A comparison study of biologically inspired propulsion systems for an autonomous underwater vehicle

The field of Autonomous Underwater Vehicles (AUVs) has increased dramatically in size and scope over the past two decades. Application areas for AUVs are numerous and varied; from deep sea exploration, to pipeline surveillance to mine clearing. However, one limiting factor with the current technology is the duration of missions that can be undertaken and one contributing factor to this is the efficiency of the propulsion system, which is usually based on marine propellers. As fish are highly efficient swimmers greater propulsive efficiency may be possible by mimicking their fish tail propulsion system. The main concept behind this work was therefore to investigate whether a biomimetic fish-like propulsion system is a viable propulsion system for an underwater vehicle and to determine experimentally the efficiency benefits of using such a system. There have been numerous studies into biomimetic fish like propulsion systems and robotic fish in the past with many claims being made as to the benefits of a fish like propulsion system over conventional marine propulsion systems. These claims include increased efficiency and greater manoeuvrability. However, there is little published experimental data to characterise the propulsive efficiency of a fish like propulsive system. Also, very few direct experimental comparisons have been made between biomimetic and conventional propulsion systems. This work attempts to address these issues by directly comparing experimentally a biomimetic underwater propulsion system to a conventional propulsion system to allow for a better understanding of the potential benefits of the biomimetic system. This work is split into three parts. Firstly, the design and development of a novel prototype vehicle called the RoboSalmon is covered. This vehicle has a biomimetic tendon drive propulsion system which utilizes one servo motor for actuation and has a suite of onboard sensors and a data logger. The second part of this work focuses on the development of a mathematical model of the RoboSalmon vehicle to allow for a better understanding of the dynamics of the system. Simulation results from this model are compared to the experimental results and show good correlation. The final part of the work presents the experimental results obtained comparing the RoboSalmon prototype with the biomimetic tail system to the propeller and rudder system. These experiments include a study into the straight swimming performance, recoil motion, start up transients and power consumption. For forward swimming the maximum surge velocity of the RoboSalmon was 0.18ms-1 and at this velocity the biomimetic system was found to be more efficient than the propeller system. When manoeuvring the biomimetic system was found to have a significantly reduced turning radius. The thesis concludes with a discussion of the main findings from each aspect of the work, covering the benefits obtained from using the tendon drive system in terms of efficiencies and manoeuvring performance. The limitations of the system are also discussed and suggestions for further work are included

Control of Autonomous Underwater Vehicles

In this thesis an overview of Autonomous Underwater Vehicles (AUV) is presented which covers the advancements in AUV technology in last two decades, different components of AUV and the applications of AUVs. A glimpse on AUV research in India is presented. A nonlinear model of AUV is obtained through kinematics and dynamics equation which is linearized about an operating point to get linearized pitch & depth plane model. A two loop controller (PI control) is used to control the pitch and in turn the depth of the AUV. After having developed, simulated and analyzed the pitch and depth controller for a single AUV, we focus our attention towards developing formation control of three AUVs. The formation control for multiple Autonomous Underwater Vehicles (AUVs) is considered in spatial motions.The objective is to drive a leader AUV along a desired trajectory, and make the follower AUVs keep a desired formation with respect to the leader’s configuration in 3-dimensional spaces (leader-follower formation control). Also, an obstacle avoidance scheme, using pitch and depth control, is used to avoid static obstacles in the path of AUV. The results of the above three control objectives such as tracking control of AUV, controller for avoiding obstacles and formation control of multiple AUVs are presented and discussed in the thesis

Control and guidance systems for the navigation of a biomimetic autonomous underwater vehicle

The field of Autonomous Underwater Vehicles (AUVs) has increased dramatically in size and scope over the past three decades. Application areas for AUVs are numerous and varied, from deep sea exploration, to pipeline surveillance to mine clearing. The main concept behind this work was the design and the implementation of a control and guidance system for the navigation of a biomimetic AUV. In particular, the AUV analysed in this project tries to imitate the appearance and approximate the swimming method of an Atlantic Salmon and, for this reason, has been called RoboSalmo

Experimental Investigation into the Boundary Layer of a Robotic Anguilliform Propulsor

Boundary layer information local to three longitudinal positions has been characterized for a 130 cm long biomimetic self-propulsor known as NEELBOT-1.1 that swims with undulatory anguilliform-like motions, via analysis of stereo particle image velocimetry (PIV) measurements for key moments in the undulation cycle and for numerous combinations of swimming conditions and motion parameters, ideal and non-ideal. No obvious turbulent flow structures or indications of boundary layer separation were observed at nonzero advance speeds, and skin friction coefficients were subsequently estimated for magnitude relative to the dynamic pressure associated with operation at the design swimming speed of Uo = 0.25 m/s. Estimates were correlated with measurements made for an oscillating and non-oscillating cylindrical test article that were benchmarked by initial mono PIV investigations of steady laminar flow over a flat plate at zero incidence which was tested while stationary and oscillating in its own plane. Behavior of boundary layer profiles pertaining to the robot, apparently significantly influenced by the traveling flexion waves characteristic of the anguilliform motions, is clearly distinguished from local oscillatory flow structures related to the other two test articles. Approximately 10–15% increases in local skin friction are observed for the robot over similar conditions for the cylinder, and downstream vortex shedding is readily observed for the oscillating cylinder. The results of this thesis will be used in validation of numerical analyses performed in parallel with this research for the purpose of calculating the time-mean frictional drag experienced by the robot and to determine whether it can produce enough thrust to overcome its drag without simultaneously increasing it beyond realizable thrust generation capabilities. Theoretical hydrodynamic descriptions of the wake velocity field agreed well with previous PIV measurements, but the theory does not treat viscous effects. Furthermore, the preliminary semi-empirical, quasi-static attempts to estimate frictional drag were shown to under-predict the actual drag by net force measurements taken while towing the robot at its design speed which was undulating for that expected swimming speed, hence the necessity of this thesis as further investigation

Design and Evaluation of a Propulsion System for Small, Compact, Low-Speed Maneuvering Underwater Vehicles

Underwater vehicles used to perform precision inspection and non-destructive evaluation in tightly constrained or delicate underwater environments must be small, have low-speed maneuverability and a smooth streamlined outer shape with no appendages. In this thesis, the design and analysis of a new propulsion system for such underwater vehicles is presented. It consists primarily of a syringe and a plunger driven by a linear actuator and uses different inflow and outflow nozzles to provide continuous propulsive force. A prototype of the proposed propulsion mechanism is built and tested. The practical utility and potential efficacy of the system is demonstrated and assessed via direct thrust measurement experiments and by use of an initial proof-of-concept test vehicle. Experiments are performed to enable the evaluation and modelling of the thrust output of the mechanism as well as the speed capability of a vehicle employing the propulsion system

Underwater Vehicles

For the latest twenty to thirty years, a significant number of AUVs has been created for the solving of wide spectrum of scientific and applied tasks of ocean development and research. For the short time period the AUVs have shown the efficiency at performance of complex search and inspection works and opened a number of new important applications. Initially the information about AUVs had mainly review-advertising character but now more attention is paid to practical achievements, problems and systems technologies. AUVs are losing their prototype status and have become a fully operational, reliable and effective tool and modern multi-purpose AUVs represent the new class of underwater robotic objects with inherent tasks and practical applications, particular features of technology, systems structure and functional properties

Investigation into the Dynamics and Control of an Underwater Vehicle-Manipulator System

This study addresses the detailed modeling and simulation of the dynamic coupling between an underwater vehicle and manipulator system. The dynamic coupling effects due to damping, restoring, and inertial effects of an underwater manipulator mounted on an autonomous underwater vehicle (AUV) are analyzed by considering the actuator and sensor characteristics. A model reference control (MRC) scheme is proposed for the underwater vehicle-manipulator system (UVMS). The effectiveness of the proposed control scheme is demonstrated using numerical simulations along with comparative study between conventional proportional-integral-derivative (PID) control. The robustness of the proposed control scheme is also illustrated in the presence of external disturbances and parameter uncertainties

Fluid-structure interaction modeling on a 3D ray-strengthened caudal fin

In this paper, we present a numerical model capable of solving the fluid-structure interaction problems involved in the dynamics of skeleton-reinforced fish fins. In this model, the fluid dynamics is simulated by solving the Navier-Stokes equations using a finite-volume method based on an overset, multi-block structured grid system. The bony rays embedded in the fin are modeled as nonlinear Euler-Bernoulli beams. To demonstrate the capability of this model, we numerically investigate the effect of various ray stiffness distributions on the deformation and propulsion performance of a 3D caudal fin. Our numerical results show that with specific ray stiffness distributions, certain caudal fin deformation patterns observed in real fish (e.g. the cupping deformation) can be reproduced through passive structural deformations. Among the four different stiffness distributions (uniform, cupping, W-shape and heterocercal) considered here, we find that the cupping distribution requires the least power expenditure. The uniform distribution, on the other hand, performs the best in terms of thrust generation and efficiency. The uniform stiffness distribution, per se, also leads to 'cupping' deformation patterns with relatively smaller phase differences between various rays. The present model paves the way for future work on dynamics of skeleton-reinforced membranes

Aerospace medicine and biology: A continuing bibliography with indexes, supplement 204

This bibliography lists 140 reports, articles, and other documents introduced into the NASA scientific and technical information system in February 1980