Study on the dynamic characteristics of a novel modular wheeled tractor

Wheeled tractors offer advantages in downhole operations, including high efficiency and extended reach, yet traction force improvement is often constrained by non-synchronized motion between multiple sections. This paper proposes a novel modular wheeled tractor with an outer diameter of 80 mm, a single-section traction force of 2000 N, and a design speed of 167 mm/s. Its core innovation is a modular joint structure based on rotary slip rings, which enables independent control of each traction section and ensures torsion-free transmission of power and signals. Based on this design, a traction dynamics model for horizontal wells was established to analyze the dynamic characteristics under synchronized motion, differential motion, and angular velocity fluctuations. Simulation results identify differential motion among drive wheel sets as the key factor causing systemic slippage and limiting traction performance. A single-section prototype was developed and tested using a full-scale experimental system. Under loaded conditions, it achieved a maximum traction force of 2240 N at a speed of 125 mm/s, thereby verifying the correctness and reliability of the proposed structure and control system. This research provides an effective technical pathway for enhancing the traction capacity of coiled tubing tractors and reducing petroleum exploration and development costs.