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

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

Control of civil engineering structures for earthquake hazard mitigation represents a relatively new area of research that is growing rapidly. Control systems for these structures have unique requirements and constraints. For example, during a severe seismic event, the external power to a structure may be severed, rendering control schemes relying on large external power supplies ineffective. Magnetorheological (MR) dampers are a new class of devices that mesh well with the requirements and constraints of seismic applications, including having very low power requirements. This paper proposes a clipped-optimal control strategy based on acceleration feedback for controlling MR dampers to reduce structural responses due to seismic loads. A numerical example, employing a newly developed model that accurately portrays the salient characteristics of the MR dampers, is presented to illustrate the effectiveness of the approach.

/pdf/modeling-and-control-of-magnetorheological-dampers-for-s0njnqew5j.pdf

Modeling and Control of Magnetorheological Dampers for Seismic Response Reduction

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.

Electrorheological materials containing a particle component and a carrier fluid that has been modified to minimize conductivity. The carrier fluid is modified by extensive purification or by the formation of a miscible solution with a low conductivity carrier fluid. The modification techniques allow previously unacceptable carrier fluids to be utilized in an electrorheological material which exhibits significant electrorheological activity over a broad temperature range.

Modified electrorheological materials having minimum conductivity

Magnetorheologische thixotrope materialien

L'invention porte sur un fluide magnetorheologique comportant un composant vecteur et un composant de particules magnetisables presentant une densite de tassement fractionne d'au moins 0,50 avant d'etre integre au fluide magnetorheologique. Ledit fluide peut accroitre la force d'un dispositif magnetorheologique sans que sa viscosite n'augmente car la concentration volumique en particules dans l'intervalle de travail du dispositif croit lors de l'application du champ magnetique.

Keith D. Weiss

Papers

Modified electrorheological materials having minimum conductivity

Magnetorheologische thixotrope materialien

Procede et composition de fluide magnetorheologique pour augmenter la force d'un dispositif a fluide magnetorheologique

Magnetorheologische materialien basiert auf legierungsteilchen.