scholarly journals Сombined ships stability analysis at the stage of design study

2021 ◽  
pp. 29-35
Author(s):  
Ilya A. Gulyaev Gulyaev ◽  
Evgeniy P. Ronnov
Keyword(s):  
Stability Analysis ◽  
Optimization Problems ◽  
Mutual Influence ◽  
Static Stability ◽  
Wind Effect ◽  
Stability Assessment ◽  
Design Study ◽  
Hull Design ◽  
The Stability ◽  
Russian River

. A method of stability analysis for combined ship (oil carrier/platform ship type) at the stage of design study is presented. It should be noted that not all of ship’s main seaworthiness and operational characteristics are the result of a simple addition of the characteristics of an oil carrier and a platform ship. Their mutual influence takes place, which should be taken into account when analysing the stability in the multivariant optimization problems of internal and external design of such ships. This leads to the requirement to adjust the known methods of stability analysis at the initial stages of ship design, which was the purpose of the present work and its originality. Taking into account the multivariance of the task and the hull design type, the stability assessment will be carried out through the analysis of the metacentric height extreme value on the assumption that the requirements of Russian River Register for admissible heeling angle at static wind effect are met. In order to account for nonlinearity of static stability curve when inclining up to the angles of deck immersion into water and emergence of bilge, it is suggested to apply an approximate method of metacentric radius determination. The proposed method of combined ship stability assessment is recommended to apply at the stage of justification and analysis of ship’s key elements as a limitation in the problems of mathematical modeling of optimization of such type of ships. The method allows to exclude from further consideration at the design study stage the possible options that do not meet the requirements of seaworthiness.

Instability of Heated Panels in Supersonic Air Flow

2008 ◽  
Vol 33-37 ◽  
pp. 1101-1108
Author(s):  
Zhi Chun Yang ◽  
Wei Xia
Keyword(s):  
Stability Analysis ◽  
Stability Boundary ◽  
Boundary Curve ◽  
Static Stability ◽  
Static Deformation ◽  
Limit Cycle Oscillation ◽  
Aerodynamic Load ◽  
Aeroelastic System ◽  
Aerodynamic Pressure ◽  
The Stability

An investigation on the stability of heated panels in supersonic airflow is performed. The nonlinear aeroelastic model for a two-dimensional panel is established using Galerkin method and the thermal effect on the panel stiffness is also considered. The quasi-steady piston theory is employed to calculate the aerodynamic load on the panel. The static and dynamic stabilities for flat panels are studied using Lyapunov indirect method and the stability boundary curve is obtained. The static deformation of a post-buckled panel is then calculated and the local stability of the post-buckling equilibrium is analyzed. The limit cycle oscillation of the post-buckled panel is simulated in time domain. The results show that a two-mode model is suitable for panel static stability analysis and static deformation calculation; but more than four modes are required for dynamic stability analysis. The effects of temperature elevation and dimensionless parameters related to panel length/thickness ratio, material density and Mach number on the stability of heated panel are studied. It is found that panel flutter may occur at relatively low aerodynamic pressure when several stable equilibria exist for the aeroelastic system of heated panel.

Walking Stability Analysis of Multi-Legged Crablike Robot over Slope

2013 ◽  
Vol 572 ◽  
pp. 636-639
Author(s):  
Xi Chen ◽  
Gang Wang
Keyword(s):  
Mathematical Model ◽  
Stability Analysis ◽  
Stability Criterion ◽  
Stability Margin ◽  
Static Stability ◽  
Matlab Simulation ◽  
And Performance ◽  
The Stability ◽  
The Mathematical Model ◽  
The Relationship

This paper deals with the walking stability analysis of a multi-legged crablike robot over slope using normalized energy stability margin (NESM) method in order to develop a common stabilization description method and achieve robust locomotion for the robot over rough terrains. The robot is simplified with its static stability being described by NESM. The mathematical model of static stability margin is built so as to carry out the simulation of walking stability over slope for the crablike robot that walks in double tetrapod gait. As a consequence, the relationship between stability margin and the height of the robots centroid, as well as its inclination relative to the ground is calculated by the stability criterion. The success and performance of the stability criterion proposed is verified through MATLAB simulation and real-world experiments using multi-legged crablike robot.

scholarly journals The Stability Analysis of a Multi-Port Single-Phase Solid-State Transformer in the Electromagnetic Timescale

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2250 ◽  
Author(s):  
Rui Wang ◽  
Qiuye Sun ◽  
Qifu Cheng ◽  
Dazhong Ma
Keyword(s):  
Stability Analysis ◽  
Solid State ◽  
Single Phase ◽  
Control Strategies ◽  
Current Source ◽  
Practical Stability ◽  
Stability Assessment ◽  
Solid State Transformer ◽  
The Stability ◽  
Signal Sinusoïdal

This paper proposes an overall practical stability assessment for a multi-port single-phase solid-state transformer (MS3T) in the electromagnetic timescale. When multiple stable subsystems are combined into one MS3T, the newly formed MS3T has a certain possibility to be unstable. Thus, this paper discusses the stability assessment of the MS3T in detail. First and foremost, the structure of the MS3T and its three stage control strategies are proposed. Furthermore, the stability analysis of each of the MS3T’s subsystems is achieved through the closed loop transfer function of each subsystem, respectively, including an AC-DC front-end side converter, dual active bridge (DAB) with a high-frequency (HF) or medium-frequency (MF) transformer, and back-end side incorporating DC-AC and dc-dc converters. Furthermore, the practical impedance stability criterion in the electromagnetic timescale, which only requires two current sensors and one external high-bandwidth small-signal sinusoidal perturbation current source, is proposed by the Gershgorin theorem and Kirchhoff laws. Finally, the overall stability assessment, based on a modified impedance criterion for the MS3T is investigated. The overall practical stability assessment of the MS3T can be validated through extensive simulation and hardware results.

Maximizing Walking Step Length for a Near Omni-Directional Hexapod Robot

2004 ◽  
Author(s):  
James P. Schmiedeler ◽  
Nathan J. Bradley ◽  
Brett Kennedy
Keyword(s):  
Stability Analysis ◽  
Step Length ◽  
Static Stability ◽  
Optimization Approach ◽  
Computationally Efficient ◽  
Constant Height ◽  
Planning Algorithm ◽  
Two Phases ◽  
The Stability ◽  
Path Planning Algorithm

A foot path planning algorithm is presented for a robot with six limbs symmetrically located on the faces of its hexagonal body, enabling it to walk at a constant height with an alternating tripod gait. The symmetry results in near omni-directional locomotion capability, so the algorithm is formulated for walking in any direction and at any height. The approach is to determine the maximum length foot path through each limb’s workspace and then modify those foot paths based upon static stability analysis. The stability analysis is conducted in two phases to ensure stability without excessively reducing step length. Compared to an optimization approach, the algorithm yields foot paths within 9.1% of the maximal foot paths for all directions and heights. Unlike the optimization approach, the developed algorithm is computationally efficient enough to be implemented in realtime.

scholarly journals Effect of Frequency Coupling on Stability Analysis of a Grid-Connected Modular Multilevel Converter System

Energies ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6580
Author(s):  
Yixing Wang ◽  
Qianming Xu ◽  
Josep M. Guerrero
Keyword(s):  
Stability Analysis ◽  
Coupling Effect ◽  
Modular Multilevel Converter ◽  
Stability Assessment ◽  
Analysis Method ◽  
Multilevel Converter ◽  
Single Input Single Output ◽  
Impedance Model ◽  
Frequency Coupling ◽  
The Stability

Due to the internal dynamics of the modular multilevel converter (MMC), the coupling between the positive and negative sequences in impedance, which is defined as frequency coupling, inherently exists in MMC. Ignoring the frequency coupling of the MMC impedance model may lead to inaccurate stability assessment, and thus the multi-input multi-output (MIMO) impedance model has been developed to consider the frequency coupling effect. However, the generalized Nyquist criterion (GNC), which is used for the stability analysis of an MIMO model, is more complicated than the stability analysis method applied on single-input-single-output (SISO) models. Meanwhile, it is not always the case that the SISO model fails in the stability assessment. Therefore, the conditions when the MIMO impedance model needs to be considered in the stability analysis of an MMC system should be analyzed. This paper quantitatively analyzes the effect of frequency coupling on the stability analysis of grid-connected MMC, and clarifies the frequency range and grid conditions that the coupling effect required to be considered in the stability analysis. Based on the quantitative relations between the frequency coupling and the stability analysis of the grid-connected MMC system, a simple and accurate stability analysis method for the grid-connected MMC system is proposed, where the MIMO impedance model is applied when the frequency coupling has a significant effect and the SISO impedance model is used if the frequency coupling is insignificant.

The Stability Analysis on the Different Types of Single Layer Latticed Shell

2013 ◽  
Vol 788 ◽  
pp. 598-601
Author(s):  
Jun Qiang Wu ◽  
Yu Cui
Keyword(s):  
Stability Analysis ◽  
Static Load ◽  
Single Layer ◽  
Static Stability ◽  
Different Types ◽  
Practical Engineering ◽  
Small Structure ◽  
The Stability ◽  
Lattice Shell ◽  
Better Than

This single-layer spherical reticulated shell has the advantages of reasonable stress,beautiful appearance ,fast construction,is widely applied in practical engineering. Through the static stability analysis of three kinds of single-layer spherical lattice shell structure using ansys, we get them in the uniform deformation under static load, the modal, buckling load. The results show that: The Kiewitt latticed shells displacement is small, structure is stable, better than SchwedLer and lianfang.

A Novel Technique for the Stability of Multiple Frequency Resonators

1999 ◽  
Author(s):  
Nejat Olgac
Keyword(s):  
Stability Analysis ◽  
Time Delays ◽  
Dimensional Space ◽  
Multiple Delays ◽  
Stability Assessment ◽  
Multiple Frequency ◽  
Novel Technique ◽  
Controlled Systems ◽  
The Stability ◽  
The Given

Abstract A novel stability analysis is presented for feedback controlled systems with multiple unrelated time delays. The concern arises in an effort creating multi-frequency delayed resonators. Despite the broad treatment of single time delay cases there is no mechanism to analyze the stability of systems involving multiple delays. The proposed method is an advancement over the D-subdivision methodology. It reduces the stability based subdivisions and search to a single dimensional space instead of multiple dimensional platform. The method is very simple to implement and it results in the stability assessment of the given system as the number of unstable root pairs present.

scholarly journals Modeling and Stability Analysis of a Novel Voltage-Oriented Power Coordination Controlled Constant-Frequency AC Microgrid System

Electronics ◽  
2021 ◽  
Vol 10 (16) ◽  
pp. 1935
Author(s):  
Xiuhui Tang ◽  
Daming Zhang ◽  
Dan Xiao ◽  
Miao Li
Keyword(s):  
Stability Analysis ◽  
Power Distribution ◽  
Reactive Power ◽  
Mutual Influence ◽  
Constant Frequency ◽  
Model Stability ◽  
Power Regulation ◽  
The Stability ◽  
Grid Side ◽  
Ac Microgrid

The conventional AC microgrid power regulation method is achieved using dual undulations of the grid-side voltage and frequency, whose complex variables and processes make the system less efficient and stable. For this problem, this paper proposes a novel two-hierarchical small signal model stability analysis for islanded AC microgrid systems with a designed power regulation algorithm under the constant frequency, mainly aimed at the continual switching microgrids, and considers the future expansion. MATLAB/Simulink simulations and experiments are conducted to validate the feasibility. It is found that there is a strong consistency between the stability of primary and overall systems, and that two key parameters affect the stability properties. Discussing the mutual influence of various parameters, k1 is positively correlated with control intensity and k2 determines the proportion of reactive power distribution in each power generation. Contrasting with the previous complex processes, the unique points of this method are the simplicity of calculation, parameter induction, response testability, strong operability, and system extensibility. The conclusion is that this constant frequency power control is simple, feasible, and stable under several specified conditions.

Tip-Over Stability Analysis of Mobile Boom Cranes With Swinging Payloads

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Andreas Rauch ◽  
William Singhose ◽  
Daichi Fujioka ◽  
Taft Jones
Keyword(s):  
Stability Analysis ◽  
Dynamic Analysis ◽  
Dynamic Stability ◽  
Dynamic Method ◽  
Static Stability ◽  
Multibody Simulation ◽  
The World ◽  
The Stability ◽  
Boom Crane ◽  
Mobile Base

Mobile boom cranes are used throughout the world to perform important and dangerous manipulation tasks. The usefulness of these cranes is greatly improved if they can utilize their mobile base when they lift and transfer a payload. However, crane motion induces payload swing. The tip-over stability is degraded by the payload oscillations. This paper presents a process for conducting a stability analysis of such cranes. As a first step, a static stability analysis is conducted to provide basic insights into the effects of the payload weight and crane configuration. Then, a semi-dynamic method is used to account for payload swing. The results of a full-dynamic stability analysis using a multibody simulation of a boom crane are then compared to the outcomes of the simpler approaches. The comparison reveals that the simple semi-dynamic analysis provides good approximations for the tip-over stability properties. The results of the stability analyses are verified by experiments. The analysis in this paper provides useful guidance for the practical tip-over stability analysis of mobile boom cranes and motivates the need to control payload oscillation.

Stability and Dynamic Analyses of Transmission Tower-Line Systems Subjected to Conductor Breaking

2017 ◽  
Vol 17 (06) ◽  
pp. 1771013 ◽  
Author(s):  
Jia-Xiang Li ◽  
Hong-Nan Li ◽  
Xing Fu
Keyword(s):  
Stability Analysis ◽  
Failure Modes ◽  
Dynamic Instability ◽  
Progressive Collapse ◽  
Static Stability ◽  
Transmission Tower ◽  
Initial Tension ◽  
Line System ◽  
Ice Loads ◽  
The Stability

Ice loads exerted on the transmission line can increase the probability of conductor breaking, which will lead to the stability failure of transmission towers. In this paper, a transmission tower-line system is established for two towers and three span lines. Then the nonlinear static stability analysis and nonlinear dynamic stability analysis induced by the conductor breaking are carried out to obtain the load versus displacement curves, while studying the failure modes of the transmission tower-line system. Moreover, the ice load and initial eccentricity are considered in the numerical simulation. In addition, a parametric analysis is performed to investigate the influence of span, insulator length and initial tension force on the stability failure of the system. The results show that the dynamic instability will occur earlier than the static instability due to the dynamic impact effect and conductor breaking with ice loads can lead to the progressive collapse of the transmission tower-line system. Finally, the span length has the greatest effect on the response of transmission tower caused by conductor breaking.

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