An innovative multi-gap clutch based on magneto-rheological fluids and electrodynamic effects: magnetic design and experimental characterization

In this paper an innovative multi-gap magnetorheological clutch is described. It is inspired by a device previously developed by the author’s research group and contains a novel solution based on electrodynamic effects, capable to considerably improve the transmissible torque during the engagement phase. Since this (transient) phase is characterized by a non-zero angular speed between the two clutch shafts, the rotation of a permanent magnets system, used to excite the fluid, induces eddy currents on some conductive material strategically positioned in the device. As a consequence, an electromagnetic torque is produced which is added to the torque transmitted by the magnetorheological fluid only. Once the clutch is completely engaged and the relative speed between the two shafts is zero, the electrodynamic effects vanish and the device operates like a conventional magnetorheological clutch. The system is investigated and designed by means a 3D FEM model and the performance of the device is experimentally validated on a prototype

Shape Localization and Recognition using a Magnetorheological-fluid Haptic Display

Smart materials such as magnetorheological fluids (MRF) offer an interesting technology for use in haptic displays as changes in the magnetic field are rapid, reversible, and controllable. These interfaces have been evaluated in a number of medical and surgical simulators where they can provide cues regarding the viscoelastic properties of tissues. The objective of the present set of experiments was first to determine whether a shape embedded in the MRF could be precisely localized and second whether 10 shapes rendered in a MRF haptic display could be accurately identified. It was also of interest to determine how the information transfer associated with this type of haptic display compares to that achieved using other haptic channels of communication. The overall performance of participants at identifying the shapes rendered in the MRF was good with a mean score of 73 percent correct and an Information Transfer (IT) of 2.2 bits. Participants could also localize a rigid object in the display accurately. These findings indicate that this technology has potential for use in training manual palpation skills and in exploring haptic shape perception in dynamic environments

A semi-anaytical model for the analysis of a Permanent Magnet Tubular Linear Generator

In this paper the authors introduce a semi-analytical model for the analysis and the design of a Permanent Magnet (PM) tubular linear generator intended for electrical energy generation from sea waves. The translator of the analyzed machine is constituted by axially magnetized ferrite PMs with alternating polarity and soft-magnetic pole-pieces in between; a two poles, double layer three-phase winding is located in the slots of the stator. The presented model, based on use of the Carter coefficient and of the Fourier transform in the direction of the motion, is able to take into account the end effects due to the finite length of the stator. The presence of slots and teeth is subsequently considered by some post processing calculation carried on the results of the semi-analytical model. Comparison with a Finite Element analysis and with measurements taken on a prototype has been performed to validate the presented model. The model can be easily extended to other translator typologies, e.g. to air core translator with Halbach array of NdFeB PMs

The AMLEV technology applied to low speed urban transportation systems

The American version of Maglev (AMLEV) was developed in the USA since 1992. It is based on the interaction between a system of permanent magnets (PMs) installed on the vehicle, and steel cores positioned along the guideway. By using an analytical model, the inventor demonstrated that the system was able to produce levitating and stabilizing forces, allowing to safely reach a speed up to 150 m/s. In the present paper, the AMLEV technology is firstly simulated by using a FEM model; then its possible application in a low speed urban transportation system is verified. Finally, a comparison in terms of energy consumption and braking energy recovery efficiency is performed

Optimal design of EMALS based on a double-sided tubular linear induction motor

A novel evolutionary algorithm is used for the optimization of the thrust force of the stages of an electromagnetic aircraft launch system, based on a double-sided tubular linear induction motor. A semianalytical model allows for a fast and accurate prediction of all the electromagnetic quantities in the device, including the thrust force, the back electromotive force, the distribution of the induced current density, and the average magnetic flux density in the teeth. Using the semianalytical formulation, the characterization of the machine is greatly facilitated, so allowing a fast evaluation of the cost function and of the design constraint

Retraction Note to: Benign splenosis mimicking peritoneal seeding in a bladder cancer patient: a case report

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A multi-gap magnetorheological clutch with permanent magnet

This paper describes the design and testing of a novel permanent magnet clutch based on a magnetorheological fluid. It was inspired by a prototype previously developed by the authors and contains a novel gap shape conceived to reduce torque loss in the disengaged operating mode. Several geometries and material arrangements were investigated and the performance in terms of transmissible torque in different operating conditions was assessed using finite element numerical models. The prototype was manufactured and some experimental tests were performed. The new prototype was rated on the basis of performance indices and the design effectiveness was proven by a higher value of efficiency in the disengaged operating mode

EMALS optimal design

A semi-analytical model of the Double Sided Tubular Linear Induction Motor (DSTLIM) is adopted for the optimization of the thrust force of the stages of an ElectroMagnetic Aircraft Launch System (EMALS). The model allows a fast and accurate prediction of all the electromagnetic quantities in the device, including the thrust force, the back-electromotive force, the distribution of the induced current and the average magnetic flux density in the teeth. This provides a basis for the design which has been performed by a novel evolutionary optimization algorithm. By using the semi-analytical formulation, the characterization of the machine is greatly facilitated so allowing a fast evaluation of the cost function and of the design constraints

Electromechanical Numerical Analysis of an Air-Core Pulsed Alternator via Equivalent Network Formulation

In this paper, the numerical analysis on an air-core pulsed alternator is presented. Since compulsators are characterized by very fast electromechanical transients, their accurate analysis requires strong coupling between the equations governing the electrical and the mechanical behaviors. The device is investigated by using a dedicated numerical code capable to take into account eddy currents, compensating windings, as well as the excitation/control circuits. Furthermore, the code is capable of modeling centrifugal forces and vibrations acting on the shaft due to electric and mechanical unbalances or to misalignments of the shaft from its centered position. This makes the code a very powerful tool during the design phase. Examples of application of the code to machines with nonuniform compensating shield and with shorted compensating windings are shown

Negative Emotions in Skin Disorders: A Systematic Review

The main purpose of this study is to describe how negative emotions were investigated in the sphere of dermatological diseases, in order (1) to summarize literature trends about skin disorders and emotions, (2) to highlight any imbalances between the most studied and neglected emotions, (3) and to offer directions for future research. A computerized literature search provided 41 relevant and potentially eligible studies. Results showed that the study of emotions in skin disease is limited to Sadness/depression and Fear/anxiety. The emotions of Anger and Disgust have been poorly explored in empirical studies, despite they could be theoretically considered a vulnerability factor for the development of skin disorders and the dermatological extreme consequences, as negative emotionality toward self and the pathological skin condition. The bibliometric qualitative analysis with VOSViewer software revealed that the majority of the studies have been focused on the relationships between vitiligo and Sadness/depression, dermatitis and Fear/anxiety, psoriasis, and Anger, suggesting the need of future research exploring Disgust and, in general, a wider emotional spectrum