65 research outputs found

    On the Role of Haptic Synergies in Modelling the Sense of Touch and in Designing Artificial Haptic Systems

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    This thesis aims at defining strategies to reduce haptic information complexity, with minimum loss of information, to design more effective haptic interfaces and artificial systems. Nowadays, haptic device design can be complex. Moreover, the artificial reproduction of the full spectrum of haptic information is a daunting task and far to be achieved. The central idea of this work is to simplify this information by exploiting the concept of synergies, which has been developed to describe the covariation patterns in multi-digit movements and forces in common motor tasks. Here I extend and exploit it also in the perceptual domain, to find projections from the heterogeneous information manifold, generated by the mechanics of touch, and what can be actually perceived by humans. In this manner, design trade-off between costs, feasibility and quality of the rendered perception can be individuated. With this as motivation, referring to cutaneous sensing, I discuss the development of a fabric-based softness display inspired by ``Contact Area Spread Rate'' hypothesis as well as the characterization of an air-jet lump display method for Robot-assisted Minimally Invasive Surgery. Considering kinaesthesia, I analyze the problem of hand posture estimation from noisy and limited in number measures provided by low cost hand pose sensing devices. By using the information about how humans most frequently use their hands, system performance is enhanced and optimal system design enabled. Finally, an integrated device, where a conventional kinaesthetic haptic display is combined with a cutaneous softness one, is proposed, showing that the fidelity by which softness is artificially rendered increases

    Design and characterization of a fabric-based softness display

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    To enable a realistic tactile interaction with remote or virtual objects, softness information represents a fundamental property to be rendered via haptic devices. What is challenging is to reduce the complexity of such an information as it arises from contact mechanics and to find suitable simplifications that can lead an effective development of softness displays. A possible approach is to surrogate detailed tactile cues with information on the rate of spread of the contact area between the object and the finger as the contact force increases, i.e. force/area relation. This paradigm is called contact area spread rate. In this paper we discuss how such a paradigm has inspired the design of a tactile device (hereinafter referred to as Fabric Yielding Display, FYD-2), which exploits the elasticity of a fabric to mimic different levels of stiffness, while the contact area on the finger indenting the fabric is measured. In this manner, the FYD-2 can be controlled to reproduce force-area characteristics. In this work, we describe the FYD-2 architecture and report a psychophysical characterization. FYD-2 is shown to be able to accurately reproduce force-area curves of typical objects and to enable a reliable softness discrimination in human users

    Shape Localization and Recognition using a Magnetorheological-fluid Haptic Display

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    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 novel tactile display for softness and texture rendering in tele-operation tasks

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    Softness and texture high-frequency information represent fundamental haptic properties for every day life activities and environment tactual exploration. While several displays have been produced to convey either softness or high-frequency information, there is no or little evidence of systems that are able to reproduce both these properties in an integrated fashion. This aspect is especially crucial in medical tele-operated procedures, where roughness and stiffness of human tissues are both important to correctly identify given pathologies through palpation (e.g. in tele-dermatology). This work presents a fabric yielding display (FYD-pad), a fabric-based tactile display for softness and texture rendering. The system exploits the control of two motors to modify both the stretching state of the elastic fabric for softness rendering and to convey texture information on the basis of accelerometer-based data. At the same time, the measurement of the contact area can be used to control remote or virtual robots. In this paper, we discuss the architecture of FYD-pad and the techniques used for softness and texture reproduction as well as for synthesizing probe-surface interactions from real data. Tele-operation examples and preliminary experiments with humans are reported, which show the effectiveness of the device in delivering both softness and texture information

    Wearable haptic systems for the fingertip and the hand: taxonomy, review and perspectives

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    In the last decade, we have witnessed a drastic change in the form factor of audio and vision technologies, from heavy and grounded machines to lightweight devices that naturally fit our bodies. However, only recently, haptic systems have started to be designed with wearability in mind. The wearability of haptic systems enables novel forms of communication, cooperation, and integration between humans and machines. Wearable haptic interfaces are capable of communicating with the human wearers during their interaction with the environment they share, in a natural and yet private way. This paper presents a taxonomy and review of wearable haptic systems for the fingertip and the hand, focusing on those systems directly addressing wearability challenges. The paper also discusses the main technological and design challenges for the development of wearable haptic interfaces, and it reports on the future perspectives of the field. Finally, the paper includes two tables summarizing the characteristics and features of the most representative wearable haptic systems for the fingertip and the hand

    Temporal integration of loudness as a function of level

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