Zero-G Class Underwater Robots and Unrestricted Attitude Control using Control Moment Gyros

Abstract

The "zero-G" is designated as a new class of underwater robot that is capable of unrestricted attitude control. A novel control scheme based on internal actuation using control moment gyros (CMGs) provides zero-G class autonomous underwater vehicles (AUVs) with this unique freedom in control. A geometric study of the singularities of a CMG pyramid is performed and together with considerations of the inverse kinematics of attitude control forms the basis of a global steering law that exactly achieves the desired torques, whilst guaranteeing real-time singularity avoidance within a constrained workspace. The development of the CMG actuated zero-G class underwater robot "IKURA" is described. The robot demonstrates its unique manoeuvring capabilities by performing vertically pitched diving and surfacing in surge. The three-dimensional manoeuvring capabilities allow zero-G class underwater robots to plan and optimise their missions in a fully three-dimensional manner, in a way that has not been possible previously.