This paper concerns about dynamic analysis of underwater tracked vehicle operating on extremely soft soil of deep-seafloor. The vehicle is assumed as a rigid-body with 6-dof. The orientation of vehicle is defined by four Euler parameters. To solve the motion equations of vehicle, Newmark numerical integrator is used in incremental-iterative algorithm. The normalization constraint of Euler parameters is satisfied by using of a sequential updating method. The hydrodynamic force and moment are included in the tracked vehicle's dynamics. The hydrodynamic effects on the performance of tracked vehicle are investigated by numerical simulations.
In the previous work by Hong et al. (2002), a comprehensive introduction about various kinds of analytical methods for prediction of performance of tracked vehicle was carried out. They developed a transient 3D dynamic analysis method for tracked vehicle working on extremely soft cohesive soil in order to utilize in development of a seafloor crawling miner for deep-seabed manganese nodules. The soil mechanics model was implemented to be relevant to the extremely soft cohesive sediment of deep seafloor. Euler angles were used to express the orientation of vehicle. Newmark-β method was used for time domain integration. Kim et al. (2003, 2004) performed a comparative study between the rigid-body vehicle model and a multi-body vehicle model on the extremely soft cohesive soil of deep-seabed. The Euler angles are frequently used for kinematics of rigid body motion (e.g. Goldstein, 1980; Haug, 1989). It is convenient for description of body rotation. However, there are some difficulties to use in numerical computation because of the large number of trigonometric functions involved and some singular orientations. Euler parameters are used much in the field of aerodynamics and multibody dynamics, because the transformation matrix using Euler parameters is expressed by algebraic terms and has no singular orientation.