Nicola Sgambelluri

Analysis and design of an electromagnetic system for the characterization of magneto-rheological fluids for haptic interfaces

In this paper, the synthesis and design of a new device for the energization and characterization of magneto-rheological fluids (MRF) for haptic interfaces are presented. Due to the core structure and feeding conditions, only a three-dimensional numerical analysis provides an accurate prediction of the electromagnetic quantities and the rheological behavior of an excited specimen. The design constraints are shown in details and the results in terms of magnetic field inside the fluid and its spatial resolution are discussed.

Sensing Glove for Brain Studies: Design and Assessment of Its Compatibility for fMRI With a Robust Test

In this paper, we describe a biomimetic-fabric-based sensing glove that can be used to monitor hand posture and gesture. Our device is made of a distributed sensor network of piezoresistive conductive elastomers integrated into an elastic fabric. This solution does not affect natural movement and hand gestures, and can be worn for a long time with no discomfort. The glove could be fruitfully employed in behavioral and functional studies with functional MRI (fMRI) during specific tactile or motor tasks. To assess MR compatibility of the system, a statistical test on phantoms is introduced. This test can also be used for testing the compatibility of mechatronic devices designed to produce different stimuli inside the MR environment. We propose a statistical test to evaluate changes in SNR and time-domain standard deviations between image sequences acquired under different experimental conditions. fMRI experiments on subjects wearing the glove are reported. The reproducibility of fMRI results obtained with and without the glove was estimated. A good similarity between the activated regions was found in the two conditions.

Electromagnetic Modeling and Design of Haptic Interface Prototypes Based on Magnetorheological Fluids

We report on the design and implementation of innovative haptic interfaces based on magnetorheological fluids (MRFs). We developed 2D and quasi-3D MRF-based devices capable of suitably energizing fluids with a magnetic field in order to build shapes that can be directly felt and explored by hand. We obtained this effect by properly creating a distribution of a magnetic field over time and space inducing the fluid to assume a desired shape and compliance. We implemented different prototypes, synthesized and designed with the help of preliminary simulations by a 3D finite-element code. In this way, both magnetic field and shear stress profiles inside the fluid could be carefully predicted. Finally, we evaluated and experimentally assessed the performance of these devices.

Haptic displays based on magnetorheological fluids: design, realization and psychophysical validation

In this paper we explore the possibility of using magnetorheological (MR) fluids in haptic interfaces, exploiting their property of changing the rheological behaviour by tuning an external magnetic field. In particular we propose two different prototypes of haptic display, for pinch grasp and for whole-hand immersive exploration. We briefly report on the design of these devices, describe few psychophysical experiments to assess their performance, and report on the experimental results. Such investigation is rather encouraging, and provides reliable cues as to how MR fluid based devices can be designed for haptic display applications.

Towards a Haptic Black Box for free-hand softness and shape exploration

In this paper we propose an innovative prototype of a haptic display for whole-hand immersive exploration. We envision a new concept of haptic display, the Haptic Black Box, which can be imagined as a box where the operator can poke his/her bare hand, and interact with the virtual object by freely moving the hand without mechanical constraints. In this way sensory receptors on the whole operators hand would be excited, rather than restricting to just one or few fingertips or phalanges. To progress towards such a challenging goal, magnetorheological (MR) fluids represent a very interesting and completely innovative technology. These fluids are composed of micronsized, magnetizable particles immersed in a synthetic oil. Exposure to an external magnetic field induces in the fluid a change in rheological behaviour turning it into a near-solid in few milliseconds. By removing the magnetic field, the fluid quickly returns to its liquid state. We briefly report on the design of this device, describe psychophysical experiments to assess performance for softness and shape exploration, and report on the experimental results.

Integrating Two Haptic devices for Performance Enhancement

This paper deals with a new configuration for a haptic system, which is able to simultaneously replicate independent force/displacement and force/area behaviors of a given material. Being force/area information a relevant additional haptic cue for improving softness discrimination, this system allows to extend the range of materials whose rheology can be carefully mimicked. Moreover, according to the Hertz theory, two objects with different curvature radius having the same force/displacement behavior can respond with different contact area to the same applied force. These behaviors can be effectively replicated by the integrated haptic system here proposed enabling and independent control of force/displacement and force/area. The system is comprised of a commercial device (delta haptic device) serially coupled with a contact area spread rate (CASR) device. Two specimens of a material and two of another one, all with different curvature radii, were identified and modeled in terms of force/area and force/displacement. These behaviors were successfully tracked by the integrated haptic system here proposed

Advanced modelling and preliminary psychophysical experiments for a free-hand haptic device

In this paper we report on a new improved free-hand haptic interface based on magnetorheological fluids (MRFs). MRFs are smart materials which change their rheology according to an external magnetic field. The new architecture here proposed results from the development and improvement of earlier prototypes. The innovative idea behind this device is to allow subjects interacting directly with an object, whose rheology is rapidly and easily changeable, freely moving their hands without rigid mechanical linkages. Numerical advanced simulation tests using algorithms based on finite element methods have been implemented, in order to analyze and predict the spatial distribution of the magnetic field. A special focus was laid on investigating on how the magnetic filed profile is altered by the introduction of the hand. Possible solutions were proposed to overcome this perturbation. Finally some preliminary psychophysical tests in order to assess the performance of the device are reported and discussed

The Role of Tactile Flow in Processing Dynamic Haptic Stimuli

Dynamic stimuli in visual and tactile sensory modalities share fundamental psychophysical features that can be explained by similar computational models. In vision, information about relative motion between objects and the observer are mainly processed by optic flow, which is a 2D field of velocities associated with variation of brightness patterns in the image plane. It provides important information about cues for region and boundary segmentation, shape recovery, and so on. For instance, radial patterns of optic flow are often used to estimate time before contact with an approaching object. We put forward the hypothesis that a similar behavior can be present in the tactile domain, in which an analogous paradigm to optic flow might exist. Moreover, as optic flow is also invoked to explain several visual illusions, including the well-known ”barber-pole” effect and Ouchi’s illusion, we investigate whether similar misperceptions can be observed in the tactile domain as well. After introducing a computational model of tactile flow, which is intimately related to existing models for the visual counterpart a set of experiments aiming at reproducing the corresponding visual illusion in the tactile domain was arranged and performed. Findings of the experiments here reported indicate that visual and tactile flow share similarities at the psychophysical and computational level and may be intended for similar perceptive goals. Results of this analysis can have great impact on engineering side to implement better haptic and multimodal interfaces for human-computer interaction.

Free Hand Haptic Interfaces Based on Magnetorheological Fluids

This paper is concerned with exploring the possibility of using Magneto-Rheological Fluids (MRF) as haptic interface. MRF are special materials capable of changing their rheological behaviour with an external magnetic field. This property suggested us to use MRF to mimic virtual objects whose compliance can be gradually modulated. Several architectures of prototypes have been envisaged. The general scheme of both prototypes refers to a Haptic Black Box (HBB) concept, intended as a box where the operator can poke his/her bare hand, and interact with the virtual object by freely moving the hand without mechanical constraints. In this way sensory receptors on the whole operator’s hand would be excited, rather than restricting to just one or few fingertips or phalanges. Here we describe the technical evolution from an earlier prototype (HBB-I) which allowed to create only planar virtual objects to a new architecture (HBB-II) capable of reproducing 3D virtual objects. A comparative description of the two devices in terms of technical details and performance is reported, using simulations based on finite element methods. A set of qualitative psychophysical experiments is also reported to assess the improved performance of HBB-II in discriminating softness and shape of virtual objects.

An Artificial Neural Network approach for Haptic Discrimination in Minimally Invasive Surgery

In this paper we investigate the possibility of processing the tactile perception by using a novel biomimetic approach for the pattern recognition module. The goal is to enhance the perception in complex virtual environments deriving from haptic displays mimicking human tactile discrimination. To do this we explored a Minimally Invasive Surgery application where the tactile information are strictly limited. In fact, this promising technique suffers from some evident limitations due to the surgeon loss of tactile perception during palpation of internal organs. This is basically due to the mechanical transmission of the elongated tools used during operation. We propose to integrate an Artificial Neural Network in an electronic board capable of processing data provided by a sensorized laparoscopic tool. The capabilities of several pattern recognition techniques present in literature, the Principal Component Analysis (PCA), a Multilayer Perception (MLP) and a Kohonen Self-Organising Map (KSOM) are investigated. The results are compared with that obtained psychophysically on five viscoelastic materials.