Showing papers by "Damien Chablat published in 1998"

Working modes and aspects in fully parallel manipulators

Abstract: The aim of this paper is to characterize the notion of aspects in the workspace and in the joint space for parallel manipulators. In opposite to the serial manipulators, the parallel manipulators can admit not only multiple inverse kinematic solutions, but also multiple direct kinematic solutions. Two Jacobian matrices appear in the kinematic relations between the joint-rate and the Cartesian-velocity vectors, which are called the "inverse kinematics" and the "direct kinematics" matrices. The study of these matrices allow one to define the parallel and the serial singularities respectively. The notion of working modes is introduced to separate inverse kinematic solutions. Thus we can find out the domains of the workspace and the joint space which exempt of singularity. An application of this study is the movability analysis in the workspace of the manipulator as well as the path-planning and control. This study is illustrated with a RR-RRR planar parallel manipulator.

Workspace and Assembly modes in Fully-Parallel Manipulators : A Descriptive Study

Abstract: The goal of this paper is to explain, using a typical example, the distribution of the different assembly modes in the workspace and their effective role in the execution of trajectories. The singular and non-singular changes of assembly mode are described and compared to each other. The non-singular change of assembly mode is more deeply analysed and discussed in the context of trajectory planning. In particular, it is shown that, according to the location of the initial and final configurations with respect to the uniqueness domains in the workspace, there are three different cases to consider before planning a linking trajectory.