Steady motion of underwater gliders and stability analysis

A disc-type underwater glider (DTUG) has a highly symmetrical shape and is characterized by omnidirectional characteristics and high maneuverability in small bodies of water. To further explore the disc shape’s advantages and characteristics in steering motion, DTUG motion was simulated by Matlab/Simulink. Based on the structural characteristics of DTUG, the motion control equations were established. The simulation of DTUG’s steering motion is carried out and compared with a previous DTUG (LUNA). The sensitivity analysis and Lyapunov stability analysis were also conducted. The results showed that the in situ steering motion can be realized by controlling the position of the center of gravity (CG) of DTUG without moving vertically, which facilitates rapid adjustment of the yaw angle and flexible movement in small bodies of water. The in situ steering motion was significantly affected by the control parameters. The parameter that had the greatest effect on it can be obtained through sensitivity analysis, which can guide DTUG to better adjust the yaw angle under different conditions. The stability analysis showed that the DTUG can remain stable within the range of the control parameter.

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Stability Analysis of Multibody Systems With Long Flexible Bodies Using the Moving Modes Method and Its Application to Railroad Dynamics

Journal of Computational and Nonlinear Dynamics ◽

10.1115/1.4025284 ◽

2013 ◽

Vol 9 (1) ◽

Cited By ~ 3

Author(s):

Rosario Chamorro ◽

José L. Escalona ◽

Antonio M. Recuero

Keyword(s):

Stability Analysis ◽

Multibody Systems ◽

Moving Load ◽

Steady Motion ◽

Frame Of Reference ◽

The Body ◽

Flexible Body ◽

Shape Functions ◽

Load Following ◽

New Formulation

In order to model a long flexible body subjected to a moving load within multibody systems, the flexibility can be considered by using a special floating frame of reference approach. In this approach the body deformations are described using shape functions defined in a frame of reference that follows the load. The definition of the deformation shape functions in the load-following frame of reference leads to additional terms of the inertia forces of the flexible body. This method was recently presented by the authors and named the moving modes method. The selected shape functions used in this work are the steady deformation shown by a flexible straight body subjected to a moving load. In this investigation the new formulation is applied to the steady motion and stability analysis of railroad vehicles moving on curved tracks.

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Performance and Stability Analysis for ZJU Glider

Marine Technology Society Journal ◽

10.4031/mtsj.48.3.6 ◽

2014 ◽

Vol 48 (3) ◽

pp. 88-103 ◽

Cited By ~ 8

Author(s):

Canjun Yang ◽

Shilin Peng ◽

Shuangshuang Fan

Keyword(s):

Stability Analysis ◽

Low Cost ◽

Equilibrium Analysis ◽

Size Analysis ◽

Moving Mass ◽

Spatial And Temporal Scales ◽

Pitch Control ◽

Underwater Gliders ◽

Ocean Sampling ◽

Analytical Approaches

AbstractUnderwater gliders provide an effective, low-cost method for sampling the ocean over large spatial and temporal scales. In this paper, we present a series of theoretical analyses to provide guidelines for vehicle design, which are used to develop a coastal 200-m-depth underwater glider known as the Zhejiang University (ZJU) glider. The ZJU glider uses a longitudinally actuated moving mass for pitch control and a rudder for turning control. Computational methods and analytical approaches are chosen to solve the viscous and inviscid terms of glider hydrodynamics, respectively. Steady flight equilibrium analysis gives the varied range of moving mass location for pitch control and varied vehicle volume for buoyancy control. Size analysis investigates the effects of glider geometric parameters on motion performance. For wings-level flight, we describe the variation in the maximum lift-to-drag ratio corresponding to a given vehicle size and speed. For turning motion, we investigate the manner in which the turning performance varies with vertical rudder configuration. Stability analysis determines the relationship between the stability of glider motion and the locations of the glider wings and rudder. Pool trials indicate that the ZJU glider functions well in water and is capable of serving as a sensor platform for ocean sampling.

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On the existence of three-dimensional convection in a rectangular box containing fluid-saturated porous material

Journal of Fluid Mechanics ◽

10.1017/s0022112078001664 ◽

1978 ◽

Vol 87 (2) ◽

pp. 385-394 ◽

Cited By ~ 23

Author(s):

Joe M. Straus ◽

Gerald Schubert

Keyword(s):

Stability Analysis ◽

Porous Material ◽

Three Dimensional ◽

Steady Motion ◽

Finite Amplitude ◽

Two Dimensional ◽

Stable Forms ◽

Rayleigh Numbers ◽

Convective Rolls ◽

Box Dimensions

On the basis of a stability analysis of finite amplitude, two-dimensional convection, we have determined the dimensions of boxes containing fluid-saturated porous material in which convection is necessarily unsteady or steady and three-dimensional. For certain box sizes, convective rolls are unstable at Rayleigh numbers Ra lower than 380, the value below which rolls are stable forms of convection between infinite parallel planes. For Ra = 100 and 200, it appears unlikely that there are any box dimensions for which there is not a stable (possibly multicellular) two-dimensional steady motion. At Ra = 340 and 400, boxes in which rolls are unstable have heights which range from one to five times their horizontal dimensions.

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