This tutorial/survey paper: (1) provides a concise point of departure for researchers and practitioners alike wishing to assess the current state of the art in the control and monitoring of civil engineering structures; and (2) provides a link between structural control and other fields of control theory, pointing out both differences and similarities, and points out where future research and application efforts are likely to prove fruitful. The paper consists of the following sections: section 1 is an introduction; section 2 deals with passive energy dissipation; section 3 deals with active control; section 4 deals with hybrid and semiactive control systems; section 5 discusses sensors for structural control; section 6 deals with smart material systems; section 7 deals with health monitoring and damage detection; and section 8 deals with research needs. An extensive list of references is provided in the references section.

Structural control: past, present, and future

MR fluid, foam and elastomer devices

Advances in soft robotics, materials science, and stretchable electronics have enabled rapid progress in soft grippers. Here, a critical overview of soft robotic grippers is presented, covering different material sets, physical principles, and device architectures. Soft gripping can be categorized into three technologies, enabling grasping by: a) actuation, b) controlled stiffness, and c) controlled adhesion. A comprehensive review of each type is presented. Compared to rigid grippers, end-effectors fabricated from flexible and soft components can often grasp or manipulate a larger variety of objects. Such grippers are an example of morphological computation, where control complexity is greatly reduced by material softness and mechanical compliance. Advanced materials and soft components, in particular silicone elastomers, shape memory materials, and active polymers and gels, are increasingly investigated for the design of lighter, simpler, and more universal grippers, using the inherent functionality of the materials. Embedding stretchable distributed sensors in or on soft grippers greatly enhances the ways in which the grippers interact with objects. Challenges for soft grippers include miniaturization, robustness, speed, integration of sensing, and control. Improved materials, processing methods, and sensing play an important role in future research.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/adma.201707035

Soft Robotic Grippers.

Magnetorheological materials are a class of smart materials whose rheological properties may be rapidly varied by application of a magnetic field These materials typically consist of micron-sized ferrous particles dispersed in a fluid or an elastomer A quasi-static, one-dimensional model is developed that examines the mechanical and magnetic properties of magnetorheological materials This model attempts to account for magnetic non-linearities and saturation by establishing a mechanism by which magnetic flux density is distributed within the composite material Experimental evidence of the viscoelastic behaviour and magnetic properties of magnetorheological fluids and elastomers suggests that the assumptions made in the model development are reasonable It is shown that the model is semi-empirical in that it must be fit to the experimental data by adjusting a parameter that accounts for unmodelled magnetic interactions

http://iopscience.iop.org/article/10.1088/0964-1726/5/5/009/pdf

A model of the behaviour of magnetorheological materials

This paper presents the results of a study to evaluate the performance of a number of recently proposed semiactive control algorithms for use with multiple magnetorheological (MR) dampers. Various control algorithms used in recent semiactive control studies are considered including the Lyapunov controller, decentralized bang-bang controller, modulated homogeneous friction algorithm, and a clipped optimal controller. Each algorithm is formulated for use with the MR damper. Additionally, each algorithm uses measurements of the absolute acceleration and device displacements for determining the control action to ensure that the algorithms could be implemented on a physical structure. The performance of the algorithms is compared through a numerical example, and the advantages of each algorithm are discussed. The numerical example considers a six-story structure controlled with MR dampers on the lower two floors. In simulation, an El Centro earthquake is used to excite the system, and the reduction in the drif...

Semiactive Control Strategies for MR Dampers: Comparative Study

This paper examines the transition area between elastic and viscous behavior for a conventional electro-rheological (ER) fluid and a state-of-the-art magneto-rheological (MR) fluid through the use of oscillatory rheometry techniques. A comparison between the yield behavior (strain and stress) measured for these two different types of controllable fluids is presented. The data obtained for MR fluids represents the initial characterization of the pre-yield properties exhibited by this type of material. Finally, a recommendation as to a key area for future R&D is highlighted.

Viscoelastic Properties of Magneto- and Electro-Rheological Fluids

A magnetorheological material containing a carrier fluid and a magnetically active particle. The particle has been modified so that the surface of the particle is substantially free of contamination products. The contamination products are removed from the surface of the particle by abrader processing, chemical treatment or a combination thereof. Magnetorheological materials prepared using the particles from which contamination products have been removed exhibit significantly enhanced magnetorheological effects.

Magnetorheological materials utilizing surface-modified particles

A container for storing and transporting field controllable fluid is disclosed. The field controllable material may be mixed and remixed in the container and the field controllable material may be flowed into or discharged from the container chamber without opening the container.

Container for transporting and storing field controllable fluid

Magnetorheological thixotropic materials

A magnetorheological fluid comprising magnetic-responsive particles, a thickener, an ionic thixotropic additive, and a carrier fluid wherein the carrier fluid comprises a glycol- water mixture comprising at least 50 percent by weight of a glycol compound. The thickener is preferably fumed silica and the ionic thixotropic additive is preferably one of sodium nitrite, sodium chloride, sodium acetate, and sodium benzoate.

Donald A. Nixon

Papers

Viscoelastic Properties of Magneto- and Electro-Rheological Fluids

Magnetorheological materials utilizing surface-modified particles

Container for transporting and storing field controllable fluid

Magnetorheological thixotropic materials

Non-settling glycol based magnetorheological fluids