Henri P. Gavin

Conference Proceedings of the American Control Conference · January 1, 2023 This paper presents a computationally efficient, heuristic-free, and nonlinear feedback control framework for the tracking control of the position and orientation of a differential drive wheeled mobile robot (WMR) subjected to high-speed maneuvers and exte ... Full text Cite

Decentralized Control of Multiagent Navigation Systems

Journal Article IEEE/CAA Journal of Automatica Sinica · May 1, 2022 In this letter, we introduce a decentralized, nonlinear, discontinuous, and computationally simple control law for large scale multiagent navigation systems. The control is based on extending Gauss's principle of least constraint with a dynamic incorporati ... Full text Cite

Gauss's Principle with Inequality Constraints for Multiagent Navigation and Control

Journal Article IEEE Transactions on Automatic Control · February 1, 2022 Multiagent navigation systems present opportunities for many applications due to their agility and cooperation. In any multiagent navigation system, it is critical that actual interagent collisions are strictly prevented. In this article, we present a solu ... Full text Cite

Unified Position-Attitude Control of A Nonlinear Quadrotor Swarm

Conference Proceedings of the American Control Conference · January 1, 2022 In this paper, we propose a novel nonlinear feedback control law to maneuver a swarm of nonlinear quadrotors with interagent collision avoidance. In contrast to the predominant hierarchical control architectures and dynamics linearization in controller syn ... Full text Cite

Decentralized Unified Position-Attitude Control of Nonlinear UAVs

Conference Proceedings of the IEEE Conference on Decision and Control · January 1, 2022 In this paper, we propose a fully decentralized, nonlinear feedback control law to maneuver multiple nonlinear quadrotor UAVs with interagent collision avoidance and natural deadlock resolution. Most existing work on this problem adopts a cascaded position ... Full text Cite

Modeling chemical releases from building materials: The search for extended validity domain and parsimony

Journal Article Building Simulation · August 1, 2021 This study aims to systematically evaluate and extend the validity domains of multiple mechanistic models of chemical emissions from building materials. We compare the validity domain of the analytical solution with four numerical solutions for a single la ... Full text Cite

Unified Position and Attitude Control of A Fully Nonlinear Quadrotor*

Conference Proceedings of the American Control Conference · May 25, 2021 This paper presents a departure from hierarchical cascade methods to control the position and attitude of a fully nonlinear quadrotor. The paper presents a nonlinear feedback control scheme that simultaneously controls position and attitude. The proposed m ... Full text Cite

Natural Deadlock Resolution for Multi-agent Multi-Swarm Navigation

Conference Proceedings of the IEEE Conference on Decision and Control · January 1, 2021 This paper presents a nonlinear and discontinuous control scheme for two-dimensional (2-D) multi-agent multi-swarm navigation that resolves deadlocks, without heuristics, by agents reacting purely to their constrained dynamics. The method is based on exten ... Full text Cite

Rolling Resistance of a Hard Sphere on Rubber Sheets: Limitations of Linear Viscoelastic Modeling and Influence of Nonlinearities

Journal Article International Journal of Applied Mechanics · August 1, 2019 A growing body of evidence suggests that limited accuracy can be expected from analytical and computational tools relying on linear viscoelasticity for the prediction of rolling resistance in real systems presenting material and geometric nonlinearities. A ... Full text Cite

The effect of boundary condition variations on the rolling resistance of a hard sphere on rubber sheets

Journal Article International Journal of Applied Mechanics · June 1, 2019 This paper makes an interesting case for the need to consider mechanistic variations in rolling resistance forces due to noncoplanar surfaces and surface roughness. An experimental apparatus is designed to measure rolling resistance in the practically impe ... Full text Cite

Inelastic condensed dynamic models for estimating seismic demands for buildings

Journal Article Engineering Structures · December 15, 2018 Computationally-efficient simulations of structural responses, such as displacements and inter-story drift ratios, are central to performance-based earthquake engineering. Calculating these responses involves potentially time-consuming response history ana ... Full text Cite

Earthquake Response Control for Civil Structures

Chapter · January 1, 2018 Cite

Earthquake Response Control for Civil Structures

Chapter · January 1, 2018 In contemporary civil engineering, performance analysis for the dynamic response of structures due to transient environmental loads constitutes a standard part of the design process. Acceptable structural designs must be resilient in the face of earthquake ... Full text Cite

Christchurch Women's Hospital: Performance Analysis of the Base-Isolation System during the Series of Canterbury Earthquakes 2011-2012

Journal Article Journal of Performance of Constructed Facilities · August 1, 2016 Live monitoring data and simple dynamic reduced-order models of the Christchurch Women's Hospital (CWH) help explain the performance of the base-isolation (BI) system of the hospital during the series of Canterbury earthquakes in 2011-2012. A Park-Wen-Ang ... Full text Cite

Temporal Coherence: A Model for Non-stationarity in Natural and Simulated Wind Records

Journal Article Boundary-Layer Meteorology · May 1, 2016 We present a novel methodology for characterizing and simulating non-stationary stochastic wind records. In this new method, non-stationarity is characterized and modelled via temporal coherence, which is quantified in the discrete frequency domain by prob ... Full text Cite

Nonholonomically constrained dynamics of rolling isolation systems

Conference Conference Proceedings of the Society for Experimental Mechanics Series · January 1, 2016 Rolling Isolation Systems provide a simple and effective means for protecting components from horizontal floor vibrations. In these systems a platform rolls on four steel balls which, in turn, rest within shallow bowls. The trajectories of the balls is uni ... Full text Cite

Inelastic base shear reconstruction from sparse acceleration measurements of buildings

Conference Conference Proceedings of the Society for Experimental Mechanics Series · January 1, 2016 This paper presents a novel method for recovering base shear forces of building structures with unknown nonlinearities from sparse seismic-response measurements of floor accelerations. The method requires only direct matrix calculations (factorizations and ... Full text Cite

Assessment of a rolling isolation system using reduced order structural models

Journal Article Engineering Structures · September 5, 2015 This paper examines the performances of lightly- and heavily-damped rolling isolation systems (RISs) located within earthquake-excited structures. Six steel structures of varying height and stiffness are selected so as to represent a range of potential RIS ... Full text Cite

Subspace identification of a 5 MW reference wind turbine

Conference Conference Proceedings of the Society for Experimental Mechanics Series · January 1, 2015 Nonlinear systems, a category into which essentially all real-world engineering systems fall, are challenging in their design, response prediction, and control. Simulating their dynamic response requires numerical solvers, and the use of frequency-domain t ... Full text Cite

Truly isotropic biaxial hysteresis with arbitrary knee sharpness

Journal Article Earthquake Engineering and Structural Dynamics · October 25, 2014 The inelastic responses of framed structures and seismic isolation systems undergoing biaxial (horizontal) shaking are coupled. In existing models for biaxial coupling of hysteretic behavior, the smoothness (or 'knee') of the transition from elastic to yie ... Full text Cite

Double rolling isolation systems: A mathematical model and experimental validation

Journal Article International Journal of Non-Linear Mechanics · May 1, 2014 Rolling isolation systems (RISs) protect fragile building contents from earthquake hazards by decoupling horizontal floor motions from the horizontal responses of the isolated object. The RISs in use today have displacement capacities of about 20 cm. This ... Full text Cite

Rolling resistance of a rigid sphere with viscoelastic coatings

Journal Article International Journal of Solids and Structures · February 1, 2014 We present a novel three-dimensional boundary-element formulation that fully characterizes the mechanical behavior of the external boundary of a multi-layered viscoelastic coating attached to a hard rotating spherical core. The proposed formulation incorpo ... Full text Cite

Two and three-dimensional boundary element formulations of compressible isotropic, transversely isotropic and orthotropic viscoelastic layers of arbitrary thickness, applied to the rolling resistance of rigid cylinders and spheres

Journal Article European Journal of Mechanics, A/Solids · January 1, 2014 New two-dimensional and three-dimensional boundary element formulations of compressible viscoelastic layers of arbitrary thickness are presented in this work. The formulations are derived in increasing order of complexity for: (i) compressible isotropic la ... Full text Cite

Assessing the Accuracy of Vision-Based Accelerometry

Journal Article Experimental Mechanics · January 1, 2014 Video-based motion measurement enables convenient tracking of multiple points in a plane with a single sensor: a CCD video camera. This paper presents a method to easily assess the accuracy of accelerations computed from the tracking of positions measured ... Full text Cite

Determining the physical limits on semi-active control performance: A tutorial

Journal Article Structural Control and Health Monitoring · January 1, 2014 Control forces in semi-active control systems are constrained by the dynamics of actuators that regulate energy transmission through variable damping and/or stiffness mechanisms. The potential benefit of the development and implementation of new semi-activ ... Full text Cite

Experimental validation of a simplified model for rolling isolation systems

Journal Article Earthquake Engineering and Structural Dynamics · January 1, 2014 Rolling isolation systems (RISs) protect mission-critical equipment and valuable property from earthquake hazards by decoupling the dynamic responses of vibration-sensitive objects from horizontal floor motions. These responses involve the constrained roll ... Full text Cite

Christchurch women's hospital: Analysis of measured earthquake data during the 2011-2012 Christchurch earthquakes

Journal Article Earthquake Spectra · January 1, 2014 A network of acceleration and displacement sensors installed in the Christchurch Women's Hospital (CWH) in July 2011 captured an extensive range of earthquake signals, allowing for a unique opportunity to analyze the performance of the New Zealand South Is ... Full text Cite

Seismic response of the Christchurch Women's Hopsital on 23 December 2011

Conference NCEE 2014 - 10th U.S. National Conference on Earthquake Engineering: Frontiers of Earthquake Engineering · January 1, 2014 The Christchurch Women's Hospital was instrumented in September 2011 with a network of highresolution accelerometers and displacement sensors in order to capture perishable data on the response of this base-isolated facility to a persistent sequence of str ... Full text Cite

Experimental validation of a model for a rolling isolation system

Conference NCEE 2014 - 10th U.S. National Conference on Earthquake Engineering: Frontiers of Earthquake Engineering · January 1, 2014 An assessment of the ability of lightly- and heavily-damped rolling isolation systems (RISs) to mitigate the hazard of seismically-induced failures requires high-fidelity models that can adequately capture the systems' intrinsic non-linear behavior. The li ... Full text Cite

Including SN-curve uncertainty in fatigue reliability analyses of wind turbines

Conference Conference Proceedings of the Society for Experimental Mechanics Series · January 1, 2014 The reliability of wind turbines with respect to fatigue loads is affected by uncertainties in dynamic load effects and the material’s resistance to the fatigue loads. The design standard published by the International Electrotechnical Commission (IEC) spe ... Full text Cite

On the chaotic response of a nonlinear rolling isolation system

Journal Article Physica D: Nonlinear Phenomena · August 1, 2013 Isolation systems protect fragile objects from potentially-damaging shocks and shakes by mechanically decoupling motions of the object from motions of the surrounding environment. Shock and vibration isolation systems have been applied to systems ranging f ... Full text Cite

The nonholonomic and chaotic nature of a rolling isolation system

Journal Article Journal of Sound and Vibration · July 8, 2013 This paper presents the modeling of a rolling isolation platform used to protect objects from the hazards of horizontal shaking. The platform is built from four pairs of recessed steel bowls: four concave-up, attached to a shaking floor via a steel frame, ... Full text Cite

Three-dimensional boundary element formulation of an incompressible viscoelastic layer of finite thickness applied to the rolling resistance of a rigid sphere

Journal Article International Journal of Solids and Structures · March 15, 2013 A three-dimensional boundary element formulation of an incompressible viscoelastic layer of finite thickness is proposed, in a moving frame of reference. The formulation is based on two-dimensional Fourier series expansions of relevant mechanical fields in ... Full text Cite

Simplified approaches to viscoelastic rolling resistance

Journal Article International Journal of Solids and Structures · March 15, 2013 Modeling approaches yielding rolling resistance estimates for rigid spheres (and cylinders) on viscoelastic layers of finite thicknesses are introduced as lower-cost alternatives to more comprehensive solution-finding strategies. Detailed examples are prov ... Full text Cite

Simple algorithms for solving steady-state frictional rolling contact problems in two and three dimensions

Journal Article International Journal of Solids and Structures · March 15, 2013 This paper presents simple, yet robust and efficient algorithms for solving steady-state, frictional, rolling/sliding contact problems, in two and three dimensions. These are alternatives to powerful, well established, but in particular instances, possibly ... Full text Cite

Experimental validation of a simplified model for rolling isolation systems

Journal Article Earthquake Engineering and Structural Dynamics · 2013 Cite

Rolling resistance of a rigid sphere with viscoelastic coatings

Journal Article International Journal of Solids and Structures · 2013 Cite

Unified constitutive modeling of rubber-like materials under diverse loading conditions

Journal Article International Journal of Engineering Science · January 1, 2013 This paper presents a new constitutive model that unifies the behavioral characterizations of rubber-like materials in a broad range of loading regimes. The proposed model combines a selection of existing components that are known to reflect, with suitable ... Full text Cite

On the chaotic response of a nonlinear rolling isolation system

Journal Article Physica D: Nonlinear Phenomena · 2013 Cite

Assessing the Accuracy of Vision-Based Accelerometry

Journal Article Experimental Mechanics · 2013 Cite

Performance of the base-isolated Christchurch women's hospital in the Sep. 4 2010 Dar field earthquake and the Feb.22 2011 Christchurch earthquake

Journal Article 20th Analysis and Computation Specialty Conference - Proceedings of the Conference · September 17, 2012 The Christchurch Women's Hospital, completed in March 2005, is the only base-isolated building in the South Island of New Zealand. The displacement capacity of the base-isolation system and the super-structure ductility capacity are designed to meet 2000-y ... Full text Cite

Optimal performance of constrained control systems

Journal Article Smart Materials and Structures · January 1, 2012 This paper presents a method to compute optimal open-loop trajectories for systems subject to state and control inequality constraints in which the cost function is quadratic and the state dynamics are linear. For the case in which inequality constraints a ... Full text Cite

A dual method for determining the performance limits of a semiactively constrained control system

Journal Article Proceedings of the American Control Conference · January 1, 2012 This paper presents an iterative method for determining control trajectories for systems subject to state and control constraints. By maximizing in the Lagrange multiplier, or dual variable, as opposed to minimizing in the control, or primal variable, cons ... Full text Cite

Design and experimental characterization of an electromagnetic transducer for large-scale vibratory energy harvesting applications

Journal Article Journal of Intelligent Material Systems and Structures · November 1, 2011 This article reports on the design and experimental characterization of an electromagnetic transducer for energy harvesting from large structures (e.g., multistory buildings and bridges), for which the power levels can be above 100 W and disturbance freque ... Full text Cite

Parametric statistical generalization of uniform-hazard earthquake ground motions

Journal Article Journal of Structural Engineering · March 1, 2011 Sets of ground-motion records used for seismic hazard analyses typically have intensity measures corresponding to a particular hazard level for a site (perhaps conditioned on a particular intensity value and hazard). In many cases the number of available g ... Full text Cite

Generation of uniform-hazard earthquake ground motions

Journal Article Journal of Structural Engineering · March 1, 2011 This paper presents statistical models for the generation of biaxial earthquake ground-motion time histories with spectra that match those from samples of ground-motion records. The model parameters define near-field characteristics such as pulse velocity ... Full text Cite

Effect of hysteretic smoothness on inelastic response spectra with constant-ductility

Journal Article Earthquake Engineering and Structural Dynamics · January 1, 2011 This paper presents an efficient methodology for computing constant-ductility inelastic response spectra. The computation of constant-ductility spectra involves numerical root-finding algorithms to find the strongest structure providing a desired ductility ... Full text Cite

Approximate solutions to nonlinearly-constrained optimal control problems

Journal Article Proceedings of the American Control Conference · January 1, 2011 The use of variational methods in optimal control problems involves solving a two-point boundary-value problem (for states and costates) and satisfying an optimality condition. For problems with quadratic integral cost that have linear state dynamics and u ... Full text Cite

Preliminary observations of the effects of the 2010 darfield earthquake on the base-isolated christchurch women's hospital

Journal Article Bulletin of the New Zealand Society for Earthquake Engineering · January 1, 2010 The Christchurch Women's Hospital, completed in March 2005, is the only base-isolated building in the South Island of New Zealand. The displacement capacity of the base-isolation system and the super-structure ductility capacity are designed to meet 2000-y ... Full text Cite

Seismic performance of reinforced concrete buildings in the september 2010 darfield (Canterbury) earthquake

Journal Article Bulletin of the New Zealand Society for Earthquake Engineering · January 1, 2010 This paper describes observations of damage to reinforced concrete buildings from the September 2010 Darfield (Canterbury) earthquakes. Data was collated from first-hand earthquake reconnaissance observations by the authors, post-earthquake surveys, and co ... Full text Cite

Performance of churches during the darfield earthquake of september 4, 2010

Journal Article Bulletin of the New Zealand Society for Earthquake Engineering · January 1, 2010 This paper focuses on the structural behaviour and types of failure of churches located in the general Canterbury area following the Darfield earthquake of September 04, 2010. Given the variability in architectural styles, structural systems and properties ... Full text Cite

Performance limits imposed by semi-active damping constraints

Journal Article Proceedings of the 2010 American Control Conference, ACC 2010 · January 1, 2010 Semi-active damping control represents a class of parametric control problems in which control decisions affect the value of positively-constrained damping parameters. Transfer functions from control to performance can not be written in closed form and per ... Full text Cite

Control objectives for seismic simulators

Journal Article Proceedings of the American Control Conference · November 23, 2009 Seismic simulators are designed to recreate the effects of seismic activity on structural and geotechnical systems. The performance objective in recreating the effects of a particular ground motion on a test article is typically for the seismic simulator t ... Full text Cite

High-order limit state functions in the response surface method for structural reliability analysis

Journal Article Structural Safety · March 1, 2008 The stochastic response surface method (SRSM) is a technique for the reliability analysis of complex systems with low failure probabilities, for which Monte Carlo simulation (MCS) is too computationally intensive and for which approximate methods are inacc ... Full text Cite

Performance and reliability of semi-active equipment isolation

Journal Article Journal of Sound and Vibration · September 25, 2007 This study examines the performance and reliability of passive and semi-active damping in equipment isolation systems for earthquake protection. Performance and reliability measures are the peak accelerations sustained by the equipment and the peak displac ... Full text Cite

Optimal semiactive control of structures with isolated base

Journal Article International Applied Mechanics · February 1, 2006 The paper investigates the benefits of implementing the semiactive control systems in relation to passive viscous damping in the context of seismically isolated structures. Frequency response functions are compiled from the computed time history response t ... Full text Cite

Smart base-isolated benchmark building. Part I: Problem definition

Journal Article Structural Control and Health Monitoring · 2006 This paper presents the benchmark problem definition for seismically excited base-isolated buildings. The objective of this benchmark study is to provide a well-defined base-isolated building with a broad set of carefully chosen parameter sets, performance ... Full text Link to item Cite

Optimal control: Basis for performance comparison of passive and semiactive isolation systems

Journal Article Journal of Engineering Mechanics · 2006 Passive damping in shock and vibration isolation systems reduces the deformation of the isolation system but can increase the acceleration sustained by the isolated object. Semiactive (i.e., controllable) damping systems offer a solution to the problem of ... Full text Link to item Cite

Reliability of base isolation for the protection of critical equipment from earthquake hazards

Journal Article Engineering Structures · August 1, 2005 As the number of critical facilities such as data centers, Internet collocation facilities, hospitals, and air traffic control centers continues to grow, the sensitivity of expensive vibration sensitive equipment in these facilities to earthquake hazards i ... Full text Cite

Guidelines for low-transmissibility semi-active vibration isolation

Journal Article Smart Materials and Structures · April 1, 2005 The modeling issues for a semi-active feedback control system incorporating an electrorheological (ER) damping wall in a small structural model were described. Experimental results show that the force in the ER wall rarely exceeds the yield force during th ... Full text Cite

Optimal control of earthquake response using semiactive isolation

Journal Article Journal of Engineering Mechanics · 2005 The responses of two, low-rise, 2-degree-of-freedom base isolated structures with different isolation periods to a set of near-field earthquake ground motions are investigated under passive linear and nonlinear viscous damping, two pseudoskyhook semiactive ... Full text Link to item Cite

Comparison of semi-active dampers in seismic isolation

Journal Article Structures - A Structural Engineering Odyssey, Structures 2001 - Proceedings of the 2001 Structures Congress and Exposition · December 1, 2004 Since the energy cost of active vibration control is an important problem and the performance of the passive devices is limited, semi-active control devices have received much attention in recent years. In this paper, we compare the performance of two pseu ... Full text Cite

Testilng of high-force ER dampers

Journal Article Structures Congress 2000: Advanced Technology in Structural Engineering · December 1, 2004 Electrorheological (ER) suspensions represent a broad class of materials which exhibit reversible property changes when subjected to high electric fields. Specifically, material properties change from those of a Newtonian liquid to a those of a viscoelasti ... Full text Cite

Smart base isolated building benchmark problem

Journal Article Proceedings of the 2004 Structures Congress - Building on the Past: Securing the Future · August 16, 2004 This is paper presents the benchmark problem definition for seismically excited base-isolated buildings. The objective of this benchmark study is to provide a well defined base isolated building with a broad set of carefully chosen parameter sets, performa ... Cite

Parametric analysis of passive damping in base isolation

Journal Article Proceedings of the 2004 Structures Congress - Building on the Past: Securing the Future · August 16, 2004 This study examines the sensitivity of structural response statistics to the characteristics of both the ground motion and the passive damping components for seismic isolation systems. Conclusions regarding appropriate levels of passive damping to protect ... Cite

Estimation of equivalent permeability in magnetorheological fluid considering cluster formation of particles

Journal Article Journal of Applied Mechanics, Transactions ASME · March 1, 2004 This paper describes a simulation method for the equivalent magnetic permeability of mangetorheological (MR) fluids considering cluster formation of suspended particles. The cluster formation under a magnetic field is simulated by cellular automata (CA.). ... Full text Cite

Study of airfoil gust response alleviation using an electro-magnetic dry friction damper. Part 1: Theory

Journal Article Journal of Sound and Vibration · January 22, 2004 An electro-magnetic controllable dry friction damper has been designed and numerically simulated. The gust response of a three degree-of-freedom typical airfoil section with a control surface using this non-linear damper has been studied theoretically. The ... Full text Cite

Study of airfoil gust response alleviation using an electro-magnetic dry friction damper. Part 2: Experiment

Journal Article Journal of Sound and Vibration · January 22, 2004 In Part 1 of this work, a theoretical simulation study of the non-linear gust response of a three degree-of-freedom typical airfoil section with a control surface using an electro-magnetic dry friction damper is presented. For validation of this theoretica ... Full text Cite

A parametric study of linear and non-linear passively damped seismic isolation systems for buildings

Journal Article Engineering Structures · January 1, 2004 The effects of near-field ground motions with large velocity pulses have motivated passive damping requirements for the protection of seismically isolated structures. Structures in which the first mode damping exceeds 20% or 30% typically do not exhibit cl ... Full text Cite

Reliability of semi-active control devices to seismic impact

Conference ISAS/CITSA 2004: International Conference on Cybernetics and Information Technologies, Systems and Applications and 10th International Conference on Information Systems Analysis and Synthesis, Vol 4, Proceedings · January 1, 2004 Link to item Cite

Gust alleviation using an electro-magnetic dry friction damper

Journal Article 44th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference · December 1, 2003 An electro-magnetic controllable dry friction damper has been designed and numerically simulated. The gust response of a three degree-of-freedom typical airfoil section with a control surface using this nonlinear damper has been studied theoretically. The ... Cite

Fault tolerance of semiactive seismic isolation

Journal Article Journal of Structural Engineering · December 1, 2003 A six-story seismically isolated structure fitted with semiactive hydraulic devices is analyzed in order to study the effect of time lag in the devices and mass eccentricity in the superstructure on the lateral-torsional behavior. The computer program 3DBA ... Full text Cite

Effects of damper force ranges and ground motion pulse periods on the performance of semi-active isolation systems

Journal Article American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP · November 24, 2003 A large-scale base-isolated steel structural frame was tested at the shaking table laboratory of the National Research Institute for Earth Sciences and Disaster Prevention. These collaborative experiments featured auto-adaptive media and devices to enhance ... Full text Cite

Fault tolerance of semiactive seismic isolation

Journal Article Journal of Structural Engineering · 2003 A six-story seismically isolated structure fitted with semiactive hydraulic devices is analyzed in order to study the effect of time lag in the devices and mass eccentricity in the superstructure on the lateral-torsional behavior. The computer program 3DBA ... Full text Link to item Cite

Theoretical/experimental study of gust alleviation using an electro-magnetic dry friction damper

Journal Article Collection of Technical Papers - AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference · January 1, 2003 An electro-magnetic controllable dry friction damper has been designed and numerically simulated. The gust response of a three degree-of-freedom typical airfoil section with a control surface using this nonlinear damper has been studied theoretically. The ... Full text Cite

Control of torsionally asymmetric structures

Journal Article Proceedings of the American Control Conference · January 1, 2002 The effects of near-field earthquakes with large velocity pulses has motivated passive damping requirements for the protection of seismically isolated structures. Structures in which the first mode damping exceeds twenty or thirty percent typically do not ... Full text Cite

Sensitivity analysis of a no-crossflow model for the transient flowmeter test

Journal Article Stochastic Environmental Research and Risk Assessment · January 1, 2002 Logarithmic sensitivities and plausible relative errors are studied in a simple no-crossflow model of a transient flowmeter test (TFMT). This model is identical to the model of a constant-rate pumping test conducted on a fully penetrating well with wellbor ... Full text Cite

Damping estimates from experimental non-linear time-series

Journal Article Journal of Sound and Vibration · October 4, 2001 This paper seeks to illustrate the utility of the Lyapunov spectrum in estimating the damping of an experimental non-linear system. A mechanical model of Duffing's equation operating in the chaotic regime is used to generate a single observable. Using stan ... Full text Cite

Annular Poiseuille flow of electrorheological and magnetorheological materials

Journal Article Journal of Rheology · July 1, 2001 Electro- (ER) and magnetorheological (MR) Materials exhibit substantial increases in yield stress when subjected to strong electric or magnetic fields. The applied electric/magnetic field satisfies Laplace's equations in the ER/MR material. In annular geom ... Full text Cite

Multi-duct electrorheological dampers

Journal Article Proceedings of SPIE - The International Society for Optical Engineering · January 1, 2001 In a cylindrical configuration, ER devices can be created by forming multiple flow paths with a set of concentric annular ducts. These ducts can be connected in parallel to maximize the range of adjustable forces or in series to maximize the absolute force ... Full text Cite

Optimal design of an MR device

Journal Article Proceedings of SPIE - The International Society for Optical Engineering · January 1, 2001 This paper presents a formulation for the optimal design of MR dampers. MR materials are suspensions of magnetically soft particles in a hydraulic medium. The application of intense magnetic flux to these materials gives rise to a fibrated microstructure w ... Full text Cite

Control of seismically excited vibration using electrorheological materials and Lyapunov methods

Journal Article IEEE Transactions on Control Systems Technology · January 1, 2001 This paper describes the use of electrorheologicai (ER) materials in a vibration control system designed to suppress earthquake-excited vibrations. A state-variable model for the ER device is based on micromechanical simulations and rheometric measurements ... Full text Cite

Multi-duct ER dampers

Journal Article Journal of Intelligent Material Systems and Structures · January 1, 2001 This paper describes the design, construction, testing and modeling of controllable damping devices utilizing electro-rheological (ER) materials. The rheological properties of ER materials (yield stress and viscoelasticity) are extremely sensitive to elect ... Full text Cite

An investigation of a rocking-sliding block

Journal Article Proceedings of the ASME Design Engineering Technical Conference · January 1, 2001 The short end of a rigid rectangular block with a 2:1 aspect ratio is placed on a flat horizontal surface. The surface exhibits a horizontal harmonic motion, and two-dimensional motions of the block are investigated numerically and experimentally. A variet ... Cite

Implementation and modeling of a semi-active control system

Journal Article Proceedings of Sessions of Engineering Mechanics 2000 - Condition Monitoring of Materials and Structures · December 1, 2000 This paper discusses implementation and modeling details for a simple semi- active control system which uses an electro-rheological (ER) damping wall as an actuator. The ER damping wall follows the principle of viscous damping walls. The control system req ... Full text Cite

Innovative technologies for scientific wetland management, conservation and restoration

Journal Article IAHS-AISH Publication · 2000 Innovative technologies are being developed within the SHYLOC project, which is partly funded by the European Commission's Space Technology programme under the 4th Framework Programme, to provide improved tools for wetland modelling and satellite-derived i ... Cite

Submerged funicular arches

Journal Article Journal of Structural Engineering · 2000 This paper evaluates momentless, or funicular, arches designed using Bernoulli-Euler beam theory and evaluates the errors associated with the Bernoulli-Euler and straight-beam approximations. When arches support hydrostatic pressure imposed by water of fin ... Full text Link to item Cite

Variable property devices for structural control

Journal Article Structures Congress - Proceedings · December 1, 1999 Base isolation reduces the base shear, inter-story drift, and absolute accelerations of structures at the expense of potentially large deflections of the isolators. By incorporating variable damping and stiffness devices into the isolation system, the isol ... Cite

Resonance suppression through variable stiffness and damping mechanisms

Journal Article Proceedings of SPIE - The International Society for Optical Engineering · January 1, 1999 This paper describes the modifications in the dynamic behavior of a building structure when devices with variable stiffness and damping are installed in parallel with a low-damping isolation system. The results of eigenvalue analyses of linear-elastic stru ... Cite

Non-proportional damping and semi-active control

Journal Article Proceedings of the International Modal Analysis Conference - IMAC · January 1, 1999 Electro-rheological (ER) and magneto-rheological (MR) materials exhibit variable stiffness and damping properties when subjected to strong electric or magnetic fields. While pre-yield visco-elasticity is a very important feature of these materials when sub ... Cite

Lyapunov-based control of a base-excited structure

Journal Article Proceedings of SPIE - The International Society for Optical Engineering · December 1, 1998 This study illustrates the behavior of a closed-loop vibration control system making use of electrorheological (ER) devices. Material properties of ER suspensions (primarily the yield stress, and visco-elastic properties) increase by several orders of magn ... Full text Cite

Construction of multi-duct electrorheological dampers

Journal Article Proceedings of SPIE - The International Society for Optical Engineering · December 1, 1998 A study on the construction of multi-duct electrorheological (ER) dampers was carried out. The ER damper features multiple concentric electrodes that are electrically in parallel, but may be hydraulically inter-connected through multiple paths. The damper ... Full text Cite

Design method for high-force electrorheological dampers

Journal Article Smart Materials and Structures · October 1, 1998 Electrorheological (ER) materials are suspensions of polarizable particles in a dielectrically strong suspension. When a strong (kV mm-1) electric field is applied to ER materials, their visco-elastic and, more importantly, yielding properties increase by ... Full text Cite

Drift-free integrators

Journal Article Review of Scientific Instruments · January 1, 1998 Bias errors introduced by systems designed to measure low-frequency transients negate zero-mean assumptions on the measurement noise. On-line signal processing methods that require accurate low-frequency information can be adversely affected by bias errors ... Full text Cite

The effect of particle concentration inhomogeneities on the steady flow of electro- and magneto-rheological materials

Journal Article Journal of Non-Newtonian Fluid Mechanics · January 1, 1997 The yield stresses of electro-rheological (ER) and magneto-rheological (MR) suspensions increase by orders of magnitude when electric or magnetic fields are applied across them. In the absence of the field, the materials are essentially Newtonian fluids. W ... Full text Cite

Electrorheological dampers, Part II: Testing and modeling

Journal Article American Society of Mechanical Engineers (Paper) · December 1, 1996 Electrorheological (ER) materials develop yield stresses on the order of 5-10 kPa in the presence of strong electric fields. Viscoelastic and yielding material properties can be modulated within milli-seconds. An analysis of flowing ER materials in the lim ... Cite

Electrorheological dampers, Part I: Analysis and design

Journal Article American Society of Mechanical Engineers (Paper) · December 1, 1996 Electrorheological (ER) materials are suspensions of specialized, micron-sized particles in nonconducting oils. When electric fields are applied to ER materials, they exhibit dramatic changes (within milli-seconds) in material properties. Pre-yield, yieldi ... Cite

Bicycle-wheel spoke patterns and spoke fatigue

Journal Article Journal of Engineering Mechanics · January 1, 1996 The radial, lateral, and tangential stiffness of spoked bicycle wheels depends upon the rim's bending inertia, torsional inertia, the spoke sizes, and the spoke geometry. The spokes of three rear bicycle wheels of different spoke patterns were instrumented ... Full text Cite

Electrorheological dampers, part i: Analysis and design

Journal Article Journal of Applied Mechanics, Transactions ASME · January 1, 1996 Electrorheological (ER) materials are suspensions of specialized, micron-sized particles in nonconducting oils. When electric fields are applied to ER materials, they exhibit dramatic changes (within milliseconds) in material properties. P reyield, yieldin ... Full text Cite

Electrorheological dampers, part ii: Testing and modeling

Journal Article Journal of Applied Mechanics, Transactions ASME · January 1, 1996 Electrorheological (ER) materials develop yield stresses on the order of 5-10 kPa in the presence of strong electric fields. Viscoelastic and yielding material properties can be modulated within milliseconds. An analysis of flowing ER materials in the limi ... Full text Cite

Electrorheological dampers and semi-active structural control

Journal Article Proceedings of the IEEE Conference on Decision and Control · December 1, 1995 Electrorheological damper technology is reviewed in the context of structural control applications. These dampers are effective when operated in their post-yield regime, as captured by a Bingham model with control dependent parameters. Feedback control law ... Cite

Electrorheological devices with annular electrodes

Journal Article Proceedings of Engineering Mechanics · January 1, 1995 Strong electric fields (kV/mm) induce yield stresses (kPa) in electrorheological (ER) materials. The attraction of ER materials for control applications lies in their fast response to the field (1 ms) and low power requirements. Furthermore, actuation via ... Cite

Closed loop structural control using electroheological dampers

Journal Article Proceedings of the American Control Conference · January 1, 1995 Electrorheological (ER) dampers are attractive in control applications where external power cannot be guaranteed. ER dampers are inherently non-linear, and the sign of the damper force is constrained by a passivity condition. Idealizing these non-lineariti ... Cite

Electrorheological dampers and semi-active structural control

Journal Article Proceedings of the IEEE Conference on Decision and Control · December 1, 1994 Electrorheological (ER) fluids have a number of properties that make them attractive for use in fluid-filled dampers. Our interest is in the use of such dampers for semi-active structural control. This paper provides an introduction to this subject, with e ... Cite

Characterization of an ER active member

Journal Article Structures Congress XII · January 1, 1994 In the presence of strong electric fields (kV/mm), electrorheological (ER) materials change form viscous fluids to yielding materials. The class of ER materials used in this study have low power consumption, large dynamic range, and other properties relate ... Cite