Research on multi-mode dynamic performance testing and load sharing behavior of rotary drilling rig

The rotary drilling rig (RDR) is a type of heavy-duty mechanical equipment extensively utilized in the fields of civil engineering and construction projects. The load fluctuations of the RDR’s powerhead under multi-mode operational conditions, coupled with the uneven load distribution behavior within its planetary gear system (PGS), constitute key factors exacerbating system vibration, impairing drilling stability, and constraining power utilization efficiency. This study aims to unveil the intrinsic mechanisms governing load fluctuations and uneven load distribution, along with their synergistic interactions, and propose effective strategies to enhance the dynamic performance and load-sharing capabilities of the powerhead. Consequently, this study first constructs a mechanical-hydraulic coupled multibody dynamics (MH-MBD) model of the PGS integrated with hydraulic automatic variable control (HA). Subsequently, dynamic performance testing under multi-mode operating conditions—including concrete, clay, and sand-gravel layers—was conducted to validate the feasibility and effectiveness of the established model. Finally, the interaction mechanism between the load sharing coefficient (LSC) and gear transmission error (TE), as well as drill pipe torque, was thoroughly investigated. This study revealed that TE is the root cause of uneven load distribution, while high drill pipe torque can mitigate the impact of such errors—a critical mechanism governing system behavior. These findings provide a theoretical foundation and engineering guidance for vibration suppression in RDRs and design optimization of the powerhead.