Active Control of Nonlinear Dynamics of Crane Loads

2000 ◽  
Author(s):  
Y.-Y. Li ◽  
B. Balachandran ◽  
K. V. Krishna
Keyword(s):  
Nonlinear Dynamics ◽  
Active Control ◽  
Mechanical Filter ◽  
Ship Roll ◽  
Present Effort

Abstract In order to suppress crane-load oscillations on ship vessels, a novel mechanism called a mechanical filter was introduced recently. This system is further numerically studied in the present effort. With the aid of active control, it is illustrated as to how the suppression bandwidth can be tailored and bifurcations in the response of the crane load can be eliminated from the considered range of disturbance parameters. Suppression of crane-load oscillations in the presence of aperiodic ship-roll motions is also addressed.

A Mechanical Filter Concept to Suppress Crane Load Oscillations

1997 ◽  
Author(s):  
B. Balachandran ◽  
Y.-Y. Li
Keyword(s):  
Nonlinear Dynamics ◽  
Dynamical Systems ◽  
Control Parameters ◽  
Pivot Point ◽  
Preliminary Results ◽  
Scalar Control ◽  
Load Response ◽  
Mechanical Filter ◽  
Circular Track ◽  
Ship Roll

Abstract In this article, preliminary results obtained in the exploration of a mechanical filter concept for suppressing crane-load oscillations on a ship vessel are presented. The pivot point about which the load oscillates is constrained to follow a circular track in the considered filter. The governing dynamical systems for the cases with and without the filter are presented, and the nonlinear dynamics of these systems is studied with respect to quasi-static variation of different scalar control parameters. It is shown that the presence of the filter helps in eliminating some of the sub-critical bifurcations that may arise in the crane-load response during periodic ship-roll excitations.

Nonlinear Dynamics and Internal Resonances of a Ship With a Rectangular Cross-Section in Head Seas

2008 ◽  
Author(s):  
A. Kleiman ◽  
O. Gottlieb
Keyword(s):  
Nonlinear Dynamics ◽  
Cross Section ◽  
Nonlinear Response ◽  
Rectangular Cross Section ◽  
Orbital Stability ◽  
Internal Resonances ◽  
Weakly Nonlinear ◽  
Strongly Nonlinear ◽  
Evolution Dynamics ◽  
Ship Roll

We investigate the nonlinear dynamics and internal resonances of a ship with a rectangular cross-section in head seas. We employ an asymptotic averaging method to obtain the slowly varying system evolution dynamics for the weakly nonlinear response, complemented by numerical integration in the strongly nonlinear regime. This combined approach resolves both parametric instabilities and internal resonances induced for both weak and finite nonlinear interactions, and culminates with criteria for orbital stability thresholds describing the onset of quasiperiodic response and magnification of energy transfer between coupled pitch-heave and ship roll that can lead to capsize.

Modelling the Nonlinear Dynamics of Combustion Instabilities in Gas Turbines Towards Active Control

1999 ◽  
Vol 32 (2) ◽  
pp. 7196-7201 ◽  
Author(s):  
G. Baldin ◽  
S. Bittanti ◽  
A. De Marco ◽  
F. Longhi ◽  
G. Poncia ◽  
...  
Keyword(s):  
Nonlinear Dynamics ◽  
Active Control ◽  
Gas Turbines ◽  
Combustion Instabilities

Dynamic Reliability of Nonlinear Systems Under Random Excitation

1995 ◽  
Author(s):  
Fritz Colonius ◽  
Gerhard Häckl ◽  
Wolfgang Kliemann
Keyword(s):  
Nonlinear Dynamics ◽  
Damage Accumulation ◽  
Life Time ◽  
Random Excitation ◽  
Reliability Theory ◽  
Roll Motion ◽  
Accumulation Rates ◽  
Dynamic Reliability ◽  
Ship Roll ◽  
Ship Roll Motion

Abstract Reliability theory analyzes failure phenomena in systems, leading to maintenance and replacement schedules as well as risk assessment and other topics. Dynamic reliability takes into account the (possibly nonlinear) dynamics of the system and of the random excitation that may lead to failure. It is shown, how some of the concepts of reliability theory can be interpreted in the dynamical systems context. Analytical results are derived for failure probabilities, for life time distributions, asymptotic damage accumulation rates, and other relevant concepts. The Takens-Bogdanov oscillator and a model for ship roll motion are analyzed in detail, together with a thorough description of the numerical methods that are available for dynamic reliability studies.

Suppression of Crane-Load Oscillations Using Shape-Controlled Mechanical Filters

2002 ◽  
Vol 8 (2) ◽  
pp. 121-134 ◽  
Author(s):  
K. V. Kaipa ◽  
B. Balachandran
Keyword(s):  
System Dynamics ◽  
Equilibrium Position ◽  
Shape Control ◽  
State Feedback ◽  
Pivot Point ◽  
Mechanical Filter ◽  
Ship Roll ◽  
Shape Controlled ◽  
Persistent Disturbances ◽  
Insight Into

In the present study, control of ship board crane-load oscillations using a shape-controlled mechanical filter is investigated. The pivot point about which the load oscillations occur is constrained to follow an actively controlled surface, which is referred to as the mechanical filter. Planar load oscillations in the presence of ship roll motions are considered, and a nonlinear system with nonautonomous terms is used to describe the motions. For the case without shape control, it is shown that with only state feedback applied to the pivot point, it is not possible to stabilize the equilibrium position (i.e., absence of load oscillations and pivot motions). In the presence of shape control, it is shown that it is possible to have an equilibrium position even in the presence of persistent disturbances. A Lyapunov function-based analysis conducted to gain insight into the system dynamics is also presented. Through numerical simulations, it is verified that the equilibrium position is stable over a range of excitation frequencies. Efforts undertaken to examine the system dynamics in the presence of both state feedback applied to the pivot and shape control are also discussed.

Pull-In Extension of MEMS Electrostatic Microactuators Using an Active Control Method

2005 ◽  
Author(s):  
Y. Sun ◽  
D. Piyabongkarn ◽  
R. Rajamani ◽  
B. J. Nelson
Keyword(s):  
Nonlinear Dynamics ◽  
Control System ◽  
Active Control ◽  
Control Method ◽  
Full Range ◽  
Silicon On Insulator ◽  
Design Parameters ◽  
System Response ◽  
Comb Drive ◽  
Model Inversion

Parallel-plate and transverse comb-drive types of electrostatic microactuators are commonly used MEMS-based devices. Although they have the advantages of favorable scaling, fast response, and low power consumption, these electrostatic microactuators have had a fundamental limitation in that the allowable travel range is limited to 1/3 of the total gap between comb capacitor plates. Travel beyond this allowable range results in “pull-in” instability, independent of mechanical design parameters such as stiffness and mass. This paper presents the extension of stable travel ranges through the development of an active control system that stabilizes electrostatic microactuators and allows travel almost over the entire available gap between comb capacitor plates, providing a practical approach to extending travel range of electrostatic microactuators for applications that require high fill factors. The addressed challenges include the nonlinear dynamics of microactuators and system parameters that vary among fabricated devices. A nonlinear model inversion technique was proposed to address the nonlinear dynamics, which allows the use of traditional linear controller design methodologies for obtaining a desired linear system response. An adaptive controller was developed to provide improved position tracking in the presence of device parameter variations caused by fabrication imperfections. For experimental verification, the control system was implemented on a transverse comb-drive electrostatic microactuator fabricated using deep reactive ion etching on silicon-on-insulator wafers. Experimental results demonstrate that the resulting system is capable of traveling 4.0μm over a 4.5μm full range without “pull in.” Satisfactory tracking performance was obtained over a wide frequency band.

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