Research On Dynamic Characteristics Of Chained Multi-unit In-pipe Robot

Chained multi-unit wheel-type in-pipe robot can achieve effective andeconomical pipeline equality testing, troubleshooting and maintenance, which iswidely used in engineering pipelines. The dynamic characteristics of in-pipe robotare associated with lots of vital issues, such as getting through pipeline systemcompliantly, predicting and distributing the limited energy, and reducing wheels’frictional wear.This paper establishes universal physical model of chained multi-unit in-piperobot system based on wheel-type in-pipe robots, and the universal physical modelcontains wheel-type in-pipe robots’ similarities and main characteristics. The posemodel in elbow is established with considering the wheels’ size. On this basis, thewheels’ theoretical angular velocity ratio relations are obtained. The staticequilibrium equation and swivel torque balance equation are established bycalculating the tractive force of driving unit may output and analysing forces thatare applied to unit. The corresponding numerical examples are given.As a multi-rigid-body system, the dynamic model of chained multi-unit in-piperobot system is established by applying Lagrange method of multi-body systemdynamics. The basic kinetic equation is created without considering pipeline’sconstraints. Contact forces of pipeline can be added in the basic kinetic equation byapplying Lagrange multipliers, then the full kinetic eqution is obtained. Thecomplementary features of contact-detach and stiction-sliding can be created fromtangential and normal direction. Finally, a standard linear complementary problem(LCP) is obtained. And the dynamic characteristics of in-pipe robot system will beobtained by solving the LCP. The numerical example while robot system running instraight pipeline with a uniform speed is given.The virtual prototype model of in-pipe robot and its pipeline system are createdin ADAMS based on virtual prototype technology. Take the theoretical angularvelocity as driving-unit wheels’ input angular velocity under different attitudeangles, and the state of motion of each driving wheel is determined. Dynamicsimulations are done and the variations of contact forces between each wheel andpipe wall are obtained.Simulation results and theoretical results are basically the same, andcorrectness of theoretical calculations is verified. The analysis results can provide atheoretical basis for wheel-type in-pipe robot’s design and control.