In this paper we describe a design of an innovative immersive Haptic Black Box (HBB) based on Magneto Rheological Fluids (MRF). By exploiting results from an accurate analysis performed on a previously operating haptic display a new device capable of exciting the MRF with improved performance in terms of magnetic field intensity and spatial resolution has been developed. Due to the core structure and feeding conditions, only a 3D numerical analysis, taking into account the material non-linearity, provides an accurate prediction of the excitation field and, consequently, of the rheological behavior of the uid. The results of the present paper will be used in subsequent work where the realization of the prototype and the results of several psychophysical tests on excited MRF in terms of softness and/or shape reconstruction will be described.
V5/MT complex responds selectively to perception of optic flow (Morrone et al., Nature Neurosci , 2001). Since similarities exist between visual and tactile perception, we hypothesized that tactile flow might also rely on V5/MT response. We and others have shown recently that visual extrastriate cortical areas respond both during visual and tactile recognition of objects, indicating that these regions are organized in a supramodal fashion. In this study, we measured neural response evoked during visual and tactile perception of coherently moving dot patterns to test the hypothesis that V5/MT may be supramodally organized and may respond also to tactile stimulation.
In this paper we report on a set of experiments involving perceptual illusions elicited by dynamic tactile stimulation of fingertips. These misperceptions are akin to some well studied optical illusions, which have been given an explanation in terms of the mechanisms of optic flow perception. We hypothesize that a similar perceptual mechanism exists for tactile flow, which is related to how humans perceive relative motion and pressure between the fingertips and objects in contact. We present a computational model of tactile flow, and discuss how it relates to accepted models of the neurophyisiology of touch. A particularly interesting phenomenon observed under some experimental circumstances, consisting of an incoherent tactile perception generating what we call a tactile vertigo, can be explained in terms of this model. The proposed tactile flow model also explains other phenomena observed in the past (namely, the Contact Area Spread Rate effect), and is of importance in designing simpler, more effective devices for artificial haptic sensing and displays.
In this paper, we consider the problem of steering complex dynamical systems among equilibria in their state space in efficient ways. Efficiency is considered as the possibility of compactly representing the (typically very large, or infinite) set of reachable equilibria and quickly computing plans to move among them. To this purpose, we consider the possibility of building lattice structures by purposefully introducing quantization of inputs. We consider different ways in which control actions can be encoded in a finite or numerable set of symbols, review different applications where symbolic encoding of control actions can be employed with success, and provide a unified framework in which to study the many different possible manifestations of the idea.
Robotic manipulation by rolling contacts is an appealing method for achieving dexterity with relatively simple hardware. While there exist techniques for planning motions of rigid bodies in rolling contact under nominal conditions, an inescapable challenge is the design of robust controllers of provable performance in the presence of model perturbations. As a preliminary step in this direction, we present in this paper an iterative robust planner of arbitrary accuracy for the plate-ball manipulation system subject to perturbations on the sphere radius. The basic tool is an exact geometric planner for the nominal system, whose repeated application guarantees the desired robustness property on the basis of the Iterative Steering paradigm. Simulation results under perturbed conditions show the effectiveness of the method.
In this paper we present results obtained in the context of Quality of Service (QoS) control for soft real-time applications. The discussion addresses the issue of dynamically adjusting the bandwidth for a set of periodic tasks, when a reservation-based (RB) CPU scheduling policy is used. RB techniques are particularly suitable for this kind of applications since they allow an accurate mathematical modelling of the dynamic evolution of the QoS experienced by tasks. Based on this model, a control policy guaranteeing specified QoS levels for different tasks is illustrated, along with necessary and sufficient conditions for its existence. Moreover, the problem of steering a task QoS back into its nominal level is tackled, in response to deviations due to temporary overload conditions. Simulation results are reported, for the purpose of validating the approach.
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.
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 concept, 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 operator's 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 technology. These fluids are composed of micron-sized, 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.
In this paper, the problem of stabilizing linear discrete time hybrid automata is considered. A synthesis methodology is obtained by extending to hybrid systems the stabilization techniques based on stable convex combinations, originally developed for switching systems. An algorithm to explore the candidate stabilizing controller actions is proposed and an application to an automotive engine control problem is described.
In this paper we present an innovative application of magnetorheological (MR) fluids to haptic interfaces. These materials consist of a suspension of a micron-sized, magnetizable particles 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. Just as quickly, the fluid can be returned to its liquid state by the removal of the field. MR fluids are already present on the market, used in devices such as valves, brakes, clutches, and dampers. In this paper we investigate the possibility of using MR fluids to mimic the compliance, damping, creep (in other terms, the rheology) of materials in order to realize a haptic display and we propose two different implementations. Here we only outline the first scheme, whose experimental results have been reported in our previous work, and will describe the second one. In this latter scheme we set up a psychophysical protocol where a group of volunteers were asked to interact with the MR fluid duly excited and qualitative results are discussed.
In this paper, we consider planning motions of objects of regular shape rolling on a plane among obstacles. Theoretical foundations and applications of this type of operations in robotic manipulation and locomotion have been discussed elsewhere. In this paper, we propose a novel algorithm that improves upon existing techniques in that: i) it is finitely computable and predictable (an upper bound on the computations necessary to reach a given goal within a tolerance can be given), and ii) it possesses a topological (local-local) property which enables obstacles and workspace limitations to be dealt with in an effective way.
In this paper we consider the reachability problem for quantized control systems, i.e. systems that take inputs from a finite set of symbols. Previous work addressed this problem for linear systems and for some specific classes of nonlinear driftless systems. In this paper we attack the study of more general nonlinear systems. To do so we find it useful to pose the problem in more abstract terms, and make use of the wealth of tools available in group theory, which enables us to proceed in our agenda of better understanding effects of quantization of inputs on dynamic systems.
