Objective In-line inspection robots are essential tools for conducting in-line inspections of oil and gas pipelines. Nevertheless, the transient and intense vibrations caused by different excitation factors within pipelines, like pipeline elbows, deformations, and welds, undermine the detection accuracy of their built-in sensors and structural reliability. This issue is particularly evident in cases of vibration stemming from pipeline elbows.

Methods This study proposed a vibration reduction philosophy focusing on the movement characteristics of in-line inspection robots maneuvering through pipeline elbows. The approach integrates damping-mass sphere buffer energy absorption and a variable centroid, drawing from the control principles of tuned mass dampers (TMD) and variable centroid for vibration reduction. Two vibration reduction structures were then developed, each embodying the variable-centroid TMD principle with single-degree-of-freedom (SDOF) and two-degree-of-freedom (2DOF), respectively. Subsequently, simulations were conducted to analyze the vibration responses of in-line inspection robots navigating pipeline elbows, supported by Automatic Dynamic Analysis of Mechanical Systems (ADAMS) and Matlab. Furthermore, a bidirectional fluid-structure interaction dynamic analysis was performed to investigate the impact and collision conditions of robots equipped with the designed vibration reduction structures passing through pipeline elbows.

Results By comparing and analyzing the time-history curves of accelerations and energy amplitudes of in-line inspection robots passing through pipeline elbows before and after the application of vibration reduction structures, the effects of vibration reduction were revealed for structures with different degrees of freedom. Compared to scenarios without vibration reduction structures, the robot within an SDOF vibration reduction structure experienced sudden acceleration changes when approaching elbows, with its maximum acceleration reaching 3.47g(1g= 9.8 m/s²). Meanwhile, the robot equipped with a 2DOF vibration reduction structure experienced reductions in acceleration maximums along the axial and horizontal swing directions by up to 48% and 39% respectively. This decrease led to a significant reduction in vibration energy.

Conclusion The novel design of variable-centroid TMD structures for in-line inspection robots makes significant contributions to vibration reduction. The study outcomes could potentially be utilized as a theoretical reference for ensuring the stable operation of in-line inspection robots.