Frequency-Weighted Variable-Length Controllers Using Anytime Control Strategies

2015 ◽  
Vol 137 (8) ◽  
Author(s):  
Bonnie H. Ferri ◽  
Aldo A. Ferri ◽  
Gundula B. Runge
Keyword(s):  
Weighting Function ◽  
Control Strategies ◽  
Low Frequency ◽  
Low Frequencies ◽  
High Frequencies ◽  
Frequency Components ◽  
Computational Resources ◽  
Weighted Variable ◽  
Sample Time ◽  
Selection Of

This paper develops an optimal frequency-weighted strategy to design anytime controllers that can react to changing computational resources. The selection of the weighting function is driven by the expectation of the situations that would require anytime operation. For example, if the anytime operation is due to occasional and isolated missed deadlines, then the weighting on high frequencies should be larger than that for low frequencies. Low frequency components will have a smaller change over one sample time, so failing to update these components for one sample period will have less effect than with the high frequency components. Additional considerations explored in this paper are stability analyses, architectural issues, and transient management. Two examples are included that demonstrate the methodology.

Frequency-Weighted Variable-Length Controllers Using Anytime Control Strategies

2011 ◽  
Author(s):  
Gundula B. Runge ◽  
Al Ferri ◽  
Bonnie Ferri
Keyword(s):  
Time Scale ◽  
Weighting Function ◽  
Control Strategies ◽  
Low Frequency ◽  
Low Frequencies ◽  
High Frequencies ◽  
Frequency Components ◽  
Computational Resources ◽  
Weighted Variable ◽  
Selection Of

This paper considers an anytime strategy to implement controllers that react to changing computational resources. The anytime controllers developed in this paper are suitable for cases when the time scale of switching is in the order of the task execution time, that is, on the time scale found commonly with sporadically missed deadlines. This paper extends the prior work by developing frequency-weighted anytime controllers. The selection of the weighting function is driven by the expectation of the situations that would require anytime operation. For example, if the anytime operation is due to occasional and isolated missed deadlines, then the weighting on high frequencies should be larger than that for low frequencies. Low frequency components will have a smaller change over one sample time, so failing to update these components for one sample period will have less effect than with the high frequency components. An example will be included that applies the anytime control strategy to a model of a DC motor with deadzone and saturation nonlinearities.

Influence of Materials on the Performance Limits of Microactuators

2007 ◽  
Vol 1052 ◽  
Author(s):  
Prasanna Srinivasan ◽  
S. Mark Spearing
Keyword(s):  
Thin Films ◽  
Shape Memory ◽  
High Performance ◽  
Low Frequency ◽  
Beam Theory ◽  
Performance Limits ◽  
Low Frequencies ◽  
Thermal Actuators ◽  
Work Volume ◽  
Selection Of

AbstractThe selection of actuators at the micro-scale requires an understanding of the performance limits of different actuation mechanisms governed by the optimal selection of materials. This paper presents the results of analyses for elastic bi-material actuators based on simple beam theory and lumped parameter thermal models. Comparisons are made among commonly employed actuation schemes (electro-thermal, piezoelectric and shape memory) at micro scales and promising candidate materials are identified. Polymeric films on Si subjected to electro-thermal heating are optimal candidates for high displacement, low frequency devices while ferroelectric thin films of Pb-based ceramics on Si/ DLC are optimal for high force, high frequency devices. The ability to achieve ∼10 kHz at scales < 100μm make electro-thermal actuators competitive with piezoelectric actuators considering the low work/volume obtained in piezoelectric actuation (∼ 10−8J.m−3.mV−2). Although shape memory alloy (SMA) actuators such as Ni-Ti on Si deliver larger work (∼ 1 J.m−3K−2) than electro-thermal actuators at relatively low frequencies (∼ 1 kHz), the critical scale associated with the cessation of the shape memory effect forms the bounding limit for the actuator design. The built-in compressive stress levels (∼ 1GPa) in thin films of Si and DLC could be exploited for realizing a high performance actuator by electro-thermal buckling.

scholarly journals Deep learning for low-frequency extrapolation from multioffset seismic data

Geophysics ◽  
2019 ◽  
Vol 84 (6) ◽  
pp. R989-R1001 ◽  
Author(s):  
Oleg Ovcharenko ◽  
Vladimir Kazei ◽  
Mahesh Kalita ◽  
Daniel Peter ◽  
Tariq Alkhalifah
Keyword(s):  
Deep Learning ◽  
Seismic Data ◽  
Signal To Noise Ratio ◽  
Waveform Inversion ◽  
Low Frequency ◽  
Low Frequencies ◽  
Seismic Surveys ◽  
Full Waveform ◽  
Frequency Components ◽  
Marine Seismic

Low-frequency seismic data are crucial for convergence of full-waveform inversion (FWI) to reliable subsurface properties. However, it is challenging to acquire field data with an appropriate signal-to-noise ratio in the low-frequency part of the spectrum. We have extrapolated low-frequency data from the respective higher frequency components of the seismic wavefield by using deep learning. Through wavenumber analysis, we find that extrapolation per shot gather has broader applicability than per-trace extrapolation. We numerically simulate marine seismic surveys for random subsurface models and train a deep convolutional neural network to derive a mapping between high and low frequencies. The trained network is then tested on sections from the BP and SEAM Phase I benchmark models. Our results indicate that we are able to recover 0.25 Hz data from the 2 to 4.5 Hz frequencies. We also determine that the extrapolated data are accurate enough for FWI application.

The Use of Optimally Shaped Piezo-electric Film Sensors in the Active Control of Free Field Structural Radiation, Part 2: Feedback Control

1996 ◽  
Vol 118 (1) ◽  
pp. 112-121 ◽  
Author(s):  
S. D. Snyder ◽  
N. Tanaka ◽  
Y. Kikushima
Keyword(s):  
Feedback Control ◽  
Control Strategies ◽  
Free Field ◽  
Low Frequency ◽  
Acoustic Power ◽  
State Equations ◽  
Subsequent Increase ◽  
Low Frequencies ◽  
Control Approach ◽  
Iir Filters

Feedback control of free field structural radiation is considered. State equations are formulated with a transformation which decouples the acoustic power error criterion. Using the resultant equations, expressed in terms of “transformed mode” states, the order of the state equations can be significantly reduced at low frequencies. Two experimental implementations of feedback control strategies using shaped piezoelectric polymer film sensors to measure the transformed system states are described. The first of these is a simple analog implementation. The second implementation is in discrete time, where an adaptive algorithm for optimizing the weights of IIR filters for practical use is described. It is shown that by using the outlined control approach significant levels of low frequency acoustic power attenuation can be obtained with no control spillover and subsequent increase in higher frequency acoustic power output.

The lung-eardrum pathway in three treefrog and four dendrobatid frog species: some properties of sound transmission.

1994 ◽  
Vol 195 (1) ◽  
pp. 329-343 ◽  
Author(s):  
G Ehret ◽  
E Keilwerth ◽  
T Kamada
Keyword(s):  
High Frequency ◽  
Body Wall ◽  
Low Frequency ◽  
Sound Intensity ◽  
The Body ◽  
Response Curves ◽  
Low Frequencies ◽  
Best Response ◽  
Lateral Body ◽  
Frequency Components

Frequency-response curves of the tympanum and lateral body wall (lung area) were measured by laser Doppler vibrometry in three treefrog (Smilisca baudini, Hyla cinerea, Osteopilus septentrionalis) and four dendrobatid frog (Dendrobates tinctorius, D. histrionicus, Epipedobates tricolor, E. azureiventris) species. The high-frequency cut-off of the body wall response was always lower than that of the tympanum. The best response frequencies of the lateral body wall were lower than those of the tympanum in some species (S. baudini, O. septentrionalis, D. tinctorius), while in the others they were rather similar. Best tympanic frequencies and best body wall response frequencies tended to differ more with increasing body size. Stimulation of the tympanum by sound transfer through 3.14 mm2 areas of the lateral body wall showed that the lung-eardrum pathway can be in two states, depending on breathing activity within the lungs: 44% (in Smilisca), 39% (in Hyla) and 31% (in Osteopilus) of the eardrum vibrations were 2.5-8 times (8-18 dB) larger when the frogs were breathing with the lungs compared with non-breathing conditions. The vibration amplitudes of the tympanum and lateral body wall of the treefrogs followed the same dependence on sound intensity, only absolute amplitudes differed between species. Our results suggest that the lung-eardrum pathway attenuates high-frequency components of species-specific calls and enhances low-frequency components. In addition, an amplitude modulation is imposed on the low frequencies during the rhythm of breathing.

Sensitive Response to Low-Frequency Cochlear Distortion Products in the Auditory Midbrain

2009 ◽  
Vol 101 (3) ◽  
pp. 1560-1574 ◽  
Author(s):  
Cornelius Abel ◽  
Manfred Kössl
Keyword(s):  
Low Frequency ◽  
Otoacoustic Emission ◽  
Threshold Level ◽  
Auditory Midbrain ◽  
Low Frequencies ◽  
Distortion Product ◽  
Distortion Products ◽  
Third Phase ◽  
Complex Stimuli ◽  
Frequency Components

During auditory stimulation with several frequency components, distortion products (DPs) are generated as byproduct of nonlinear cochlear amplification. After generated, DP energy is reemitted into the ear channel where it can be measured as DP otoacoustic emission (DPOAE), and it also induces an excitatory response at cochlear places related to the DP frequencies. We measured responses of 91 inferior colliculus (IC) neurons in the gerbil during two-tone stimulation with frequencies well above the unit's receptive field but adequate to generate a distinct distortion product (f2-f1 or 2f1-f2) at the unit's characteristic frequency (CF). Neuronal responses to DPs could be accounted for by the simultaneously measured DPOAEs for DP frequencies >1.3 kHz. For DP frequencies <1.3 kHz ( n = 25), there was a discrepancy between intracochlear DP magnitude and DPOAE level, and most neurons responded as if the intracochlear DP level was significantly higher than the DPOAE level in the ear channel. In 12% of those low-frequency neurons, responses to the DPs could be elicited even if the stimulus tone levels were below the threshold level of the neuron at CF. High intracochlear f2-f1 and 2f1-f2 DP-levels were verified by cancellation of the neuronal DP response with a third phase-adjusted tone stimulus at the DP frequency. A frequency-specific reduction of middle ear gain at low frequencies is possibly involved in the reduction of DPOAE level. The results indicate that pitch-related properties of complex stimuli may be produced partially by high intracochlear f2-f1 distortion levels.

Low frequency damping and ultrasonic attenuation in Ti3Sn-based alloys

1994 ◽  
Vol 9 (6) ◽  
pp. 1441-1448 ◽  
Author(s):  
Catherine R. Wong ◽  
Robert L. Fleischer
Keyword(s):  
High Temperature ◽  
Room Temperature ◽  
Ultrasonic Attenuation ◽  
Low Frequency ◽  
Basic Mechanism ◽  
Low Frequencies ◽  
High Frequencies ◽  
Young’S Moduli ◽  
High Temperature Alloys ◽  
Damping Behavior

Studies of high-temperature alloys in the Ti-Sn system based on the intermetallic compound Ti3Sn have identified alloys that damp strongly both at low frequencies (0.1 to 10 Hz) and high frequencies (5 to 20 MHz). The low frequency damping behavior shows loss factors as high as 0.04 at room temperature and Young's moduli that rise with temperature from 40 °C to 100 °C for two alloys. Although the basic mechanism or mechanisms of energy dissipation are presently unknown, the alloys are notable for unusual shapes of microhardness indentations. The deformations imply that large reversible strains can occur at temperatures from 23 °C to 1150 °C.

scholarly journals Laboratory measurements of low- and high-frequency elastic moduli in Fontainebleau sandstone

Geophysics ◽  
2013 ◽  
Vol 78 (5) ◽  
pp. D369-D379 ◽  
Author(s):  
Emmanuel C. David ◽  
Jérome Fortin ◽  
Alexandre Schubnel ◽  
Yves Guéguen ◽  
Robert W. Zimmerman
Keyword(s):  
Bulk Modulus ◽  
Elastic Moduli ◽  
High Pressures ◽  
Low Frequency ◽  
Frequency Dispersion ◽  
Low Frequencies ◽  
High Frequencies ◽  
Fontainebleau Sandstone ◽  
Wave Velocities ◽  
Water Saturated

The presence of pores and cracks in rocks causes the fluid-saturated wave velocities in rocks to be dependent on frequency. New measurements of the bulk modulus at low frequencies (0.02–0.1 Hz) were obtained in the laboratory using oscillation tests carried out on two hydrostatically stressed Fontainebleau sandstone samples, in conjunction with ultrasonic velocities and static measurements, under a range of differential pressures (10–95 MPa), and with three different pore fluids (argon, glycerin, and water). For the 13% and 4% porosity samples, under glycerin- and water-saturated conditions, the low-frequency bulk modulus at 0.02 Hz matched well the low-frequency and ultrasonic dry bulk modulus. The glycerin- and water-saturated samples were much more compliant at low frequencies than at high frequencies. The measured bulk moduli of the tested rocks at low frequencies (0.02–0.1 Hz) were much lower than the values predicted by the Gassmann equation. The frequency dispersion of the P and S velocities was much higher at low differential pressures than at high pressures, due to the presence of open cracks at low differential pressures.

Permeability and borehole Stoneley waves: Comparison between experiment and theory

Geophysics ◽  
1989 ◽  
Vol 54 (1) ◽  
pp. 66-75 ◽  
Author(s):  
Kenneth W. Winkler ◽  
Hsui‐Lin Liu ◽  
David Linton Johnson
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Theoretical Models ◽  
Oil Field ◽  
Stoneley Wave ◽  
Biot Theory ◽  
Frequency Dependent ◽  
Low Frequencies ◽  
High Frequencies ◽  
Theoretical Predictions

We performed laboratory experiments to evaluate theoretical models of borehole. Stoneley wave propagation in permeable materials. A Berea sandstone and synthetic samples made of cemented glass beads were saturated with silicone oils. We measured both velocity and attenuation over a frequency band from 10 kHz to 90 kHz. Our theoretical modeling incorporated Biot theory and Deresiewicz‐Skalak boundary conditions into a cylindrical geometry and included frequency‐dependent permeability. By varying the viscosity of the saturating pore fluid, we were able to study both low‐frequency and high‐frequency regions of Biot theory, as well as the intermediate transition zone. In both low‐frequency and high‐frequency regions of the theory, we obtained excellent agreement between experimental observations and theoretical predictions. Velocity and attenuation (1/Q) are frequency‐dependent, especially at low frequencies. Also at low frequencies, velocity decreases and attenuation increases with increasing fluid mobility (permeability/viscosity). More complicated behavior is observed at high frequencies. These results support recent observations from the oil field suggesting that Stoneley wave velocity and attenuation may be indicative of formation permeability.

scholarly journals Spectra of Low-Frequency Ground Vibrations Generated by High-Speed Trains on Layered Ground

1997 ◽  
Vol 16 (4) ◽  
pp. 257-270 ◽  
Author(s):  
V.V. Krylov
Keyword(s):  
High Speed ◽  
Low Frequency ◽  
Ground Vibration ◽  
Ground Vibrations ◽  
Frequency Spectra ◽  
Low Frequencies ◽  
High Speed Trains ◽  
Frequency Components ◽  
Noticeable Reduction ◽  
Layered Ground

Increase in speeds of modern railway trains is usually accompanied by higher levels of generated ground vibrations. In the author's earlier paper [V.V. Krylov, Applied Acoustics, 44, 149–164 (1995)], it has been shown that especially large increase in vibration level may occur if train speeds v exceed the velocity of Rayleigh surface waves in the ground cR., i.e., v > cR. Such a situation might arise, for example, with French TGV trains for which speeds over 515 km/h have been achieved. The present paper investigates the effect of geological layered structure of the ground on ground vibrations generated by high-speed trains. It is shown that, since Rayleigh wave velocities in layered ground are dispersive and normally increase at lower frequencies associated with deeper penetration of surface wave energy into the ground, the trans-Rayleigh condition v > cR may not hold at very low frequencies. This will cause a noticeable reduction in low-frequency components of generated ground vibration spectra. Theoretical results are illustrated by numerically calculated frequency spectra of ground vibrations generated by single axle loads travelling at different speeds and by TGV or Eurostar high-speed trains.

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