The control-based method developed for force estimation is compatible with the neurosurgical application and is also capable of measuring tissue resistance without any additional sensors. Force feedback in minimally invasive surgery allows the human operator to manipulate tissues as if his/her hands were in contact with the patient organs.

Abstract. This paper presents various procedures that can be used in order to numerically evaluate what the maximum Z−width that can be rendered by a mobile haptic interface will be given few parameters that characterize the haptic device and the mobile platform that make up such interface. Such procedures are applied to the case of two different mobile haptic interfaces. Results are encouraging, even though limitations to the proposed procedure exist.

A technique to animate a realistic hand avatar with 20 DoFs based on the biomechanics of the human hand is presented. The animation does not use any sensor glove or advanced tracker with markers. The proposed approach is based on the knowledge of a set of kinematic constraints on the model of the hand, referred to as postural synergies, which allows to represent the hand posture using a number of variables lower than the number of joints of the hand model. This low-dimensional set of parameters is estimated from direct measurement of the motion of thumb and index finger tracked using two haptic devices. A kinematic inversion algorithm has been developed, which takes synergies into account and estimates the kinematic configuration of the whole hand, i.e., also of the fingers whose end tips are not directly tracked by the two haptic devices. The hand skin is deformable and its deformation is computed using a linear vertex blending technique. The proposed synergy-based animation of the hand avatar involves only algebraic computations and is suitable for real-time implementation as required in haptics.

The growing interest in haptic applications suggests that haptic digital media will soon become widely available, and the need will arise to protect digital haptic data from misuse. In this article, we present our study and findings on psychophysical experiments regarding human abilities to perceive a digital watermark, or hidden signal, through a haptic interface.H aptic interfaces allow physical interactions with virtual 3D objects through the sense of touch. Possible applications include training for minimally invasive or microscopic surgical procedures, interacting with sculptures such as Michelangelo's David that we can't directly touch, perceptualizing multidimensional data sets such as earthquake simulations that we can't easily comprehend through visual displays alone, and assistance to sensory-impaired individuals by displaying visual and/or audio information through the haptic sensory channel.Because of the expected growing importance that digital haptic data will have in the near future, it's easy to predict that the need will soon arise to protect such data from misuse, like unauthorized copying and distribution, or false ownership claims. Among the available technologies to protect digital data, digital watermarking is receiving increased attention, thanks to its unique capability of persistently hiding a piece of information within the to-be-protected data. 1 We can use this hidden information to prove ownership, deny permission of copying the data, or detect tampering.In this article, we present the results of two psychophysical experiments that investigated the perceptibility and detectability of a hidden signal in the macro-and microgeometry of the virtual object's surface. In the first experiment, we embedded the watermark into a virtual surface's macrogeometry by modifying the underlying 3D model's wireframe. To begin with, we chose a flat surface so that signals related to the object's shape wouldn't inadvertently mask the watermark's detection. Nevertheless, we represented the surface with a 3D mesh so that we could readily extend this initial work to objects with arbitrary surface shapes. We modeled the watermark as an additive white noise superimposed on the host surface. The goal of the experiment was to estimate the noise intensity threshold as a function of the underlying mesh's resolution.Our second experiment focused on the microgeometry of object surfaces by embedding the watermark in the texture data. We used a simple one-dimensional sinusoidal model for both the watermark and the host signal. The goal of this experiment was to investigate whether existing detection threshold data 2,3 could successfully predict the perceptibility of the watermark. Despite the texture model's simplicity, this experiment provided the first evidence of the possibility of embedding a haptically imperceptible watermark that can later be detected via spectral analysis.Before going further into these experiments, we first provide a little background information regarding the basic issues and requirements ...

Abstract-The increasing demand for virtual reality applications in several scientific disciplines feeds new research perspectives dealing with robotics, automation, and computer science. In this context, one of the topics is the design of advanced force-feedback devices allowing not only kinesthetic interaction with virtual objects but also locomotion and navigation inside virtual worlds. This has the main advantage to stimulate human vestibular apparatus, thus increasing the overall realism of simulation. Particularly, this paper deals with mobile haptic interfaces (MHIs), built by combining standard force-feedback devices with mobile platforms. We investigated which factors may affect the transparency of this kind of devices, identifying in mobile robot dynamics a possible cause of loss of transparency. Hence, in this paper, we present a method to analyze dynamic performance of an MHI and some basic guidelines to design controller in order to meet desired specifications. Experimental validation of the theoretical results is reported.