The Influence of Hold-Back Vessels on the Operation of a DP Drilling Rig: Control System and Stability Analysis

2017 ◽  
Author(s):  
Alex S. Huang ◽  
Eduardo Aoun Tannuri ◽  
Asdrubal N. Queiroz Filho ◽  
André S. S. Ianagui ◽  
Douglas G. T. Yuba ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Dynamic Instability ◽  
Simplified Model ◽  
Fast Time ◽  
Dynamic Simulations ◽  
Positioning Systems ◽  
Time Dynamic ◽  
Drilling Rig ◽  
The Stability ◽  
Drilling Rigs

Certain maritime operations require the accurate positioning of the vessel, and in order to accomplish that DP (dynamic positioning) systems were developed. It combines the information obtained from sensors with the expected dynamic of the ship to better estimate its actual position and the external forces, and with those information the controller allocates the forces among the available actuators so the vessel keeps a desired position. In situations where drift of the vessel could cause great harm (human, material or environmental losses) it might be necessary to provide additional safeguards. One possible solution is to connect an AHTS (anchor handling tug supply) to the original DP vessel, in order to complement the forces generated by its thrusters. However as shown by Jensen (2008) and IMCA M 185 (2012), this connection could actually degrade the position keeping ability of the vessel, nullifying the purpose of improving the safety of the operation. The objective of the present paper is to confirm the hypothesis that the use of hold-back vessels to support DP drilling rigs may degrade the performance of the DP system, causing dynamic instability, and to determine the boundaries of operation under which this phenomenon occurs: sea state, parameters of the vessels and force transmitted by the hold-back vessel. Firstly, an analytical study of the system was done. It was considered a simplified model of two vessels connected by a cable with two degrees of freedom (one for each vessel), since the force applied by a cable is unidirectional. Using control theory, the limiting stiffness of the cable was determined by analyzing the poles of the system. Considering a catenary model for the connecting cable, it was possible to determine the maximum force that could be transmitted between the vessels without the system becoming unstable. The influence of the Kalman Filter in the stability of the system was also studied. Those results were then compared and confirmed with fast time dynamic simulations of the system, in which the influence of different environmental conditions were also added to the analysis. To complete the study, real time simulations were done on a full mission simulator, equipped with the original Kongsberg DP system for the drilling rig. The simplified model showed consistent results, validated by the simulations, demonstrating it can be a useful tool when analyzing the stability of two connected vessels.

Non-Linear Aeroelastic Stability of Wind Turbines

2013 ◽  
Vol 569-570 ◽  
pp. 531-538 ◽  
Author(s):  
Z.L. Zhang ◽  
M.T. Sichani ◽  
Jie Li ◽  
J.B. Chen ◽  
S.R.K. Nielsen
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Degrees Of Freedom ◽  
Dynamic Instability ◽  
Maximum Lyapunov Exponent ◽  
Moving Frames ◽  
Internal Resonances ◽  
Wind Turbine System ◽  
Non Linear ◽  
The Stability

As wind turbines increase in magnitude without a proportional increase in stiffness, the risk of dynamic instability is believed to increase. Wind turbines are time dependent systems due to the coupling between degrees of freedom defined in the fixed and moving frames of reference, which may trigger off internal resonances. Further, the rotational speed of the rotor is not constant due to the stochastic turbulence, which may also influence the stability. In this paper, a robust measure of the dynamic stability of wind turbines is suggested, which takes the collective blade pitch control and non-linear aero-elasticity into consideration. The stability of the wind turbine is determined by the maximum Lyapunov exponent of the system, which is operated directly on the non-linear state vector differential equations. Numerical examples show that this approach is robust for stability identification of the wind turbine system.

Stability and Dynamics of Axially Moving Unidirectional Plates Partially Immersed in a Liquid

2014 ◽  
Vol 14 (04) ◽  
pp. 1450010 ◽  
Author(s):  
Yan Qing Wang ◽  
Xing Hui Guo ◽  
Zhen Sun ◽  
Jian Li
Keyword(s):  
Degrees Of Freedom ◽  
Dynamic Instability ◽  
Plate Theory ◽  
Fluid Pressure ◽  
Added Mass ◽  
Chaotic Motions ◽  
Bernoulli’S Equation ◽  
Singular Functions ◽  
Axially Moving ◽  
The Stability

The stability and dynamics of an axially moving unidirectional plate partially immersed in a liquid and subjected to a nonlinear aerodynamic excitation are investigated. The method of singular functions is adopted to study the dynamic characteristics of the unidirectional plates with discontinuous characteristics. Nonlinearities due to large-amplitude plate motions are considered by using the classical nonlinear thin plate theory, with allowance for the effect of viscous structural damping. The velocity potential and Bernoulli's equation are used to describe the fluid pressure acting on the unidirectional plate. The effect of fluid on the vibrations of the plate may be equivalent to added mass of the plate. The formulation of added mass is obtained from kinematic boundary conditions of the plate–fluid interfaces. The system is discretized by Galerkin's method while a model involving two degrees of freedom, is adopted. Attention is focused on the behavior of the system in the region of dynamic instability, and several motions are found by numerical simulations. The effects of the moving speed and some other parameters on the dynamics of the system are also investigated. It is shown that chaotic motions can occur in this system in several certain regions of parameter space.

scholarly journals Methodology for Assessing the Stability of Drilling Rigs Based on Analytical Tests

Energies ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 8588
Author(s):  
Łukasz Bołoz ◽  
Artur Kozłowski
Keyword(s):  
Computational Model ◽  
Design Process ◽  
Computational Models ◽  
Dynamic Models ◽  
Graphical Representation ◽  
Underground Mining ◽  
Drilling Rig ◽  
Centre Of Gravity ◽  
The Stability ◽  
Drilling Rigs

Underground mining machines, such as wheel-tyre drilling rigs, are articulated and equipped with booms that project far beyond the undercarriage. Such a structure makes these machines prone to losing stability. Hence, it is necessary to analyse the distribution of masses and geometry as well as their broadly understood stability during the entire design process, taking into account many factors resulting from the manner and conditions of their operation. However, there are no appropriate computational models that would enable analytical tests to be carried out for machines with this kind of construction. This article is concerned with the author’s computational model, which allows the stability of single- and twin-boom drilling rigs to be quickly assessed. The model makes it possible to perform analyses without having to solve differential equations that are present in dynamic models or using specialist software based on CAD and CAE tools. The developed model allows determination of the pressure of wheels and jacks as a function of many important parameters and variables. Additionally, the distances of the centre of gravity from the tipping edge are calculated. The developed computational model was verified by comparing the obtained results with the results of the full dynamic model, the results of model tests carried out in the CAD/CAE program, and the results of empirical tests of wheel and jack pressures on the ground for the selected drilling rig. The model was subjected to verification and validation, which proved that it was fully correct and useful. The model was used to prepare a practical and user-friendly calculation sheet. Apart from the numerical values, the calculation sheet contains a graphical representation of the machine, the location of the centre of gravity, the tipping edges, as well as graphs of the wheel and jack pressures. Next, analytical tests of the stability of the selected drilling rig were carried out. The obtained calculation results are consistent with the results of empirical research. The computational model and the spreadsheet provide handy tools used during the design process by one of the Polish company’s producing drilling rigs.

Methodology for Definition of New Sectors for DP Assisted Offloading Operations in Spread Moored Platforms

2016 ◽  
Author(s):  
Ana Luisa de Barros Orsolini ◽  
Eduardo Aoun Tannuri ◽  
Felipe Santana Castelpoggi ◽  
Douglas Gustavo Takashi Yuba
Keyword(s):  
Risk Analysis ◽  
Static Analysis ◽  
Critical Conditions ◽  
Fast Time ◽  
Dynamic Simulations ◽  
Time Dynamic ◽  
Quantitative Analyses ◽  
Sector Angle ◽  
Definition Of ◽  
Real Time Simulations

This project defines a methodology for analyzing the proposition of expanding the operational sector of DP shuttle tankers in offloading operations in Spread Moored Platforms and still guaranteeing the operations’ safety. The methodology consists at first in an evaluation of the reduction of the operation’s downtime as a function of sector angle increase by performing static analysis. These simulations are calibrated and validated by performing fast time dynamic simulations. Then, a Preliminary Risk Analysis is made to assess the potential hazards associated with the operation on the new expanded sector and, if necessary, some quantitative analyses take place. Finally, the methodology proposes that real time simulations are performed so that most critical conditions are recreated in the presence of an experienced Captain so he can give his opinion on how safe the operation would be.

The Dynamic Simulations of the Ship Towing System in Random Waves

2009 ◽  
Vol 46 (02) ◽  
pp. 107-115
Author(s):  
Ming-Chung Fang ◽  
Jiun-Han Ju
Keyword(s):  
Degrees Of Freedom ◽  
Dynamic Properties ◽  
Time History ◽  
Random Waves ◽  
Dynamic Simulations ◽  
Operation Conditions ◽  
Runge Kutta Method ◽  
Course Stability ◽  
Calm Water ◽  
The Stability

In order to investigate the dynamic stability and safety for a ship towing system operated in waves, the present paper develops a nonlinear mathematical model, including seakeeping and maneuvering characteristics, to simulate dynamic behaviors of the towing system in random waves. In addition to waves, wind is also included in the calculations. The time history simulations of six degrees of freedom motion for both the towing and the towed ships are solved by the fourth-order Runge-Kutta method. Because of the waves, the dynamic properties including the towline tension, ship speeds, headings, and distance between two ships are different from those that occur in calm water. The effects of the towpoint's position, towline length, and towing speed on the ship course stability and towline tension are analyzed with respect to different wave and wind headings. In the present study, the suitable operation conditions for the ship towing system are investigated and can be suggested as a reference for improving the stability and safety of towing operation tasks at sea.

scholarly journals Velocity and acceleration level inverse kinematic calculation alternatives for redundant manipulators

Meccanica ◽  
2021 ◽  
Author(s):  
Dóra Patkó ◽  
Ambrus Zelei
Keyword(s):  
Degrees Of Freedom ◽  
Direct Method ◽  
Tracking Error ◽  
Inverse Kinematic ◽  
Linear Feedback ◽  
Joint Position ◽  
Stability Properties ◽  
Acceleration Level ◽  
Error Elimination ◽  
The Stability

AbstractFor both non-redundant and redundant systems, the inverse kinematics (IK) calculation is a fundamental step in the control algorithm of fully actuated serial manipulators. The tool-center-point (TCP) position is given and the joint coordinates are determined by the IK. Depending on the task, robotic manipulators can be kinematically redundant. That is when the desired task possesses lower dimensions than the degrees-of-freedom of a redundant manipulator. The IK calculation can be implemented numerically in several alternative ways not only in case of the redundant but also in the non-redundant case. We study the stability properties and the feasibility of a tracking error feedback and a direct tracking error elimination approach of the numerical implementation of IK calculation both on velocity and acceleration levels. The feedback approach expresses the joint position increment stepwise based on the local velocity or acceleration of the desired TCP trajectory and linear feedback terms. In the direct error elimination concept, the increment of the joint position is directly given by the approximate error between the desired and the realized TCP position, by assuming constant TCP velocity or acceleration. We investigate the possibility of the implementation of the direct method on acceleration level. The investigated IK methods are unified in a framework that utilizes the idea of the auxiliary input. Our closed form results and numerical case study examples show the stability properties, benefits and disadvantages of the assessed IK implementations.

Stability of Ring-Type MEMS Gyroscopes Subjected to Stochastic Angular Speed Fluctuation

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Samuel F. Asokanthan ◽  
Soroush Arghavan ◽  
Mohamed Bognash
Keyword(s):  
Angular Velocity ◽  
Degrees Of Freedom ◽  
Microelectromechanical Systems ◽  
Damping Ratio ◽  
Operating Conditions ◽  
System Stability ◽  
System Response ◽  
Ring Type ◽  
Mems Gyroscopes ◽  
The Stability

Effect of stochastic fluctuations in angular velocity on the stability of two degrees-of-freedom ring-type microelectromechanical systems (MEMS) gyroscopes is investigated. The governing stochastic differential equations (SDEs) are discretized using the higher-order Milstein scheme in order to numerically predict the system response assuming the fluctuations to be white noise. Simulations via Euler scheme as well as a measure of largest Lyapunov exponents (LLEs) are employed for validation purposes due to lack of similar analytical or experimental data. The response of the gyroscope under different noise fluctuation magnitudes has been computed to ascertain the stability behavior of the system. External noise that affect the gyroscope dynamic behavior typically results from environment factors and the nature of the system operation can be exerted on the system at any frequency range depending on the source. Hence, a parametric study is performed to assess the noise intensity stability threshold for a number of damping ratio values. The stability investigation predicts the form of threshold fluctuation intensity dependence on damping ratio. Under typical gyroscope operating conditions, nominal input angular velocity magnitude and mass mismatch appear to have minimal influence on system stability.

Study on human-induced vibration of a cable-stayed bridge without backstays located in abrupt valley

2021 ◽  
pp. 136943322110203
Author(s):  
Yanru Wu ◽  
Junxin Li ◽  
Qing Sun
Keyword(s):  
Empirical Formula ◽  
Dynamic Instability ◽  
Vertical Vibration ◽  
Comfort Level ◽  
Tuned Mass Dampers ◽  
Dynamic Simulations ◽  
Maximum Acceleration ◽  
Cable Stayed Bridge ◽  
Crowd Density ◽  
Lateral Modes

This research aims to assess the pedestrian comfort and to control human-induced vibration of an arch tower cable-stayed bridge without backstays located in canyon. Dynamic simulations of human-induced vibration were carried out with a mode-by-mode approach, and the results indicated that a total of seven lateral and vertical modes of the bridge may suffer from excessive vibrations at the design crowd density. Based on the periodic walking force, the structure response under pedestrian loads was evaluated performing dynamic analyses with two Finite Element models of the footbridge. A single tuned mass damper (STMD) control system was developed for control of human-induced vibration, which consisted of four tuned mass dampers mounted on the mid-span of bridge to enhance damping ratios of lively modes. The results indicate that the maximum acceleration for the first-order lateral and second-order vertical vibration at the design crowd density exceed the associated threshold values referring to the comfort level 1 (CL1) Criteria. The critical pedestrian number of lateral dynamic instability estimated by the Dallard’s empirical formula is much smaller than the dynamic design pedestrian number; and the Dallard’s empirical formula is applicable to estimate the critical pedestrian number of lateral dynamic instability for this bridge by comparing with Pedroe Inês footbridge. The damping ratios for both the vertical and lateral modes increase appreciably after installing the tuned mass dampers and no evidence of large-amplitude vibrations has been observed, leading to the realization of satisfactory comfort levels, which can provide reference for vibration reduction design of this kind of bridge.

scholarly journals Galloping Stability and Wind Tunnel Test of Iced Quad Bundled Conductors considering Wake Effect

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Xiaohui Liu ◽  
Ming Zou ◽  
Chuan Wu ◽  
Mengqi Cai ◽  
Guangyun Min ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Transmission Lines ◽  
Degrees Of Freedom ◽  
Wind Tunnel Test ◽  
Aerodynamic Coefficients ◽  
Wake Effect ◽  
Aerodynamic Coefficient ◽  
Set Up ◽  
The Stability ◽  
Three Degrees Of Freedom

A new quad bundle conductor galloping model considering wake effect is proposed to solve the problem of different aerodynamic coefficients of each subconductor of iced quad bundle conductor. Based on the quasistatic theory, a new 3-DOF (three degrees of freedom) galloping model of iced quad bundle conductors is established, which can accurately reflect the energy transfer and galloping of quad bundle conductor in three directions. After a series of formula derivations, the conductor stability judgment formula is obtained. In the wind tunnel test, according to the actual engineering situation, different variables are set up to accurately simulate the galloping of iced quad bundle conductor under the wind, and the aerodynamic coefficient is obtained. Finally, according to the stability judgment formula of this paper, calculate the critical wind speed of conductor galloping through programming. The dates of wind tunnel test and calculation in this paper can be used in the antigalloping design of transmission lines.

RTCONTACT: An Efficient Wheel-Rail Contact Algorithm for Real-Time Dynamic Simulations

2012 ◽  
Author(s):  
N. Bosso ◽  
A. Gugliotta ◽  
N. Zampieri
Keyword(s):  
Real Time ◽  
Computational Efficiency ◽  
Simulation Models ◽  
Experimental Tests ◽  
Contact Forces ◽  
Dynamic Simulations ◽  
Time Dynamic ◽  
Contact Algorithm ◽  
Complex Simulation ◽  
Precise Representation

Determination of contact forces exchanged between wheel and rail is one of the most important topics in railway dynamics. Recent studies are oriented to improve the existing contact methods in terms of computational efficiency on one side and on the other side to develop more complex and precise representation of the contact problem. This work shows some new results of the contact code developed at Politecnico di Torino identified as RTCONTACT; this code, which is an improvement of the CONPOL algorithm, is the result of long term activities, early versions were used in conjunction with MBS codes or in Matlab® environment to simulate vehicle behaviour. The code has been improved also using experimental tests performed on a scaled roller-rig. More recently the contact model was improved in order to obtain a higher computational efficiency that is a required for the use inside of a Real Time process. Benefit of a Real Time contact algorithm is the possibility to use complex simulation models in diagnostic or control systems in order to improve their performances. This work shows several comparisons of the RTCONTACT contact code respect commercial codes, standards and benchmark results.

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