Mobility and agility analysis of a multi-legged subsea robot system

Abstract

This paper presents a unified mathematical framework for the analysis of mobility and agility of a multi-legged subsea robot. The aim of this research is to analyze a dynamic performance on the multi-legged robot in an underwater environment conditions with hydrodynamic forces, seabed friction, gravity, buoyancy, and so on. The dynamic performance is represented by both translational acceleration (mobility) and rotational acceleration (agility) that ensures no slip at each foot of robot under given a robot's configuration, joint torque boundaries, and environment conditions. To analyze the performance, this work includes the derivation of a dynamic equation and a joint torque constraint equation and the establishment of mathematical framework by using its two equations. The dynamic equation is the relationship equation between joint actuator torques and body acceleration, which is derived from subsea robot dynamics and force and acceleration relationship of body and leg. The joint torque constraint equation for ensuring no slip at the contact point is derived from frictional force constraint conditions. In this paper, the resultant accelerations are represented as polytopes through the mathematical framework and given joint torque bounds. To verify the proposed method, the simulations of 4 and 6-legged robots were performed with the consideration of differential pose, environment, and tidal current.