An optimal nonlinear guidance logic for the trajectory tracking of supercavitating vehicles

Supercavitating vehicles (SV) are a class of high-speed autonomous underwater vessels. They present a great challenge in designing the guidance law in comparison with the traditional autonomous underwater vehicles. This is due to the fact that their constraints and working environment are much more complex. To tackle the above challenge, an optimal nonlinear midcourse guidance logic is proposed by considering the wake terminal guidance and the remote target attack tasks. The proposed guidance logic is optimized by using an efficient genetic algorithm to obtain its optimal parameters. The results from our simulation case study suggest that the proposed guidance logic can meet both the motion requirements and navigation constraints while effectively cooperating with the wake terminal guidance. Moreover, it has potential in reducing the energy consumption to significantly improve the overall vehicle energy efficiency

Some ways of hydrodynamic fin application for underwater supercavitating vehicles

The paper deals with considering the two non-traditional ways of application of hydrodynamic fins for a high-speed underwater supercavitating vehicles. The techniques for active roll stabilization and course control of the moving supercavitating vehicle are developed that use the regulation of the roll angle by means of both the special roll fin, and the automatic error-closing control system. The examples of a computer simulation of the course of maneuvering of the supercavitating vehicle controlled with the vertical hydrodynamic fins having zero roll angle stabilization are given along with the cases of the roll angle regulation. A method for determining the equilibrium motion parameters (balancing) of the supercavitating vehicle is developed for the case when a pair of identical horizontal cavity-piercing fins is used for complete or partial compensation of the vehicle's weight. The examples of a computer simulation of the motion of the supercavitating vehicle with horizontal fins in both the planing avoidance mode, and the combined mode are presented. It is shown that the steady-state longitudinal motion of the balanced supercavitating vehicle in the planing avoidance mode is stable "in the small", in contrast to its motion with planing in the cavity. It is found that, the horizontal fins in the combined motion mode can play a damping role suppressing the supercavitating vehicle motion instability "in the small", however, after a long time interval, the motion loses the global stability. The computer simulation suggests that the activation of the automatic depth stabilization makes the supercavitating vehicle motion stable in general in all the examined cases. Also it is revealed that course maneuverability of the supercavitating vehicle controlled with the vertical fins is maximal when starting the balancing in planing avoidance mode, but it deteriorates dramatically when starting the balancing in the combined mode.Рассмотрены два нетрадиционных способа применения гидродинамических рулей при движении высокоскоростных подводных суперкавитирующих аппаратов. Разработан метод активной стабилизации движения суперкавитирующего аппарата по крену и метод управления его движением по курсу путем регулирования угла крена с помощью специального руля крена и автоматической системы управления с обратной связью. Приведены примеры компьютерного моделирования маневрирования суперкавитирующего аппарата по курсу при управлении с помощью вертикальных гидродинамических рулей со стабилизацией нулевого угла крена и путем регулирования угла крена. Разработан метод нахождения равновесных значений параметров движения (балансировки) суперкавитирующего аппарата в случае, когда для полной или частичной компенсации его веса используется пара одинаковых горизонтальных рулей, проникающих из каверны в воду. Приведены примеры компьютерного моделирования движения суперкавитирующего аппарата с горизонтальными рулями в режиме без глиссирования и в смешанном режиме. Показано, что установившееся продольное движение сбалансированного суперкавитирующего аппарата без глиссирования, в отличие от его движения в режиме глиссирования в каверне, является устойчивым "в малом". Установлено, что в смешанном режиме движения горизонтальные рули могут играть демпфирующую роль, подавляя неустойчивость движения аппарата "в малом", однако на большом интервале времени движение теряет устойчивость в целом. Моделирование показало, что применение автоматической стабилизации движения по глубине во всех рассмотренных случаях делает его устойчивым в целом. Показано также, что курсовая маневренность такого аппарата при управлении с помощью вертикальных рулей максимальна при начальной балансировке в режиме без глиссирования, но резко ухудшается при начальной балансировке в смешанном режиме.Розглянуто два нетрадиційні способи застосування гідродинамічних рулів при русі високошвидкісних підводних суперкавітуючих апаратів. Розроблено метод активної стабілізації руху суперкавітуючого апарату за креном і метод керування його рухом за курсом шляхом регулювання кута крену за допомогою спеціального руля крену й автоматичної системи керування зі зворотним зв'язком. Наведено приклади комп'ютерного моделювання маневрування суперкавітуючого апарату за курсом при керуванні за допомогою вертикальних гідродинамічних рулів зі стабілізацією нульового кута крену і шляхом регулювання кута крену. Розроблено метод знаходження рівноважних значень параметрів руху (балансування) суперкавітуючого апарату у випадку, коли для повної чи часткової компенсації ваги апарату використовується пара однакових горизонтальних рулів, які проникають з каверни у воду. Наведено приклади комп'ютерного моделювання руху суперкавітуючого апарату з горизонтальними рулями в режимі без глісування і в змішаному режимі. Показано, що усталений поздовжний рух збалансованого суперкавітуючого апарату без глісування, на відміну від його руху в режимі глісування в каверні, є стійким "в малому". Встановлено, що в змішаному режимі руху горизонтальні рулі можуть грати демпфуючу роль, пригнічуючи нестійкість руху апарату "в малому", однак на великому інтервалі часу рух втрачає стійкість в цілому. Моделювання показало, що застосування автоматичної стабілізації руху по глибині у всіх розглянутих випадках робить його стійким в цілому. Показано також, що курсова маневровість такого апарату при керуванні за допомогою вертикальних рулів максимальна при початковому балансуванні в режимі без глісування, але різко погіршується при початковому балансуванні в змішаному режимі

Bubble density gradient with laser detection : a wake-homing scheme for supercavitating vehicles

The poor mobility and complex target motion estimation are the two main challenges in the anti-ship attack missions of high-speed guided missiles. In this study, a new wake-homing scheme of supercavitating vehicles is proposed using the gradient wake flow phenomenon. The basic principle of the wake-homing with laser detection and the information which can be obtained are studied. According to the idiosyncrasy of laser detection, the geometrical characteristics of the vessel wake, and the bubble distribution characteristics, the three-dimensional model of bubble density gradient in horizontal plane of the maneuvering target ship wake flow is first built; the guidance law based on the gradient wake flow is designed and tested. Then, simulation results show the validity of the model wake, the guidance law based on the wake gradient information can accurately track the target. From the simulation results, we also can see that the new wake-homing scheme effectively improve the hit probability, reduce the range of loss, reduce power consumption and gentle guidance trajectory, greatly reduce the mobility requirements of the supercavitating vehicle

Aeronautical Engineering: A special bibliography, supplement 60

This bibliography lists 284 reports, articles, and other documents introduced into the NASA scientific and technical information system in July 1975

Control Methods for High-Speed Supercavitating Vehicles

Supercavitation is an emerging technology that enables underwater vehicles to reach un- precedented speed. With proper design of cavitator attached to the vehicle nose, the vehicle body is surrounded by water vapor cavity, eliminating skin friction drag. This technology offers unprecedented drag reduction, though poses problems for vehicle design. The gas bubble surrounding the hull introduces highly coupled dynamic behavior, representing a challenge for the control designer. Development of stable, controllable supercavitating vehi- cles requires solution for several open problems. This dissertation addresses the problem of control oriented modeling, stability augmentation, and reference tracking using parameter dependent control techniques for supercavitating vehicles.\ud The thesis is divided into three parts. A nonlinear dynamical model capturing the most important properties of the vehicle motion is developed from a control design perspective. The model includes memory effects associated with the time evolution of the cavity and uses lookup tables to determine forces.\ud To aid understanding the cavity-vehicle interaction, a longitudinal control scenario is developed for a simplified longitudinal dynamical model with guaranteed properties. Sig- nificant insight is gained on planing behavior and operating envelope using constrained control inputs.\ud Extending the longitudinal control problem, a linear parameter varying model of the coupled motion is developed to provide a platform for parameter dependent control syn- thesis. The mathematical model is scheduled with aerodynamic angles, uses steady-state approximation of the cavity, leading to uncertainty in the governing equations. Two Linear Parameter Varying (LPV) controllers are synthesized for the angle rate tracking problem, taking uncertainty into account. One uses traditional decoupled loops for pitch-, roll- and yaw-rate tracking. Ignoring the cross coupling, leads to more tractable subproblems . A controller, taking advantage of the coupling, is also presented in the thesis. The complexity of the coupled dynamics prohibits the synthesis of the controller as a single entity. Sev- eral LPV controllers synthesized for smaller overlapping regions of the parameter space are blended together, providing a single controller for the full flight envelope. Time-domain simulations of different vehicle-controller configurations, implemented on high-fidelity sim- ulations, provide insight into the capabilities of the supercavitating vehicle

Aeronautical Engineering: A continuing bibliography, supplement 120

This bibliography contains abstracts for 297 reports, articles, and other documents introduced into the NASA scientific and technical information system in February 1980

Dictionary of Hydromechanics

This Dictionary is intended for a broad readership including practising naval architects who wish to acquire and apply knowledge of hydrodynamics and also physicists and theoretical hydrodynami-cists who wish to apply their particular knowledge to the solution of ship problems

Aeronautical engineering: A special bibliography, supplement 44

This special bibliography lists 249 reports, articles, and other documents introduced into the NASA scientific and technical information system in April 1974

Hydrodynamic behaviour of gliding hydrofoil crafts

A new type of high-speed craft, called a Gliding-Hydrofoil Craft (GHC), has recently been developed in Jiangsu University of Science and Technology, China. This craft is similar to a planing hull but with a hydrofoil in the front part of its body. The fixed hydrofoil improves the seakeeping properties and stability of the craft compared with a conventional planing hull. In addition, the GHC has a more simple structure and higher stability when compared to a hydrofoil craft. Unlike conventional planing hulls and hydrofoil crafts, the study of hydrodynamics of GHC has been overlooked. The present work aims to advance our understanding on hydrodynamics of GHC, both model tests and numerical investigations are presented. To study its hydrodynamic characteristics, model tests are carried out in a towing tank, and the total resistance, trim angle and wetted area of the craft in the cases with different Froude numbers are measured. For the purpose of comparison, model tests have also been carried out for the hull without the hydrofoil. This thesis presents analysis on the experimental data and discusses the effects of the submerged depth and initial attack angle of the hydrofoil on the hydrodynamic features of the GHC. On this basis, the FLUENT software is then adopted to numerically investigate the hydrodynamics of the GHC. The accuracy of the FLUENT addressing this problem is validated by comparing the numerical solutions with the experimental data. The validation cases include 2D hydrofoil in current, Wigley hull with steady forward speed. Good agreement between numerical results and experimental data was obtained. Considering the significance of the turbulence involved in the problem, especially near the hydrofoil, a numerical investigation aiming to find a suitable turbulence model has been carried out. After being validated, 3D numerical simulations on both the planing craft and the GHC in steady flow are considered. The resistance coefficient, pressure coefficient and wave pattern with different Froude number are investigated. Some results are compared with experiment data obtained in the model tests. The wave pattern, velocity field and pressure distribution near the hulls are discussed in detail as well as the influence of the hydrofoil. Finally, the hydrodynamic performance of GHC in unsteady flow is investigated. Three cases were considered: ship berthing, leaving the harbour and turning navigation direction; which are very commonly seen unsteady examples in reality. The preliminary results presented in this thesis have confirmed the significant effects due to the unsteady procedure and imply the need of carrying out unsteady simulations in the future

The Hydrodynamic and Hydroelastic Responses of Rigid and Flexible Surface-Piercing Hydrofoils in Multi-Phase Flows

Ventilation and vaporous cavitation are multi-phase flows with critical effects upon the performance, stability, and controllability of high-speed marine vessels. The entrainment of air from the free surface (ventilation) or the formation of water-vapor-filled voids (cavitation) can cause dramatic reductions in the efficiency of lifting surfaces, large dynamic loads, and strongly hysteretic flows. This thesis investigates the hydrodynamic and hydroelastic performance of surface-piercing hydrofoils through experiments on three hydrofoil models (one rigid and two flexible), which were tested in a towing tank and in a free-surface cavitation tunnel. The results reveal four distinct flow regimes, which are defined by their parametric stability regions. The concept of flow stability is used to describe transitional flow and resulting hysteresis to yield a holistic description of ventilation on surface piercing hydrofoils. These concepts are used to develop scaling relations for the washout of ventilated cavities. Hydrodynamic loads are shown to vary as functions of the attack angle, immersion depth, forward speed, cavitation number, and flow regime. Flexibility of the hydrofoil model modifies the hydrodynamic loads and stability regions through hydroelastic coupling. Flow-induced vibration and lock-in are shown to result from coherent vortex shedding at all speeds tested. Fitted transfer functions are used to develop reduced-order models and to estimate modal parameters of a flexible hydrofoil, demonstrating that both modal resonance frequencies and modal damping ratios are dependent upon immersion depth, forward speed, and flow regime. A robust shape-sensing strut is also developed to measure the textit{in-situ} structural motions of deformable lifting-surfaces in real time. The work presented in this thesis contributes significantly toward the study of multi-phase flows and fluid-structure interactions through the establishment of experimental methodologies, the construction of a versatile experimental platform with original instrumentation, and the collection and thorough interpretation of a large, rich dataset. The insights gained from the work significantly improve our understanding of ventilation, cavitation, and their interactions with structural dynamics, thereby aiding future researchers and designers to perform robust experiments, validate numerical solvers, and design safe, efficient, and controllable marine devices.PHDNaval Architecture & Marine EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/135891/1/cmharwoo_1.pd