Journal articles: 'Acoustics, Dynamics, and Controls'

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Tucker, Albert J. "Active control: New paradigms for structural acoustics and dynamics." Journal of the Acoustical Society of America 97, no. 5 (May 1995): 3266. http://dx.doi.org/10.1121/1.411652.

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Maeda, Kazuki, and Tim Colonius. "Bubble cloud dynamics in an ultrasound field." Journal of Fluid Mechanics 862 (January 16, 2019): 1105–34. http://dx.doi.org/10.1017/jfm.2018.968.

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The dynamics of bubble clouds induced by high-intensity focused ultrasound is investigated in a regime where the cloud size is similar to the ultrasound wavelength. High-speed images show that the cloud is asymmetric; the bubbles nearest the source grow to a larger radius than the distal ones. Similar structures of bubble clouds are observed in numerical simulations that mimic the laboratory experiment. To elucidate the structure, a parametric study is conducted for plane ultrasound waves with various amplitudes and diffuse clouds with different initial void fractions. Based on an analysis of the kinetic energy of liquid induced by bubble oscillations, a new scaling parameter is introduced to characterize the dynamics. The new parameter generalizes the cloud interaction parameter originally introduced by d’Agostino & Brennen (J. Fluid Mech., vol. 199, 1989, pp. 155–176). The dynamic interaction parameter controls the energy localization and consequent anisotropy of the cloud. Moreover, the amplitude of the far-field, bubble-scattered acoustics is likewise correlated with the proposed parameter. Findings of the present study not only shed light on the physics of cloud cavitation, but may also be of use for the quantification of the effects of cavitation on outcomes of ultrasound therapies including high-intensity focused ultrasound-based lithotripsy.

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Gabbert, Ulrich, Fabian Duvigneau, and Stefan Ringwelski. "NOISE CONTROL OF VEHICLE DRIVE SYSTEMS." Facta Universitatis, Series: Mechanical Engineering 15, no. 2 (August 2, 2017): 183. http://dx.doi.org/10.22190/fume170615009g.

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The paper presents an overall simulation approach to control the noise emission of car engines at a very early stage of the design process where no real prototypes are available. The suggested approach combines different physical models and couples different software tools such as multi-body analysis, fluid dynamics, structural mechanics, magneto-electrodynamics, thermodynamics, acoustics and control as well. The general overall simulation methodology is presented first. Then, this methodology is applied to a combustion engine in order to improve its acoustical behavior by passive means, such as changing the stiffness and the use of damping materials to build acoustic and thermal encapsulations. The active control by applying piezoelectric patch actuators at the oil sump as the noisiest part of the engine is discussed as well. The sound emission is evaluated by hearing tests and a mathematical prediction model of the human perception. Finally, it is shown that the presented approach can be extended to electric engines, which is demonstrated at a newly developed electric wheel hub motor.

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Mahdal, Miroslav, Josef Dobeš, and Milada Kozubková. "Measurement of Aerodynamic and Acoustic Quantities Describing Flow around a Body Placed in a Wind Tunnel." Measurement Science Review 19, no. 1 (February 1, 2019): 20–28. http://dx.doi.org/10.2478/msr-2019-0004.

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Abstract Aerodynamically generated noise affects passenger comfort in cars, high-speed trains, and airplanes, and thus, automobile manufacturers aim for its reduction. Investigation methods of noise and vibration sources can be divided into two groups, i.e. experimental research and mathematical research. Recently, owing to the increase in computing power, research in aerodynamically generated noise (aero-acoustics) is beginning to use modern methods such as computational fluid dynamics or fluid-structure interaction. The mathematical model of turbulent flow is given by the system of partial differential equations, its solution is ambiguous and thus requires verification by physical experiment. The results of numerical methods are affected by the boundary conditions of high quality gained from the actual experiment. This article describes an application of complex measurement methodology in the aerodynamic and acoustic (vibro-acoustic) fields. The first part of the paper is focused on the specification of the experimental equipment, i.e. the wind tunnel, which was significantly upgraded in order to obtain the relevant aerodynamics and vibro-acoustics data. The paper presents specific results from the measurement of the aerodynamic and vibro-acoustic fields.

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Ruzzene, Massimo. "Sensors, dynamics, and control: Program overview and relevance to acoustics research." Journal of the Acoustical Society of America 137, no. 4 (April 2015): 2365. http://dx.doi.org/10.1121/1.4920594.

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von Flotow, A. H. "The acoustic limit of control of structural dynamics." Journal of the Acoustical Society of America 82, S1 (November 1987): S14. http://dx.doi.org/10.1121/1.2024667.

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Brunton, Steven. "Data-driven discovery of dynamics for control." Journal of the Acoustical Society of America 144, no. 3 (September 2018): 1743. http://dx.doi.org/10.1121/1.5067728.

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Tzou, H. S. "Non-linear joint dynamics and controls of jointed flexible structures with active and viscoelastic joint actuators." Journal of Sound and Vibration 143, no. 3 (December 1990): 407–22. http://dx.doi.org/10.1016/0022-460x(90)90732-f.

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Heertjes, Marcel, and Nathan van de Wouw. "Nonlinear Dynamics and Control of a Pneumatic Vibration Isolator." Journal of Vibration and Acoustics 128, no. 4 (April 11, 2005): 439–48. http://dx.doi.org/10.1115/1.2128642.

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The nonlinear dynamics of a single-degree-of-freedom pneumatic vibration isolator are studied. Based on a physical model, a nonsymmetric stiffness nonlinearity is derived to describe the stiffness property of the isolator. For a full nonlinear pneumatic isolator model, the response to two different types of disturbances is studied: forces applied to the isolated payload and base vibrations. The dynamic behavior of the isolator in case of a disturbance applied to the payload is studied using the generalized force-mobility function and features coexisting steady-state responses and a superharmonic resonance. Base vibrations transmitted via the isolator are studied on the basis of the generalized transmissibility function again showing rich nonlinear dynamic behavior. The presence of a nonsymmetric nonlinearity also induces high-energy low-frequency response to multiple high-frequency excitation. For both types of excitation, the nonlinear behavior is seriously compromising the performance of the isolator. To avoid any expression of nonlinearity whatsoever and, at the same time, to enhance the performance of the passive isolator, an overall nonlinear control design is proposed. It consists of a linear PID-based controller together with a nonlinear computed torque controller (CTC). For either linear or nonlinear control, the isolator performance is quantified in terms of generalized force mobility and transmissibility. The latter with a special focus on multiple high-frequency excitation.

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Jerrelind, Jenny, and Harry Dankowicz. "A Global Control Strategy for Efficient Control of a Braille Impact Hammer." Journal of Vibration and Acoustics 128, no. 2 (May 11, 2005): 184–89. http://dx.doi.org/10.1115/1.2159033.

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A combined control scheme relying on feedback-based local control in the vicinity of periodic system responses and global control based on a coarse-grained approximation to the nonlinear dynamics is developed to achieve a desirable dynamical behavior of a Braille printer impact hammer. The proposed control methodology introduces discrete changes in the position of a system discontinuity at opportune moments during the hammer motion while the hammer is away from the discontinuity, thereby exploiting the recurrent contacts with the discontinuity to achieve the desired changes in the transient dynamics. It is argued that, as the changes in the position of the discontinuity affect the motion only indirectly through changes in the timing and state at the subsequent contact, the control actuation can be applied over an interval of time during the free-flight motion as long as it is completed prior to contact. A forced, piecewise smooth, single-degree-of-freedom model of a Braille impact hammer is used to illustrate the methodology and to yield representative numerical results.

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Majcher, Andrzej. "Event Driven Networked Control System for Impact Load Monitoring." Solid State Phenomena 237 (August 2015): 169–74. http://dx.doi.org/10.4028/www.scientific.net/ssp.237.169.

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The article describes the application of the event-driven networked control system (NCS) for impact load monitoring. The main problem in this type of application is measurement synchronization, which should provide full information about the impact in terms of stochastic delays introduced by the network and stochastic characteristics of the actuator. Using the simulation model of the NCS system, the method of solving this particular problem was developed. The results of verification tests for the real object and a synchronized dynamic measurement of signals from resistance strain gauges are presented. The described system can find use in monitoring and fault detection, in tasks connected with dynamics of liquids and gases, acoustics, and the analysis of resistance properties of materials and technical objects. Key words: Networked control system (NCS), event maintenance, event synchronization, impact monitoring, measurement trigger, strain gauge.

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Tzou, H. S., and Y. H. Zhou. "Nonlinear Piezothermoelasticity and Multi-Field Actuations, Part 2: Control of Nonlinear Deflection, Buckling and Dynamics." Journal of Vibration and Acoustics 119, no. 3 (July 1, 1997): 382–89. http://dx.doi.org/10.1115/1.2889734.

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Linear dynamics and distributed control of piezoelectric laminated continua have been intensively investigated in recent years. In this study, dynamics, electromechanical couplings, and control of thermal buckling of a nonlinear piezoelectric laminated circular plate with an initial large deformation are investigated. It is assumed that the transverse nonlinear component is much more prominent than the other two in-plane components—the von Karman type geometrical nonlinearity. In addition, the piezoelectric layers are uniformly distributed on the top and bottom surfaces of the circular plate. Accordingly, the control effect is introduced via an equivalent control moment on the circumference. Dynamic equations and boundary conditions including the elastic and piezoelectric couplings are formulated, and solutions are derived. Active control of plate’s nonlinear deflections, thermal buckling, and natural frequencies using high control voltages are studied, and their nonlinear effects are evaluated.

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Carroll, James M., Leal K. Lauderbaugh, and Michael L. Calvisi. "Nonlinear dynamics and control of ultrasound contrast agent microbubbles." Journal of the Acoustical Society of America 134, no. 5 (November 2013): 3991. http://dx.doi.org/10.1121/1.4830552.

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Genta, Giancarlo, and Reginald H. Keith. "Vibration Dynamics and Control." Noise Control Engineering Journal 57, no. 2 (2009): 156. http://dx.doi.org/10.3397/1.3110987.

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Watson, Leighton M., Jonatan Werpers, and Eric M. Dunham. "What controls the initial peak of an air-gun source signature?" GEOPHYSICS 84, no. 2 (March 1, 2019): P27—P45. http://dx.doi.org/10.1190/geo2018-0298.1.

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Seismic air guns are broadband sources that generate acoustic waves at many frequencies. The low-frequency waves can be used for imaging, whereas the high-frequency waves are attenuated and/or scattered before they can reflect from targets of interest in the subsurface. It is desirable to reduce the amplitude of the high-frequency acoustic waves because they are thought to be disruptive, and potentially damaging, to marine life and are not useful for geophysical purposes. The high-frequency acoustic waves are primarily associated with the initial expansion of the air-gun bubble and associated peak in the acoustic pressure time series, which is commonly referred to as the source signature of the air gun. We have developed a quasi-1D model of a seismic air gun coupled to a spherical bubble that accounts for gas dynamics and spatially variable depressurization inside the firing chamber to investigate controls on the initial peak of the source signature. The model is validated against data collected during field tests in Lake Seneca, New York. Simulations and field data show that the initial peak is primarily dependent on the operating pressure. A lower gun pressure results in a smaller peak amplitude and a slower rise time. The slope, the amplitude of the initial peak divided by the rise time, is used as a proxy for environmental impact and can decrease by as much as 50% when the air-gun pressure is reduced from 2000 to 1000 psi. The low frequencies are controlled by the total discharged mass, which is dependent upon the gun volume and pressure. Decreasing the operating pressure while simultaneously increasing the gun volume will reduce the high frequencies while maintaining the desirable low-frequency signals.

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Richards, Geo A., Jimmy D. Thornton, Edward H. Robey, and Leonell Arellano. "Open-Loop Active Control of Combustion Dynamics on a Gas Turbine Engine." Journal of Engineering for Gas Turbines and Power 129, no. 1 (March 16, 2006): 38–48. http://dx.doi.org/10.1115/1.2204978.

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Combustion dynamics is a prominent problem in the design and operation of low-emission gas turbine engines. Even modest changes in fuel composition or operating conditions can lead to damaging vibrations in a combustor that was otherwise stable. For this reason, active control has been sought to stabilize combustors that must accommodate fuel variability, new operating conditions, etc. Active control of combustion dynamics has been demonstrated in a number of laboratories, single-nozzle test combustors, and even on a fielded engine. In most of these tests, active control was implemented with closed-loop feedback between the observed pressure signal and the phase and gain of imposed fuel perturbations. In contrast, a number of recent papers have shown that open-loop fuel perturbations can disrupt the feedback between acoustics and heat release that drives the oscillation. Compared to the closed-loop case, this approach has some advantages because it may not require high-fidelity fuel actuators, and could be easier to implement. This paper reports experimental tests of open-loop fuel perturbations to control combustion dynamics in a complete gas turbine engine. Results demonstrate the technique was very successful on the test engine and had minimal effect on pollutant emissions.

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Elbeyli, O., and J. Q. Sun. "Covariance Control of Nonlinear Dynamic Systems via Exact Stationary Probability Density Function." Journal of Vibration and Acoustics 126, no. 1 (January 1, 2004): 71–76. http://dx.doi.org/10.1115/1.1640355.

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This paper presents a method for designing covariance type controls of nonlinear stochastic systems. The method consists of two steps. The first step is to find a class of nonlinear feedback controls with undetermined gains such that the exact stationary PDF of the response is obtainable. The second step is to select the control gains in the context of the covariance control method by minimizing a performance index. The exact PDF makes the solution process of optimization very efficient, and the evaluation of expectations of nonlinear functions of the response very accurate. The theoretical results of various orders of response moments by the present method have been compared with Monte Carlo simulations. Special cases are studied when the approximate methods based on the maximum entropy principle or other closure schemes leads less accurate response estimates, while the present method still works fine.

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Cox, D. E., G. P. Gibbs, R. L. Clark, and J. S. Vipperman. "Experimental Robust Control of Structural Acoustic Radiation." Journal of Vibration and Acoustics 121, no. 4 (October 1, 1999): 433–39. http://dx.doi.org/10.1115/1.2893999.

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This work addresses the design and application of robust controllers for structural acoustic control. Both simulation and experimental results are presented. H∞ and μ-synthesis design methods were used to design feedback controllers which minimize power radiated from a panel while avoiding instability due to unmodeled dynamics. Specifically, high-order structural modes which couple strongly to the actuator-sensor path were poorly modeled. This model error was analytically bounded with an uncertainty model which allowed controllers to be designed without artificial limits on control effort. It is found that robust control methods provide the control designer with physically meaningful parameters with which to tune control designs and can be very useful in determining limits of performance. However, experimental results also showed poor robustness properties for control designs with ad-hoc uncertainty models. The importance of quantifying and bounding model errors is discussed.

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Menzies, Dylan. "Composing instrument control dynamics." Organised Sound 7, no. 3 (December 2002): 255–66. http://dx.doi.org/10.1017/s1355771802003059.

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The expression gestural mapping is well imbedded in the language of instrument designers, describing the function from interface control parameters to synthesis control parameters. This function is in most cases implicitly assumed to be instantaneous, so that at any time its output depends only on its input at that time. Here more general functions are considered, in which the output depends on the history of input, especially functions that behave like physical dynamic systems, such as a damped resonator. Acoustic instruments are rich in dynamical behaviour. Introducing dynamics at the control stage of an electronic instrument can help compensate for lack of dynamics in later non-physical synthesis stages. A broadening of the function space offers new aesthetic possibilities for composing instruments. Examples are presented to illustrate the new design/composition mode as well as practical techniques. In this context, it is suggested that the word mapping be updated with the more descriptive expression dynamic control processing.

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Wouters, J., and M. W. Macon. "Control of spectral dynamics in concatenative speech synthesis." IEEE Transactions on Speech and Audio Processing 9, no. 1 (2001): 30–38. http://dx.doi.org/10.1109/89.890069.

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Abderrahmane, Belkallouche, Tahar Rezoug, and Laurent Dala. "Passive control of cavity acoustics via the use of surface waviness at subsonic flow." Aircraft Engineering and Aerospace Technology 91, no. 2 (February 4, 2019): 296–308. http://dx.doi.org/10.1108/aeat-01-2018-0061.

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PurposeAircraft noise is dominant for residents near airports when planes fly at low altitudes such as during departure and landing. Flaps, wings, landing gear contribute significantly to the total sound emission. This paper aims to present a passive flow control (in the sense that there is no power input) to reduce the noise radiation induced by the flow over the cavity of the landing gear during take-off and landing.Design/methodology/approachThe understanding of the noise source mechanism is normally caused by the unsteady interactions between the cavity surface and the turbulent flows as well as some studies that have shown tonal noise because of cavity resonances; this tonal noise is dependent on cavity geometry and incoming flow that lead us to use of a sinusoidal surface modification application upstream of a cavity as a passive acoustics control device in approach conditions.FindingsIt is demonstrated that the proposed surface waviness showed a potential reduction in cavity resonance and in the overall sound pressure level at the majority of the points investigated in the low Mach number. Furthermore, optimum sinusoidal amplitude and frequency were determined by the means of a two-dimensional computational fluid dynamics analysis for a cavity with a length to depth ratio of four.Research limitations/implicationsThe noise control by surface waviness has not implemented in real flight test yet, as all the tests are conducted in the credible numerical simulation.Practical implicationsThe application of passive control method on the cavity requires a global aerodynamic study of the air frame is a matter of ongoing debate between aerodynamicists and acousticians. The latter is aimed at the reduction of the noise, whereas the former fears a corruption of flow conditions. To balance aerodynamic performance and acoustics, the use of the surface waviness in cavity leading edge is the most optimal solution.Social implicationsThe proposed leading-edge modification it has important theoretical basis and reference value for engineering application it can meet the demands of engineering practice. Particularly, to contribute to the reduce the aircraft noise adopted by the “European Visions 2020”.Originality/valueThe investigate cavity noise with and without surface waviness generation and propagation by using a hybrid approach, the computation of flow based on the large-eddy simulation method, is decoupled from the computation of sound, which can be performed during a post-processing based on Curle’s acoustic analogy as implemented in OpenFOAM.

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Gaitan, D. Felipe, and Steven L. Garrett. "Dynamics of a dual‐driver acoustic resonator and control system used in a thermoacoustic refrigerator." Journal of the Acoustical Society of America 94, no. 3 (September 1993): 1773. http://dx.doi.org/10.1121/1.408016.

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Chen, Yu, Guolai Yang, and Quanzhao Sun. "Dynamic simulation on vibration control of marching tank gun based on adaptive robust control." Journal of Low Frequency Noise, Vibration and Active Control 39, no. 2 (May 2, 2019): 416–34. http://dx.doi.org/10.1177/1461348419846685.

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In order to better understand the dynamic behavior and decrease the muzzle vibration of marching tank, a mechanical–electrical–hydraulic integrated dynamic model of marching tank was established based on a novel dynamic co-simulation method. The hydraulic system model was modeled in Amesim and the dynamic model of marching tank was established in RecurDyn based on multi-body system theory, vehicle terramechanics, and gun launch dynamics. The control system model was modeled in MATLAB/Simulink. Therein, the adaptive robust control algorithm was introduced to design the vertical stabilizer controller and the simulation program of the designed controller was developed by C language. The simulation results show that the muzzle vibration of marching tank can be controlled effectively by the ARC method. Furthermore, the muzzle error compensation signal was added in the designed controller to weaken the detrimental effect of the barrel flexibility on muzzle vibration. This work provides an approach to investigate the dynamic behavior of marching tank considering effects among the mechanical, hydraulic, and control subsystems.

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Li, Zhengminqing, Hao Wang, and Rupeng Zhu. "Effect predictions of web active control on dynamic behaviors of face gear drives." Journal of Low Frequency Noise, Vibration and Active Control 38, no. 2 (January 7, 2019): 753–64. http://dx.doi.org/10.1177/1461348418821587.

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Face gear dynamics is addressed by many scholars, and vibration suppression of face gear drives is always one of study focuses of face gear dynamics. However, vibration active control solutions of face gear drives are still yet to be constructed. Thus, in the study, a web active control solution of face gear drives, in which face gear web structures are employed to achieve static transmission error active control, is proposed, and a web circumference deformation calculation solution is constructed, as well as a four-degrees of freedom dynamic model of face gear drives is established, and two version control methods of static transmission error are presented. Furthermore, an example case of face gear drives associated with the proposed web active control solution is simulated. The results indicate that effects of the proposed web active control solution on dynamic behaviors of face gear drives are significant, and the fidelity of the proposed web active control solution could be accepted. These contributions would benefit to improve face gear vibrations and engineering applications of face gear drives.

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Tjaden, Kris, Jennifer Lam, and Greg Wilding. "Vowel Acoustics in Parkinson's Disease and Multiple Sclerosis: Comparison of Clear, Loud, and Slow Speaking Conditions." Journal of Speech, Language, and Hearing Research 56, no. 5 (October 2013): 1485–502. http://dx.doi.org/10.1044/1092-4388(2013/12-0259).

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Purpose The impact of clear speech, increased vocal intensity, and rate reduction on acoustic characteristics of vowels was compared in speakers with Parkinson's disease (PD), speakers with multiple sclerosis (MS), and healthy controls. Method Speakers read sentences in habitual, clear, loud, and slow conditions. Variations in clarity, intensity, and rate were stimulated using magnitude production. Formant frequency values for peripheral and nonperipheral vowels were obtained at 20%, 50%, and 80% of vowel duration to derive static and dynamic acoustic measures. Intensity and duration measures were obtained. Results Rate was maximally reduced in the slow condition, and vocal intensity was maximized in the loud condition. The clear condition also yielded a reduced articulatory rate and increased intensity, although less than for the slow or loud conditions. Overall, the clear condition had the most consistent impact on vowel spectral characteristics. Spectral and temporal distinctiveness for peripheral–nonperipheral vowel pairs was largely similar across conditions. Conclusions Clear speech maximized peripheral and nonperipheral vowel space areas for speakers with PD and MS while also reducing rate and increasing vocal intensity. These results suggest that a speech style focused on increasing articulatory amplitude yields the most robust changes in vowel segmental articulation.

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Chang, Shun-Chang, and Hai-Ping Lin. "Non-linear dynamics and chaos control for an electromagnetic system." Journal of Sound and Vibration 279, no. 1-2 (January 2005): 327–44. http://dx.doi.org/10.1016/j.jsv.2003.11.033.

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Lim, S., and T. Y. Jung. "DYNAMICS AND ROBUST CONTROL OF A HIGH SPEED OPTICAL PICKUP." Journal of Sound and Vibration 221, no. 4 (April 1999): 607–21. http://dx.doi.org/10.1006/jsvi.1998.2042.

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GE, Z. M., and J. S. SHIUE. "NON-LINEAR DYNAMICS AND CONTROL OF CHAOS FOR A TACHOMETER." Journal of Sound and Vibration 253, no. 4 (June 2002): 773–93. http://dx.doi.org/10.1006/jsvi.2001.3774.

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Chen, Min-Shin, and Ren-Jay Fu. "An Active Control Design for a Class of Parametrically Excited Systems Based on the Gradient Algorithm." Journal of Vibration and Acoustics 120, no. 3 (July 1, 1998): 727–32. http://dx.doi.org/10.1115/1.2893890.

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This paper introduces a new control design for a dynamic system subject to stationary or nonstationary parametric excitations. In this new design, the system dynamics is transformed into one with a null system matrix using the variation of parameters method. A stabilizing state feedback control can then be immediately obtained by following the gradient algorithm that is originally developed for the parameter identification purpose. Such a design has the advantage that the control requires only past and present information of the time-varying parametric excitations while previous control designs usually require prediction of future information of the excitations. The closed-loop system stability is guaranteed if the open-loop state response does not diverge too fast. The control design approach can also be applied to the observer design in case where there is only partial observation of the system state.

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Do, K. D., and J. Pan. "Boundary control of transverse motion of marine risers with actuator dynamics." Journal of Sound and Vibration 318, no. 4-5 (December 2008): 768–91. http://dx.doi.org/10.1016/j.jsv.2008.05.009.

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Tzou, H. S., and Y. H. Zhou. "DYNAMICS AND CONTROL OF NON-LINEAR CIRCULAR PLATES WITH PIEZOELECTRIC ACTUATORS." Journal of Sound and Vibration 188, no. 2 (November 1995): 189–207. http://dx.doi.org/10.1006/jsvi.1995.0586.

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Nagy, Peter B. "Ultrasonic Processes and Machines: Dynamics, Control and ApplicationsUltrasonic Processes and Machines: Dynamics, Control and ApplicationsVladimir K.AstashevVladimir I.BabitskySpringer-Verlag, Berlin and Heidelberg, 2007. 332 pp. price $169.00 (hardcover), ISBN: 978-3-540-72060-7." Journal of the Acoustical Society of America 123, no. 3 (March 2008): 1217. http://dx.doi.org/10.1121/1.2836753.

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Schlotter, Michael, and Patrick S. Keogh. "Synchronous Position Recovery Control for Flexible Rotors in Contact with Auxiliary Bearings." Journal of Vibration and Acoustics 129, no. 5 (February 2, 2007): 550–58. http://dx.doi.org/10.1115/1.2731414.

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This paper details a methology for the active recovery of contact free levitation of a rotor from a state of persistent contact with auxiliary bearings. An analytical method to describe contact dynamics of flexible rotors is presented. It shows that synchronous unbalance forces can cause a rotor to adopt stable contact modes, which are characterized by periodic motion and a fixed contact point in a rotating frame of reference. Based on these observations, a recovery strategy is developed to return the rotor to a contact free state. Compensation forces may be applied by magnetic bearings to reduce the effective synchronous forcing which is driving the contact, so that the rotor can progress to a contact free orbit. It is shown that even in the presence of highly nonlinear contact dynamic effects, a linear finite element rotor model can be used to calculate appropriate influence coefficients. The contact recovery procedure is successfully verified by simulations and measurements on a flexible rotor test facility. Allowable bounds on the phase of the synchronous recovery forces are investigated and limitations of the method are discussed.

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Chandiramani, N. K. "Active control of a piezo-composite rotating beam using coupled plant dynamics." Journal of Sound and Vibration 329, no. 14 (July 2010): 2716–37. http://dx.doi.org/10.1016/j.jsv.2010.01.023.

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Lenci, S., and G. Rega. "A unified control framework of the non-regular dynamics of mechanical oscillators." Journal of Sound and Vibration 278, no. 4-5 (December 2004): 1051–80. http://dx.doi.org/10.1016/j.jsv.2003.12.010.

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Beijen, Michiel A., Marcel F. Heertjes, Hans Butler, and Maarten Steinbuch. "Disturbance feedforward control for active vibration isolation systems with internal isolator dynamics." Journal of Sound and Vibration 436 (December 2018): 220–35. http://dx.doi.org/10.1016/j.jsv.2018.09.010.

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IDER, S. KEMAL. "INVERSE DYNAMICS CONTROL OF CONSTRAINED ROBOTS IN THE PRESENCE OF JOINT FLEXIBILITY." Journal of Sound and Vibration 224, no. 5 (July 1999): 879–95. http://dx.doi.org/10.1006/jsvi.1999.2202.

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LENCI, S., and G. REGA. "NUMERICAL CONTROL OF IMPACT DYNAMICS OF INVERTED PENDULUM THROUGH OPTIMAL FEEDBACK STRATEGIES." Journal of Sound and Vibration 236, no. 3 (September 2000): 505–27. http://dx.doi.org/10.1006/jsvi.2000.2991.

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Alloush, Menemsha, Douglas Scofield, Susanne Marczak, Robin Jones, Kristine Kaiser, Mark Oliva, Peter M. Narins, and Katherine Martineau. "When sounds collide: the effect of anthropogenic noise on a breeding assemblage of frogs in Belize, Central America." Behaviour 148, no. 2 (2011): 215–32. http://dx.doi.org/10.1163/000579510x551660.

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AbstractMany organisms depend on acoustic communication for myriad functions, and have evolved behaviours to minimize effects of naturally occurring acoustic interference. However, as habitats are subject to increased alteration, anthropogenic noise becomes unavoidable, and how animals overcome such interference is not well understood. In most ecosystems, only a subset of frog species is associated with disturbed habitats; the ability of these species to overcome exogenous noise suggests that habitat associations may be related to species' response to noise. We tested the hypothesis that frogs associated with largely undisturbed forest habitat would be less likely to increase call output in response to exogenous noise than would those associated with disturbed or open habitat. While this relationship was not significant, we found a slight trend supporting the hypothesis. We then asked whether anthropogenic noise affects chorus tenure at individual- or at chorus-levels. Male frogs exposed to anthropogenic noise decreased both the number of days present at the chorus and the nightly chorus duration relative to controls. Because females generally join choruses late at night to breed, the effects of noise shown here are likely to substantially decrease frog reproductive success; thus, the acoustic environment may play an important role in shaping population dynamics and in amphibian declines.

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Lee-Glauser, G., Jer-Nan Juang, and J. L. Sulla. "Optimal Active Vibration Absorber: Design and Experimental Results." Journal of Vibration and Acoustics 117, no. 2 (April 1, 1995): 165–71. http://dx.doi.org/10.1115/1.2873874.

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An optimal active vibration absorber can provide guaranteed closed-loop stability and control for large flexible space structures with collocated sensors/actuators. The active vibration absorber is a second-order dynamic system which is designed to suppress any unwanted structural vibration. This can be designed with minimum knowledge of the controlled system. Two methods for optimizing the active vibration absorber parameters are illustrated: minimum resonant amplitude and frequency matched active controllers. The Controls-Structures Interaction Phase-1 Evolutionary Model at the NASA Langley Research Center is used to demonstrate the effectiveness of the active vibration absorber for vibration suppression. Performance is compared numerically and experimentally using acceleration feedback.

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Gosavi, S. V., and A. G. Kelkar. "Modelling, Identification, and Passivity-Based Robust Control of Piezo-actuated Flexible Beam." Journal of Vibration and Acoustics 126, no. 2 (April 1, 2004): 260–71. http://dx.doi.org/10.1115/1.1687392.

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This paper presents modelling, system identification, simulation, and experimental results for passivity-based robust control of piezo-actuated flexible beam. The flexible beam configuration considered is a cantilever aluminum beam with a piezoelectric transducer used as the actuator and tip-accelerometer as the sensor. The actuator and sensor are non-collocated. The Lagrangian formulation is used to obtain mathematical model of the flexible link dynamics with piezo actuator. For control design purposes, a finite dimensional approximate model is derived using assumed modes approach. It is shown that the approximate model compares very well with the experimentally identified model. Since the system is inherently not passive, passification techniques are used to render the system robustly passive which enables the use of passivity-based feedback control design. The controller design is validated both in simulation as well as in experiments. The simulation and experimental results demonstrate the effectiveness of controller in suppressing the tip vibrations of the link. The controller design is shown to be robust to both parametric uncertainties and unmodeled dynamics.

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Kitio Kwuimy, C. A., B. R. Nana Nbendjo, and P. Woafo. "Optimization of electromechanical control of beam dynamics: Analytical method and finite differences simulation." Journal of Sound and Vibration 298, no. 1-2 (November 2006): 180–93. http://dx.doi.org/10.1016/j.jsv.2006.05.019.

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Yabuno, Hiroshi. "Stabilization and utilization of nonlinear phenomena based on bifurcation control for slow dynamics." Journal of Sound and Vibration 315, no. 3 (August 2008): 766–80. http://dx.doi.org/10.1016/j.jsv.2008.03.018.

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Rahn, C. D., and S. Joshi. "Modeling and Control of an Electrorheological Sandwich Beam." Journal of Vibration and Acoustics 120, no. 1 (January 1, 1998): 221–27. http://dx.doi.org/10.1115/1.2893809.

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This paper introduces models for electrorheological (ER) structures based on visco-elasticity and sandwich beam theory. The partial differential equations describing the dynamics of an ER sandwich beam are derived and a modal analysis is performed. Feedback controllers, derived using Lyapunov theory, ensure stability of all modes of the beam. Feedback from an axial velocity sensor to the applied ER beam voltage provides an implementable approximation to the control law. Simulations of a cantilevered ER beam show the stable response and improved transient decay provided by the control system.

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RAJARAM, RAJESH, and TIM LIEUWEN. "Acoustic radiation from turbulent premixed flames." Journal of Fluid Mechanics 637 (September 24, 2009): 357–85. http://dx.doi.org/10.1017/s0022112009990681.

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Turbulent combustion processes are inherently unsteady and, thus, a source of acoustic radiation. While prior studies have extensively characterized their total sound power, their spectral characteristics are not well understood. This work investigates these acoustic spectral features, including the flame's low- and high-frequency characteristics and the scaling of the frequency of peak acoustic emissions. The spatiotemporal characteristics of the flame's chemiluminescence emissions, used as a marker of heat release fluctuations, were measured and used to determine the heat release spectrum, spatial distribution and spatial coherence characteristics. These heat release characteristics were then used as inputs to an integral solution of the wave equation and compared to measured acoustic spectra obtained over a range of conditions and burners and at several spatial locations. The spectral characteristics of the flame's acoustic emissions are controlled by two processes: the underlying spectrum of heat release fluctuations that are ultimately the combustion noise source, and the transfer function relating these heat release and acoustic fluctuations. An important result from this work is the clarification of the relative roles of these two processes in controlling the shape of the acoustic spectrum. This transfer function is primarily controlled by the spatiotemporal coherence characteristics of the heat release fluctuations which are, in turn, strongly influenced by burner configuration/geometry and operating conditions. Low-frequency acoustic emissions are controlled by the heat release spectrum essentially independent of flame geometry. Both the heat release spectrum and heat release-acoustic transfer function are important at intermediate and high frequencies. An important feature of the investigated geometry that controls the heat release phase dynamics is the high-velocity flow relative to the flame speed and anchored character of the flame. This leads to convection of flame sheet disturbances (i.e. heat release fluctuations) along the front that dominates the high frequency and peak frequency scaling of the flame's acoustic emissions.

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Hannsen Su, J., and C. E. Ruckman. "Mechanisms of Localized Vibration Control in Complex Structures." Journal of Vibration and Acoustics 118, no. 1 (January 1, 1996): 135–39. http://dx.doi.org/10.1115/1.2889627.

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This paper describes a numerical study of mechanisms for controlling all six degrees of freedom in localized areas of a complex structure. In localized vibration control, the controller attempts to stabilize one or more localized areas on the structure rather than attempting to stabilize the entire structure. The relative performance levels of different control strategies are evaluated by examining a frequency-dependent disturbance rejection property. A flat plate supported by two box girders is used as an example realistic structure. Plant dynamics from a finite-element model are used to draw general conclusions regarding the mechanisms by which localized vibration control is exerted.

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Dev, Ashwani, and George A. McMechan. "Interpreting structural controls on hydrate and free-gas accumulation using well and seismic information from the Gulf of Mexico." GEOPHYSICS 75, no. 1 (January 2010): B35—B46. http://dx.doi.org/10.1190/1.3282680.

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The effect of the structural setting on gas hydrate and free-gas accumulation near the East Casey fault zone at Keathley Canyon in the Gulf of Mexico is investigated using well logs and 2D and 3D acoustic-impedance inversions. We interpret two zones from the well logs: a probable hydrate zone and a dissociating hydrate zone. We interpret hydrates as fracture fillings in the clay-dominated formation with maximum saturation of approximately 30% of the available pore space, and maximum volumetric concentration of approximately 12%. The maximum free-gas concentration below the interpreted bottom simulating reflector (BSR) is less than 4%. Resistivity measurements alone are incon-clusive; complimentary measurements, such as sonic, reduce hy-drate interpretation ambiguities. Seismic data in 3D and the derived acoustic-impedance volume are interpreted in terms of a BSR, a high [Formula: see text]-impedance hydrate zone, and free gas. We interpret two bright, low [Formula: see text]-impedance features terminating at the BSR as free-gas accumulations. The contrast in average [Formula: see text]-impedance across the fault suggests a change in lithology across the fault zone, and free-gas transport along, and to the west of, the fault. Variations in depths of interpreted free-gas zones suggest either a significant lateral variation in the hydrate stability across the fault zone, or coexistence of hydrates and free gas within the hydrate stability zone, or both. The dynamics of the tectonic environment imply nonequilibrium conditions of time-dependent temperature, pressure, or fluid transport.

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Fang, Yunmei, Juntao Fei, and Tongyue Hu. "Adaptive backstepping fuzzy sliding mode vibration control of flexible structure." Journal of Low Frequency Noise, Vibration and Active Control 37, no. 4 (March 27, 2018): 1079–96. http://dx.doi.org/10.1177/1461348418767097.

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An adaptive backstepping fuzzy sliding mode control is proposed to approximate the unknown system dynamics for a cantilever beam in this paper. The adaptive backstepping fuzzy sliding mode control is developed by combining the backstepping method with adaptive fuzzy strategy, where backstepping design approach is used to drive the trajectory tracking errors to converge to zero rapidly with global asymptotic stability and fuzzy logic system is designed to approximate the unknown nonlinear function in the adaptive backstepping fuzzy sliding mode control. The proposed backstepping controllers can ensure proper tracking of the reference trajectory, and impose a desired dynamic behavior, giving robustness and insensitivity to parameter variations. Numerical simulation for cantilever beam is investigated to verify the effectiveness of the proposed adaptive backstepping fuzzy sliding mode control scheme and demonstrate the satisfactory vibration suppression performance.

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Tzou, H. S., and R. Ye. "Piezothermoelasticity and Precision Control of Piezoelectric Systems: Theory and Finite Element Analysis." Journal of Vibration and Acoustics 116, no. 4 (October 1, 1994): 489–95. http://dx.doi.org/10.1115/1.2930454.

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Piezothermoelastic effects of distributed piezoelectric sensor/actuator and structural systems are studied. Distributed controls (static and dynamic) of piezoelectric laminates subjected to a steady-state temperature field are investigated. Piezothermoelastic constitutive equations are defined, followed by three energy functionals for the displacement, electric, and temperature fields, respectively. A new 3-D piezothermoelastic thin hexahedron finite element with three internal degrees of freedom is formulated using a variational formulation which includes thermal, electric, and mechanical energies. A system equation for the piezoelectric continuum exposed to combined displacement, electric, and temperature fields is formulated. Distributed sensing and control equations of piezoelectric laminates in a temperature field are derived. Thermal influences on the sensing and control of piezoelectric PZT/steel laminates are investigated in case studies.

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Cican, Grigore, and Daniel Eugeniu Crunteanu. "Aerodynamic Noise Control Study of Nozzles with Triangular Chevrons." Applied Mechanics and Materials 436 (October 2013): 25–31. http://dx.doi.org/10.4028/www.scientific.net/amm.436.25.

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This paper has a small part of notion of chevron and the process that helps reducing the noise pollution. Based on the gas dynamic and geometrical parameters of a single flow jet engine one does a model of CFD data processing. In this process one observes the influence of chevrons on acoustic wave intensity produced by the jet . One studies a series of tests on triangular chevrons: immersions, the influence of the number of chevrons in order to settle the influence of the geometrical parameters on the flow and on the jet acoustics. Finally one presents the contribution of chevrons in noise pollution reduction.

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Journal articles on the topic 'Acoustics, Dynamics, and Controls'

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