scholarly journals Amplification of useful vibration using on-off damping

2020 ◽  
Author(s):  
La Duc Viet
Keyword(s):  
Single Variable ◽  
Variable Function ◽  
Electrical Damping ◽  
Fixed Times ◽  
Excited Oscillator ◽  
Damping Controller

This paper points out how much useful vibration can be extracted from a base-excited oscillator, which is controlled by the on-off electrical damping. We study the class of on-off electrical damping controller, which switches the damping level from high to low and back at fixed times every quarter of period. The problem reduces to the maximization of a single-variable function. This result can open the new direction to amplify the useful vibration using controllable dampings.

Upper Bound of Power Harvested by an On-Off Electrical Damping in a State Space System

2021 ◽  
Author(s):  
Viet, Duc La
Keyword(s):  
Upper Bound ◽  
Switching Time ◽  
Linear Time ◽  
Optimal Switching ◽  
Vibration Energy Harvester ◽  
Energy Harvesters ◽  
Linear Time Invariant ◽  
Piezoelectric Energy ◽  
Variable Function ◽  
Electrical Damping

Abstract This paper presents the theoretical upper bound of the harvested power, which is amplified by a generalized electrical damping switching controller in a linear time invariant system. The upper bound is found by maximizing a single-variable function with respect to the switching time. The upper bound shows the possibility of raising the power-frequency curve over the optimal passive curves reported in literature. The optimal switching time of the upper bound shows the mechanics that determine the optimality. The upper bound solution is not only a good benchmark to evaluate but also a clear guide to design any other practical controllers. To demonstrate these two benefits, four examples in literature were revisited: the Single DOF electromagnetic and piezoelectric energy harvesters, the Dual-mass vibration energy harvester and the quarter car hybrid electromagnetic suspension. A demonstration controller is proposed in all examples. The upper bound is used to evaluate the demonstration controller. The optimal switching time is used to explain the reason of a good or bad controller.

scholarly journals Tangent Orbital Rendezvous Using Linear Relative Motion withJ2Perturbations

2013 ◽  
Vol 2013 ◽  
pp. 1-8
Author(s):  
Gang Zhang ◽  
Dongzhe Wang ◽  
Xibin Cao ◽  
Zhaowei Sun
Keyword(s):  
Relative Motion ◽  
Single Variable ◽  
Transfer Time ◽  
Orbital Rendezvous ◽  
Numerical Example ◽  
Difference Function ◽  
Elliptic Orbits ◽  
Rendezvous Problem ◽  
Variable Function ◽  
Initial Impulse

The tangent-impulse coplanar orbit rendezvous problem is studied based on the linear relative motion forJ2-perturbed elliptic orbits. There are three cases: (1) only the first impulse is tangent; (2) only the second impulse is tangent; (3) both impulses are tangent. For a given initial impulse point, the first two problems can be transformed into finding all roots of a single variable function about the transfer time, which can be done by the secant method. The bitangent rendezvous problem requires the same solution for the first two problems. By considering the initial coasting time, the bitangent rendezvous solution is obtained with a difference function. A numerical example for two coplanar elliptic orbits withJ2perturbations is given to verify the efficiency of these proposed techniques.

Research of Sub-Synchronous Oscillations in HVDC and SSDC Designing

2014 ◽  
Vol 960-961 ◽  
pp. 1062-1067
Author(s):  
Han Chen ◽  
Chun Lin Guo ◽  
Qin Lei Chen ◽  
Zhe Ci Tang ◽  
Ya Nan Li ◽  
...  
Keyword(s):  
Simulation Model ◽  
Compensation Method ◽  
Frequency Range ◽  
Synchronous Oscillation ◽  
Phase Compensation ◽  
Frequency Scanning ◽  
Synchronous Oscillations ◽  
Electrical Damping ◽  
Oscillation Damping ◽  
Damping Controller

SSDC(Supplementary sub-synchronous oscillation damping controller) is one of effective measures to suppress the SSO(sub-synchronous oscillations) caused by HVDC. The article researched the phase compensation method of SSDC on the basis of studying the SSO and the SSDC mechanism in depth. We verified the validity of the method used by designing SSDC in an large domestic HVDC simulation model. And we find that the SSDC designed can effectively increase the positive electrical damping in the sub-synchronous frequency range with the sub-synchronous frequency scanning to suppress the SSO.

scholarly journals Lower bound of performance index of anti-sway control of a pendulum using on-off damping radial spring-damper

2019 ◽  
Author(s):  
La Duc Viet ◽  
Nguyen Trong Kien
Keyword(s):  
Lower Bound ◽  
Performance Index ◽  
Frequency Curve ◽  
Fixed Times ◽  
Sway Motion ◽  
Damping Controller

An on-off damping radial spring-damper can be attached to a pendulum to suppress its nonlinear sway motion. This paper studies the class of on-off damping controller, which switches the damping level from high to low and back at fixed times every quarter of period. Among this class, this paper shows the solution of the lower bound controller producing the lowest amplitude-frequency curve. The lower bound curve shows some fundamental natures of the system and gives some useful directions for a good on-off damping controller. 

Theoretical Upper and Lower Bounds of the Performance of an On-Off Damping Dynamic Vibration Absorber Attached to a Multi-Degree-of-Freedom System

2019 ◽  
Vol 141 (3) ◽  
Author(s):  
La Duc Viet ◽  
Phan Thi Tra My
Keyword(s):  
Lower Bounds ◽  
Harmonic Excitation ◽  
Upper And Lower Bounds ◽  
Vibration Absorber ◽  
Amplitude Curve ◽  
Dynamic Vibration Absorber ◽  
Mass System ◽  
Variable Function ◽  
Frequency Curves ◽  
Damping Controller

This paper reveals the theoretical (upper and lower) bounds of the performance of an on-off damping vibration absorber attached to an undamped multi-degrees-of-freedom (MDOF) system under harmonic excitation. The solution reduces to the maximization or minimization problem of a simple single-variable function. Among the class of on-off damping controller, which switches the damping level from high to low and back at fixed times every half period, the revealed solutions produce the highest and lowest amplitude–frequency curves. These curves are the good theoretical benchmarks to measure how good or bad an on-off damping controller is. To demonstrate the usefulness of the theoretical bound solutions, two versions of power flow-driven controller are introduced to produce the amplitude–frequency curves tracing the lowest-amplitude curve. A case study of a four-mass system is discussed.

scholarly journals The Monomial Difference Majorized by Single Variable Function

2015 ◽  
Vol 48 (1) ◽  
Author(s):  
Dorota Budzik
Keyword(s):  
Single Variable ◽  
Variable Function

AbstractWe deal with the monomial difference n!F(y) - △

scholarly journals Permeability Coefficient of Low Permeable Soils as a Single-Variable Function of Soil Parameter

Water ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2500 ◽  
Author(s):  
Tomasz Kozlowski ◽  
Agata Ludynia
Keyword(s):  
Experimental Data ◽  
Flow Velocity ◽  
Permeability Coefficient ◽  
Empirical Relationship ◽  
Hydraulic Gradient ◽  
Plasticity Index ◽  
Model Parameters ◽  
Cohesive Soils ◽  
Single Variable ◽  
Variable Function

Based on the results of experimental studies concerning the filtration coefficient, the Darcianity of the observed flows for eight cohesive soils at four hydraulic gradients was analyzed. It is observed that linear dependence of flow velocity on hydraulic gradient is an approximation only, and it is the worse the more cohesive a given soil is. Despite this, Darcy’s law can be a correct approximation of the empirical relationship between hydraulic gradient and the flow velocity, also in very cohesive soils. A statistical analysis was carried out to identify correlation between soil properties and permeability coefficient. For each soil, 109 parameters were analyzed, among others applying mercury intrusion porosimetry, scanning electron microscopy, dynamic image analysis, and laser diffraction. Ultimately, three single-variable models best fitted to the experimental data were found, using the plasticity index IP as the independent variable, the average pore diameter DP, and the convexity of silt fraction particles. All model parameters are statistically significant at p < 0.05. Comparison with reference multi-variable models showed that the best fit for experimental data is observed by the model with the plasticity index, while the results suggest low usability of single-variable models with structural parameters.

CALCULATION-EXPERIMENTAL METHOD FOR DEFINITION OF LOWEST FREQUENCY IN BENDING VIBRATIONS OF COACH CAR BODY IN VERTICAL PLANE BASED ON IDENTIFICATION OF ITS BENDING STIFFNESS

2020 ◽  
Vol 2020 (9) ◽  
pp. 35-46
Author(s):  
Aleksandr Skachkov ◽  
Viktor Vasilevskiy ◽  
Aleksey Yuhnevskiy
Keyword(s):  
Least Squares Method ◽  
Vertical Plane ◽  
Bending Stiffness ◽  
Dimensional Problem ◽  
Euler Beam ◽  
Bending Vibrations ◽  
Car Body ◽  
Variable Function ◽  
Experimental Values ◽  
Definition Of

The consideration of existing methods for a modal analysis has shown a possibility for the lowest frequency definition of bending vibrations in a coach car body in a vertical plane based on an indirect method reduced to the assessment of the bending stiffness of the one-dimensional model as a Bernoulli-Euler beam with fragment-constant parameters. The assessment mentioned can be obtained by means of the comparison of model deflections (rated) and a prototype (measured experimentally upon a natural body) with the use of the least-squares method that results in the necessity of the solution of the multi-dimensional problem with the reverse coefficient. The introduction of the hypothesis on ratability of real bending stiffness of the prototype and easily calculated geometrical stiffness of a model reduces a multi-dimensional problem incorrect according to Adamar to the simplest search of the extremum of one variable function. The procedure offered for the indirect assessment of bending stiffness was checked through the solution of model problems. The values obtained are offered to use for the assessment of the lowest frequency of bending vibrations with the aid of Ritz and Grammel methods. In case of rigid poles it results in formulae for frequencies into which there are included directly the experimental values of deflections.

Sign in / Sign up

Export Citation Format

Share Document