Claude Andriot

Realistic haptic rendering of interacting deformable objects in virtual environments

A new computer haptics algorithm to be used in general interactive manipulations of deformable virtual objects is presented. In multimodal interactive simulations, haptic feedback computation often comes from contact forces. Subsequently, the fidelity of haptic rendering depends significantly on contact space modeling. Contact and friction laws between deformable models are often simplified in up to date methods. They do not allow a realistic rendering of the subtleties of contact space physical phenomena (such as slip and stick effects due to friction or mechanical coupling between contacts). In this paper, we use Signorinis contact law and Coulombs friction law as a computer haptics basis. Real-time performance is made possible thanks to a linearization of the behavior in the contact space, formulated as the so-called Delassus operator, and iteratively solved by a Gauss-Seidel type algorithm. Dynamic deformation uses corotational global formulation to obtain the Delassus operator in which the mass and stiffness ratio are dissociated from the simulation time step. This last point is crucial to keep stable haptic feedback. This global approach has been packaged, implemented, and tested. Stable and realistic 6D haptic feedback is demonstrated through a clipping task experiment.

Signorini's contact model for deformable objects in haptic simulations

In this paper we consider deformable objects in haptic simulations. The physical simulation that drives haptic perception requires a good dynamic behavior. The inputs of the deformable model come from the treatment of the collision. We propose to focus on the contact restitution between deformable objects to guarantee physical and perceptual realisms of the haptic feedback. Signorini, in 1933, proposed a physical model of contact for deformable objects interacting with rigid static bodies (Signorini, S, 1933). This paper shows that the Signorinis model extents to contacts between two deformable objects using Gauss-Seidel resolution of complementarity problems. An interactive resolution of the overall formulation is presented and experienced on deformable objects using the finite linear-elements method.

A multi-threaded approach for deformable/rigid contacts with haptic feedback

This paper presents a physically based method to deal with haptic feedback of manipulated deformable virtual objects in contact with rigid or deformable environment. The haptic rendering algorithm is based on the Signorinis formulation of the contact as proposed in theoretical mechanics. Since haptic interaction requires high refresh rates, a multi-threaded methodology, sharing configuration values of the contact, ensures good stability and transparency performances. Thus, the interactive simulation gathers three synchronized process: the visualization process, the deformation/contact computation process, and the haptic rendering process.

Passive control architecture for virtual humans

In the present paper, we introduce a new control architecture aimed at driving virtual humans in interaction with virtual environments, by motion capture. It brings decoupling of functionalities, and also of stability thanks to passivity. We show projections can break passivity, and thus must be used carefully. Our control scheme enables task space and internal control, contact, and joint limits management. Thanks to passivity, it can be easily extended. Besides, we introduce a new tool as for manikins control, which makes it able to build passive projections, so as to guide the virtual manikin when sharp movements are needed.

Design of a wearable haptic interface for precise finger interactions in large virtual environments

In this article, we present a new wearable haptic interface developed at CEA-LIST for precise finger interactions within virtual reality applications in large environments. The hand movements are tracked using a stereoscopic visual tracking system, allowing large movements in free space. Moreover, the device integrates two three degrees of freedom with force feedback robots associated with index and thumb fingers, allowing virtual objects fine manipulation. Finally, a two degrees of freedom tactile actuator is integrated under the pulp of each fingertip in order to improve the high frequency response of the haptic interface and to provide information on the texture and the shape of the virtual objects manipulated.

Large Workspace Haptic Devices for Human-Scale Interaction: A Survey

One aim of haptic interfaces is to enhance the users immersion in a virtual environment through the stimulation of the haptic sense. Some applications demand a large-volume workspace to allow human-scale interaction. Different design approaches aimed at addressing this issue, such as specific non redundant devices, redundant robots, mobile or wearable haptic interfaces and tensed cable architectures are reviewed and compared in this paper, concluding with some guidelines for their applicability.

Widening 6-DOF haptic devices workspace with an additional degree of freedom

The aim of haptic interfaces is to enhance the users immersion in a virtual environment through the stimulation of the haptic sense. In the context of scale one applications in immersive environments, the haptic interface must provide a very large workspace without degrading transparency. To reach this goal, we investigated the addition of a 7th axis with larger range to a 6-DOF haptic device. This way, the workspace is increased while with a proper control scheme the dynamic properties of the initial device are saved. To ensure good control on this redundant system we use the notion of generalised dynamically consistent inverse of the Jacobian within a position-position control approach

Real-time finite element finger pinch grasp simulation

This paper addresses physically-based simulation of human fingers for virtual reality applications with haptic feedback. Deformation and contact models are based on finite element method. We show that with good assumptions for the finite element model and with a corotational approach, we can achieve virtual fingers to perform an interactive grasp task. We also show that thanks to the Gauss-Seidel type resolution method we can speed up the CPU time for complex multi-contact simulations with friction. We describe preliminary results in 2D for grasping rigid objects with deformable fingers in real-time.

6DOF Haptic Cooperative Virtual Prototyping over High Latency Networks

In this paper, we propose a networked shared 6-DOF haptic cooperation system, based on several distributed physical simulations dedicated to CAD objects simulation. The simulations are linked together with a spring-damper coupling scheme. This system achieves good local responsiveness and enables remote users to perform complex virtual prototyping tasks. n nA preliminary test was conducted on this system using a complex industrial virtual prototyping scenario. This test required a good coordination between participants. These first experimentations give promising results to carry on prototyping task over large delayed networks.