# Analysis of a Tracked In-Pipe Robot's Obstacle-Crossing Performance
###### Abstract  
Pipeline transportation of oil and gas is widespread. To improve inspection and maintenance, a pipeline inspection robot was developed in our study. We employed a threaded nut mechanism with a preload spring and diameter-adjustment methods. A torque output formula was derived. At maximum (340 mm) and minimum (260 mm) diameters, angles \(\alpha\) and \(\beta\) were given. A pipeline obstacle model was established with a maximum crossing height of 7.5 mm. Simulation and experiments showed that the robot could cross up to 7.8 mm, performed well, and operated stably, which met our expectations.  
diameter adaptation; obstacle-crossing performance; pipeline robot; mechanical analysis 2020 IEEE/RSJ International Conference on Robotics and Automation (ICRA), Vol., pp. 2008-2008,  
driving modules and a set of driving arms to navigate smoothly through external obstacles (such as fixtures, flanges, and valves) as well as pipeline components (such as elbows and T-joints) [16]. Its wheeled movement mode endows it with a high operating speed. Moreover, that robot's design incorporates worm and screw transmission mechanisms, which enhance its stability when traversing pipelines. [PERSON] et al. from Hong Kong Polytechnic University proposed a tethered soft-rigid pipe-climbing robot. This robot utilizes soft components and a wheeled mechanism to achieve external pipe movement through the traction force of compressed air and wheels [17]. Additionally, that robot's soft material enables it to traverse pipes of varying diameters. Elastic dampers installed between the wheels and body enhance its ability to smoothly overcome obstacles, thereby demonstrating strong adaptability. [PERSON] et al. from Andong National University designed a pipe robot with adjustable drive-wheel length, which is capable of accommodating various pipe diameters [18; 19]. The robot was designed to inspect both straight and curved pipes with a diameter of 435 mm. It employs support-force control and flexibility mechanisms to precisely manage the radial position of the drive wheels, ensuring no slip-page occurs. To effectively handle typical pipeline obstacles such as flanged couplings, pipe supports, T-joints, and Y-joints, the robot was designed with a mechanism that allows its drive modules to rotate along the main body. Additionally, a control method that leverages the interaction between the supports and drive modules was implemented. Extra contact points were added to enhance stability. [PERSON] et al. from Southeast University proposed a flexible obstacle-surmounting pipeline-climbing robot with composite wheels [20; 21]. This robot features an elastic shock-absorbing suspension mechanism and a composite-wheel mechanism, which provide strong stability and enhanced obstacle-surmounting capabilities. Its adjustable frame and rotating-joint mechanism enable the robot to adapt to different pipe diameters and curvatures. Additionally, obstacle-mechanics models were established for this robot, and then analyzed and simulated. Obstacle-surmounting tests demonstrated that the robot can overcome 20 mm obstacles and exhibited stable movement with excellent performance during obstacle surmounting.  
This paper reviews the development of pipeline robots in recent years and provides an in-depth discussion of the current challenges associated with obstacle surmounting within pipelines [22; 23; 24; 25]. Based on this, a robot was designed and analyzed, and obstacle-surmounting models for this pipeline robot were established to evaluate its obstacle-surmounting performance. Additionally, simulation and experimental verification analyses of this robot's obstacle-surmounting performance were conducted.