Development of an Analog Controller for Tuning an Adaptive-Passive Control Device

2005 ◽  
Author(s):  
Marty Johnson ◽  
Edward C. Diggs
Keyword(s):  
Passive Control ◽  
Low Frequency ◽  
Helmholtz Resonator ◽  
Dc Motor ◽  
Control Device ◽  
Inner Product ◽  
Variable Cross ◽  
Error Signal ◽  
Cross Sectional ◽  
Drive Frequency

Adaptive-passive devices such as adaptive Helmholtz Resonators (HR) and tunable vibration absorbers have been shown to be suitable for controlling both narrowband disturbances and lightly damped structural/acoustic modes driven by broadband disturbances. In order to track changes in the disturbance or changes in the modes, the natural frequency of the absorber, ωn, is tuned to match the observed signals. This is achieved by altering some physical parameter of the control device such as the stiffness of a vibration absorber or the neck cross-sectional area of a Helmholtz resonator. In order to automatically adjust these devices, control systems and tuning algorithms have been developed, most of which involve a digital controller. However, this paper looks specifically at the development of a simple analog controller used to drive a DC motor in order to tune a mechanical device. A two sensor dot product method is employed where one sensor is placed inside of the control device, such as a Helmholtz Resonator, and the other on/in the system under control, such as in a room. The outputs from the two sensors are multiplied together and subsequently low passed in order to extract a low frequency “DC” voltage which acts as an error signal. The error signal is related to the relative phase of the two sensor signals and determines the direction in which the device should be tuned. When the two signals are 90° apart, the system is tuned (i.e. the inner product produces zero DC level). If the drive frequency ω is different than the tuned frequency, then the system is mis-tuned. The relationship between the mis-tuning, ωn-ω, and the error is not linear, but for small perturbations a linear approximation can be used to investigate the stability and performance of the system. The gradient of the function is shown to be largest when the mis-tuning error is zero and is inversely proportional to the damping level in the control device. Once stability of the system has been ensured the ability of the system to track changes in drive frequency is investigated experimentally. The control system is demonstrated using an adaptive Helmholtz resonator which has a variable cross-sectional neck via an iris diaphragm. The iris is controlled using a small DC motor; two microphones (one mounted internally and one externally) are used to supply the driving signal to the circuit.

A Theoretical Approach for Passive Control of Thermoacoustic Oscillations: Application to Ducted Flames

2013 ◽  
Vol 135 (9) ◽  
Author(s):  
Luca Magri ◽  
Matthew P. Juniper
Keyword(s):  
Heat Release ◽  
Passive Control ◽  
Local Variation ◽  
Control Device ◽  
Adjoint Equations ◽  
Hot Wire ◽  
Adjoint Sensitivity ◽  
Cross Sectional ◽  
Rijke Tube ◽  
Thermoacoustic Oscillations

In this paper, we develop a linear technique that predicts how the stability of a thermoacoustic system changes due to the action of a generic passive feedback device or a generic change in the base state. From this, one can calculate the passive device or base state change that most stabilizes the system. This theoretical framework, based on adjoint equations, is applied to two types of Rijke tube. The first contains an electrically heated hot wire, and the second contains a diffusion flame. Both heat sources are assumed to be compact, so that the acoustic and heat release models can be decoupled. We find that the most effective passive control device is an adiabatic mesh placed at the downstream end of the Rijke tube. We also investigate the effects of a second hot wire and a local variation of the cross-sectional area but find that both affect the frequency more than the growth rate. This application of adjoint sensitivity analysis opens up new possibilities for the passive control of thermoacoustic oscillations. For example, the influence of base state changes can be combined with other constraints, such as that the total heat release rate remains constant, in order to show how an unstable thermoacoustic system should be changed in order to make it stable.

scholarly journals Study on Inorganic Modification of Damping Capacity of Polyurethane Materials for Building

2018 ◽  
Vol 175 ◽  
pp. 01016
Author(s):  
Zhou Feng ◽  
Gan Jianjun ◽  
Du Xin ◽  
Cui Ligang
Keyword(s):  
Viscoelastic Material ◽  
Passive Control ◽  
Testing Machine ◽  
Low Frequency ◽  
Control Device ◽  
Frequency Region ◽  
Damping Capacity ◽  
Polyurethane Elastomer ◽  
Load Testing ◽  
Engineering Structures

As a kind of passive control device, viscoelastic damper has been successfully applied to allkinds of engineering structures. However, the viscoelastic material in viscoelastic dampers is mainly basedon rubber. Therefore, in this thesis, the viscoelastic material is the main line of study. Different viscoelasticmaterial formulas are being used to make the corresponding damper and study the correlation performanceof such damper in the low frequency region. In this thesis, we mainly study the polyurethane elastomermaterial, but simplex polyurethane elastomer materials have low damping and cannot achieve the effect ofbuilding damping, so it's necessary to study the modification. In this experiment, four kinds of inorganicfillers, mica powder, zinc oxide, silica and glass fiber were used to modify the polyurethane elastomer. Itsdamping performance then is tested by a dynamic load testing machine in a low frequency region of 0.1Hz-1.0Hz.

DETERMINATION OF THE FUNCTION OF THE ROD’S CROSS-SECTIONAL AREA USING VIBRATION EIGENFREQUENCIES

2020 ◽  
Vol 0 (4) ◽  
pp. 19-24
Author(s):  
I.M. UTYASHEV ◽  
◽  
A.A. AITBAEVA ◽  
A.A. YULMUKHAMETOV ◽  
◽  
...  
Keyword(s):  
Cross Sectional Area ◽  
Variable Cross ◽  
Sectional Area ◽  
Longitudinal Vibrations ◽  
Cross Sectional ◽  
Method Error ◽  
Various Boundary Conditions ◽  
Elastic Fixation ◽  
Crosssectional Area

The paper presents solutions to the direct and inverse problems on longitudinal vibrations of a rod with a variable cross-sectional area. The law of variation of the cross-sectional area is modeled as an exponential function of a polynomial of degree n . The method for reconstructing this function is based on representing the fundamental system of solutions of the direct problem in the form of a Maclaurin series in the variables x and λ. Examples of solutions for various section functions and various boundary conditions are given. It is shown that to recover n unknown coefficients of a polynomial, n eigenvalues are required, and the solution is dual. An unambiguous solution was obtained only for the case of elastic fixation at one of the rod’s ends. The numerical estimation of the method error was made using input data noise. It is shown that the error in finding the variable crosssectional area is less than 1% with the error in the eigenvalues of longitudinal vibrations not exceeding 0.0001.

Longitudinal oscillation of a rod with a variable cross section

2019 ◽  
Vol 14 (2) ◽  
pp. 138-141
Author(s):  
I.M. Utyashev
Keyword(s):  
Cross Section ◽  
Natural Frequencies ◽  
Liouville Problem ◽  
Variable Cross Section ◽  
Variable Cross ◽  
Longitudinal Vibrations ◽  
Cross Sectional ◽  
Independent Functions ◽  
The Cross ◽  
The Right

Variable cross-section rods are used in many parts and mechanisms. For example, conical rods are widely used in percussion mechanisms. The strength of such parts directly depends on the natural frequencies of longitudinal vibrations. The paper presents a method that allows numerically finding the natural frequencies of longitudinal vibrations of an elastic rod with a variable cross section. This method is based on representing the cross-sectional area as an exponential function of a polynomial of degree n. Based on this idea, it was possible to formulate the Sturm-Liouville problem with boundary conditions of the third kind. The linearly independent functions of the general solution have the form of a power series in the variables x and λ, as a result of which the order of the characteristic equation depends on the choice of the number of terms in the series. The presented approach differs from the works of other authors both in the formulation and in the solution method. In the work, a rod with a rigidly fixed left end is considered, fixing on the right end can be either free, or elastic or rigid. The first three natural frequencies for various cross-sectional profiles are given. From the analysis of the numerical results it follows that in a rigidly fixed rod with thinning in the middle part, the first natural frequency is noticeably higher than that of a conical rod. It is shown that with an increase in the rigidity of fixation at the right end, the natural frequencies increase for all cross section profiles. The results of the study can be used to solve inverse problems of restoring the cross-sectional profile from a finite set of natural frequencies.

scholarly journals Association between Metabolic Syndrome Components and Cardiac Autonomic Modulation among Children and Adolescents: A Systematic Review and Meta-Analysis

Biology ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 699
Author(s):  
Rashmi Supriya ◽  
Fei-Fei Li ◽  
Yi-De Yang ◽  
Wei Liang ◽  
Julien S. Baker
Keyword(s):  
Risk Factors ◽  
Young People ◽  
Correlation Coefficient ◽  
High Frequency ◽  
Meta Analysis ◽  
Low Frequency ◽  
Autonomic Modulation ◽  
Cross Sectional ◽  
Cross Sectional Studies ◽  
Positive Correlations

Background: the clustering of metabolic syndrome (MetS) risk factors is becoming more prevalent in children, leading to the development of type 2 diabetes (T2D) and cardiovascular diseases in early adulthood. The impact of MetS risk factors on cardiac autonomic modulation (CAM) or vice versa has been noted to track from childhood to pre-adolescence and adolescence. Understating associations in this age group may help to improve the clinical outcomes of the MetS, even when MetS symptoms are not visible. Potential damage from each individual MetS component and the ability to predict early cardiac damage or upcoming cardiovascular events is very important. Therefore, the present systematic review and meta-analysis investigated the associations between CAM and MetS risk factors individually to verify which of the MetS risk components were significantly correlated with heart rate variability (HRV) indices before or at the onset of the MetS among young people. The purpose of this review was to outline the importance of potentially screening HRV indices in young people even with only one MetS risk factor, as a pre-indicator for early cardiovascular risk stratification. Methods: cross-sectional studies that examined the relationship of MetS risk factors with HRV indices were searched using four databases including PubMed, the Cochrane clinical trials library, Medline and the Web of Science. Correlation coefficients with 95% confidence intervals (95% CI), and random effects meta-analyses of the association between MetS risk factors with HRV indices were performed. Results: out of 14 cross-sectional studies and one case-control study, 8 studies (10 data sets) provided association data for the meta-analysis. Our results indicated significant positive correlations for systolic blood pressure (SBP) (correlation coefficient 0.13 (95%CI: 0.06; 0.19), I2 = 47.26%) and diastolic blood pressure (DBP) (correlation coefficient 0.09 (95%CI: −0.01; 0.18), I2 = 0%) with a Low Frequency/High Frequency ratio (LF/HF). Significant negative correlations for waist circumference (WC) (correlation coefficient −0.12 (95%CI: −0.19; −0.04), I2 = 51.50%), Triglycerides (TGs) (correlation coefficient −0.09 (95%CI: −0.15; −0.02), I2 = 0%) and ≥2 MetS risk factors (correlation coefficient −0.10 (95%CI: −0.16; −0.03), I2 = 0%); with high frequency (HF) were revealed. Significant positive correlations for high density lipoprotein (HDL) (correlation coefficient 0.08 (95%CI: 0.05; 0.11), I2 = 0%) and significant negative correlations of ≥2 MetS risk (correlation coefficient −0.04 (95%CI: −0.12; 0.03), I2 = 0.0%) with low frequency (LF) were revealed. Significant negative correlations for TGs (correlation coefficient −0.09 (95%CI: −0.23; 0.05), I2 = 2.01%) with a mean square root of the sum of differences between mean time between two successive intervals (rMSSD) and significant positive correlation of HDL (correlation coefficient 0.09 (95%CI: −0.01; 0.19), I2 = 0.33%) with standard deviation of the time between two successive intervals (SDNN) were also revealed. An Egger’s test indicated that there was no obvious publication bias for any of the above relationships except for TGs and rMSSD. The significance level stipulated for the meta-analysis was p < 0.05. Conclusions: lipid profiles (HDL and TGs), WC and BP were associated with CAM in young people up to the age of 19 years. The use of HRV indices to predict future MetS risk, and relationships with individual risk factors including HDL, BP, WC and TGs, were established. Future studies related to young people (up to the age of 19 years) are recommended to explore the associations reported here further.

Seismic Control Effect for Nonlinear Benchmark Building Using Passive or Semi-Active Damper

2002 ◽  
Author(s):  
Akira Fukukita ◽  
Tomoo Saito ◽  
Keiji Shiba
Keyword(s):  
Active Control ◽  
Passive Control ◽  
Feedforward Control ◽  
Electrical Power ◽  
Control Device ◽  
Control Effect ◽  
Damping Force ◽  
Active Device ◽  
Seismic Control ◽  
Control Forces

We study the control effect for a 20-story benchmark building and apply passive or semi-active control devices to the building. First, the viscous damping wall is selected as a passive control device which consists of two outer plates and one inner plate, facing each other with a small gap filled with viscous fluid. The damping force depends on the interstory velocity, temperature and the shearing area. Next, the variable oil damper is selected as a semi-active control device which can produce the control forces by little electrical power. We propose a damper model in which the damping coefficient changes according to both the response of the damper and control forces based on an LQG feedback and feedforward control theory. It is demonstrated from the results of a series of simulations that the both passive device and semi-active device can effectively reduce the response of the structure in various earthquake motions.

Active Helmholtz Resonator With Positive Real Impedance

2006 ◽  
Vol 129 (1) ◽  
pp. 94-100 ◽  
Author(s):  
Jing Yuan
Keyword(s):  
Noise Control ◽  
Helmholtz Resonator ◽  
Control Device ◽  
Positive Real ◽  
Noise Field ◽  
Strictly Positive Real ◽  
Control Devices ◽  
Passive Noise ◽  
Active Resonator ◽  
Electronic Resonance

The impedance of a passive noise control device is strictly positive real, if the device is installed in noise fields with weak mean flows. Passive noise control devices are, therefore, more reliable than active ones. Active control may be applied to a Helmholtz resonator to introduce electronic resonance. It will affect the impedance Zact of the resonator. A controller may be designed such that (a) Zact is small and resistive at some tunable frequencies; and (b) Re{Zact}⩾0 in the entire frequency range of interest. If criterion (a) is satisfied, the active resonator can suppress duct noise at tunable frequencies. It is difficult to design a controller to satisfy criterion (b) because parameters of the controller depend on acoustic parameters of the noise field. A new method is proposed here to design an active controller to meet both criteria simultaneously. The satisfaction of criterion (b) implies a positive real Zact and a robust active resonator with respect to parameter variation in the noise field. Experimental results are presented to verify the performance of the active resonator.

An Analytical Model for the Interaction of Mass Inclusions in Heterogeneous (HG) Blankets

2011 ◽  
Vol 133 (6) ◽  
Author(s):  
A. Wagner ◽  
M. E. Johnson ◽  
K. Idrisi ◽  
D. P. Bartylla
Keyword(s):  
Elastic Layer ◽  
Analytical Approach ◽  
Low Frequency ◽  
Control Device ◽  
Effective Stiffness ◽  
Special Focus ◽  
Dynamic Vibration Absorber ◽  
Low Frequencies ◽  
Dynamic Vibration ◽  
The Masses

The heterogeneous (HG) blanket is a passive treatment used to reduce the low frequency transmission of sound through partitions. HG blankets, glued onto a structure, consist of an elastic medium with embedded mass inhomogeneities that mechanically replicate a mass-spring-damper system to reduce efficient radiating structural modes at low frequencies. The elastic layer typically used has sound absorption properties to create a noise control device with a wide bandwidth of performance. The natural frequency of an embedded dynamic vibration absorber is determined by the mass of the inhomogeneity as well as by its effective stiffness due to the interaction of the mass inclusion with the elastic layer. A novel analytical approach has been developed to describe in detail the interaction of the mass inclusions with the elastic layer and the interaction between the masses by evaluating special elastomechanical concepts. The effective stiffness is predicted by the analytical approach based on the shape of the mass inclusions as well as on the thickness and material properties of the layer. The experimental validation is included and a simplified direct equation to calculate the effective stiffness of a HG blanket is proposed. Furthermore, the stress field inside the elastic material will be evaluated with focus on the stresses at the base to assess the modeling of one or more masses placed on top of the elastic layer as dynamic vibration absorbers. Finally, the interaction between two (or more) masses placed onto the same layer is studied with special focus on the coupling of the masses at low distances between them.

Nonlinear behavior of Helmholtz resonator with a compliant wall for low frequency, broadband noise control

2021 ◽  
pp. 1-29
Author(s):  
Maya Pishvar ◽  
Ryan L Harne
Keyword(s):  
Dynamic Response ◽  
Low Frequency ◽  
Nonlinear Behavior ◽  
Helmholtz Resonator ◽  
Broadband Noise ◽  
Sound Attenuation ◽  
Wall Material ◽  
Modeling Framework ◽  
Compliant Wall ◽  
Broadband Sound

Abstract Low frequency sound attenuation is often pursued using Helmholtz resonators (HRs). The introduction of a compliant wall around the acoustic cavity results in a two-degree-of-freedom (2DOF) system capable of more broadband sound absorption. In this study, we report the amplitude-dependent dynamic response of a compliant walled HR and investigate the effectiveness of wall compliance to improve the absorption of sound in linear and nonlinear regimes. The acoustic-structure interactions between the conventional Helmholtz resonator and the compliant wall result in non-intuitive responses when acted on by nonlinear amplitudes of excitation pressure. This paper formulates and studies a reduced order model to characterize the nonlinear dynamic response of the 2DOF HR with a compliant wall compared to that of a conventional rigid HR. Validated by experimental evidence, the modeling framework facilitates an investigation of strategies to achieve broadband sound attenuation, including by selection of wall material, wall thickness, geometry of the HR, and other parameters readily tuned by system design. The results open up new avenues for the development of efficient acoustic resonators exploiting the deflection of a compliant wall for suppression of extreme noise amplitudes.

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