Design And Analysis Of Modular Three Axis Differential Pipeline Robot

In this paper,a three-axis differential pipeline robot is designed,which is used in the periodic maintenance stage of oil pipeline.The robot can actively adapt to the straight pipe with the inner diameter of 300～350 mm,and the curved pipe with minimum radius of curvature is 1.5 times of the inner diameter and the minimum angle is 90°.According to the idea of modularization,the robot is designed into three parts: the differential mechanism,the driving end of the reducing mechanism and the driven end of the reducing mechanism.The three parts can be assembled and disassembled flexibly and conveniently.The differential mechanism makes the rotational speed of the driving wheel automatically distribute according to the external constraints,and the input energy is equally distributed when the external constraints are the same;the differential mechanism is realized by a two-stage differential gear train composed of cylindrical gears,which reduces the manufacturing cost and installation difficulty.The reducing mechanism is different from the previous screw type reducing mechanism,which is composed of rack and pinion and slider crank mechanism.The reducing parts are almost in the same plane,which reduces the length diameter ratio of the robot and improves the trafficability of the elbow;the reducing mechanism is distributed on both sides of the differential mechanism,which can change the diameter actively,increasing the adaptive range of the robot to the inner diameter of the pipe.The three-axis differential mechanism is designed in three stages,and the relationship between the input torque and the output torque is verified through the force analysis of the differential mechanism.This paper analyzes the differential characteristics of the robot passing through straight pipe and curved pipe.The design of the differential gear train not only makes the rotation speed of each driving wheel automatically distribute when passing through the curved pipe,but also makes it easier for the driving motor to control the robot’s bending speed.This paper analyzes the transmission efficiency of the differential gear train,gives the theoretical calculation method of the transmission efficiency,and draws the conclusion that the efficiency of the differential gear train is related to the three output speeds.The force analysis of the robot’s reducing mechanism is carried out,and the method to control the positive pressure of the robot’s wheel is studied,as well as the determination of the spring stiffness in the elastic connecting rod and the output torque of the reducing motor.This paper analyzes the obstacle surmounting of the robot wheel,and studies how to design the robot to ensure a larger obstacle surmounting height.The calculation method of traction force under the influence of self weight of robot and the condition of stable operation of robot are given.The static finite element analysis of key parts is carried out in ANSYS Workbench software,and its structure basically meets the requirements of stiffness and strength.The virtual prototype simulation experiments are carried out in ADAMS software,and a variety of simulation test platforms are built for dynamic simulation.The animation of the robot through the pipeline and the related curves of driving wheel speed,driving motor torque,wheel contact force are output.The differential characteristics,wheel positive pressure control,traction force,driving force of the designed three-axis differential pipeline robot are verified.The energy distribution and the adaptability of the robot to different pipes are analyzed,and the advantages of active reducing when the robot passes through the elbow are proposed.The robot prototype is made by using 3D printing parts.The robot can carry infrared distance sensor,temperature and humidity sensor,encoder,camera and other sensors into the pipeline to realize the detection function.Two experimental platforms are built to verify the passing ability of the designed robot to the elbow,and can complete the tasks of temperature and humidity perception,obstacle recognition,image acquisition and so on.The trafficability of the robot through different inclined pipes is verified,and the average speed of the robot through three inclined pipes is obtained.