Mobility and agility of a multi-legged subsea robot considering tidal current

This paper presents a unified method for analysis of a mobility and agility of a multi-legged subsea robot in consideration of the tidal current and frictional ground contact. The aim of this research is to analyze an influence of tidal current on the multi-legged robot by utilization of hydrodynamic forces acting on its body and legs. This method derives the region of both linear acceleration (mobility) and angular acceleration (agility) that ensures no slip at each foot with given torque bound of each joint and hydrodynamic force due to underwater environment. After deriving a differential equation including joint actuator torques and body acceleration from subsea robot dynamics and frictional contact condition, we have derived a joint torque constraint equation for ensuring no slip at the contact point. Under the torque limits in infinite norm-sense, the resultant accelerations are represented as a polytope. The proposed method is verified by simulations of a simplified 6-legged subsea robot.