There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Numerical Initial Value Problems in Ordinary Differential Equations

Semiactive control devices have received significant attention in recent years because they offer the adaptability of active control devices without requiring the associated large power sources. Magnetorheological (MR) dampers are semiactive control devices that use MR fluids to produce controllable dampers. They potentially offer highly reliable operation and can be viewed as fail-safe in that they become passive dampers should the control hardware malfunction. To develop control algorithms that take full advantage of the unique features of the MR damper, models must be developed that can adequately characterize the damper's intrinsic nonlinear behavior. Following a review of several idealized mechanical models for controllable fluid dampers, a new model is proposed that can effectively portray the behavior of a typical MR damper. Comparison with experimental results for a prototype damper indicates that the model is accurate over a wide range of operating conditions and is adequate for control design an...

Phenomenological model for magnetorheological dampers

A scheme for understanding the organization of human postural movements is developed in the format of a position paper. The structural characteristics of the body and the geometry of muscular actions are incorporated into a three-dimensional graphical representation of human movement mechanics in the sagittal plane. A series of neural organizational hypotheses limit a theoretically infinite number of combinations of muscle contractions and associated movement trajectories for performing postural corrections: (1) Controls are organized to use the minimum number of muscles; (2) frequently performed movements are organized to require a minimum of neural decision-making.These hypotheses lead to the prediction that postural movements are composed of muscle contractile strategies derived from a limited set of distinct contractile patterns. The imposition of two mechanical constraints related to the configuration of support and to requirements for body stability with respect to gravity predict the conditions under which individual movement strategies will be deployed.A complementary organizational scheme for the senses is developed. We show that organization of postural movements into combinations of distinct strategies simplifies the interpretation of sensory inputs. The fine-tuning of movement strategies can be accomplished by breaking down the complex array of feedback information into a series of scalar quantities related to the parameters of the movement strategies. For example, the magnitude, aim, and curvature of the movement trajectory generated by an individual strategy can be adjusted independently.The second half of the report compares theoretical predictions with a series of actual experimental observations on normal subjects and patients with known sensory and motor disorders. Actual postural movements conform to theoretical predictions about the composition of individual movement strategies and the conditions under which each strategy is used. Observations on patients suggest how breakdowns in individual steps within the logical process of organization can lead to specific movement abnormalities.Discussion focuses on the areas needing further experimentation and on the implications of the proposed organizational scheme. We conclude that although our organizational scheme is not new in demonstrating the need for simplifying the neural control of movement, it is perhaps original in imposing discrete logical control upon a continuous mechanical system. The attraction of the scheme is that it provides a framework compatible with both mechanical and physiological information and amenable to experimental testing.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0140525X00020008

The organization of human postural movements: A formal basis and experimental synthesis

In recent years, considerable attention has been paid to research and development of structural control devices, with particular emphasis on alleviation of wind and seismic response of buildings and bridges. In both areas, serious efforts have been undertaken in the last two decades to develop the structural control concept into a workable technology. Full-scale implementation of active control systems have been accomplished in several structures, mainly in Japan; however, cost effectiveness and reliability considerations have limited their wide spread acceptance. Because of their mechanical simplicity, low power requirements, and large, controllable force capacity, semiactive systems provide an attractive alternative to active and hybrid control systems for structural vibration reduction. In this paper we review the recent and rapid developments in semiactive structural control and its implementation in full-scale structures.

/pdf/state-of-the-art-of-structural-control-20ojs9jpb9.pdf

State of the art of structural control

In this study, the temperature dependent dynamic behavior of a magnetorheological (MR) damper was characterized. To this end, an MR damper, which was designed and fabricated for a ground vehicle seat suspension application, was tested over temperatures ranging from 0 °C to 100 °C at a constant frequency of 4 Hz and a constant amplitude of 7.62 mm on an MTS-810 material testing system equipped with a temperature-controlled environmental chamber. And, the widely adopted Bouc-Wen model was assessed to characterize the temperature dependency of the MR damper through examining the trends of the model parameters. It was observed that although mBW model could capture the MR damper behavior well, some of the model parameters did not represent the physical realization of the damper based on the physical structure of the model. This is attributed to the fact that mBW has differential terms and thus, an infinite solution space and different combinations of the model parameters may yield similar results. Therefore, it was concluded that mBW model was not successful to model the temperature dependency of MR damper behavior. Full Text: View full text in PDF format (1027KB)

Sensitivity of magnetorheological damper behavior to perturbations in temperature via bouc - wen model

Quasisteady modeling of linear stroke flow mode magnetorheological (MR) and electrorheological (ER) dampers has focused primarily on the utilization of the Bingham-plastic constitutive model to assess performance metrics such as damping capacity. In such Bingham-plastic MR (or ER) flows, the yield stress of the fluid, τy , is activated by applying magnetic (or electric) field. The Bingham-plastic model assumes that the material is in either (1) a preyield condition where the local shear stress is less than the yield stress, τ τy , so that the material flows with a constant postyield viscosity. The objective of this paper is to analyze the damping capacity of such a controllable MR or ER damper in the situation when the field dependent fluid exhibits postyield shear thinning or thickening behavior, that is, the postyield viscosity is a function of shear rate. A Herschel-Bulkley model with a field dependent yield stress is proposed, and the impact of shear rate dependent viscosity on damping capacity is assessed. Key analysis results — velocity profile, shear stress profile, and damping coefficient — are presented in a nondimensional formulation that is consistent with prior results for the Bingham-plastic analysis. The nondimensional analysis formulated here clearly establishes the Bingham number as the independent variable for assessing flow mode damper performance.Copyright © 2003 by ASME

Nondimensional Analysis of Electrorheological and Magnetorheological Dampers Using a Herschel-Bulkley Constitutive Model

A rate-dependent elastoslide model is developed to study the quasi-steady and dynamic behavior of a magnetorheological damper. This time-domain model uses a rate-dependent slide and a parallel viscous damping to describe the practical yield behavior demonstrated by field-activated magnetorheological fluids, and it uses a stiff spring in series with the slide to represent the preyield stiffness of the damper. A method of determination of the model parameters is developed using single-frequency hysteresis data of the magnetorheological damper. The model parameters are determined using virtual loading curves identified from the force-displacement and force-velocity hysteretic diagrams. A relationship between current controllable parameters and current input is established. The fidelity of the model is justified by a good correlation between modeling results and experimental steady-state data over a broad amplitude and moderate-frequency range. Significantly, this model captures nonlinear amplitude- and frequency-dependent behavior of magnetorheological dampers using constant model parameters and trivial computational effort.

Rate-Dependent Elastoslide Model for Magnetorheological Damper

Adaptive Magnetorheological Landing Gear Dampers Employing Passive Valves to Maximize Applicable Sink Rate Range

This paper addresses the feasibility and applicability of a semi-active magnetorheological (MR) damper shock isolation
system to replace a passive friction damper-based shock isolation system for commercial-off-the-shelf (COTS)
equipment. To the end, a shock isolation system using an MR damper was theoretically configured and its mechanical
model was developed. From the mechanical model, the governing equation of motion for the shock isolation system with
the MR damper was derived and semi-active controls such as skyhook and sliding mode control were formulated based
on the derived governing equation of the system. Simulated control responses of the semi-active MR damper shock
isolation system with either skyhook, or sliding mode control, were evaluated and compared to those of the passive
friction shock isolation system under two different representative shock loads for COTS equipment.

Shock isolation systems using magnetorheological dampers

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

Norman M. Wereley

Author Tools

Chat about Author