This review comprises a detailed survey of ongoing methodologies for soft actuators, highlighting approaches suitable for nanometer- to centimeter-scale robotic applications. Soft robots present a special design challenge in that their actuation and sensing mechanisms are often highly integrated with the robot body and overall functionality. When less than a centimeter, they belong to an even more special subcategory of robots or devices, in that they often lack on-board power, sensing, computation, and control. Soft, active materials are particularly well suited for this task, with a wide range of stimulants and a number of impressive examples, demonstrating large deformations, high motion complexities, and varied multifunctionality. Recent research includes both the development of new materials and composites, as well as novel implementations leveraging the unique properties of soft materials.

Soft Actuators for Small-Scale Robotics.

Recent advances in nonlinear passive vibration isolators

Structural systems often show nonlinear behavior under severe excitations generated by natural hazards. In that condition, the restoring force becomes highly nonlinear showing significant hysteresis. The hereditary nature of this nonlinear restoring force indicates that the force cannot be described as a function of the instantaneous displacement and velocity. Accordingly, many hysteretic restoring force models were developed to include the time dependent nature using a set of differential equations. This survey contains a review of the past, recent developments and implementations of the Bouc-Wen model which is used extensively in modeling the hysteresis phenomenon in the dynamically excited nonlinear structures.

The Hysteresis Bouc-Wen Model, a Survey

Leakage in water distribution systems is an important issue which is affecting water companies and their customers worldwide. It is therefore no surprise that it has attracted a lot of attention by both practitioners and researchers over the past years. Most of the leakage management related methods developed so far can be broadly classified as follows: (1) leakage assessment methods which are focusing on quantifying the amount of water lost; (2) leakage detection methods which are primarily concerned with the detection of leakage hotspots and (3) leakage control models which are focused on the effective control of current and future leakage levels. This paper provides a comprehensive review of the above methods with the objective to identify the current state-of-the-art in the field and to then make recommendations for future work. The review ends with the main conclusion that despite all the advancements made in the past, there is still a lot of scope and need for further work, especially in area of rea...

A review of methods for leakage management in pipe networks

A hysteresis model for the field-dependent damping force of a magnetorheological damper

Electro-rheological (ER) fluids are now regarded as one of the most versatile of the materials available for building smart structures and machines. In principle, ER fluids promise an elegant means of providing continuously variable forces for the control of mechanical vibrations. In practice, the development of industrial devices has been hampered by the unavailability of suitable ER fluids. Prompted by recent advances in ER fluid development this paper provides a comprehensive survey of ER devices for vibration control. The key modes of operation are identified and progress towards a unified approach to visualizing the macroscopic behaviour is summarized before presenting a comprehensive survey which includes contributions to the identification of ER fluid dynamics and the application of feedback control. The discussion of results includes some thoughts on future trends.

https://iopscience.iop.org/article/10.1088/0964-1726/5/4/011/pdf

Applications of electro-rheological fluids in vibration control: a survey

This paper describes progress on a new technique to detect pipeline features and leaks using signal processing of a pressure wave measurement. Previous work (by the present authors) has shown that the analysis of pressure wave reflections in fluid pipe networks can be used to identify specific pipeline features such as open ends, closed ends, valves, junctions, and certain types of bends. It was demonstrated that by using an extension of cross-correlation analysis, the identification of features can be achieved using fewer sensors than are traditionally employed. The key to the effectiveness of the technique lies in the artificial generation of pressure waves using a solenoid valve, rather than relying upon natural sources of fluid excitation. This paper uses an enhanced signal processing technique to improve the detection of leaks. It is shown experimentally that features and leaks can be detected around a sharp bend and up to seven reflections from features/leaks can be detected, by which time the wave has traveled over 95 m. The testing determined the position of a leak to within an accuracy of 5%, even when the location of the reflection from a leak is itself dispersed over a certain distance and, therefore, does not cause an exact reflection of the wave.

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Pipeline Network Features and Leak Detection by Cross-Correlation Analysis of Reflected Waves

A smart fluid is defined as one in which the resistance to flow can be controlled through the application of an electric or magnetic field. Such fluids can be used as the basis for constructing controllable damping devices that can generally outperform traditional passive dampers without involving the cost, weight, and complexity problems associated with fully active schemes. In this paper, the authors present a state-of-the-art review of smart fluids in vibration control. A comprehensive survey article appeared as recently as 1996, but progress since then has been so rapid and dramatic as to warrant an update. After summarizing the operating mechanisms of the two key smart fluids-electro-rheological (ER) and magneto-rheological (MR)-it is shown how they can be harnessed for vibration control. Progress over the past three years is categorized under four headings: the rise of MR fluids, the development of effective mathematical models of ER and MR fluids, the emergence of techniques for dynamic control, and the exploitation of promising new areas of application. The paper concludes with a discussion of possible avenues for future development. Some problems that await resolution are also mentioned.

Vibration control using smart fluids : A state-of-the-art review

It is now well known that smart fluids (electrorheological (ER) and magnetorheological) can form the basis of controllable vibration damping devices. With both types of fluid, however, the force/velocity characteristic of the resulting damper is significantly nonlinear, possessing the general form associated with a Bingham plastic. In a previous paper the authors suggested that by using a linear feedback control strategy it should be possible to produce the equivalent of a viscous damper with a continuously variable damping coefficient. In the present paper the authors describe a comprehensive investigation into the implementation of this linearization strategy on an industrial scale ER long-stroke vibration damper. Using mechanical excitation frequencies up to 5 Hz it is shown that linear behaviour can be obtained between well defined limits and that the slope of the linearized force/velocity characteristic can be specified through the choice of a controller gain term.

https://iopscience.iop.org/article/10.1088/0964-1726/8/5/311/pdf

Roger Stanway

Papers

Applications of electro-rheological fluids in vibration control: a survey

Pipeline Network Features and Leak Detection by Cross-Correlation Analysis of Reflected Waves

Vibration control using smart fluids : A state-of-the-art review

Controllable viscous damping: an experimental study of an electrorheological long-stroke damper under proportional feedback control

The electrorheological long-stroke damper: a new modelling technique with experimental validation