Papers by Author: Grigore Gogu

Abstract: Machine tools and robots have both evolved fundamentally and we can now question the abilities of new industrial robots concerning accurate task realization under high constraints. Requirements in terms of kinematic and dynamic capabilities in High Speed Machining (HSM) are increasingly demanding. To face the challenge of performance improvement, parallel and hybrid robotic architectures have emerged and a new generation of industrial serial robots with the ability to perform machining tasks has been designed. In this paper, we propose to evaluate the performance criteria of an industrial robot included in a kinematically redundant robotic cell dedicated to a machining task. Firstly, we present the constraints of the machining process (speed, accuracy etc.). We then detail the direct geometrical model and the kinematic model of a robot with closed chain in the arm and we propose a procedure for managing kinematic redundancy whilst integrating various criteria. Finally, we present the evolution of the criteria for a given trajectory in order to define the best location for a rotary table and to analyze the manipulators stiffness.

Abstract: This article presents a new approach of soft material modeling for robotic manipulation which combines physical modeling and tracking of a deformable object. We discuss the construction of geometrical models using MRI system and how to overcome the problem of variability. The physical model focuses on meat/muscles deformation. We introduce the principal criteria for choosing most appropriate models and discuss two modeling methods which suit our problem: mass spring model and tensor mass model. The introduction of anisotropy in these models allows results to be more realistic but evolves an increasing of computing time.

Abstract: This paper presents a set of techniques based on the use of CAD geometric approaches for singularity surfaces and total operational workspace and joint space determination. The main emphasis is given to the use of CAD tools used to characterize and analyze the performance of planar parallel robot manipulators. The CAD environment provides powerful tools for the graphical programming and geometric feature handling. This paper points out the effectiveness of such a method in the robot design process. These developments are illustrated by the 3-RPR planar parallel manipulator case study. All of the proposed geometric algorithms are implemented in the CATIA CAD environment.

Abstract: In this paper a new method for determination and optimization of the workspace of parallel manipulators is presented. The proposed method is based on a geometrical approach, and offers the possibility to generate automatically the workspace in a CAD environment. Thus, the relationship between the geometrical design parameters of the parallel manipulator and its workspace can be analyzed without difficulty. Optimization problem considered in this paper consists in determining the dimensions of a parallel manipulator having the closest workspace to a prescribed task region. Finally, numerical applications of two types of planar parallel manipulators are presented in order to illustrate the proposed approach.