod 22. The upper end face of the rear rod assembly 23 is connected to the lower end face of the middle rod 22. The cylindrical boss on the upper end face of the rear rod assembly 23 fits precisely with the round hole on the lower end face of the middle rod 22 to determine the radial relative position relationship between the rear rod assembly 23 and the middle rod 22. The rear rod assembly 23 is connected to the middle rod 22 by evenly distributed rear section connecting screws 26, and then, using the rear section positioning pins 27, a "one plane and two holes" positioning method is formed to prevent the rear rod assembly 23 from having a slight rotation relative to the middle rod 22, thereby accurately determining the relative position relationship between the rear rod assembly 23 and the middle rod 22.

[0075] As Figure 4As shown, the front section component 21 of the rod consists of a front section base 211 of the rod, a rope perforation bushing 212, an outer front section base 213 of the rod, and a locking screw 217 for the outer front section base of the rod; the Hooke's joint component includes a driven fork 214 with one end connected to the previous rod component 2, a connecting screw 215 for the driven fork, and a positioning pin 216 for the driven fork. A number of outer semi-circular grooves for installing the rope perforation bushing 212 are distributed on the edge of the front section base 211 of the rod. The rope perforation bushing 212 and the outer semi-circular grooves on the edge of the front section base 211 of the rod form a mating relationship. A number of inner semi-circular grooves are also correspondingly distributed on the inner edge of the outer front section base 213 of the rod, and the inner semi-circular grooves also form a mating relationship with the rope perforation bushing 212. Since the rope perforation bushing 212 is only used for passing the rope and does not bear the tension of the rope, the outer shape of the rope perforation bushing 212 can be made cylindrical, and the corresponding grooves on the outer edge of the front section base 211 of the rod and the inner edge of the outer front section base 213 of the rod can be made circular arc-shaped. After the rope perforation bushing 212 is installed in the groove on the outer edge of the front section base 211 of the rod, the outer front section base 213 of the rod is connected to the front section base 211 of the rod by the locking screw 217 for the outer front section base of the rod, and the rope perforation bushing 212 also enters the corresponding groove on the outer front section base 213 of the rod. Since the diameter of the outer front section base 213 of the rod is slightly larger than the diameter of the front section base 211 of the rod, by appropriately increasing the pre-tightening force of the locking screw 217 for the outer front section base of the rod, the pressing force of the front section base 211 of the rod and the outer front section base 213 of the rod on the rope perforation bushing 212 can be increased to prevent the rope perforation bushing 212 from falling out of the groove jointly formed by the front section base 211 of the rod and the outer front section base 213 of the rod. The lower end face of the driven fork 214 contacts the end face of the front section base 211 of the rod. The driven fork 214 is connected to the front section base 211 of the rod by the connecting screw 215 for the driven fork, and the position relationship between the driven fork 214 and the front section base 211 of the rod is accurately determined by the positioning pin 216 for the driven fork.

[0076] As Figure 5As shown, the upper and lower end faces of the middle section 22 of the rod are flange structures. A number of threaded holes are distributed on the end faces of the flange plates. The upper and lower end faces are respectively in contact with the end faces of the front section assembly 21 and the rear section assembly 23 of the rod, and are connected to the front section assembly 21 and the rear section assembly 23 of the rod by screws respectively. In order to reduce the weight, the middle section 22 of the rod is a hollow structure. The precision machining holes at both ends are respectively matched with the cylindrical stop mouths on the end faces of the front section assembly 21 and the rear section assembly 23 of the rod to determine the radial position relationship between the middle section 22 of the rod and the front section assembly 21 and the rear section assembly 23 of the rod. A number of positioning pin holes are distributed on the end faces of the flange plates. By inserting positioning pins into the positioning pin holes, the slight rotation of the front section assembly 21 and the rear section assembly 23 of the rod relative to the middle section 22 of the rod can be avoided, so as to accurately determine the relative position relationship between the front section assembly 21 and the rear section assembly 23 of the rod and the middle section 22 of the rod. There are a number of pin holes on the flange end face. By inserting positioning pins into different positioning pin holes, the relative postures of the front section assembly 21 and the rear section assembly 23 of the rod and the middle section 22 of the rod can be adjusted, so as to change the motion parameters of the snake-shaped robotic arm joint and adapt to the requirements of different spatial ranges. In order to further reduce the weight, a number of slots are cut in the middle of the middle section 22 of the rod.

[0077] As Figure 6As shown in the figure, the rear section component 23 of the rod is composed of a rear section base 231 of the rod, a rope perforation bushing 232, a rope locking bushing 233, an outer rear section base 234 of the rod, and a locking screw 238 for the outer rear section base of the rod; the Hooke joint component includes a driving fork 235 with the other end connected to the rear rod component 2, a driving fork connection screw 236, and a driving fork positioning pin 237. A number of outer semi-circular arc grooves for installing the rope perforation bushing 232 are distributed on the edge of the rear section base 231 of the rod. The rope perforation bushing 232 and the outer semi-circular arc grooves on the edge of the rear section base 231 of the rod form a mating relationship. A number of inner semi-circular arc grooves are also correspondingly distributed on the inner edge of the outer rear section base 234 of the rod, and the inner semi-circular arc grooves also form a mating relationship with the rope perforation bushing 232. Since the rope perforation bushing 232 is only used for passing the rope and does not bear the tension of the rope, the outer shape of the rope perforation bushing 232 can be made cylindrical, and the corresponding grooves on the outer edge of the rear section base 231 of the rod and the inner edge of the outer rear section base 234 of the rod can be made circular arc-shaped. A number of outer semi-circular arc grooves for installing the rope locking bushing 233 are distributed on the edge of the rear section base 231 of the rod. The semi-circular platform shape of the rope locking bushing 233 and the outer semi-circular arc grooves on the edge of the rear section base 231 of the rod form a mating relationship. A number of inner semi-circular arc grooves are also correspondingly distributed on the inner edge of the outer rear section base 234 of the rod, and the inner semi-circular arc grooves also form a mating relationship with the semi-circular platform shape of the rope perforation bushing 232. Since the rope locking bushing 233 is used for locking the rope and bears the tension of the rope, the outer shape of the rope perforation bushing 232 can be made frustum-shaped. After the rope is tightened, relying on the conical shape of the frustum can not only ensure that the rope locking bushing 233 will not be separated from the rear section base 231 of the rod and the outer rear section base 234 of the rod due to the tension, but also realize the reliable locking and positioning of the rope in the axial direction. After the rope perforation bushing 232 and the rope locking bushing 233 are installed in the grooves on the outer edge of the rear section base 231 of the rod, the outer rear section base 234 of the rod is connected to the rear section base 231 of the rod through the locking screw 238 for the outer rear section base of the rod, and the rope perforation bushing 232 and the rope locking bushing 233 also enter the corresponding grooves on the outer rear section base 234 of the rod. Since the diameter of the outer rear section base 234 of the rod is slightly larger than the diameter of the rear section base 231 of the rod, by appropriately increasing the pre-tightening force of the locking screw 238 for the outer rear section base of the rod, the pressing force of the rear section base 231 of the rod and the outer rear section base 234 of the rod on the rope perforation bushing 232 and the rope locking bushing 233 can be increased, preventing the rope perforation bushing 232 and the rope locking bushing 233 from falling off from the grooves jointly formed by the rear section base 231 of the rod and the outer rear section base 234 of the rod. The lower end face of the driving fork 235 contacts the end face of the rear section base 231 of the rod. The driving fork 235 is connected to the rear section base 231 of the rod through the driving fork connection screw 236, and the position relationship between the driving fork 235 and the rear section base 231 of the rod is accurately determined by the driving fork positioning pin 237.

[0078] In this embodiment, the rod assembly 2 is divided into three parts: the front section, the middle section, and the rear section. The front section includes a front base, and the driven fork is installed on the front base. The driven fork is connected to the previous rod assembly 2 through a cross shaft; the rear section includes a rear base, and the driving fork is installed on the rear base. The driving fork is connected to the next rod assembly 2 through a cross shaft; the middle section connects the front section and the rear section to form a rod. The advantage of this split structure is that when rods of different lengths are required for different tasks, only the middle section customized according to serialization needs to be replaced, which improves the quick response ability.

[0079] As Figure 7 shown, the rope locking bushing 233 is composed of a left half bushing 2331 and a right half bushing 2332. The outer parts of the left half bushing 2331 and the right half bushing 2332 are frustum-shaped and are matched with the conical grooves in the rear base 231 of the rod and the outer rear base 234 of the rod. The inner parts are engaging surfaces, and engaging grooves for the rope to pass through are arranged on the engaging surfaces. It can be understood that arc grooves are evenly cut along the axial direction at intervals inside. The left half bushing 2331 and the right half bushing 2332 are combined into the rope locking bushing 233, and there is a gap in the middle. The gap is slightly smaller than the diameter of the rope. When the rope is locked, the rope can be deformed to increase the friction force and improve the locking effect.

[0080] In this embodiment, in order to facilitate the insertion of the towing rope and the removal and replacement of the rope locking bushing 233, the front / rear base is split into three parts: a disc-shaped inner base and two semi-circular ring-shaped outer bases. The original front / rear base is divided along the circumference where the center of the through hole is located. The internal disc-shaped part is the inner base, and half through holes are distributed on the outer circumference of the inner base; the external circular ring-shaped part is evenly cut into two identical semi-circular ring-shaped parts, which are called outer bases. The inner base and the two outer bases are assembled into a component to form the base. When it is necessary to insert the rope and remove and replace the rope locking bushing 233, the two outer bases are removed, and the remaining through hole formed by splicing has a groove less than a semi-circle. The rope carrying the rope locking bushing 233 can easily escape from the groove, without being restricted by transition fit or interference fit, and the operating space is no longer restricted by the structure of the snake-shaped robotic arm. After inserting the rope or replacing the rope locking bushing 233, the rope locking bushing 233 is pressed into the groove of the inner base, and then the two outer bases are sleeved and tightened, and the work of inserting the rope and removing and replacing the rope locking bushing 233 can be completed.

[0081] Furthermore, due to limited space, the hole through which the traction rope is inserted and locked is also relatively small, making it difficult to lock the traction rope using other methods. The hole is tapered, with a small hole at the rope entry end and a large hole at the rope exit end. Two identical left and right half bushings 2331 and 2332 form a tapered rope locking bushing 233. The outer surface of the rope locking bushing 233 matches the tapered hole. The inner surfaces of the left and right half bushings 2331 and 2332 are cut with cylindrical grooves with a radius slightly smaller than the rope radius, and several fine grooves are cut along the axial direction. The two identical left and right half bushings 2331 and 2332 form a conical rope locking bushing 233. When the rope is tightened, the friction force is increased, achieving the purpose of locking the rope. After the rope is tightened, the rope locking bushing 233 automatically centers and is tightened to the limit position in the mounting hole. The rope locking bushing 233 can also be pressed against the large hole to prevent it from moving backward. At this point, the position of the rope in the rope locking bushing 233 and the position of the rope locking bushing 233 in the hole no longer change, and the traction rope is locked.

[0082] like Figure 8 , Figure 9 As shown, the cross-shaft assembly 3 consists of a cross-shaft 31 and a cross-shaft bushing 32. The cross-shaft bushing 32 is installed on the shaft diameter at both ends of each rotating shaft of the cross-shaft 31. The inner diameter of the cross-shaft bushing 32 forms a matching relationship with the outer diameter of the shaft diameter of the cross-shaft 31, and the cross-shaft 31 can rotate within the cross-shaft bushing 32. The active fork 235 and the driven fork 214 are provided with holes for installing the outer diameter of the cross-shaft bushing 32. The outer diameter of the cross-shaft bushing 32 forms a transition or interference fit relationship with the hole diameter of the active fork 235 and the driven fork 214. The cross-shaft bushing 32 does not produce relative movement within the holes of the active fork 235 and the driven fork 214. Each rotating shaft of the cross-shaft 31 is composed of two opposing short shafts, which are coaxial. The two rotating shafts of the cross-shaft 31 are perpendicular to each other, and their axes intersect. The two end faces of each rotating shaft of the cross-shaft 31 are prefabricated with measurement holes for installing the laser tracker target.

[0083] like Figure 9As shown in the figure, the Hooke joint assembly is composed of a cross shaft 31, a cross shaft bushing 32, a driven fork 214, and a driving fork 235. Since the cross shaft of the snake-like robotic arm is not subject to large forces, and both the rotation angle and acceleration are relatively small, the holes in the driving fork 235 and the driven fork 214 for installing the cross shaft assembly 3 are cut to form an open structure. The opening size is slightly larger than the shaft diameter of the cross shaft 31, and the cross shaft 31 is inserted from the open area. The four shoulders of the cross shaft 31 respectively form a mating relationship with the inner end faces of the driving fork 235 and the driven fork 214, eliminating the axial adjustment links of each shaft of the cross shaft 31, canceling the adjustment shims, and improving the axial position accuracy of the cross shaft 31. Then, cross shaft bushings 32 are installed at both ends of each rotating shaft of the cross shaft 31 as sliding bearings, reducing the structural size while reducing the motion friction. The outer diameter of the cross shaft bushing 32 is larger than the opening size of the driving fork 235 and the driven fork 214 to ensure that the assembled cross shaft assembly 3 will not come out from the opening.

[0084] As Figure 10 shown, the measuring assembly 5 for measuring the position of the Hooke joint axis is composed of a laser tracker target seat 51 and a laser tracker target ball 52. A laser tracker target seat 51 is installed at both ends of each rotating shaft of the cross shaft 31. The cylindrical end of the laser tracker target seat 51 is inserted into the installation holes at both ends of each rotating shaft of the cross shaft 31. The installation holes can be round holes. The shoulder of the laser tracker target seat 51 contacts the shaft end face of the cross shaft 31, and the laser tracker target ball 52 is magnetically adsorbed in the ball seat of the laser tracker target seat 51.

[0085] As Figure 11 shown, the position of the Hooke joint axis can be measured using the laser tracker target seat 51 and the laser tracker target ball 52. The center positions of the laser tracker target balls 52 installed at both ends of the same shaft on the cross shaft 31 are measured using a laser tracker. The line connecting the center positions of the laser tracker target balls 52 at both ends is the axis of this shaft. Similarly, the axis of the other shaft can be determined. According to the actually measured axes of the two shafts, by using the usual calibration method to construct an error function, the rotation center of the Hooke joint can be calibrated.

[0086] As Figure 12 shown, angle sensors 53 are respectively installed on the driving fork 235 and the driven fork 214 to measure the rotation angles of the two rotating shafts of the cross shaft 31 relative to the driving fork 235 and the driven fork 214, and feed them back to the motion control system to achieve closed-loop feedback control of each rotating shaft.

[0087] In the above embodiments, since this assembly method does not require closing the ends of the cross shafts, measurement points for calibration are provided at the ends of the cross shafts. Holes for installing the targets of the laser tracker are machined at both ends of each shaft. The axes of the target holes at both ends of each shaft are coaxial with the axis of the shaft. By using the laser tracker to measure the positions of the targets of the laser tracker installed at both ends of the same shaft, the axis of this shaft can be determined. Similarly, the axis of the other orthogonal shaft can be determined.

[0088] Please refer to Figures 13 - 20 shown in the flowchart of the method for passing through holes inside the cabin provided by the preferred embodiment of the present application. According to different requirements, the order of the steps in the flowchart can be changed, and some steps can be omitted.

[0089] In an embodiment of the present application, the method for passing through holes inside the cabin is applied to an electronic device wirelessly communicatively connected to a serpentine robotic arm, or directly applied to the serpentine robotic arm. Hereinafter, the method for passing through holes inside the cabin will be taken as an example for description.

[0090] A method for passing through holes inside a cabin includes the following steps:

[0091] Step S100: Obtain the starting point of the entrance hole and the target point of the exit hole of the path planning task;

[0092] As Figure 13 shown, it is a typical working environment for passing through holes inside the cabin. Inside the cabin, there is a hole on each of the two partitions with an included angle of α, and the thicknesses of the partitions are h s and h e , the center O s of the cabin entrance hole on the inner surface of the cabin has coordinates (x s , y s , z s ), the center O e of the cabin exit hole on the inner surface of the cabin has coordinates (x e , y e , z e ), that is, the starting point O s of the entrance hole has coordinates (x s , y s , z s ), the target point O e of the exit hole has coordinates (x e , y e , z e ). The serpentine robotic arm enters from the starting point of the cabin entrance hole and exits from the target point of the cabin exit hole. Usually, it is desired to use the fewest rods, and the ratio of the working rotation angles of each rod to the rotation angle limit is balanced to meet the vast majority of subsequent path planning requirements.

[0093] Step S200: Make a plane passing through the starting point and the target point, and determine whether there are obstacles in the plane;

[0094] Step S300: When there are no obstacles, perform the following acquisition steps:

[0095] Step S301: Calculate the maximum turning angles respectively from the starting point and the target point, and obtain the intersection distance of the snake-like robotic arm from entering the cabin to leaving the cabin under the maximum turning angle. Among them, the intersection distance is the distance between the intersection point of the axis and the inner surface of the entrance hole of the cabin when the rod deflects to the limit position in the entrance hole, and the intersection point of the axis and the inner surface of the exit hole of the cabin when the rod deflects to the limit position;

[0096] Step S302: According to the projection relationship of the vectors of each rod of the snake-like robotic arm on the intersection distance, use the ratio k of the actual turning angle and the stroke of the rod of the snake-like robotic arm i as the motion coefficient;

[0097] Step S303: Plan the path of the snake-like robotic arm by adjusting the motion coefficient of the rod;

[0098] Step S400: When there are obstacles, perform the following acquisition steps:

[0099] Step S401: Re-find a plane without obstacles passing through the starting point and the target point;

[0100] Step S402: If there is a plane meeting the requirements, continue with the steps of S301 - S303;

[0101] Step S403: If there is no plane meeting the requirements, intersect the plane passing through the starting point and the target point with the obstacle, and by setting an obstacle avoidance threshold, set path intermediate points on each path segment to plan the path of the snake-like robotic arm.

[0102] In the above steps S200 - S400, since there can be countless smooth curves between the starting point O s and the target point O e , therefore, it is necessary to analyze according to different environmental conditions, mainly including two cases:

[0103] (1) In the case of no obstacles

[0104] As Figure 13 shown, make a plane passing through the starting point O s and the target point O e , and establish a coordinate system as shown in the figure; the specific steps are as follows:

[0105] Step S201: According to the known starting point Os Coordinates (x s , y s , z s ) and the target point O e with coordinates (x e , y e , z e ), obtain the starting point O s 's projection coordinate point O sXY on the XOY plane with coordinates (x s , y s , 0) and the target point O e 's projection coordinate point O eXY on the XOY plane with coordinates (x e , y e , 0);

[0106] Step S202: According to the coordinates (x sXY , y s , 0) of the projection coordinate point O s and the coordinates (x eXY , y e , 0) of the projection coordinate point O e , obtain the vector O s from the starting point O e to the target point O s O e =(x e - x s y e - y s z e - z s ) T and the vector O sXY from the projection coordinate point O eXY to the projection coordinate point O sXY O eXY =(x e - x s y e - y s 0) T ;

[0107] Step S203: Cross - multiply the vector O s O e with the vector O sXY O eXY to obtain the normal vector p s O e of the plane formed by the vector O sXY O eXY =( - y se + y e x s xe -x s 0) T ;

[0108] Step S204: Perform a cross product of the vector O s O e and the normal vector p se to obtain the vector nse, where

[0109] Step S205: Normalize the vector n se to obtain the unit vector n of the plane, where

[0110] When planning the motion path of the snake-like robotic arm in the plane with the normal vector n, a shorter path can be obtained. The i-th rod entering the cabin entrance and the n-th rod exiting the cabin exit of the snake-like robotic arm both deflect in this plane.

[0111] As Figure 14 shown, starting from the cabin entrance, the snake-like robotic arm passes through the cabin exit. A path with fewer joints and shorter length is from the point O' si (the intersection of the axis and the inner surface of the cabin entrance when the i-th rod deflects to the limit position in the entrance hole) of the cabin entrance, along a smooth curve, to the point O' en (the intersection of the axis and the inner surface of the cabin exit when the n-th rod deflects to the limit position) of the cabin exit.

[0112] As Figure 15 shown, the motion mode of each rod is that each rod deflects by a certain angle on the basis of the previous rod, and the rotation angles of each rod are balanced, and the shape of the snake-like robotic arm maintains a smooth transition.

[0113] As Figure 16 shown, the included angle between the axes of the cabin entrance and the cabin exit is α. That is, if the snake-like robotic arm enters along the axis of the cabin entrance and exits along the axis of the cabin exit, the snake-like robotic arm deflects by a total of α angles. This is the result of the deflection of all rods. Then there is:

[0114]

[0115] As Figure 17 shown, calculate the limit position that the snake-like robotic arm can reach after entering the cabin entrance. The entrance aperture is D i , assuming that the i-th rod with a diameter of d i enters the cabin entrance, and deflects by θ i angle (the maximum rotation angle can reach θ imax ) in the entrance hole. At this time, it is equivalent to a length of L'i The i-th rod starts from point O'. si Set out.

[0116] From Figure 17 it can be seen that

[0117]

[0118] Then there is

[0119]

[0120] Since there is

[0121]

[0122] Substituting into (Equation 2), we can get

[0123] D i cosθ imax -h s sinθ imax =d i (Equation 7)

[0124] According to Equation (4), the maximum rotation angle θ of the i-th rod in the hole can be solved imax

[0125]

[0126] Similarly, let the exit hole diameter be D n , assuming that the n-th rod with a diameter of d n enters the cabin exit, the maximum rotation angle θ of the n-th rod in the hole can be solved emax

[0127]

[0128] Since the deflections of the i-th rod entering the cabin entrance and the n-th rod passing through the cabin exit are both restricted by the hole, and the maximum deflection angles are θ imax and θ emax respectively, so there is

[0129]

[0130] Due to the deflection of rod i, when the rod passes through the inner surface of the entrance and enters the interior of the cabin, the intersection point of the rod axis and the inner surface of the entrance is O' si , the intersection point of the entrance hole axis and the inner surface of the entrance is O s , when the rod touches the hole edge, the distance between point O s and point O' si is:

[0131]

[0132] When the deflection of the rod i in the entrance hole reaches the limit value θ imax , the point O s and the point O' si The distance between them is the largest, which is

[0133]

[0134] Due to the deflection of the rod n, when the rod passes through the inner surface of the exit and enters the outside of the cabin, the intersection point of the axis of the rod and the inner surface of the exit is O' en , at this time, it is equivalent to the nth rod with a length of L' n reaching the point O' en , the intersection point of the axis of the exit hole and the inner surface of the exit is O e , when the rod touches the edge of the hole, the point O e and the point O' en The distance between them is:

[0135]

[0136] When the deflection of the rod n in the exit hole reaches the limit value θ emax , the point O e and the point O' en The distance between them is the largest, which is:

[0137]

[0138] As Figure 18 shown, it is the shortest distance for the snake-like robotic arm to enter and leave the cabin.

[0139] The coordinates of the intersection point Q of the partition at the entrance and the partition at the exit are (x Q , y Q , z Q ), and the distance ||QO s || between the point Q and the point O is: s || is:

[0140]

[0141] Then the distance ||QO' si || between the point Q and the point O' is: si || is:

[0142]

[0143] The distance ||QO e || between the point Q and the point O is: e || is:

[0144]

[0145] Then the distance between point Q and point O' en ||QO' en || is:

[0146]

[0147] O' si O' en and QO' si and QO' en form a triangle. According to the cosine theorem, it can be calculated that:

[0148]

[0149] According to the sine theorem, calculate the included angle β' between O' si O' en and QO' si si

[0150]

[0151] As Figure 19 shown, the motion task of the snake-like robotic arm is: starting from point O' si and finally reaching the point O' s with an included angle θ si O' en || and a distance of ||O' en . The included angle θ s is:

[0152] θ s = 90° - θ i - β' si (Formula 21)

[0153] According to the motion relationship, it can be known that the sum of the projection lengths of each link vector on O' si O' en is equal to ||O' si O' en ||. Then there is:

[0154]

[0155] In the formula, ||O' si O' en || is the intersection distance, θ s is the total angle that the snake-like robotic arm needs to turn, L' i is the length of the i-th link, and L' n is the length of the n-th link.

[0156] ​To ensure that sufficient movement margins are reserved for the rotation angles of each rod, facilitating subsequent motion planning, the ratio k of the actual rotation angle of the rod to the stroke i is used as the motion coefficient, and let

[0157] θ i = k i θ imax (Formula 23)

[0158] Therefore, the path of the snake-like robotic arm can be planned by adjusting the motion coefficient of the rod.

[0159] (2) In the presence of obstacles

[0160] According to the distribution characteristics of the obstacles, it is divided into two cases:

[0161] 1) Planning in a plane without obstacles

[0162] Pass through point O s and point O e to make a plane, find a plane that does not intersect with the obstacles, and use the method shown Figure 17 to perform path planning in this plane. If the number of rods required does not increase significantly and there is still a certain movement margin for the rotation angle of the rods, the above method can be used.

[0163] 2) Planning in a plane with obstacles

[0164] As shown Figure 20 pass through point O s and point O e to make a plane. If the plane intersects with the obstacles, then according to the set obstacle avoidance threshold, set the intermediate points of the path, and use the above method for each segment of the path to plan the path segment by segment.

[0165] For those skilled in the art, it is obvious that the present application is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present application, the present application can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present application is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be encompassed within the present application. Any reference signs in the claims should not be regarded as limiting the claimed rights. In addition, obviously the word "including" does not exclude other units or steps, and the singular does not exclude the plural. The multiple units or devices stated in the apparatus claims can also be implemented by the same unit or device through software or hardware. First, second, etc. are used to denote names and do not denote any specific order.

[0166] The above embodiments are only used to illustrate the technical solutions of the present application and not to limit them. Although the present application has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present application can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. A method for passing through holes inside a cabin, characterized in that, It includes the following steps: S100: Obtain the starting point of the entrance hole and the target point of the exit hole of the path planning task; S200: Make a plane passing through the starting point and the target point, and determine whether there are obstacles in the plane; S300: When there are no obstacles, perform the following obtaining steps: S301: Calculate the maximum turning angle respectively from the starting point and the target point to obtain the intersection distance of the snake-like robotic arm from entering the cabin to leaving the cabin under the maximum turning angle. Wherein, the intersection distance is the distance between the intersection point of the axis and the inner surface of the entrance hole of the entrance hole when the rod deflects to the limit position in the entrance hole, and the intersection point of the axis and the inner surface of the exit hole of the exit hole when the rod deflects to the limit position; S302: According to the projection relationship of each rod vector of the snake-like robotic arm on the intersection distance, use the ratio ki of the actual turning angle and the stroke of the rod of the snake-like robotic arm as the motion coefficient; S303: Plan the path of the snake-like robotic arm by adjusting the motion coefficient; In the step S200, the step of making a plane passing through the starting point and the target point includes: S201: According to the known starting point O s coordinates (x s , y s , z s ) and the target point O e coordinates (x e , y e , z e ), obtain the projection coordinate point O s of the starting point O sXY on the XOY plane, with coordinates (x s , y s , 0) and the projection coordinate point O e of the target point O eXY on the XOY plane, with coordinates (x e , y e , 0); S202: According to the projection coordinate point O sXY with coordinates (x s , y s , 0) and the projection coordinate point O eXY with coordinates (x e , y e , 0), obtain the vector O s from the starting point O e to the target point O s O e = (x e - x s y e - y s z e - z s ) T , and the vector O sXY from the projection coordinate point O eXY to the projection coordinate point O sXY O eXY = (x e - x s y e - y s 0) T ; S203: Take the vector O s O e and cross - multiply it with the vector O sXY O eXY to obtain the vector O s O e and the normal vector p sXY O eXY of the plane formed by the vector O se = (-y e +y s x e -x s 0) T ; S204: Take the vector O s O e and perform a cross product with the normal vector p se to obtain the vector n se , where S205: Unitize the vector n se to obtain the unit vector n of the plane, where 2. The internal through-hole crossing method of a cabin body according to claim 1, characterized in that It also includes step S400: When there are obstacles, perform the following obtaining steps: S401: Re-search for an obstacle-free plane passing through the starting point and the target point; S402: If there is an obstacle-free plane that meets the requirements, continue to perform the steps of S301 - S303; S403: If there is no obstacle-free plane that meets the requirements, intersect the plane passing through the starting point and the target point with the obstacle, and set path intermediate points on each path by setting an obstacle avoidance threshold to segment and plan the path of the snake-like robotic arm.

3. The method for passing through holes inside a cabin as described in claim 1, characterized in that The maximum rotation angle θ of the rod of the i-th serpentine robotic arm within the inlet hole imax is calculated by the formula: Wherein, the D i is the aperture diameter of the inlet hole, the d i is the rod diameter of the i-th serpentine robotic arm, and the h s is the depth of the inlet hole.

4. The internal through-hole traversing method of a cabin body according to claim 1, characterized in that The maximum rotation angle θ of the rod of the nth serpentine robotic arm within the outlet hole emax is calculated by the formula: Wherein, the D n is the aperture diameter of the outlet hole, the d n is the rod diameter of the nth serpentine robotic arm, and the h e is the depth of the outlet hole.

5. A method for passing through internal through-holes of a cabin body according to claim 1, characterized in that, In step S302, the projection relationship of the vectors of each rod of the serpentine robotic arm on the intersection distance is as follows: the sum of the lengths of the projections of the vectors of each rod onto O' si O′ en is equal to ||O' si O′ en ||, where: Wherein, ||O′ si O′ en || is the intersection distance, θ s is the total angle to be turned by the snake-shaped robotic arm, L′ i is the length of the i-th rod, L′ n is the length of the n-th rod.

6. A serpentine robotic arm passing through an internal through-hole of a cabin, characterized in that, It includes: A snake-like arm body, which includes a plurality of rod assemblies coupled together, and Hooke joint assemblies located therebetween and arranged orthogonally. Wherein, the Hooke joint assembly includes a cross shaft, a driving fork and a driven fork respectively connected to both ends of the cross shaft. Installation holes are provided at both ends of each rotating shaft of the cross shaft; A driving component, which is connected to the snake-like arm body and is used to drive the rod assembly of the snake-like arm body to rotate around the cross shaft; and, A measuring component, which includes a laser tracker target seat, a laser tracker target ball, a laser tracker and an angle sensor. Wherein, a laser tracker target seat is installed in each of the installation holes at both ends of each rotating shaft of the cross shaft, and the laser tracker target ball is arranged in the laser tracker target seat; the laser tracker is installed at the central position of the two laser tracker target balls at both ends of the same rotating shaft of the cross shaft; angle sensors are respectively installed on the driving fork and the driven fork to measure the rotation angles of the two rotating shafts of the cross shaft relative to the driving fork and the driven fork.

7. The snake-shaped robotic arm passing through the internal through-hole of the cabin as described in claim 6, characterized in that, The rod component includes a front rod component, and the front rod component includes a front rod base, a rope perforation bushing, and an outer front rod base. A number of outer semi-circular arc grooves for installing the rope perforation bushing are distributed on the edge of the front rod base, and a number of inner semi-circular arc grooves for installing the rope perforation bushing are correspondingly distributed on the inner edge of the outer front rod base. An installation area for installing the rope perforation bushing is formed between the outer semi-circular arc groove and the inner semi-circular arc groove; the outer front rod base is composed of two semi-ring parts, and the two semi-ring parts are detachably arranged on the front rod base.

8. The snake-shaped robotic arm passing through the internal through-hole of the cabin as described in claim 6, characterized in that, The Hooke joint component further includes a cross shaft bushing. The cross shaft bushing is installed on the shaft diameters at both ends of each rotating shaft of the cross shaft. The inner diameter of the cross shaft bushing is sleeved outside each rotating shaft of the cross shaft bushing. Each rotating shaft of the cross shaft is rotatably arranged relative to the cross shaft bushing. The driving fork and the driven fork are provided with holes for installing the outer diameter of the cross shaft bushing, and the holes for installing the outer diameter of the cross shaft bushing are open structures for placing each rotating shaft of the cross shaft.

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