This paper describes the process of developing a novel biomimetic autonomous underwater vehicle (AUV) inspired by jellyfish locomotion. Our interest in an AUV that mimics jellyfish locomotion stems from the jellyfish’s simplistic and robust physiology and neurological makeup. Jellyfish swimming gates are controlled by a neural architecture consisting of an outer nerve ring and an inner nerve ring. The inner nerve ring is responsible for incorporating the sensory input from the outer ring and innervating the subumbrellar swimming muscles. Additionally, cells in the inner ring generate endogenous rhythms and act as pacemakers. The system of pacemakers generates the highly maneuverable swimming gates that can be observed in jellyfish; swimming vertically, turning and hovering. The swimming gates have been shown to correspond to the dynamics of the response of a system of coupled identical van der Pol oscillators. These oscillators are capable of creating in-phase, out-of-phase and “asymmetric” phase-locked dynamics that are plausibly related to the basic modes of jellyfish locomotion of coordinated bout swimming, hovering, and turning, respectively. In addition, the system of oscillators is fault tolerant; if the modeled system of oscillators is disrupted, analogous to sections of the jellyfish being damaged, the oscillators adjust and maintain effective swimming gates allowing the jellyfish to remain mobile. The simplicity and fault tolerance of the oscillatory system makes it an ideal model for a locomotion control system for an AUV. The objective of the Jellyfish AUV project is to emulate the locomotion and control mechanisms of the biological jellyfish to create a simple and robust AUV, which is both highly maneuverable and low in cost. The iterative design process that resulted in a working Jellyfish AUV is detailed in this paper. Numerous designs were created, exploring different combinations of actuator mechanisms, body types and control systems. Different actuators were evaluated for their ability to meet our design requirements. These actuators ranged from off the shelf servos to the more exotic shape memory alloys (SMAs) and ionic polymer metal composites (IPMCs.) By the completion of the prototyping phase of the Jellyfish AUV project we had created a low cost AUV using off the shelf components including, servos, linkages and a microprocessor based control system. The input to the servos was derived from a system of coupled oscillators which were tuned to mimic the observation jellyfish gates. In addition, using the Jellyfish AUV prototype, we showed that the identified servo input patterns roughly translate to swimming, hovering, and turning.
Synthesis of a PID-controller of a trim robust control system of an autonomous underwater vehicle
