Natural-frequency concept utilized in remote probing of the earth

2003 ◽  
Vol 81 (4) ◽  
pp. 705-712 ◽  
Author(s):  
S T Bishay ◽  
O M Abo-Seida ◽  
G M Sami
Keyword(s):  
Natural Frequency ◽  
Analytical Form ◽  
Step Response ◽  
Earth Model ◽  
Induced Voltage ◽  
Diagnostic Features ◽  
Vertical Magnetic Dipole ◽  
Remote Probing ◽  
Displacement Currents ◽  
Layered Ground

The complete time-domain fields due to a vertical magnetic dipole on the surface of a two-layered earth model are derived in an analytical form using the natural-frequency concept. In these expressions, the displacement currents in the earth's layers are taken into consideration. The step responses of the induced voltage in a horizontal receiving loop is found to have definite diagnostic features for the ground beneath. These features are demonstrated by numerical results and shown by figures. The clear distinction between the step response of the homogeneous and the two-layered ground suggests that this response can be used for the detection of the stratification. PACS Nos.: 41.20.Jb, 42.25.Bs, 42.25.Gy, 44.05.+e

Time-domain study of transient fields for a thin circular loop antenna

2002 ◽  
Vol 80 (9) ◽  
pp. 995-1003 ◽  
Author(s):  
S T Bishay ◽  
G M Sami
Keyword(s):  
Time Domain ◽  
Analytical Form ◽  
Loop Antenna ◽  
Inverse Laplace Transform ◽  
Wave Number ◽  
Earth Model ◽  
Circular Loop ◽  
Wave Forms ◽  
Displacement Currents ◽  
The Time Domain

The transient fields in the time-domain of a thin circular loop antenna on a two-layer conducting earth model are expressed in analytical form. In these expressions, the displacement currents both in the two-layer ground and in the air region are taken into consideration. The closed-form expressions of the time-domain are obtained as the inverse Laplace transform of the derived full-wave time-harmonic solution. These time-domain solutions are obtained as a summation of wave-guide modes plus contributions from branch cuts in the complex plane of the longitudinal wave number. Numerical examples are given to indicate the important features in the wave forms of the surface fields due to step and pulsed current excitation. These features provide the means of detecting the earth's stratification, measuring the overburden height, and determining the ratio of the conductivities of the layers. PACS Nos.: 41.20Jb, 42.25Bs, 42.25Gy, 44.05+e

scholarly journals Dynamic Characteristics Analysis of the Six-Axis Force/Torque Sensor

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Liyue Fu ◽  
Aiguo Song
Keyword(s):  
Natural Frequency ◽  
Dynamic Characteristics ◽  
Dynamic Models ◽  
Dynamic Range ◽  
Model Identification ◽  
Step Response ◽  
Fe Model ◽  
De Algorithm ◽  
Characteristics Analysis ◽  
Experimental Values

In this study, dynamic characteristics of a robot six-axis wrist force/torque (F/T) sensor with crossbeam elastomer are analyzed by two methods of model identification, a method for simultaneous identification of order and parameters of the model (SIM) and a method based on the differential evolution (DE) algorithm. Firstly, by establishing the simplified mechanical model and finite element (FE) model, respectively, natural frequency of the six-axis wrist F/T sensor is calculated. Secondly, dynamic calibration experiment is conducted. Lastly, two dynamic models of the sensor are identified by SIM and DE methods and the dynamic characteristics of the sensor, such as natural frequency and working band, are further analyzed. Comparing experimental values with the theoretical values, the results show that this sensor has a wide dynamic range with the first natural frequency at more than 1600 Hz, working bands (±5%) are more than 400 Hz, and the step response oscillation is intense. This study can provide a reference for the application of the six-axis F/T sensor in the field of dynamic measurement.

STUDY OF THE DYNAMIC CHARACTERISTICS OF PIEZOELECTRIC MICROCANTILEVER PROBE

2013 ◽  
Vol 27 (23) ◽  
pp. 1350165 ◽  
Author(s):  
AN-PING LIU ◽  
XIAO-NAN SUN ◽  
XING-XING YAO
Keyword(s):  
Natural Frequency ◽  
Dynamic Characteristics ◽  
Resonance Effect ◽  
Dynamic Mode ◽  
Force Frequency ◽  
Induced Voltage ◽  
Position Change ◽  
Peak Voltage ◽  
Static Mode ◽  
Piezoelectric Microcantilever

A piezoelectric microcantilever probe is designed for the scanning probe microscope working in tapping mode, and the dynamic characteristics of the piezoelectric microcantilever probe are tested by experiments. The results indicate that due to the resonance effect, induced voltage and sensitivity of microcantilever are not only associated with force magnitude, but also with the force frequency. When the frequency is close to the first natural frequency 97.04 Hz, the output voltage rapidly increases and reaches a maximum value 62.0 mV. The peak voltage value and its position change as the structure size changes. In dynamic mode, the peak voltage is an order of magnitude higher than that in the static mode, and the dynamic mode is more sensitive. Selecting a reasonable size for the device can help to improve the first-order natural frequency and improve the response speed of piezoelectric microcantilever probe during nanomicro detecting.

Using the natural-frequency concept in remote probing of the earth

Radio Science ◽  
1976 ◽  
Vol 11 (3) ◽  
pp. 199-209 ◽  
Author(s):  
R. J. Lytle ◽  
D. L. Lager
Keyword(s):  
Natural Frequency ◽  
The Earth ◽  
Remote Probing

Wave-tilt characteristics of TE-mode waves

1981 ◽  
Vol 18 (2) ◽  
pp. 382-385 ◽  
Author(s):  
Ramesh P. Singh ◽  
Tarkeshwar Lal
Keyword(s):  
Dielectric Constants ◽  
Phase Changes ◽  
Earth Model ◽  
Frequency Range ◽  
Homogeneous Half Space ◽  
Te Mode ◽  
Tm Mode ◽  
Displacement Currents ◽  
Lower Frequency Region ◽  
Wave Tilt

The dependence of TE-mode wave-tilt on frequency and altitude of measurement, and the resistivity and dielectric constants of the ground have been investigated. Computational results showing the influence of these parameters on the amplitude and phase of the wave-tilt over a homogeneous half-space earth model have been presented. In contrast to TM-mode waves, the wave-tilt effects for TE-mode are stronger in the lower frequency region. In the lower frequency range, the amplitude decreases with the increase in resistivity of the ground, whereas it increases for an increase in dielectric constant value. When the displacement currents are ignored, the magnitude of amplitude of wave-tilt is reduced considerably. The altitude of measurement has minimal effect on the amplitude, but the phase changes appreciably in some cases.

Vibration control of a servomotor-driven coupled elastic shaft-elastic beam system

2004 ◽  
Vol 218 (10) ◽  
pp. 1115-1124
Author(s):  
H Diken ◽  
A Ankarali
Keyword(s):  
Control System ◽  
Natural Frequency ◽  
Frequency Ratio ◽  
Damping Ratio ◽  
Elastic Beam ◽  
Step Response ◽  
Elastic Shaft ◽  
Disc Rotation ◽  
Frequency Ratios ◽  
System Frequency

In this study an elastodynamic control system consisting of servomotor, elastic shaft, disc and elastic beam, which is attached to the disc, is considered. Non-dimensional parametric equations of motions are obtained. The control system damping ratio, the frequency ratio of the torsional natural frequency to the beam natural frequency and also the frequency ratio of the beam natural frequency to the control system frequency are used as parameters. Simulation results are obtained for the step response of the disc rotation and for the beam tip vibration for different frequency ratios. Results show that even for highly flexible systems the effect of flexibility on the control system behaviour can be substantially reduced by proper selection of the control system frequency.

scholarly journals Hybrid posicast controller for a DC-DC buck converter

2008 ◽  
Vol 5 (1) ◽  
pp. 121-138 ◽  
Author(s):  
Udhayakumar Kaithamalai ◽  
Lakshmi Ponnusamy ◽  
Boobal Kandasamy
Keyword(s):  
Natural Frequency ◽  
Traditional Method ◽  
Pid Controller ◽  
Feedback Loop ◽  
Buck Converter ◽  
Step Response ◽  
Loop Design ◽  
Hybrid Controller ◽  
Damped System ◽  
Lower Noise

A new Posicast compensated hybrid controller for the DC-DC Buck converter is investigated. Posicast is a feed forward compensator, which eliminates the overshoot in the step response of a lightly damped system. However, the traditional method is sensitive to variations in natural frequency. The new method described here reduces this undesirable sensitivity by using Posicast within the feedback loop. Design of the Posicast function is independent of computational delay. The new controller results in a lower noise in the control signal, when compared to a conventional PID controller.

Determination of frequency response from step response: application to fluid-filled catheters

1979 ◽  
Vol 236 (2) ◽  
pp. H376-H378 ◽  
Author(s):  
S. A. Glantz ◽  
J. V. Tyberg
Keyword(s):  
Decay Rate ◽  
Frequency Response ◽  
Natural Frequency ◽  
Damping Ratio ◽  
Step Change ◽  
Step Response ◽  
Undamped Natural Frequency

The performance of a fluid-filled catheter can be described by reporting its undamped natural frequency and damping ratio. These parameters can be measured by subjecting the catheter to sinusoidally varying pressures at a wide variety of frequencies to obtain the frequency response. They can also be computed from the response to a step change in pressure, which is often easier to produce. This paper derives the required equations and includes a graph which permits one to look up the undamped natural frequency after measuring the period and decay rate of the oscillation following a step change in pressure.

The Size-Dependent Electromechanical Coupling Response in Circular Micro-Plate due to Flexoelectricity

2016 ◽  
Vol 33 (6) ◽  
pp. 873-883 ◽  
Author(s):  
X. Ji ◽  
A.-Q. Li
Keyword(s):  
Size Effect ◽  
Natural Frequency ◽  
Circular Plate ◽  
Electromechanical Coupling ◽  
Initial Conditions ◽  
Couple Stress Theory ◽  
Piezoelectric Response ◽  
Induced Voltage ◽  
Cylindrical Coordinates ◽  
Size Dependent

AbstractFlexoelectricity, the coupling of strain gradient to polarization, enhances the properties of piezoelectric response desirable for advanced MEMS dramatically even in centrosymmetric dielectrics. In this paper, the general formulations of the flexoelectric couple stress theory presented by Hadjesfandiari in orthogonal curvilinear coordinate system are derived, and are then specified for the case of cylindrical coordinates. A size-dependent flexoelectric model of circular plate is established based on the current formulations in cylindrical coordinates. The governing equations, boundary conditions and initial conditions are derived by applying Hamilton's principle. The static bending and free vibration problems of a simply supported axisymmetric circular plate are carried out to illustrate the applicability of the present model. Numerical results reveal that a homogeneous electric field between the up and down surfaces of the circular plate is induced indeed. The generated deflection, induced voltage and natural frequency show obvious size effect, but the size effect is almost diminishing as the thickness of the plate is far greater than the material length scale parameter. As the increase of the flexoelectric coefficient, the induced voltage increases evidently and the generated deflection and the natural frequency increase weakly.

scholarly journals Dynamic Analysis and Experiment of 6-DOF Compliant Platform Based on Bridge-Type Amplifier

Micromachines ◽  
2020 ◽  
Vol 11 (11) ◽  
pp. 1024
Author(s):  
Chao Lin ◽  
Shan Zheng ◽  
Mingdong Jiang
Keyword(s):  
Dynamic Model ◽  
Natural Frequency ◽  
Theoretical Calculations ◽  
Lagrange Equation ◽  
Damping Ratio ◽  
Elastic Beam ◽  
Analytical Models ◽  
Step Response ◽  
Element Analysis ◽  
Bridge Type

In this paper, we establish a dynamic model of a six-degrees-of-freedom (6-DOF) compliant positioning platform based on bridge-type amplifiers. Based on the elastic beam theory and energy relationship, we derived the bridge-type amplifier’s dynamic model using the Lagrange equation. Then, we established a dynamic model of the compliant platform based on the equivalent mass and equivalent stiffness of the bridge-type amplifier, and the analysis formula of the natural frequency was derived. Finally, the analytical models of natural frequencies of the bridge-type amplifier and the compliant platforms were verified using the finite element analysis (FEA) method. Through modal experiments, the damping ratio and natural frequency were identified. Step response experiments in the X/Y direction and Z direction were performed. The phenomenon that the experimental results appeared to match the theoretical calculations indicates that the dynamic model was accurate.

Sign in / Sign up

Export Citation Format

Share Document