Design and comparative analysis of self-propelling drill bit applied to deep-sea stratum drilling robot

Abstract

Robotic subsea stratum drilling robot is a method for new subsea stratigraphic geological investigation and resource exploration. Resistance at the front end is the main source of resistance to the robot’s motion in the strata. Since there is no continuous and strong downward drilling force as in conventional drilling rigs, robot movement relies heavily on the drill bit to reduce the drilling resistance. In this study we propose a self-propelling drill bit that can discharge soil debris to provide propulsive force and reduce the resistance. The key parameter of the drill bit design, the spiral blade lead angle, was determined by theoretical analysis of the drill bit’s soil discharging effect. To verify the structural advantages of the self-propelling drill bit in reducing resistance, a comparative analysis with a conventional conical drill bit was conducted. The drilling process of both bits was simulated using finite element simulation at various rotation speeds, the penetration force and torque data of both drill bits were obtained, and tests prepared accordingly in subsea soil were conducted. The simulations and tests verified that the penetration force of the self-propelling drill bit was lower than that of the conventional conical drill bit. The self-propelling drill bit can reduce the resistance effectively, and may play an important role in the stratum movement of drilling robots.