Showing papers by "Lorenzo Sciavicco published in 1991"

Closed-loop inverse kinematics schemes for constrained redundant manipulators with task space augmentation and task priority strategy

Abstract: This article presents new closed-loop schemes for solving the inverse kinematics of constrained redundant manipula tors. In order to exploit the space of redundancy, the end- effector task is suita...

Global task space manipulability ellipsoids for multiple-arm systems

Abstract: New definitions of force and velocity manipulability ellipsoids for multiple-arm systems are given. A suitable kinetostatic formulation for multiple cooperating arms is adopted that allows a global task space description of external and internal forces as well as absolute and relative velocities at the object level. The concept of a force manipulability ellipsoid for a single arm is formally extended to the multi-arm case by regarding the whole system as a mechanical transformer from the extended joint space to the global task space. Kinetostatic duality properties are then exploited to derive velocity manipulability ellipsoids for the multiple-arm system. The proposed method is compared with other approaches using numerical examples. >

Task space dynamic analysis of multiarm system configurations

Abstract: The aim of this article is to provide a systematic method to perform dynamic analysis in the task space for a sys tem composed of multiple arms holding a rigid object. The dynamic manipulability ellipsoid is introduced to obtain quantitative indices of the system's capability, in each configuration, of performing object accelerations along given task space directions. The ellipsoid is derived on the basis of the mapping of object accelerations onto joint driving torques via the proper kineto-static and dynamic equations of the system. The maximum joint torque limits are taken into account, and the effects of gravitational loads onto the ellipsoid are evidenced. Anal ysis of multiarm system configurations is carried out in a number of case studies.

Reformulation of dynamic manipulability ellipsoid for robotic manipulators

Abstract: A reformulation of the dynamic manipulability ellipsoid for robotic manipulators is established. This ellipsoid is a common tool in robotics for measuring the ability of a manipulator to produce arbitrary accelerations of the end effector for a given set of torques at the joints. As opposed to the original approach where gravitational forces were imputed to compress the volume of the ellipsoid, it is shown that the effect of gravity can be taken into account by translating the center of the ellipsoid without affecting its volume. The ellipsoid for redundant manipulators is characterized by investigating the properties of the manipulator Jacobian involved in the core of the ellipsoid. Numerical case studies are developed. >

Control of robotic systems through singularities

Abstract: The goal of this work is to provide an overview of major control techniques that manage the occurrence of singularities for robotic systems. The common feature of these methods is a modification of the inverse differential kinematic mapping which is ill-conditioned in the neighbourhood of a singularity. The following solutions are discussed; namely, the Jacobian transpose, the Jacobian pseudoinverse, and the damped least-squares Jacobian inverse.