Active Control of a Reduced Scale Riser Undergoing Vortex-Induced Vibrations

2013 ◽  
Vol 135 (1) ◽  
Author(s):  
Eugenio Fortaleza
Keyword(s):  
Dynamic Behavior ◽  
Active Control ◽  
Water Channel ◽  
Control Design ◽  
Order System ◽  
Excited Mode ◽  
Resonant Modes ◽  
Vortex Induced Vibrations ◽  
Scale Experiment ◽  
Reduced Scale

This article concerns the use of an active control applied to a reduced scale riser undergoing vortex-induced vibrations (VIV). The control system relies upon the fact that a flexible structure undergoing VIV oscillates at frequencies corresponding to the structure resonant modes. These experiments were carried out in a recirculating water channel at IFP. For control design, the structure dynamic behavior is approximated by the dynamic behavior of its most excited mode. This is achieved through modal analysis and leads to a simple linear second order system. Its input is a displacement at the structure top end; its output is the structure displacement of a point away from the top end. The input is computed to attenuate the vibrations associated the most excited mode. This control strategy has been tested on a reduced scale experiment. These results are shown to agree with numerical results obtained on a phenomenological model. Both suggest a VIV reduction about 30%.

Simplified analysis of a stochastic system

1979 ◽  
Vol 44 (2) ◽  
pp. 328-339
Author(s):  
Vladimír Herles
Keyword(s):  
Statistical Analysis ◽  
Dynamic Behavior ◽  
Stochastic System ◽  
Additive Noise ◽  
Random Parameter ◽  
Systematic Difference ◽  
Order System ◽  
Constant Parameter ◽  
Random Parameters ◽  
Simplified Analysis

Contradictious results published by different authors about the dynamics of systems with random parameters have been examined. Statistical analysis of the simple 1st order system proves that the random parameter can cause a systematic difference in the dynamic behavior that cannot be (in general) described by the usual constant-parameter model with the additive noise at the output.

Transient response of the 1-st order dynamic system with fluctuating parameters

1979 ◽  
Vol 44 (7) ◽  
pp. 2184-2195
Author(s):  
Vladimír Herles ◽  
Jan Čermák ◽  
Antonín Havlíček
Keyword(s):  
Dynamic System ◽  
Dynamic Behavior ◽  
Transient Response ◽  
Flow Model ◽  
Stirred Tank ◽  
Order System ◽  
Random Parameters ◽  
Stirred Tank Reactor ◽  
Tank Reactor ◽  
Theoretical Results

The paper deals with the analysis of the dynamic behavior of the 1st order system with two random parameters. The theoretical results have been compared with experiments on flow model of a stirred tank reactor.

Research on Reduced Scale Experiment of Induced Overvoltage on Distribution Line

2014 ◽  
Vol 556-562 ◽  
pp. 1708-1711
Author(s):  
Ying Huang ◽  
Bo Tang ◽  
Zhan Qing Yu
Keyword(s):  
Comprehensive Understanding ◽  
Distribution Line ◽  
Scale Experiment ◽  
Reduced Scale

Lightning is one of the most important reason of outage of distribution line. And nearly 90% of the accidents of lightning failure is result of lightning induced overvoltage. In order to protect the distribution line from lightning, it is required to have a comprehensive understanding of characteristic of lightning induced overvoltage. Due to the advantage of reduced scale experiment, which are controllable and practical, the characteristic of lightning induced overvoltage is got from it. Comparing the results of experiment with the results of calculation, it is found that changes of overvoltage with height and distance match well with the calculated results, which show that the reduced scale experiment is effective and proper.

Three Practical Examples of Magnetic Bearing Control Design Using a Modern Tool

2002 ◽  
Vol 124 (4) ◽  
pp. 1025-1031 ◽  
Author(s):  
M. Spirig ◽  
J. Schmied ◽  
P. Jenckel ◽  
U. Kanne
Keyword(s):  
Dynamic Behavior ◽  
High Speed ◽  
Control Design ◽  
Industrial Applications ◽  
Magnetic Bearing ◽  
Engineering Practice ◽  
Digital Implementation ◽  
Bearing Characteristic ◽  
Multistage Centrifugal Compressor ◽  
Modern Tool

The use of magnetic bearing in industrial applications has increased due to their unique properties. Nowadays efficiency and predictability in handling rotors on magnetic bearings is asked with the same standard as conventional rotors on oil or roller bearings. First of all one must be aware of the special technical properties of magnetic bearing designs. The dynamic behavior of the rotor combined with requirements of the application define the desired bearing characteristic. With modern tools covering the mechanical aspects as well as the electronic controllers and their digital implementation on a DSP, these properties can be designed. However, despite the use of such efficient tools engineering practice is needed. Therefore this paper summarizes the major steps in the control design process of industrial applications. Three rotors supported on magnetic bearing with their specific dynamic behavior are presented: a very small high speed spindle (120,000 rpm); a small industrial turbo molecular pump rotor (36,000 rpm); and a large multistage centrifugal compressor (600 to 6300 rmp). The results of the analyses and their experimental verification are given.

Many-Objective Optimal Design of Sliding Mode Controls

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Yousef Sardahi ◽  
Jian-Qiao Sun
Keyword(s):  
Optimal Design ◽  
Pareto Front ◽  
Sliding Mode ◽  
Design Method ◽  
Tracking Error ◽  
Control Design ◽  
Processing Algorithm ◽  
Order System ◽  
Post Processing ◽  
Control Effort

This paper presents a many-objective optimal (MOO) control design of an adaptive and robust sliding mode control (SMC). A second-order system is used as an example to demonstrate the design method. The robustness of the closed-loop system in terms of stability and disturbance rejection are explicitly considered in the optimal design, in addition to the typical time-domain performance specifications such as the rise time, tracking error, and control effort. The genetic algorithm is used to solve for the many-objective optimization problem (MOOP). The optimal solutions known as the Pareto set and the corresponding objective functions known as the Pareto front are presented. To assist the decision-maker to choose from the solution set, we present a post-processing algorithm that operates on the Pareto front. Numerical simulations show that the proposed many-objective optimal control design and the post-processing algorithm are promising.

Short Comments on an Energy Pumping Levels in a “MEMS” Gyroscope Vibrating Problem, by Using of an Global and Local Optimal Linear Control Design

2009 ◽  
Author(s):  
Fa´bio Roberto Chavarette ◽  
Jose´ Manoel Balthazar ◽  
Marat Rafikov
Keyword(s):  
Nonlinear Dynamical System ◽  
Control Design ◽  
Normal Vector ◽  
Nonlinear Dynamical ◽  
Mems Gyroscope ◽  
Energy Pumping ◽  
Resonant Modes ◽  
Oscillatory Movement ◽  
Optimal Linear ◽  
Global And Local

This paper deals with an energy pumping that occurs in a (MEMS) Gyroscope nonlinear dynamical system, modeled with a proof mass constrained to move in a plane with two resonant modes, which are nominally orthogonal. The two modes are ideally coupled only by the rotation of the gyro about the plane’s normal vector. We also developed a linear optimal control design for reducing the oscillatory movement of the nonlinear systems to a stable point.

scholarly journals Assessment of dynamic behaviour of earth dams taking into account large strains

2019 ◽  
Vol 97 ◽  
pp. 05019 ◽  
Author(s):  
Mirziyod Mirsaidov ◽  
Tokhirjon Sultanov ◽  
Javlon Yarashov ◽  
Elyor Toshmatov
Keyword(s):  
Mathematical Model ◽  
Dynamic Behavior ◽  
Geometric Nonlinearity ◽  
Dynamic Behaviour ◽  
Large Strains ◽  
Earth Dams ◽  
Kinematic Effect ◽  
Resonant Modes

This paper presents the results of the assessment and prediction of the dynamic behavior of earth dams of various heights, taking into account large strains (geometric nonlinearity) and inhomogeneous features of structures under multi-component kinematic effects. A mathematical model, methodology and algorithm for estimating dynamic behavior of earth dams taking into account inhomogeneous features of structures and large strains in spatial and plane statements are given. Dynamic behavior of the models of the Pachkamar, Gissarak and Nurek earth dams has been studied taking into account large strains and inhomogeneous features of structures in various pre-resonant and resonant modes under multi-component kinematic effect. A number of new effects associated with the manifestation of large strains in the structure under various dynamic influences are revealed.

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