ABSTRACT:

This paper deals with computational method on coupled dynamics of tracked vehicle on seafloor and long flexible pipe. The tracked vehicle is modeled as rigid-body vehicle, and the linked flexible pipe is discretized according to a lumped-parameter model. The equations of motion of the rigid-body vehicle on the soft seafloor are combined with the governing equations of flexible pipe dynamics. Four Euler parameters method is used to expressed the orientations of the vehicle and the flexible pipe. In order to solve the coupled dynamics of vehicle and flexible pipe an incremental-iterative formulation is implemented. For the time-domain integration Newmark-β method is adopted. The total Jacobean matrix has been derived based on the incremental-iterative formulation. The interactions between the dynamics of flexible pipe and the mobility of the tracked vehicle on soft seafloor are simulated.

INTRODUCTION

Since the end of 1970's, the concept of self-propelled miner sweeping polymetallic nodules from deep-seabed has been investigated for commercial scale deep-ocean mining, e.g. Brink and Chung (1981), Chung (1996, 2003), Herrouin et al. (1989), Amann et al. (1991), Liu and Yang (1999), Hong and Kim (1999), Deepak et al. (2001), Handschuh et al. (2001) and etc. Tracked vehicles are preferred because of the better floatation and the larger traction force, which are required for the extremely weak deep-seabed soil. A large number of literatures are found in experimental and theoretical works on the performance analysis of tracked vehicles for soft soil (see in Hong et al. 2002). As recent works, Schulte et al. (2003) suggested an empirical function to convert the measured shear stress of benthonite-water mixture to the traction force of track segment. Choi et al. (2003) conducted a series of experiments and showed the design directions for tracked vehicle on cohesive soft soil to achieve smaller slip.

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