Energy Based Gait Control of an Under Actuated Robotic Fish

Abstract

The recent explosion of interest in sub sea research and industries has led to a demand for efficient versatile submarine robots to perform interaction and survey tasks. Whilst most of these robots employ conventional propeller or thruster based locomotion, there has been a growing interest in the development of biologically inspired robotic swimmers (or robotic fish). In a hope to gain some of the manoeuvrability and efficiency advantages characteristic of their biological counterparts. Early robotic fish achieved their gait, by directly controlling the relative angel between each vertebrae, using multiple active actuators. Following observations that many biological locomotory gaits, utilize spring dynamics to create efficient oscillatory motion with minimal active input, there has been a recent trend towards the development of under-actuated robotics utilizing dynamics to achieve harmonic locomotory gaits, examples can be found in McGeer's passive dynamic walkers, or MIT's compliant swimming devices. For a harmonic dynamic system, the path is dependent on the total energy in the system. By controlling the total energy in the system the gait can be controlled by varying a single degree of freedom. This paper aims to explore the potential for energy based control to produce an effective propulsive gait. © 2012 by World Scientific Publishing Co. Pte. Ltd.