1,721,021 research outputs found
Hand-Held Object Force Direction Identification Thresholds at Rest and during MovementHaptics: Generating and Perceiving Tangible Sensations
No full textSeries viscoelastic actuators can match human force perception
Full text linkSeries elastic actuators (SEAs) are frequently used for force control in haptic interaction, because they decouple actuator inertia from the end effector by a compliant element. This element is usually a metal spring or beam, where the static force-deformation relationship offers a cheap force sensor. For high-precision force control, however, the remaining small inertia of this elastic element and of the end effector still limit the sensing performance and rendering transparency. Here, we extend the concept to deformable end effectors manufactured of viscoelastic materials. These materials offer the advantage of extremely low mass at high maximum deformation and applicable load. However, force and deformation are no longer statically related, and history of force and deformation has to be accounted for. We describe an observer-based solution, which allows drift-free force measurement with high accuracy and precision. Although the description of the viscoelastic behavior involves higher-order derivatives, the proposed observer does not require any numerical differentiation. This new integrated concept of sensing and actuation, called series viscoelastic actuator (SVA), is applied to our high-precision haptic device OSVALD, which is targeted at perception experiments that require sensing and rendering of forces in the range of the human tactile threshold. User-device interaction force is controlled using state-of-the-art control strategies of SEAs. Force estimation and force control performance are evaluated experimentally and prove to be compatible with the intended applications, showing that SVAs open up new possibilities for the use of series compliance and damping in high-precision haptic interfaces
Self-adaptive games for rehabilitation at home
Full text linkComputer games are a promising tool to support rehabilitation at home. It is widely recognized that rehabilitation
games should (i) be nicely integrated in generalpurpose rehabilitation stations, (ii) adhere to the constraints posed by the clinical protocols, (iii) involve movements that are functional to reach the rehabilitation goal, and (iv) adapt
to the patients’ current status and progress. However, the vast majority of existing rehabilitation games are stand-alone applications (not integrated in a patient station), that rarely
adapt to the patients’ condition. In this paper, we present the first prototype of the patient rehabilitation station we developed that integrates video games for rehabilitation with methods of computational intelligence both for on-line monitoring the movements execution during the games and for adapting the
gameplay to the patients’ status. The station employs a fuzzy system to monitor the exercises execution, on-line, according to the clinical constraints defined by the therapist at configuration
time, and to provide direct feedback to the patients. At the same time, it applies real-time adaptation (using the Quest Bayesian adaptive approach) to modify the game play according both (i) to the patient current performance and progress and (ii) to the exercises plan specified by the therapist. Finally, we present
one of the games available in our patient stations (designed in tight cooperation with therapists) that integrates monitoring functionalities with in-game self-adaptation to provide the best
support possible to patients during their routine
Pointing to Kinesthetic Targets in Space
No full textAn experiment investigated in human adults the sensorimotor transformation involved in pointing to a spatial target identified previously by kinesthetic cues. In the “locating phase,” a computer-controlled mechanical arm guided the left [condition LR (left–right)] or right [condition RR (right–right)] finger of the blindfolded participant to one of 27 target positions. In the subsequent “pointing phase,” the participant tried to reach the same position with the right finger. The final finger position and the posture of the arm were measured in both conditions. Constant errors were large but consistent and remarkably similar across conditions, suggesting that, whatever the locating hand, target position is coded in an extrinsic frame of reference (target position hypothesis). The main difference between the same-hand (RR) and different-hand (LR) conditions was a symmetric shift of the pattern of endpoints with respect to the midsagittal plane. This effect was modeled accurately by assuming a systematic bias in the perception of the postural angles of the locating arm. The analysis of the variable errors indicated that target position is represented internally in a spherical coordinate system centered on the shoulder of the pointing arm and that the main source of variability is within the planning stage of the pointing movement. Locating and pointing postures depended systematically on target position. We tested qualitatively the hypothesis that the selection of both postures (inverse kinematic problem) is constrained by a minimum-distance principle. In condition RR, pointing posture depended also on the locating posture, implying the presence of a memory trace of the previous movement. A scheme is suggested to accommodate the results within an extended version of the target position hypothesis.</jats:p
cChai3D: CHAI3D+Unity3D made easy
No full textCHAI3D is a powerful open-source cross-platform C++ simulation framework for haptic applications (Modified BSD License). It implements state-of-the-art algorithms to render object geometries and material properties such as weight, friction and texture. CHAI3D also integrates graphical rendering (Open GL) and physical simulation engines to develop full-fledged virtual reality applications. Despite its rich set of features, CHAI3D is not used as a general-purpose game engine because game developers tend to prefer other alternatives that offer features such as state machines, animation support, and Graphical User Interfaces (GUIs) that simplify the development of games. In this poster, we present a haptic plugin for Unity3D (https://unity3d.com/), a popular choice for game development. Previous attempts to integrate CHAI3D with Unity3D are either incomplete [3], [4] or no longer available [5]. At the lowest level of the plugin, we wrote cChai3d, a C wrapper around a lightweight version of CHAI3D that included only the force-rendering algorithms. The wrapper has C bindings to facilitate the integration with any programming language and framework. It also includes a high-frequency thread that handle all haptic rendering computation. Full integration between Unity3D and CHAI3D is achieved via Unity3D C# scripts that give haptic properties to Unity3D GameObjects with simple drag-and-drop operations. The position and orientation of the haptic device in the world is configurable and handled transparently. Haptic properties supported by CHAI3D such as stiffness, friction, viscosity and textures can be set via the Unity3D GUI and changed in real time while the simulation is running. Haptic interaction with moving objects is supported within the limits allowed by the update rate of Unity3D main loop. The plugin is compatible with any haptic device supported by CHAI3D. The haptic plugin has been used to implement a study on the haptic perception of virtual textures in Unity 3D and is currently used to implement a serious game to teach 3D geometry to young children
cChai3D: CHAI3D+Unity3D made easy
No full textCHAI3D is a powerful open-source cross-platform C++ simulation framework for haptic applications (Modified BSD License). It implements state-of-the-art algorithms to render object geometries and material properties such as weight, friction and texture. CHAI3D also integrates graphical rendering (Open GL) and physical simulation engines to develop full-fledged virtual reality applications. Despite its rich set of features, CHAI3D is not used as a general-purpose game engine because game developers tend to prefer other alternatives that offer features such as state machines, animation support, and Graphical User Interfaces (GUIs) that simplify the development of games. In this poster, we present a haptic plugin for Unity3D (https://unity3d.com/), a popular choice for game development. Previous attempts to integrate CHAI3D with Unity3D are either incomplete [3], [4] or no longer available [5]. At the lowest level of the plugin, we wrote cChai3d, a C wrapper around a lightweight version of CHAI3D that included only the force-rendering algorithms. The wrapper has C bindings to facilitate the integration with any programming language and framework. It also includes a high-frequency thread that handle all haptic rendering computation. Full integration between Unity3D and CHAI3D is achieved via Unity3D C# scripts that give haptic properties to Unity3D GameObjects with simple drag-and-drop operations. The position and orientation of the haptic device in the world is configurable and handled transparently. Haptic properties supported by CHAI3D such as stiffness, friction, viscosity and textures can be set via the Unity3D GUI and changed in real time while the simulation is running. Haptic interaction with moving objects is supported within the limits allowed by the update rate of Unity3D main loop. The plugin is compatible with any haptic device supported by CHAI3D. The haptic plugin has been used to implement a study on the haptic perception of virtual textures in Unity 3D and is currently used to implement a serious game to teach 3D geometry to young children
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