Ultrasonic vibration is employed to modify the friction of a finger pad in way that induces haptic sensations. A combination of intermittent contact and squeeze film levitation has been previously proposed as the most probable mechanism. In this paper, in order to understand the underlying principles that govern friction modulation by intermittent contact, numerical models based on finite element (FE) analysis and also a spring-Coulombic slider are developed. The physical input parameters for the FE model are optimized by measuring the contact phase shift between a finger pad and a vibrating plate. The spring-slider model assists in the interpretation of the FE model and leads to the identification of a dimensionless group that allows the calculated coefficient of friction to be approximately superimposed onto an exponential function of the dimensionless group. Thus, it is possible to rationalize the computed relative reduction in friction being (i) dependent on the vibrational amplitude, frequency, and the intrinsic coefficient of friction of the device, and the reciprocal of the exploration velocity, and (ii) independent of the applied normal force, and the shear and extensional elastic moduli of the finger skin provided that intermittent contact is sufficiently well developed. Experimental validation of the modelling using real and artificial fingertips will be reported in part 2 of this work, which supports the current modelling.

Electrovibration tactile displays exploit the polarisation of the finger pad, caused by an insulated high voltage supplied plate. This results in electrostatic attraction, which can be used to modulate the users perception of an essentially flat surface and induce texture sensation. Two analytical models of electrovibration, based on parallel plate capacitor assumption, are demonstrably taken and assessed by comparisons with experimental results published in literature. In addition, an experimental setup was developed to measure the electrostatic force between the finger pad and a high voltage supplied plate in a static and out-of-contact state in order to support the use of parallel plate capacitor model. Development, validation, and application of a computational framework for modelling tactile scenarios on real and virtual surfaces rendered by electrovibration technique is presented. The framework incorporates fully parametric model in terms of materials and geometry of the finger pad, virtual and real surfaces, and can serve as a tool for virtual prototyping and haptic rendering in electrovibration tactile displays. This is achieved by controlling the applied voltage signal in order to guarantee similar lateral force cues in real and simulated surfaces.

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The aim of ongoing research is to develop a multi-scale multi-physics computational framework for modelling of human touch in order to provide understanding of fundamental biophysical mechanisms responsible for tactile sensation. The paper presents the development of a macro-scale global finite element model of the finger pad and calibration of applied material models against experimental results using inverse method. The developed macro model serves as a basis for down-scaling to micro finite element models of mechanoreceptors and further implementations and applications as a virtual tool in scientific or industrial applications related to neuroscience, haptics, prosthetics, virtual touch and packaging.

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Electrovibration technique can modify user's perception of a surface through the modulation of the sliding friction accordingly to the voltage applied. This paper is introducing a novel approach to virtual haptic rendering in electrovibration based haptic displays in order to provide realistic feeling of a simulated surface, where the required voltage signal is obtained using a simplified equation. The approach was validated by the use of a finite element computational framework able to simulate tactile scenarios on real and virtual surfaces. A database of precompiled tactile scenarios was generated to predict outputs for custom parametric surfaces through a conditional average estimator method. In addition, an experimental database obtained by active exploration of different surfaces, is utilised for texture rendering. A web application, comprising the algorithms described in the paper, has also been developed, and is freely available to use at http://www.haptictexture.com.

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The stiffness of rubber bearings, which are widely used for the seismic isolation of different types of structures, changes under different seismic intensities. These bearings are typically designed considering only lateral displacements induced by design earthquakes. At lower displacements, induced by weaker earthquakes, the stiffness of rubber bearings is typically increased, and the efficiency of the seismic isolation is thus reduced. To improve the response of rubber isolators at lower seismic intensities, a new isolation device, which can adjust itself to the intensity of the load, has been developed. It is fabricated from a magnetically controlled elastomer (MCE), whose stiffness can be varied by applying a magnetic field. Variation of the device stiffness is regulated by a specifically designed control unit. The seismic response of this new device was tested experimentally and analytically. This study showed that the new device can substantially reduce the seismic demand, particularly in the case of fairly stiff structures, and the equipment installed in such structures. It was found that the group of equipment, which is critical in the case of weak earthquakes, can be substantially reduced or even completely eliminated when stiff structures are isolated using MCE devices.