Dynamic Simulation: Model, Basic Algorithms, and Optimization

this paper, we will focus on the modeling and algorithmic problems we have recently solved for making the system more efficient and consistent at any time with the basic principles Physics. We will show how we have drastically reduced the required computing time, and how the consistency properties can be guaranteed by controlling the incurred errors and the numerical convergence of the differential equations solver

Combining Geometric and Physical Models: The Case of a Dextrous Hand

Planning robust grasping operations involving a dextrous robotics hand and an object located in a three dimensional workspace requires to combine two main types of techniques: a geometric based reasoning aimed at producing a grasping strategy (preshape of the hand, grasping parameters, type of motion to execute), and a physical analysis of the object/hand interactions. The second type of technique is clearly necessary to conclude on the feasibility of the chosen grasping strategy (stability in particular) and to determine the type of control to apply onto the hand. The purpose of this paper is to propose a technique based upon the concept of "physical models" for solving this problem. We will show how physical models can be constructed and used to solve the associated stability and control strategy problems. We will also show how the related techniques has been combined with more classical geometric methods to solve the whole problem. We successively describe the modeling of the task, ..

Fast contact detection between moving deformable polyhedra

ftp://ftp.inrialpes.fr/pub/sharp/publications/joukhadar:etal:iros:99.pdf.gz (not accepted here, non vectorial font)/http://www.ieee.orgThis paper presents an approach to detect and localize contact between deformable polyhedra, which can be convex or concave depending on the time step. Usual contact detection algorithms, defined for convex polyhedra, cannot be used efficiently as they would imply to compute the convex decomposition of the considered polyhedra at each time step, as it can change due to the deformability of these polyhedra. The computation of this convex decomposition being very expensive (in complexity and computation time), we propose an algorithm to detect and localize the contact in linear time wrt the number of vertices. This algorithm returns the direction of this contact and the value of the maximum intersection distance between the convex hulls of the two considered polyhedra. Experimental results, taken from a dynamic simulation application, are presented with their computation time to complete the complexity analysis

Models and Algorithms for the Collision of Rigid and Deformable Bodies

In this report, we describe models and algorithms designed to produce efficient and physically consistent dynamic simulations. These models and algorithms have been implemented in a unique framework, modeling both deformations and contacts through visco-elastic relations. Since this model of interaction (known as «penalty based») is much debated, we present a compared study of two contact models; «penalty» and «impulse». Indeed, the «penalty» based model is supposed to have two major drawbacks : - determin- ing the visco-elastic parameters and - choosing the computation time step. We present a solution for both problems based on physical concepts. Finally, we will present results comparing real data, «impulse» based simulation and «penalty» based simulation

Solving Complex Motion Planning Problems by Combining Geometric and Physical Models: The Cases of a Rover and of a Dextrous Hand

This paper addresses motion planning for robots subjected to strong physical interaction constraints. More precisely, we will show how to solve two particular instances of this general problem: the case of a rover moving on a hilly three dimensional terrain, and the case of a dextrous hand executing a grasping operation. In addition to the high dimension of the associated search spaces, such motion planning problems exhibit new difficulties coming from the fact that the dynamics of the robot/ environment interactions may strongly modify the characteristics of the generated motion. Indeed, parameters like friction, inertia, or accelerations generate physical phenomena like sliding or skidding which may obviously affect the final behaviour of the robot. Therefore, such physical characteristics have to be carefully modeled and integrated into the motion planning paradigm. The purpose of this paper is to show how this goal can be achieved by appropriately combining geometric and physical m..

Penetration of Moxifloxacin into Healthy and Inflamed Subcutaneous Adipose Tissues in Humans

The present study addressed the ability of moxifloxacin to penetrate into healthy and inflamed subcutaneous adipose tissues in 12 patients with soft tissue infections (STIs). Penetration of moxifloxacin into the interstitial space fluid of healthy and inflamed subcutaneous adipose tissues was measured by use of in vivo microdialysis following administration of a single intravenous dosage of 400 mg in six diabetic and six nondiabetic patients with STIs. For the entire study population, the mean time-concentration profile of free moxifloxacin in plasma was identical to the time-concentration profile of free moxifloxacin in tissue (P was not significant). For healthy and inflamed adipose tissues for the diabetic subgroup, the mean moxifloxacin areas under the concentration-time curves (AUCs) from 0 to 8 h (AUC(0-8)s) were 8.1 ± 7.1 and 3.7 ± 1.9 mg·h/liter, respectively (P was not significant). The ratios of the mean AUC(0-8) for inflamed tissue/AUC(0-8) for free moxifloxacin in plasma were 0.5 ± 0.4 for diabetic patients and 1.2 ± 0.8 for nondiabetic patients (P was not significant). The ratios of the AUCs from 0 to 24 h for free moxifloxacin in plasma/MIC at which 90% of isolates are inhibited were >58 and 121 h for Streptococcus species and methicillin-sensitive Staphylococcus aureus, respectively. Concentrations of moxifloxacin effective against clinically relevant bacterial strains are reached in plasma and in inflamed and healthy adipose tissues. Thus, the pharmacokinetics of moxifloxacin in tissue and plasma support its use for the treatment of STIs in diabetic and nondiabetic patients