scholarly journals Increase in Stability of an X-Configured AUV through Hydrodynamic Design Iterations with the Definition of a New Stability Index to Include Effect of Gravity

2021 ◽  
Vol 9 (9) ◽  
pp. 942
Author(s):  
Lakshmi Miller ◽  
Stefano Brizzolara ◽  
Daniel J. Stilwell
Keyword(s):  
Dynamic Stability ◽  
Autonomous Underwater Vehicle ◽  
Fluid Dynamic ◽  
Vertical Plane ◽  
Stability Index ◽  
Lumped Parameter Model ◽  
Restoring Force ◽  
Baseline Design ◽  
Course Stability ◽  
Hull Design

A study about the effect of different configurations of stationary and movable appendages on the dynamic stability of an autonomous underwater vehicle (AUV) is presented. A new stability index that can be used to assess dynamic stability in the vertical plane is derived. It improves upon the vertical plane stability index by accurately accounting for the contribution of hydrostatic forces to dynamic stability, even at low speeds. The use of the new stability index is illustrated by applying it to a set of AUV configurations based on an AUV initially designed at Virginia Tech and built by Dive Technologies. The applicability of this index depends on the speed of the craft. The range of applicability in terms of speed is presented for the DIVE craft as an example. The baseline design of the DIVE craft has asymmetry in the vertical plane and symmetry in the horizontal plane. A virtual planar motion mechanism (VPMM) is used to obtain the hydrodynamic coefficients of the hull. Design iterations are performed on the baseline design by varying the appendages in shape and size, adding appendages and adding features on appendages. The best and the baseline design from this effort are incorporated in a 6 DOF lumped-parameter model (LPM) to compare results of a straight line maneuver. A computational fluid dynamic (CFD) tool is used to obtain the trajectory comparison of turn-circle maneuver for these two designs. A principal conclusion is the important contribution of a hydrostatic restoring force at low-moderate speeds by using GVgrav and the influence of design of control surfaces, both stationary and non-stationary, in the achievement of control-fixed course stability.

Dynamic Stability Analysis of a Flexible Rotor Filled With Liquid Based on Three-Dimensional Flow

2018 ◽  
Vol 141 (5) ◽  
Author(s):  
Guangding Wang ◽  
Huiqun Yuan
Keyword(s):  
Dynamic Stability ◽  
Numerical Technique ◽  
Fluid Dynamic ◽  
Dynamic Pressure ◽  
Three Dimensional ◽  
Frequency Equation ◽  
Fourier Series Expansion ◽  
Flexible Rotor ◽  
Three Dimensional Flow ◽  
Dimensional Flow

This paper deals with the dynamic stability of a flexible liquid-filled rotor. On the basis of three-dimensional flow, the fluid perturbation motion is analyzed and the fluid–structure interaction equation is established, combining with continuity equation, the expression of fluid force exerted on rotor is derived in terms of Fourier series expansion. Considering the complex nonlinear relationship between fluid dynamic pressure and the rotor deformation function, they are expanded in terms of the eigenfunction of a dry rotor. The whirling frequency equation of a flexible rotor partially filled with liquid is obtained based on the rotor static equilibrium equation. Finally, the numerical technique is used to analyze the dynamic stability of the rotor system, and the influences of system parameters on unstable region are discussed.

Dynamic stability index and vibration analysis of a flexible Stewart platform

2007 ◽  
Vol 307 (3-5) ◽  
pp. 495-512 ◽  
Author(s):  
Parthajit Mukherjee ◽  
Bhaskar Dasgupta ◽  
A.K. Mallik
Keyword(s):  
Dynamic Stability ◽  
Vibration Analysis ◽  
Stability Index ◽  
Stewart Platform

Development of a Dynamic Stability Simulator for Articulated and Conventionaltractors Useful for Real-Time Safety Devices

2013 ◽  
Vol 394 ◽  
pp. 546-553 ◽  
Author(s):  
Fabrizio Mazzetto ◽  
Marco Bietresato ◽  
Renato Vidoni
Keyword(s):  
Real Time ◽  
Dynamic Stability ◽  
Stability Problem ◽  
Stability Index ◽  
Real Field ◽  
Circular Trajectory ◽  
Safety Devices ◽  
Test Platform ◽  
Agricultural Tractors ◽  
The Stability

The safety of agricultural tractors drivers is a very actual topic, especially when tractors operate on side slopes, such as in terraced vineyards. This work approaches the stability problem of articulated tractors by modelling, simulating and quantifying the safety of the driver with respect to both roll and pitch overturns. First of all, an articulated tractor has been modelled and simplified, after that a stability index has been defined and calculatedin several simulated slope conditions when the tractor travels along a circular trajectory; then, the obtained results have beencompared with respect to a conventional tractor. This work is a preliminary studyfor a tilting test platform for real vehicles, capable to reproduce real field conditions (slope, obstacles, roughness). Finally, some directives on how exploiting the obtained results for real-time safety devices have been formulated.

Inner Flow-Induced Buckling of Fiber-Reinforced Polymeric Catenary Risers

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Dimitrios G. Pavlou
Keyword(s):  
Dynamic Stability ◽  
Natural Frequencies ◽  
Inertial Force ◽  
Motion Equation ◽  
Fiber Reinforced ◽  
Flexible Riser ◽  
Restoring Force ◽  
Surrounding Water ◽  
Buckling Modes ◽  
Detailed Interpretation

Abstract Production and deep-sea mining risers should have sufficient flexibility to avoid severe loading due to vessel motions. Free hanging catenary is the simplest and cheapest configuration because of the ease of installation and the minimal requirements for subsea infrastructure. The interaction of the inner flow with the moving riser dominates the dynamic stability of the system. In the present work, the motion equation for a long, multilayered, fiber-reinforced polymeric (FRP) flexible riser is formulated, and a numerical method for critical inner flow velocities causing buckling in risers is proposed. Taking into account the motion equation, the physics of the inner flow-induced buckling phenomena is analyzed and a detailed interpretation of the terms of the motion equation is carried out. With the aid of transfer matrices and finite elements, the dynamic buckling modes and the natural frequencies are determined. It is proved that the dynamic stability of the riser is affected by the balance of the elastic flexural restoring force, the centrifugal force of the fluid flow in the curved portions, the Coriolis force of the fluid, the inertial force of the fluid and pipe mass, and the damping due to the effect of the surrounding water.

scholarly journals Stability and nonlinear controllability analysis of a quadrotor-like autonomous underwater vehicle considering variety of cases

2018 ◽  
Vol 15 (6) ◽  
pp. 172988141881940 ◽  
Author(s):  
Liwei Kou ◽  
Ji Xiang ◽  
Yanjun Li ◽  
Jingwei Bian
Keyword(s):  
Horizontal Plane ◽  
Autonomous Underwater Vehicle ◽  
Vertical Plane ◽  
Underwater Vehicle ◽  
Plane Motion ◽  
Small Time ◽  
Degree Of Freedom ◽  
Local Controllability ◽  
Actuation System ◽  
Nonlinear Controllability

A quadrotor-like autonomous underwater vehicle that is similar to, yet different from quadrotor unmanned aerial vehicles, has been reported recently. This article investigates the stability and nonlinear controllability properties of the vehicle. First, the 12-degree-of-freedom model of the vehicle deploying an X shape actuation system is developed. Then, a stability property is investigated showing that the vehicle cannot be stabilized by a time invariant smooth state feedback law. After that, by adopting a nonlinear controllability analysis tool in geometric control theory, the small-time local controllability of the vehicle is analyzed for a variety of cases, including the vertical plane motion, the horizontal plane motion, and the three-dimensional space motion. Finally, different small-time local controllability conditions for different cases are developed. The result shows that the small-time local controllability holds for vertical plane motion and horizontal plane motion. However, the full degree of freedom kinodynamics model (i.e. 12 states) of the vehicle does not satisfy the small-time local controllability from zero-velocity states.

Numerical and Experimental Analyses of a Variable Buoyancy System for an Autonomous Underwater Vehicle

2021 ◽  
Vol 163 (A1) ◽  
pp. 87-100
Author(s):  
B K Tiwari ◽  
R Sharma
Keyword(s):  
Autonomous Underwater Vehicle ◽  
Autonomous Underwater Vehicles ◽  
Vertical Plane ◽  
Linear Quadratic Regulator ◽  
High Energy ◽  
Experimental Investigations ◽  
Linear Quadratic ◽  
Positive Displacement ◽  
Depth Control ◽  
Lqr Controller

Autonomous Underwater Vehicles (AUVs) are widely used for marine survey, in both the coastal and deep sea areas and they are applicable to both civil and defense applications. They are pre-programmed and can operate without human intervention and this makes them attractive to many marine industries. A concern with AUVs is the high energy consumption required by their thrusters for depth control, buoyancy change and manoeuvrability and that adversely affects their performance and endurance. This paper presents the design and development of novel stand-alone variable buoyancy system for AUVs and investigates its performance through numerical and experimental investigations. The design idea is based upon the Pump Driven Variable Buoyancy System (PDVBS) and uses a hydraulic based method to control the buoyancy. The VBS is integrated into a medium sized AUV of 3 m length and the performance of the vehicle in vertical plane is investigated. The results are presented for a buoyancy change requirement of 5 kg and a diaphragm type positive displacement pump, with a buoyancy change rate of 5 kg/min, is utilized. Depth control performance of the AUV and its hovering capabilities, at a desired depth of 60 m using the Linear Quadratic Regulator (LQR) controller, are analysed in detail. Finally, the results indicate that the designed and developed VBS is effective in changing the buoyancy and controlling the heave velocity. These two features are expected to provide higher endurance and better performance in AUVs involved in rescue/attack operations.

scholarly journals The total cavopulmonary connection resistance: a significant impact on single ventricle hemodynamics at rest and exercise

2008 ◽  
Vol 295 (6) ◽  
pp. H2427-H2435 ◽  
Author(s):  
Kartik S. Sundareswaran ◽  
Kerem Pekkan ◽  
Lakshmi P. Dasi ◽  
Kevin Whitehead ◽  
Shiva Sharma ◽  
...  
Keyword(s):  
Heart Rate ◽  
Single Ventricle ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Lumped Parameter Model ◽  
Total Cavopulmonary Connection ◽  
Dynamic Simulations ◽  
Lumped Parameter ◽  
The Impact ◽  
Cavopulmonary Connection

Little is known about the impact of the total cavopulmonary connection (TCPC) on resting and exercise hemodynamics in a single ventricle (SV) circulation. The aim of this study was to elucidate this mechanism using a lumped parameter model of the SV circulation. Pulmonary vascular resistance (1.96 ± 0.80 WU) and systemic vascular resistances (18.4 ± 7.2 WU) were obtained from catheterization data on 40 patients with a TCPC. TCPC resistances (0.39 ± 0.26 WU) were established using computational fluid dynamic simulations conducted on anatomically accurate three-dimensional models reconstructed from MRI ( n = 16). These parameters were used in a lumped parameter model of the SV circulation to investigate the impact of TCPC resistance on SV hemodynamics under resting and exercise conditions. A biventricular model was used for comparison. For a biventricular circulation, the cardiac output (CO) dependence on TCPC resistance was negligible (sensitivity = −0.064 l·min−1·WU−1) but not for the SV circulation (sensitivity = −0.88 l·min−1·WU−1). The capacity to increase CO with heart rate was also severely reduced for the SV. At a simulated heart rate of 150 beats/min, the SV patient with the highest resistance (1.08 WU) had a significantly lower increase in CO (20.5%) compared with the SV patient with the lowest resistance (50%) and normal circulation (119%). This was due to the increased afterload (+35%) and decreased preload (−12%) associated with the SV circulation. In conclusion, TCPC resistance has a significant impact on resting hemodynamics and the exercise capacity of patients with a SV physiology.

Effects of Peroneal Muscles Fatigue on Dynamic Stability Following Lateral Hop Landing: Time to Stabilization Versus Dynamic Postural Stability Index

2019 ◽  
Vol 28 (1) ◽  
pp. 17-23 ◽  
Author(s):  
Kazem Malmir ◽  
Gholam Reza Olyaei ◽  
Saeed Talebian ◽  
Ali Ashraf Jamshidi ◽  
Majid Ashraf Ganguie
Keyword(s):  
Dynamic Stability ◽  
Postural Stability ◽  
Force Plate ◽  
Stability Index ◽  
Voluntary Contraction ◽  
Lower Extremity Injury ◽  
Resultant Vector ◽  
Time To Stabilization ◽  
Quasi Experimental ◽  
Dynamic Postural Stability

Context: Dynamic stability is a necessary requirement in many sports competitions. Muscle fatigue, which can impair stability, may be occurred in many sports competitions in which lateral movements and landing repeated frequently. Objective: To assess the effects of peroneal muscles fatigue on dynamic stability following lateral hop landing through measuring time to stabilization (TTS) and dynamic postural stability index (DPSI). Design: Quasi-experimental. Setting: Laboratory study. Participants: A total of 20 recreationally active, healthy males with no lower-extremity injury during the previous 6 months participated in this study. Intervention: Participants performed a lateral hop on a force plate before and immediately after a fatigue intervention using a Biodex dynamometer. For inducing fatigue, the participant made a prolonged eversion effort with 40% of the maximal voluntary contraction. Fatigue was met when the eversion torque declined by 50% of the initial value. TTS and DPSI were calculated using sequential averaging method and relevant formulas, respectively. Main Outcome Measures: Premeasures and postmeasures of TTS in the anteroposterior, mediolateral and vertical directions, resultant vector of TTS, stability indices in the anteroposterior, mediolateral and vertical directions, and DPSI. Results: Means of the DPSI or its components did not change significantly due to fatigue (P > .05). Means of the TTS in the anteroposterior and mediolateral directions, and the mean of the resultant vector of the TTS increased significantly after fatigue (P < .05). Conclusions: The question that the dynamic stability is affected or not affected by fatigue depends on which of the TTS or DPSI is used for analysis. The TTS may be a sensitive measure to detect subtle changes in postural stability due to fatigue. But, the DPSI which may be changed after a more strenuous fatigue may be related to actual fatiguing situations.

scholarly journals Energy-saving control of long-range autonomous underwater vehicle vertical plane based on human simulating intelligent control method

2020 ◽  
Vol 17 (5) ◽  
pp. 172988142094474
Author(s):  
Hao Xu ◽  
Guo-cheng Zhang ◽  
Yu-shan Sun ◽  
Shuo Pang
Keyword(s):  
Energy Consumption ◽  
Long Range ◽  
Intelligent Control ◽  
Autonomous Underwater Vehicle ◽  
Control Method ◽  
Vertical Plane ◽  
Vertical Motion ◽  
Underwater Vehicle ◽  
Simulation Experiments ◽  
Wide Range

The long-range autonomous underwater vehicle is a new underwater vehicle with capability of stereoscopic observation of the ocean over a wide range of time series. This article proposed a novel control strategy for the long-range autonomous underwater vehicle considering the energy consumption. The vertical motion model of long-range autonomous underwater vehicle and the mathematical model of energy consumption of motion actuators are established in this article, and the maneuverability simulation experiments were carried out to analyze its motion and energy consumption characteristics. A hybrid controller based on human simulating intelligent control and S-plane control is designed. Considering the moment caused by the asymmetry of the hull in motion, an adaptive dynamic control allocation strategy is designed. Simulation experiments are conducted to demonstrate the performance of the scheme proposed.

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