Multifunctional materials and structures possess the ability to perform multiple tasks by combining structural integrity
with sensing and actuating capabilities. Recent progress in the development of such materials/structures
has made concepts like load-bearing antennas or load-bearing batteries feasible and formed new research possibilities.
Load-bearing antenna structures are multifunctional sensing and actuating devices integrated with a
load-bearing structure, i.e. they can simultaneously function as a mechanical structure and an electromagnetic
antenna. Such an antenna structure is subjected to mechanical forces, temperature gradients, and electromagnetic
fields, giving rise to highly-coupled nonlinear thermo-electro-magneto-mechanical (TEMM) behavior. The
current research focuses on modeling and characterizing the nonlinear 3-D coupled behavior of TEMM materials,
consistent with first principles. This theoretical framework is specifically aimed at modeling and analysis of
load-bearing antenna structures.
In this paper we demonstrate the development of analytical techniques and computational tools for multiscale,
multi-physics modeling of load-bearing antenna structures. The mathematical model, based predominantly
on first principles, employs the thermomechanical governing equations coupled with Maxwell's equations. Our
modeling has identified 92 nondimensional numbers which quantify the competition between physical effects in
the operation of load-bearing antenna. A fixed relative ordering of all competing effects determines a regime of
antenna/environment interaction. In this work, we demonstrate a comprehensive framework to derive the 3-D
governing equations for a given regime. For thin geometries, these equations are further reduced to 2-D model,
using series expansion and perturbation techniques. Mathematical modeling of thin electro-magneto-mechanical
plates can have applications like design and optimization of load-bearing antennas structures. This framework
can be extended to model various regimes of behavior of any device/material with coupled electro-magentomechanical
Magnetorheological (MR) fluids have rheological properties, such as the viscosity and yield stress that can be altered by
an external magnetic field. The design of novel devices utilizing the MR fluid behavior in multi-degree of freedom
applications require three dimensional models characterizing the coupling of magnetic behavior to mechanical behavior
in MR fluids. A 3-D MR fluid model based on multiscale kinetic theory is presented. The kinetic theory-based model
relates macroscale MR fluid behavior to a first-principle description of magnetomechanical coupling at the microscale. A
constitutive relation is also proposed that accounts for the various forces transmitted through the fluid. This model
accounts for the viscous drag on the spherical particles as well as Brownian forces. Interparticle forces due to
magnetization and external magnetic forces applied to ferrous particles are considered. The tunable rheological
properties of the MR fluids are studied using a MR rheological instrument. High and low viscosity carrier fluids along
with small and large carbonyl iron particles are used to make and study the behavior of four different MR fluids.
Experiments measuring steady, and dynamic oscillatory shear response under a range of magnetic field strengths are
performed. The rheological properties of the MR fluid samples are investigated and compared to the proposed kinetic
theory-based model. The storage (G') and loss (G") moduli of the MR fluids are studied as well.
The overall goal of the research conducted in this paper is to develop next generation force feedback systems by
combining novel Magnetorheological (MR) fluid based systems with microstructural analysis and advanced control
system design. A novel 5-DOF MR fluid-based robotic arm is designed and prototyped. The 5-DOF system is used to
control a remote 5-DOF robot (the slave). Force feedback control is employed to replicate in the master those forces
encountered in the slave.
The idea of this paper is to design a Magnetorheological (MR) fluid based damper for steer-by-wire systems to provide sensory feedback to the driver. The advantages of using MR fluids in haptic devices stem from the increase in transparency gained from the lightweight semiactive system and controller implementation. The performance of MR fluid based steer-by wire system depends on MR fluid model and specifications, MR damper geometry, and the control algorithm. All of these factors are addressed in this study. The experimental results show the improvements in steer-by-wire by adding force feedback to the system.
In this study the authors develop haptic systems for telerobotic surgery. In order to model the full range of tactile force exhibited from an MR damper a microstructural, kinetic theory-based model of Magnetorheological (MR) fluids has been developed. Microscale constitutive equations relating flow, stress, and particle orientation are produced. The model developed is fully vectorial and relationships between the stress tensor and the applied magnetic field vector are fully exploited. The higher accuracy of the model in this regard gives better force representations of highly compliant objects. This model is then applied in force feedback control of single degree of freedom (SDOF) and two degrees of freedom (2DOF) systems. Carbonyl iron powders with different particle sizes mixed with silicone oils with different viscosities are used to make several sample MR fluids. These MR fluid samples are then used in three different designed MR dampers. A State feedback control algorithm is employed to control a SDOF system and tracking a 2-D profile path using a special innovative MR force feedback joystick. The results indicate that the MR based force feedback dampers can be used as effective haptic devices. The systems designed and constructed in this paper can be extended to a three degree of freedom force feedback system appropriate for telerobotic surgery.