Showing papers in "Journal of Vibration and Control in 2000"
TL;DR: The proposed entropy-based measure of uncertainty is well-suited for making quantitative evaluations and comparisons of the quality of the parameter estimates that can be achieved using sensor configurations with different numbers of sensors in each configuration.
Abstract: A statistical methodology is presented for optimally locating the sensors in a structure for the
purpose of extracting from the measured data the most information about the parameters of the model used
to represent structural behavior. The methodology can be used in model updating and in damage detection
and localization applications. It properly handles the unavoidable uncertainties in the measured data as well
as the model uncertainties. The optimality criterion for the sensor locations is based on information entropy,
which is a unique measure of the uncertainty in the model parameters. The uncertainty in these parameters is
computed by a Bayesian statistical methodology, and then the entropy measure is minimized over the set of
possible sensor configurations using a genetic algorithm. The information entropy measure is also extended
to handle large uncertainties expected in the pretest nominal model of a structure. In experimental design,
the proposed entropy-based measure of uncertainty is also well-suited for making quantitative evaluations
and comparisons of the quality of the parameter estimates that can be achieved using sensor configurations
with different numbers of sensors in each configuration. Simplified models for a shear building and a truss
structure are used to illustrate the methodology.
299 citations
TL;DR: In this article, experimental results on nonlinearity-induced cross-modulation of a high-frequency (HF) f = 15-30 kHz signal by a lowfrequency (LF) F = 20 - 60 Hz vibration in an aluminum plate with a small single crack are reported.
Abstract: The nonlinear vibro-acoustic response of solid samples containing quite a small amount of defects can be anomalously high in magnitude compared to the case of undamaged intact solids. Functional de pendencies of the nonlinear effects exhibit rather interesting behavior. In this paper, experimental results on nonlinearity-induced cross-modulation of a high-frequency (HF) f = 15 — 30 kHz signal by a low-frequency (LF) F = 20 - 60 Hz vibration in an aluminum plate with a small single crack are reported. Comparison with a reference sample (the identical plate without a crack) has proven that the presence of such a small defect can be easily detected due to its nonlinear manifestations. It is demonstrated that under proper choice of the sounding signal parameters, the effect level can be so pronounced that the amplitude of the modulation side-lobes originated due to the nonlinearity exceeds the amplitude of the fundamental harmonic of the HF signal. Main functional features of the observed phenomena are analyz...
86 citations
TL;DR: A novel class of controllers, called resetting virtual absorbers, is proposed as a means for achieving energy dissipation and stability of the closed-loop system is analyzed.
Abstract: A novel class of controllers, called resetting virtual absorbers, is proposed as a means for achieving energy dissipation. A general framework for analyzing resetting virtual absorbers is given, and stability of the closed-loop system is analyzed. Special cases of resetting virtual absorbers, called the virtual trap-door absorber and the virtual one-way absorber, are described, and some illustrative examples are given.
75 citations
TL;DR: A new bearing defect diagnostic and classification method based on pattern recognition of statistical parameters that is effective in indicating both the location and the severity of bearing defects is proposed.
Abstract: In this paper, a new bearing defect diagnostic and classification method is proposed based on pattern recognition of statistical parameters. Such a pattern recognition problem can be described as transformation from the pattern space to the feature space and then to the classification space. Based on trend analysis of six commonly used statistical parameters, four parameters, namely, RMS, Kurtosis, Crest Factor, and Impulse Factor, are selected to form a pattern space. A 2-D feature space is formulated by a nonlinear transformation. An intraclass transformation is used to cluster the data of different bearing defects into different regions in the feature space. The classification space is constructed by piecewise linear discriminant functions. Training the classification space is performed, in this paper, by using data of bearings with seeded defects. Diagnosis of the defected bearings in the classification space then becomes straightforward. Numerical experiments show that the proposed method is effectiv...
60 citations
TL;DR: In this article, the damping coefficient of the car suspension is selected in a way that the resulting semiactive system approximates the performance of an active suspension system designed to produce sky-hook damping.
Abstract: Dynamics of a controlled quarter-car model is investigated. In this model, the damping coefficient of the car suspension is selected in a way that the resulting semiactive system approximates the performance of an active suspension system designed to produce sky-hook damping. According to this control strategy, the damping coefficient switches between two different values, leading to a piecewise linear dynamical model. For this model, the equation of motion is first presented in a general normalized form. Then, an appropriate methodology is applied for obtaining exact periodic motions for the case of forcing resulting from a road with harmonic profile. This methodology is based on employing the exact solution form within response intervals where the damping coefficient remains constant. The unknowns of the problem are then determined by imposing a set of periodicity and matching conditions. The stability analysis of the located motions is also performed by applying a method that is suitable for piecewise ...
52 citations
TL;DR: In this paper, a method for simulating unsteady, nonlinear, subsonic aeroelastic behavior of an aircraft wing is described, where the flowing air and deforming structure are treated as the elements of a single dynamic...
Abstract: A method for simulating unsteady, nonlinear, subsonic aeroelastic behavior of an aircraft wing is described. The flowing air and deforming structure are treated as the elements of a single dynamic ...
52 citations
TL;DR: In this article, the optimal shape design of the rotor shaft to change the critical speeds under the constraints of the constant mass was investigated. And the results showed that the critical speed of the system can be increased by using the genetic algorithm.
Abstract: In general, the dynamic design of a rotor system is to optimize the system in stability at the operating speed, unbalance response in the vicinity of the rotor critical speeds, and minimize the system weight considering economics. This paper deals with the optimum shape design of the rotor shaft to change the critical speeds under the constraints of the constant mass. As to the design procedures, the genetic algorithm was applied to find the optimum diameters of a rotor shaft so that the optimized rotor system can yield the critical speeds as far from the operating speed as possible. Genetic algorithm is a search algorithm based on the natural world, which states that the individual with the superior character creates the superior descendant because of having excellent adaptability, high survivability, and more crossing chance, and the natural genetics that repeatedly perform the process of reproduction, crossover, and mutation. The results show that the critical speeds of the rotor-bearing systems can be...
51 citations
TL;DR: In this article, the authors investigate theoretically and experimentally the performance of a recently developed quadratic vibration absorber that is based on the saturation phenomenon and consider the problem o...
Abstract: The authors investigate theoretically and experimentally the performance of a recently developed quadratic vibration absorber that is based on the saturation phenomenon. They consider the problem o...
48 citations
TL;DR: In this article, a new technique for the suppression of machine tool chatter in turning based on modulation of the system impedance is analyzed, and the modulation frequency is selected as half the spindle frequency.
Abstract: A new technique for the suppression of machine tool chatter in turning based on modulation of the system impedance is analyzed. The modulation frequency is selected as half the spindle frequency. Using the method of harmonic balance and a numerical root finding scheme on the transcendental characteristic equation, stability diagrams arc computed for a variety of modulation amplitudes. The stability boundaries are verified by using the Nyquist stability criterion and growth exponents computed from transient simulations of the vibratory response. It is shown in this way that the impedance modulation technique successfully scrambles the regenerative process that leads to chatter and widens the stability region (by increasing the maximum allowed cutting depth), particularly for low values of the spindle speed.
38 citations
TL;DR: In this article, an experimental analytical investigation on the dynamic behavior of steel-concrete composite beams subject to small vibrations is presented, where the elements connecting the steel beam and the reinforced concrete slab are described by means of a strain energy density function defined throughout the beam axis.
Abstract: This paper is an experimental analytical investigation on the dynamic behavior of steel-concrete composite beams subject to small vibrations. A one-dimensional model of a composite beam is presented, where the elements connecting the steel beam and the reinforced concrete slab are described by means of a strain energy density function defined throughout the beam axis. The problem of small vibrations of the system is formulated and solved through an analytical procedure where a coupling between longitudinal and transver sal motions, due to the presence of the connection, takes place. The analytical model is used with a view to interpreting a series of dynamic tests performed on composite beams whose connections have different linear densities. Experimental results proved consistent with theoretical estimates and allowed the identification of some important physical parameters of the system and the characterization of the connection.
31 citations
TL;DR: In this paper, a hybrid solution to the corresponding Hamilton-Jacobi-Bellman (or HJB) equation is obtained for the case of a linear controlled system, where an exact analytical solution is obtained within a certain outer domain with respect to a "strip" with switching lines, indicating optimality of a "dry-friction," or the simplest version of the "bang-bang" control law within this domain.
Abstract: A single-degree-of-freedom system is excited by a white-noise random force. The system's re sponse can be reduced by a control force of limited magnitude R, and the problem is to minimize the expected response energy at a given time instant T under this constraint. A "hybrid" solution to the corresponding Hamilton-Jacobi-Bellman (or HJB) equation is obtained for the case of a linear controlled system. Specif ically, an exact analytical solution is obtained within a certain outer domain with respect to a "strip" with switching lines, indicating optimality of a "dry-friction," or the simplest version of the "bang-bang" control law within this domain. This explicit solution is matched by a numerical solution within an inner domain, where switching lines are illustrated. In the limiting case of a weak control, or small R, the hybrid solution leads to a simple asymptotically suboptimal "dry-friction" control law, which is well-known for deterministic optimal control problems; more precisely, the difference in ...
TL;DR: The conditions under which the controller stabilizes the slipping system are vestigated and an effective alternative control strategy for the slip system is proposed for the case when the original controller fails to stabilize the system and where the uncontrolled rolling system is unstable.
Abstract: The paper addresses dynamic and control issues related to a dynamical model called the classi cal shimmying wheel. The classical shimmying wheel models the rolling dynamics of many physical rolling systems such as aircraft nose wheels, motorcycles, automotive systems, and tractor-trailer systems. Such a system can exhibit undesirable unstable rolling motion, that is, shimmying, which can often lead to disastrous results. Prior work with this particular model has focused on the stability of the system as well as an analysis of the qualitative nature of its dynamics, including numerical observation of possible chaotic behavior. Such behavior is observed when the rolling element is allowed to slip under certain conditions, which is intended to realistically model real physical rolling systems. In cases where the rolling dynamics of the system arc un stable, the dynamics are characterized by the presence of an attractor wherein the system repeatedly switches back and forth between rolling and slipping. We pre...
TL;DR: In this article, the authors analyze the problem of model reduction in structural dynamics for unforced conservative systems having static, cubic nonlinearities and propose a model partitioning framework.
Abstract: The authors analyze the problem of model reduction in structural dynamics for unforced conser vative systems having static, cubic nonlinearities. The framework is the classical one of partitioning ...
TL;DR: In this paper, a spectral finite element model is developed to accurately reproduce the wave propagation phenomena inside the composite rod and to model its dynamic behavior with a significantly reduced number of elements.
Abstract: Longitudinal wave propagation is controlled using shape memory inserts placed along rods. The inserts act as sources of impedance mismatch with tunable characteristics. Such characteristics are attributed to the unique behavior of the shape memory alloy whereby the elastic modulus significantly increases as the alloy undergoes a phase transformation from martensite to austenite. With such controllable capability, the inserts can introduce the proper impedance mismatch necessary to impede the wave propagation along the rods. A spectral finite element model is developed to accurately reproduce the wave propagation phenomena inside the composite rod and to model its dynamic behavior with a significantly reduced number of elements. The theoretical predictions are compared with the experimental performance of rods with one, two, and three shape memory inserts. The behavior of the composite is evaluated at different activation temperatures of the shape memory material. The obtained results indicate significant ...
TL;DR: In this article, an exact explicit analytical solution for the Lagrange cost function was derived for the Hamilton-Jacobi-Bellman (HJB) equation within a certain "outer" domain, providing boundary conditions for numerical simulation of the HJB equation within the remaining "inner" domain.
Abstract: A single-degree-of-freedom mass-spring system is considered under white-noise excitation. To reduce expected response energy of the system, a bounded control force can be applied and optimal control law is sought for. An exact explicit analytical solution, for the Lagrange cost function, is derived for the Hamilton-Jacobi-Bellman (HJB) equation within a certain "outer" domain. This solution provides boundary conditions for numerical simulation of the HJB equation within the remaining "inner" domain. Comparison of optimal control law, with a previously obtained one for the Mayer cost function, is made. The analytical solution to the HJB equation for the "combined" Boltz cost function is derived for the outer domain as a linear combination of the solutions for the Mayer and Lagrange cost functions. Sensitivity of the Bellman functional to the above optimal control laws is analyzed.
TL;DR: In this paper, two configurations of the resulting hybrid treatment are considered, where active control and passive control operate separately, whereas in the second configuration, the two operate in unison to maximize the energy dissipation characteristics.
Abstract: Conventional passive constrained layer damping treatments with viscoelastic cores are provided with built-in sensing and actuation capabilities to actively control and enhance their vibration damping charac teristics. Two configurations of the resulting hybrid treatment are considered in this paper. In the first configuration, the active control and passive operate separately, whereas in the second configuration, the two operate in unison to maximize the energy dissipation characteristics. In this study, three objectives are accomplished. The first objective aims at the design and implementation of robust H∞) controllers for the separated and unified control strategies. In the second, the performance of the H∞ controllers at different operating frequencies and temperatures is compared with that of a conventional proportional/derivative controller to demonstrate robustness. Finally, a control effort study involving the H∞ controllers for the separated and unified control strategies is shown to assess the e...
TL;DR: In this paper, the authors provide a methodology for designing reduced-order controllers for large-scale, linear systems represented by differential equations having time-periodic coefficients using Lyapunov-Floquet transformation.
Abstract: This paper provides methodology for designing reduced-order controllers for large-scale, linear systems represented by differential equations having time-periodic coefficients. The linear time-periodic sys tem is first converted into a form in which the system stability matrix is time invariant. This is achieved by the application of Lyapunov-Floquet transformation. Then a completely time-invariant auxiliary system is constructed and order reduction algorithms are applied to this system to obtain a reduced-order system. The control laws are calculated for the reduced-order system by minimizing the least square error between the auxiliary and the transformed system. These control laws are then transformed to obtain the desired control action in the original domain. The schemes formulated arc illustrated by designing full-state feedback and output feedback controllers for a five-mass inverted pendulum exhibiting parametric instability
TL;DR: In this paper, the performance of an LQG/LTR-based multi-input multi-output robust vibration control system for a laminated composite beam is investigated using a finite element model based on a higher order shear defor mation theory and accounting for piezoelectric effects.
Abstract: The performance of an LQG/LTR-based multi-input multi-output robust vibration control system for a laminated composite beam is investigated. A finite element model based on a higher order shear defor mation theory and accounting for piezoelectric effects is developed. The model is thus applicable to both thick and thin laminated composite beams. The lateral strain is also incorporated in the model by a systematic re duction of two-dimensional plate constitutive equations. The mode superposition method is used to transform the coupled finite element equations of motion in the physical coordinates into a set of reduced uncoupled equations in the modal coordinates. The state space model of the system is obtained in the reduced-order modal coordinates. An LQG/LTR-based robust controller is designed using the reduced-order state space model of the structure. The performance of the controller is verified for various arbitrary initial conditions of the beam. The effect of structural parameter variation on the cl...
TL;DR: In this article, the authors analyzed and performed experiments on the instability of a multiple cylindrical structure system that has dual flexible weir shells and found that self-excited oscillations were found to occur at the same natural frequency of the sloshing in the restitution plenum.
Abstract: Self-excited oscillations of the structure coupled with inner fluid occurred in the insulation wall cooling system of the fast breeder reactor Super-Phenix-1 (SPX-1) in France during test operations. In this system, lower temperature sodium going up along the inside of the main vessel in a feeding plenum brims over a cylindrical flexible weir shell and flows into a restitution plenum. It is reported that the self-excited oscillations were found to occur at the same natural frequency of the sloshing in the restitution plenum, the free surface of the fluid in both feeding and restitution plenums oscillated at large amplitudes, and the cylindrical shell was found to oscillate with an oval vibration mode instability. Such an instability is called a coupled sloshing mode. In this study, the authors analyzed and performed experiments on the instability of a multiple cylindrical structure system that has dual flexible weir shells. They measured self-excited oscillations changing various parameters such as discha...
TL;DR: In this paper, the dynamics of two oscillators coupled with quadratic nonlinearities in the case of two-to-one internal resonance when the higher mode is subjected to a principal parametric excitation was investigated.
Abstract: The authors study the dynamics of two oscillators coupled with quadratic nonlinearities in the case of two-to-one internal resonance when the higher mode is subjected to a principal parametric excitation. They use the method of multiple scales to obtain an approximate solution to the equations of motion and investigate theoretically its stability. Then, they verify the analysis experimentally. The authors use a cantilever steel beam and an analog second-order circuit to represent the two oscillators. The interaction between the two systems is achieved by fitting the beam with piezoceramic actuators and a strain gage and coupling the beam with the circuit through electronically generated quadratic nonlinearities. They subject the first mode of the beam to a principal parametric excitation and tune the frequency of the circuit to approximately one-half the frequency of the first mode of the beam. The theoretical and experimental results indicate that the system exhibits complicated responses, such as jumps,...
TL;DR: In this paper, discrete domain analysis is presented and it is shown that discrete domain control design for DR yields better vibration suppression considering the sampled control structure in implementations.
Abstract: The delayed resonator (DR) is a new active vibration absorption technique that uses time-delayed partial state feedback to generate ideal resonance on a passive vibration absorber. It has many attractive features such as real-time tunability, ease of implementation, and total suppression of vibration for tonal frequency disturbances. The DR controller has been developed in continuous domain until now. In this paper, discrete domain analysis is presented. Simulation results indicate an expected dependency of stability on the sampling period for this active control strategy. A major advantage of discrete domain analysis is the reduction of characteristic roots from infinite to finite numbers and consequent simplicity in the analysis and design of the controller. It is shown that discrete domain control design for DR yields better vibration suppression considering the sampled control structure in implementations.
TL;DR: In this article, the authors examined the effects of surface deck irregularities on the dynamic response of a bridge, during the passage of a light or heavy vehicle, and tried to find the effect.
Abstract: This paper examines the effects of the surface deck irregularities on the dynamic response of a bridge, during the passage of a light or heavy vehicle The authors especially try to find the effect
TL;DR: In this paper, an investigation of the application of constrained-layer damping to computer disk drives is pre sented, and nine constrainedlayer disks were manufactured and tested to determine their modal parameters.
Abstract: An investigation of the application of constrained-layer damping to computer disk drives is pre sented. Nine constrained-layer disks were manufactured and tested to determine their modal parameters...
TL;DR: In this article, an approximate model for wave propagation in rods of rectangular cross section was developed that is based on neglecting the dependence of the shear stresses and the longitudinal displacement on on...
Abstract: An approximate model for wave propagation in rods of rectangular cross section was developed that is based on neglecting the dependence of the shear stresses and the longitudinal displacement on on...
TL;DR: In this paper, an adaptive force trajectory control of a flexible beam using a piezoceramic actuator based on the variable structure model reference adaptive control theory is presented. But the authors assume that parameters of the beam and contact surface stiffness are unknown.
Abstract: This paper presents an adaptive force trajectory control of a flexible beam using a piezoceramic actuator Based on the variable structure model reference adaptive control theory, a new force control system using only force measurement is designed For the derivation of the control law, it is assumed that parameters of the beam and contact surface stiffness are unknown It is shown that in the closed-loop system, the contact force tracks a given reference trajectory and the beam vibration is suppressed as well Digital simulations results show that the closed-loop system has good transient behavior and robust performance in the presence of uncertainties in the parameters of the flexible beam and the contact surface, and unmodeled dynamics as well
TL;DR: In this paper, the authors investigate the source of the oscillatory behavior and determine whether feedback control can be employed to stabilize such a system, which is a potential advantage for some robot manipulator designs because of its simplicity, compactness and capacity for large speed reduction ratios.
Abstract: The worrnscrew gearset provides a potential advantage for some robot manipulator designs because of its simplicity, compactness, and capacity for large speed-reduction ratios. However, an oscillatory behavior has been observed in such implementations that, depending on the extension and loading of the manipulator, tends to grow as the manipulator is lowered under the influence of gravity and disappears as the manipulator is raised. The oscillations can become quite large, crippling the utility of the manipulator The growing oscillations are indicative of an instability. However, it is not immediately apparent why such a system should be unstable. The objectives of this work were to find the source of the oscillatory behavior and to determine whether feedback control can be employed to stabilize such a system.
TL;DR: In this article, a new three-dimensional thin laminated shell element for the structure containing an integrated distributed piezoelectric sensor and actuator is proposed, and the optimal shape control of structure is derived.
Abstract: In this paper, a new three-dimensional thin laminated shell element for the structure containing an integrated distributed piezoelectric sensor and actuator is proposed. A finite element formulation is derived for modeling the dynamic as well as static response of laminated shell with piezoelectric sensors/actuators. The performance of the shell elements is improved by reduced integration technique. The optimal shape control of structure is derived. The shell element is verified by calculating piezoelectric polymeric PVDF bimorph beam. The results agreed with those obtained by theoretical analysis fairly well. Finally, the optimal shape control of a paraboloid antenna is studied.
TL;DR: In this paper, the performance of two position control systems was studied and the results clearly showed a decrease in control effort for the system using non linear control when compared to a similar response for the systems using PD control.
Abstract: The performance of two position control systems was studied. Proportional plus derivative (PD) feedback control was considered along with PD plus position times velocity feedback. An analytical model of the plant (a single link, very flexible manipulator) was identified, and computer simulations using the two controllers were performed. The results clearly showed a decrease in control effort for the system using non linear control when compared to a similar response for the system using PD control. Experimental results on a slewing beam system verified this result. The system using the proposed nonlinear feedback control re quired significantly less energy to complete the same maneuver as the system using the standard PD feedback control. Other measures of performance (e.g., rise time, settling time, overshoot) showed marginal improve ment when the nonlinear feedback was added to the controller. The principal issue here is the control effort required by the linear versus nonlinear controller to obtain the...
TL;DR: In this paper, a new exact approach that combines the general solutions and recurrence formula was developed for determining natural frequencies and mode shapes of multistep flexural beams with varying frequencies and modes.
Abstract: A new exact approach that combines the general solutions and recurrence formula developed in this paper for determining natural frequencies and mode shapes of multistep flexural beams with varying ...
TL;DR: In this article, an adaptive control algorithm for the vibration suppression of a space truss structure using modal filters for independent modal space control and a neural network for online system identification is investigated.
Abstract: An adaptive control algorithm is investigated for the vibration suppression of a space truss structure using modal filters for independent modal space control and a neural network for online system identification. The modal filters are computed off-line using measured frequency response functions and estimated pole values for the modes of interest. They are used to conduct transformation of response measurements from physical coordinates to modal coordinates. The time histories in the modal coordinates are then processed in real time by the neural network to extract estimates of modal parameters, namely, natural frequency, damping ratio, and modal gain. To examine the performance of the adaptive control approach, a controller was designed using the modal filters and implemented on a laboratory space truss using a single reaction-mass actuator and 32 accelerometers. The performance of the modal filter-based controller is compared to that of a local rate feedback controller using the same actuator. The appl...