The development of a collision- and self-collision-avoidance scheme for redundant manipulators is discussed in this paper. The method is based on modeling the arm and its environment by simple geometric primitives (cylinders and spheres). A compact method of detecting collisions between two cylinders is introduced. By resorting to the notions of dual angles and dual vectors for representing the axes of cylinders in space, a characterization of different types of collisions is introduced. The performance of the proposed scheme is demonstrated for a seven degrees-of-freedom redundant manipulator via simulations and experiments. © 2005 Wiley Periodicals, Inc.

A collision-avoidance scheme for redundant manipulators: Theory and experiments

This study is intended to build a controller of redundant manipulator with the simultaneous ability of trajectory tracking and obstacle avoidance without any preparation of path planning to achieve full automation even for one production of one kind, while keeping the avoidance ability high and keeping its shape away from obstacle to reduce the possibility that the manipulator crashes to the obstacle. To evaluate the avoidance ability of the intermediate links, a scalar value of avoidance manipulability shape index (AMSI) was proposed, which is independent of the obstacle's shape. On the other hand, the danger to crash to the obstacle is depending on the shape of the obstacle, which could be evaluated by the potential field set around the obstacle. This paper just proposes a control method of the manipulator's shape based on avoidance manipulability shape index with potential (AMSIP) to simultaneously avoid obstacle and keep the avoidance ability high while tracking the hand trajectory

On-line Optimization of Avoidance Ability for Redundant Manipulator

In this paper, we propose a new index of dynamic manipulability for humanoid robot to estimate dynamic ability to change configuration by using remaining redundancy, while prior task is being controlled, e.g., face and eyes being directed to some object. Several indexes have been proposed so far to measure statical and dynamical capability of robot manipulator. For example, Dynamic Manipulability Ellipsoid (DME) describes a distribution of hand acceleration produced by normalized joint torque. On the other hand, Reconfiguration Manipulability Ellipsoid (RME) denotes a distribution of each link velocity produced by joint angular velocity. This paper shows new index of Dynamic Reconfiguration Manipulability (DRM) combined dynamic manipulability and reconfiguration manipulability, and we have adopted the DRM to a humanoid robot, exhibiting how the DRM indicates directly the configuration-changeability of walking humanoid robot.

Dynamic Reconfiguration Manipulability analyses of humanoid bipedal walking

A 3’DOF robot finger is fixed to the end-effector of a 6’DOF robot arm to construct a redundant macro-micro robot system that is able to emulate the finger-arm system of a human being. However, determining joint angles and velocities of a redundant robot system in a natural way remains a difficult issue. This paper describes a method to control the system so as to generate common motions emulating the hand-arm movement of a human. To achieve this purpose, the finger is primarily supposed to complete delicate local motions while the arm moves to assist the finger when the manipulability of the finger is too low and the system is about to miss the desired target. The effectiveness on motion generation and the relation between kinetic energy and manipulability by using the proposed method has been experimentally demonstrated and discussed.

Control of a Macro-Micro Robot System Using Manipulability of the Micro Robot

In this paper, a 3-DOF robot finger is fixed onto the end-effector of a 6-DOF robot arm to realize a finger-arm robot. As in the case of the upper limb of a human being, the finger- arm robot possesses a high degree of freedom. This paper describes a new method to control the finger-arm robot so as to simply generate a natural motion emulating the movement of a human upper limb. To achieve this, a control method based on the manipulability of the finger is proposed. By using the proposed method, the finger primarily moves to complete a delicate local task, while the arm only moves to assist the finger when the manipulability of the finger falls below a reference value. The proposed method was applied to the task of drawing two 3D figures. The obtained results clarify the relation between manipulability and kinetic energy and also demonstrate the effectiveness of the proposed method.

Emulating the Motion of a Human Upper Limb: Controlling a Finger-arm Robot by using the Manipulability of its Finger

This paper is concerned with avoidance manipulability of redundant manipulators for trajectory tracking and obstacle avoidance. Possibility of avoiding a collision with obstacles during tracking a desired hand trajectory is discussed with proposed avoidance matrix, avoidance manipulability ellipsoid and avoidance manipulability measure which are defined on each link constructing the manipulator except top link. A necessary and sufficient condition that the intermediate links can avoid obstacles in a work space is indicated that a dimension of range space of the avoidance matrix coincides with the one of the work space of the manipulator. That means the avoidance manipulability ellipsoid is expanded in the whole work space. Relations of the ellipsoids and factors which influence the shape, namely, a posture of the manipulator, redundant degree, a serial position of the intermediate link from base, and priorities of the avoiding tasks, are also analyzed. Finally we show analyzed results of avoidance possibility with the proposed avoidance manipulability by numerical examples.

Mamoru Minani

Papers

Avoidance Manipulability for Redundant Manipulators