| As a large-volume and pressure-bearing sealed container,the spherical tank needs regular weld inspection to ensure its safety.At present,manual inspection with low detection efficiency and poor safety is still the main method in industry application.It is an inevitable trend to replace manual operation with wallclimbing robot.However,due to factors such as floating rust,oil stains and welds inside the spherical tank,the adsorption capacity of the robot is affected.On the other hand,the three-dimensional positioning of the detection robot inside the spherical tank,as well as the welding seam tracking and optimal detection path planning problems under the complex distribution of welding seams limit the automatic detection ability of the spherical tank weld detection robot.In order to solve the above problems,this paper proposes a passive support mechanism fixed to the spherical tank,which is used to improve the adsorption capacity of the robot and realize the position detection of the robot.At the same time,the weld seam tracking and the shortest path planning based on traversing all welds are researched.Based on the analysis of the working environment inside the spherical tank,a spherical coordinate support mechanism with reproducible expansion is designed.The configuration of the structure is determined from the perspective of ensuring structural rigidity and reducing weight,and the telescopic locking joints and other key structures are designed.A three-dimensional coordinate calculation of the robot based on the cantilever attitude detection of the support mechanism is proposed.The influence of the structure parameters of the main body on its static stiffness is studied,and after summarizing the rule with the help of finite element software,the appropriate structure parameters are selected and the stability of the mechanism is checked.At the same time,theoretically deducing the thrust required to prevent the robot from sliding and overturning,and establishing a mathematical model to study the influence of the deformation of the mechanism on its supporting ability and positioning accuracy.The autonomous navigation technology of welding seam detection robot is studied,and two kinds of weld seam tracking technologies are proposed,including a tracking algorithm that matches the adjacent welding seam according to the robot's position when the weld distribution map is known,and a tracking algorithm that uses convolutional neural network to identify the weld seam in real time and advances the centerline.In this paper,the shortest path planning problem of traversing all the welds is discussed,the twodimensional map is established according to the three-dimensional distribution of welds,and the mathematical model is analyzed as the postman problem.Based on the graph theory,a shortest path planning algorithm with traversing all weld is realized.The hardware composition of the positioning and navigation system is planned,and its software is realized,including data acquisition of the lower computer and remote monitoring of the upper computer.A prototype of the supporting mechanism was built,and the supporting capability and positioning accuracy of the supporting mechanism were tested on the existing cylindrical iron cans in the laboratory,and the feasibility of the scheme was verified.Images of weld seams were collected to verify the weld tracking algorithm based on convolutional neural network,and the results showed that the algorithm had a good effect on single weld and cross weld. |
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