Influence of Sea Current on Stabilization of Moments and Forces in Risers

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Iwona Adamiec-Wójcik ◽  
Lucyna Brzozowska ◽  
Stanisław Wojciech
Keyword(s):  
Optimization Problem ◽  
Bending Moment ◽  
Constant Load ◽  
Sea Waves ◽  
Dynamic Optimization Problem ◽  
Finite Segment ◽  
Sea Current ◽  
Vertical Displacements ◽  
Finite Segment Method ◽  
Horizontal Displacements

Abstract One of the important aspects in the design of floating, production, storage, and offloading (FPSO) systems is to ensure a fairly constant load on risers despite the base motion caused by sea waves. The paper presents the authors’ own formulation of the finite segment method for dynamic analysis of risers and its application to the solution of a dynamic optimization problem. This task consists in defining vertical displacements of the top of the riser which compensate horizontal movements of the vessel or platform caused by sea waves. Compensation involves stabilizing the bending moment in the risers or the force in the connection of the riser and the wellhead. The model takes into account the influence of the sea by means of Morison equations. Different sea current profiles are considered. Calculation of vertical displacements of the top of the riser is carried out in order to stabilize the force or the bending moment for a defined function of horizontal displacements of the riser.

Quasi-Static Modelling and Computer Simulation of Hanging Cables on Robots

1994 ◽  
Author(s):  
Li-Ping Yang ◽  
Shin-Min Song
Keyword(s):  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Finite Segment ◽  
Revolute Joints ◽  
Highly Nonlinear ◽  
Finite Segment Method ◽  
Newton Raphson ◽  
Static Modelling ◽  
Parameter Perturbation Method ◽  
Raphson Method

Abstract This paper presents a computer method to simulate the quasi-static motion of hanging cables on robots. The shape of the flexible cable is changing during motion and the finite segment method is applied to determine its configuration. The cable is modeled as a series of rigid segments segments connected together through revolute joints in 2-D case and spherical joints in 3-D case. The elasticity of cable is represented by torsional springs at the joints. In both cases, a set of highly nonlinear equations are derived based on force equilibrium and the Newton-Raphson method is applied to calculate the solution. In order to assure convergence and improve computational efficiency, the parameter perturbation method is applied together with the Newton-Raphson method. Also, some computational strategies are developed to simplify the three dimensional problem. Finally, the developed methods are demonstrated in displaying the motion of a hanging cable which is attached to a revolute joint, a prismatic joint and a three degrees of freedom robot.

Studying and Simulation Analysis for Rubber Track of Rescue Robot

2013 ◽  
Vol 457-458 ◽  
pp. 643-648
Author(s):  
Hong Wei Ma ◽  
Chuan Wei Wang
Keyword(s):  
Simulation Analysis ◽  
Flexible Multibody Dynamics ◽  
Single Step ◽  
Secondary Development ◽  
Body System ◽  
Finite Segment ◽  
Flexible Joint ◽  
Rescue Robot ◽  
Finite Segment Method ◽  
Stress And Deformation

Rubber track of Rescue Robot was dispersed into limited number of track blocks by the method of finite segment method used in flexible multibody dynamics. The two neighbor track blocks were connected by springs and dampers, then the moldel was become a multi-rigid-body system with flexible joint. Rubber track was modeled with the help of macro command used in the secondary development of virtual prototype technique software named ADAMS. Flexible connection was realized by the method of adding Bushing, and then a new method was proposed to build rubber track model. The obstacle-surmounting simulation of climbing the barrier of single step was carried out. It intuitively reflected the stress and deformation under the condition of climbing barrier. The method mentioned above laid good foundation for studying obstacle-surmounting abilities of the rubber-tracked robots and dynamic characteristic of the tracks.

scholarly journals Tracking Moving Optima Using Kalman-Based Predictions

2008 ◽  
Vol 16 (1) ◽  
pp. 1-30 ◽  
Author(s):  
Claudio Rossi ◽  
Mohamed Abderrahim ◽  
Julio César Díaz
Keyword(s):  
Evolutionary Algorithms ◽  
Dynamic Optimization ◽  
Optimization Problem ◽  
Moving Objects ◽  
Fitness Landscape ◽  
Experimental Comparison ◽  
Motion Information ◽  
Dynamic Optimization Problem ◽  
First Order ◽  
Robotic Application

The dynamic optimization problem concerns finding an optimum in a changing environment. In the field of evolutionary algorithms, this implies dealing with a time-changing fitness landscape. In this paper we compare different techniques for integrating motion information into an evolutionary algorithm, in the case it has to follow a time-changing optimum, under the assumption that the changes follow a nonrandom law. Such a law can be estimated in order to improve the optimum tracking capabilities of the algorithm. In particular, we will focus on first order dynamical laws to track moving objects. A vision-based tracking robotic application is used as testbed for experimental comparison.

Shear Lag Effect of Continuous Curved Box Girder with Initial Curvature

2012 ◽  
Vol 538-541 ◽  
pp. 1701-1704
Author(s):  
You Ming Wu ◽  
Yong Jun Lu ◽  
Han Shi
Keyword(s):  
Model Tests ◽  
Shear Lag ◽  
Shear Lag Effect ◽  
Box Girder ◽  
Finite Segment ◽  
Homogeneous Solutions ◽  
Initial Curvature ◽  
Lag Effect ◽  
Finite Segment Method ◽  
Displacement Patterns

The homogeneous solutions of the governing differential equations for shear lag are used as the displacement patterns of the finite segment are presented. A finite segment model with consideration of initial curvature, bending, torsion and shear lag is established. In addition, the tests of the two-span continuous curved box girder and numerical calculations of the model tests by finite segment method and finite element method are made. The results of the model tests and numerical calculation are consistent with each other. An actual example was given to investigate the shear lag effect of a continuous curved box girder under load. The research results show that the initial curvature has an obvious influence on the shear lag effect of a continuous curved box girder.

Deformation in Multilayer Stacked Assemblies

1990 ◽  
Vol 112 (1) ◽  
pp. 30-34 ◽  
Author(s):  
Tsung-Yu Pan ◽  
Yi-Hsin Pao
Keyword(s):  
Thermal Loading ◽  
Bending Moment ◽  
Radius Of Curvature ◽  
Element Analysis ◽  
First Order ◽  
Strain Behavior ◽  
Linear Elastic ◽  
Nonlinear Stress ◽  
Order Polynomial ◽  
Vertical Displacements

A linear-elastic analytical model has been developed to describe the deformed geometry of a multi-layered stack assembly subject to thermal loading. The model is based on Timoshenko’s bimetal thermostat analysis [1] and consists of a series of first-order polynomial equations. The radius of curvature, bending moment, force, horizontal and vertical displacements can be determined numerically. These quantities match well with finite element analysis. Calculations for silicon power transistor stacks are presented in order to demonstrate the model capability. The results from this analyitcal model have been found to correlate well with experimental measurements when an appropriate secant modulus is used to represent the nonlinear stress-strain behavior of solder.

Sign in / Sign up

Export Citation Format

Share Document