scholarly journals Analysis of inertial amplification mechanism with smart spring-damper for attenuation of beam vibrations

2018 ◽  
Vol 157 ◽  
pp. 03002 ◽  
Author(s):  
Mateusz Barys ◽  
Robert Zalewski
Keyword(s):  
Complex Systems ◽  
Real Time ◽  
Active Control ◽  
Smart Materials ◽  
Low Frequency ◽  
Frequency Range ◽  
Longitudinal Vibrations ◽  
The Real ◽  
Resonance Frequencies ◽  
Amplification Mechanism

In this paper an inertial amplification mechanism with an embedded smart spring-damper device for attenuation of longitudinal vibrations in continuous structures is analyzed. The complex systems are the extension of the already investigated inertial mechanism, here additionally equipped with the vacuum controlled spring-damper device which shows features of smart materials. This allows the semi-active control to affect different frequency vibration ranges in the real time. The fea.tures of the basic inertia amplification mechanism are preserved as a possibility to generate two neighbouring anti-resonance frequencies between resonance peaks in the low frequency range.

Bandgap Properties of Two-Layered Locally Resonant Phononic Crystals

2020 ◽  
Vol 12 (07) ◽  
pp. 2050075
Author(s):  
Hongyun Wang ◽  
Heow Pueh Lee ◽  
Wei Xu
Keyword(s):  
Coating Thickness ◽  
Low Frequency ◽  
Phononic Crystals ◽  
Formation Mechanisms ◽  
Frequency Range ◽  
The Third ◽  
Resonance Frequencies ◽  
Rubber Coating ◽  
Lower Frequency Range ◽  
Mass Spring

Multi-layered locally resonant phononic crystals (LRPCs) with wider and multiple bandgaps (BGs) in low frequency range and small size of the unit cell have promising applications in noise and vibration controls. In this paper, a 2D two-layered ternary LRPC consisting of a periodical array of cylindrical inclusions embedded in an epoxy matrix is investigated by the finite element method (FEM), where the inclusion is comprised of two coaxial cylindrical steel cores with rubber coating. It is found that the size of the inclusion of the 2D two-layered ternary LRPC has significant effects on the BG properties. With the increase of the core radius and coating thickness, the first BG would shift to lower frequency range with its width decreasing, and the second BG width would become wider until the third BG appears. Especially, with the increase of the coating thickness, more bands and BGs would appear in the lower frequency range. Based on the formation mechanisms of the BGs, several mass-spring models to predict the frequencies of the first two BG edges are developed. The results calculated by these mass-spring models are in good agreement with those by the FEM except for the upper edge frequency of the second BG when the rubber coating thickness exceeds a certain value and the third BG is opened up. These proposed mass-spring models would allow for quick pre-estimation of the resonance frequencies, and facilitate the selection of possible parameters for the wider and lower frequency BGs to obtain the desired attenuation bands. The studies would also benefit the design of multiple BGs for some device applications.

Active Control of Low-Frequency Sound Radiation From Vibrating Panel Using Planar Sound Sources

2001 ◽  
Vol 124 (1) ◽  
pp. 2-9 ◽  
Author(s):  
Kean Chen ◽  
Gary H. Koopmann
Keyword(s):  
Active Control ◽  
Near Field ◽  
Low Frequency ◽  
Sound Radiation ◽  
Sound Field ◽  
Sound Power ◽  
Frequency Range ◽  
Sound Sources ◽  
Frequency Sound ◽  
Secondary Sources

Active control of low frequency sound radiation using planar secondary sources is theoretically investigated in this paper. The primary sound field originates from a vibrating panel and the planar sources are modeled as simply supported rectangular panels in an infinite baffle. The sound power of the primary and secondary panels are calculated using a near field approach, and then a series of formulas are derived to obtain the optimum reduction in sound power based on minimization of the total radiate sound power. Finally, active reduction for a number of secondary panel arrangements is examined and it is concluded that when the modal distribution of the secondary panel does not coincide with that of the primary panel, one secondary panel is sufficient. Otherwise four secondary panels can guarantee considerable reduction in sound power over entire frequency range of interest.

Dynamic analysis and vibration reduction of articulated silicone gel column with varying geometry

2021 ◽  
pp. 1-13
Author(s):  
Ji-Hou Yang ◽  
Xiao-Dong Yang ◽  
Qing-Kai Han ◽  
Jinguo Liu
Keyword(s):  
Frequency Band ◽  
Vibration Reduction ◽  
Low Frequency ◽  
Vibration Absorber ◽  
Frequency Range ◽  
Dynamic Vibration Absorber ◽  
Dynamic Vibration ◽  
Silicone Gel ◽  
Resonance Frequencies ◽  
Reduction Effect

Abstract To improve vibration reduction effect in low-frequency band of dynamic vibration absorber (DVA), a novel type of articulated silicone gel column (SGC) is introduced in the design of the tuned dynamic vibration absorber. The nonlinear variation of frequency of SGC with varying geometry is obtained by both finite element simulation and experiments. The most sensitive mode is located, which has wider frequency range by varying the geometry. The polynomial fitting is used to describe nonlinear relation between frequency and geometry. By tuning the geometry, the equivalent stiffness and then resonance frequencies can be manipulated to behave as an active vibration absorber. The vibration reduction experiment of SGC vibration absorbers is investigated. It is found that SGC has better vibration reduction effect in low-frequency band. The experimental results in the current design demonstrate that the vibration reduction effect can reach 94.03% when tuning SCG to the first order main resonance. The dimensions and material parameters of SGC should be altered for specific frequency range and vibration strength.

Early Warning of Low Frequency Oscillation and Analysis of its Related Issues

2012 ◽  
Vol 433-440 ◽  
pp. 7465-7470
Author(s):  
Chao Dong ◽  
Di Chen Liu ◽  
Zhen Chuan Du ◽  
Qing Fen Liao ◽  
Lei Yun ◽  
...  
Keyword(s):  
Real Time ◽  
Early Warning ◽  
Low Frequency ◽  
Local Maximum ◽  
Weak Links ◽  
Frequency Oscillation ◽  
Low Frequency Oscillation ◽  
The Real ◽  
Time Dynamic ◽  
Interconnected Power System

This paper set up the model of power transmissive observational section and put forward the real-time tracking method of power angle curve in steady state which could be used to identify and focus on monitoring the weak links, then to take early warnings of low frequency oscillation. On the dynamic situation of system been disturbed, we extracted the real-time dynamic damping value of the observational section, calculated its fitting curve of local maximum points and took the slope of curve as the criteria, in order to achieve early warning of low frequency oscillation under multiple disturbances in the interconnected power system.

Active Control of Non-Linear System by a Fuzzy-Optimal Control Technique

2010 ◽  
Author(s):  
Takashi Mochio
Keyword(s):  
Optimal Control ◽  
Nonlinear System ◽  
Control Theory ◽  
Real Time ◽  
Active Control ◽  
Optimal Control Theory ◽  
Time Dependent ◽  
Control Technique ◽  
The Real ◽  
Non Linear System

The purpose of this paper is to estimate the real time vibration control of an actively-controlled nonlinear structure due to non-stationary external loads. When the optimal control theory is adopted as a control law against the concerned task, the derivation of time dependent optimal control gains may be required because of a remarkable non-stationarity of response amplitude. In addition, since the system is nonlinear, it takes more time to calculate those time dependent gains. This means that it is difficult to strictly execute the real time active control with optimal control theory as for the non-stationary and nonlinear system. In this paper, therefore, one approximate technique, coupled fuzzy-optimal control, is proposed in order to realize the real time control of non-stationary and nonlinear system. Finally, results by deterministic analysis based on numerical simulations are compared with those by stochastic analysis using statistical equivalent linearization technique.

Bending Vibrations of the Femur and the Oscillatory Behavior of a Cemented Femoral Hip Endoprosthesis

2000 ◽  
Vol 122 (4) ◽  
pp. 416-422
Author(s):  
M. Thomsen ◽  
A. Go¨rtz ◽  
U. V. Na¨gerl ◽  
D. Kubein-Meesenburg ◽  
W. Go¨rtz ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Low Frequency ◽  
Oscillatory Behavior ◽  
Measuring System ◽  
Frequency Range ◽  
Entire Frequency Range ◽  
Bending Vibrations ◽  
Low Frequencies ◽  
Hip Endoprosthesis ◽  
Resonance Frequencies

The paper presents a novel method for recording amplitude and phase of 6D-vibrations of a spatial pendulum over a wide frequency range (10 Hz up to 20 kHz). The six degrees of freedom of the pendulum mass were monitored by three electrodynamic stereo pickups. At rest, the tips of the needles and the pendulum’s center of mass defined the reference system with respect to which the oscillations of the mass were recorded in terms of their amplitudes and phases. Its small dimensions, constant transfer characteristics, linearity, high dynamics, and virtual lack of reaction onto the moving system over the entire frequency range provided the advantages of the measuring system. This method was used to analyze the spatial 6D-vibrations of the head of a cemented femoral hip endoprosthesis when the femur was stimulated to bending vibrations. The head of the prosthesis carried out axial rotational vibrations at every frequency used to stimulate the femur. The amplitudes of the axial rotations of the cortical bone were small in comparison to the ones of the prosthesis head, indicating that axial rotational vibrations following femur bending vibrations mainly stressed the spongiosa and the cement layer. This was observed over the entire frequency range, including at the low frequencies relevant for gait. Over the low-frequency range, as well as at some of the higher resonance frequencies, stationary instantaneous helical axes characterized the vibrations. The measurements suggest the mechanism that the interface “implant-bone” may already be stressed by axial torsional loads when the femur is loaded by bending impacts that are known to occur during walking. [S0148-0731(00)01604-6]

Active attenuation of sound transmission through a soft-core sandwich panel into an acoustic enclosure using volume velocity cancellation

2015 ◽  
Vol 229 (17) ◽  
pp. 3096-3112 ◽  
Author(s):  
Kiran Chandra Sahu ◽  
Jukka Tuhkuri ◽  
JN Reddy
Keyword(s):  
Active Control ◽  
Sandwich Panel ◽  
Control Method ◽  
Low Frequency ◽  
Sound Transmission ◽  
Soft Core ◽  
Frequency Range ◽  
Broad Frequency Range ◽  
Volume Velocity ◽  
Numerical Studies

In this paper, active control of harmonic sound transmitted through a soft-core sandwich panel into a rectangular enclosure is studied. As it has already been shown for the low frequency region, the noise transmission through a soft-core sandwich panel mainly occurs due to the flexural and the dilatational modes. Therefore, in this study, volume velocity cancellation control strategy is used to control these modes, and achieve sound attenuation in a broad frequency range. Point force and uniformly distributed force actuators are used as the secondary actuator to cancel the volume velocity of the bottom faceplate, which opens to the cavity, of the sandwich panel. Cancelling the net volume velocity of the bottom faceplate is compared not only in terms of the reduction in sound transmission through the sandwich panel into cavity but also in terms of the faceplate velocities. Also, the effectiveness of the volume velocity cancellation strategy has been studied for different values of isotropic loss factor of the core. Sound transmission into the cavity has also been calculated by considering the effect of cavity pressure on the sandwich panel. Numerical studies indicate that the active control method controls both the flexural and the dilatational modes of the sandwich panel and therefore, attenuates significant amount of sound pressure inside the cavity irrespective of the isotropic loss factors of the viscoelastic core in a broad frequency range. Also a finite element study has been done in the commercially available COMSOL Multiphysics software to compare with the analytical results.

ANALYZING THE REAL-TIME PROPERTIES OF A U.S. NAVY SIGNAL PROCESSING SYSTEM

2001 ◽  
Vol 08 (04) ◽  
pp. 301-322 ◽  
Author(s):  
STEVE GODDARD ◽  
KEVIN JEFFAY
Keyword(s):  
Signal Processing ◽  
Real Time ◽  
State Of The Art ◽  
Low Frequency ◽  
Processing System ◽  
The State ◽  
Signal Processing System ◽  
Processing Application ◽  
The Real ◽  
On Line

The state of the art in verifying the real-time requirements of applications developed using general processing graph models relies on simulation or off-line scheduling. We extend the state of the art by presenting analytical methods that support the analysis of cyclic processing graphs executed with on-line schedulers. We show that it is possible to compute the latency inherent in a processing graph independent of the hardware hosting the application. We also show how to compute the real-time execution rate of each node in the graph. Using the execution rate of each node and the time it takes per execution on a given processor, the resulting CPU utilization can be computed, as shown here for the Directed Low Frequency Analysis and Recording (DIFAR) acoustic signal processing application from the Airborne Low Frequency Sonar (ALFS) system of the SH-60B LAMPS MK III anti-submarine helicopter.

scholarly journals Monitoring Location Prototype Using Lora Module

2018 ◽  
Vol 218 ◽  
pp. 03007 ◽  
Author(s):  
Mia Rosmiati ◽  
Mochammad Fachru Rizal ◽  
Irma Wanti
Keyword(s):  
Real Time ◽  
Data Transmission ◽  
Low Frequency ◽  
Line Of Sight ◽  
The Internet ◽  
The Real ◽  
Child Abduction ◽  
Internet Network

The number of child abduction cases in Indonesia today is always increasing every year, this has given concern to parents in leaving their children to play outside the home. Therefore, a device that can detect the presence of children when outside the home was needded. At this time, some devices can monitor ones location easily and quickly, such as Smartwatch and GPS Tracker, but the device must be connected to the internet With these conditions, it needs a device that can transmit information in real time without any dependence LoRa module are using low frequency radio as data transmission medium, can be built a Location monitoring prototype without connecting to internet network. From the examination results, the built system successfully shows the real time location coordinate point with a maximum data transmission limit of 2 KM for Line Of Sight (LOS).

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