Failure-tolerant path planning for kinematically redundant manipulators anticipating locked-joint failures

Abstract

Abstract-This work considers kinematic failure tolerance when obstacles are present in the environment. It addresses the issue of finding a collision-free path such that a redundant robot can successfully move from a start to a goal position and/or orientation in the workspace despite any single locked-joint failure at any time. An algorithm is presented that searches for a simply-connected, obstacle-free surface with no internal local minimum or maximum in the configuration space that guarantees the existence of a solution. The method discussed is based on the following assumptions: a robot is redundant relative to its task, only a single locked-joint failure occurs at any given time, the robot is capable of detecting a joint failure and immediately locks the failed joint, and the environment is static and known. The technique is illustrated on a seven degree-of-freedom commercially available redundant robot. Although developed and illustrated for a single degree of redundancy, it is possible to extend the algorithm to higher degrees of redundancy.

Fundamental Limitations on Designing Optimally Fault-Tolerant Redundant Manipulators

“…G. planning [23], and kinematic failure recovery [24]. Work that considers obstacles in the workspace include [25] and [26]. One approach to the problem of designing fault-tolerant robots is to optimize some measure of fault tolerance.…”

“…This measure can be either global, i.e., over a specified region of the workspace, or local, i.e., at a specific configuration. Global measures, such as those in [25] and [27], are more appropriate for tasks that require large motions throughout the workspace, whereas local measures [11], [28] are more appropriate for dexterous operations in a relatively small location, e.g., laser pointing [6] and manipulation of nuclear material [9]. In this paper, we focus on a local measure called the relative manipulability index, which was first introduced in [12] to quantify the fault tolerance of kinematically redundant serial manipulators.…”

Suppression Control for Joint Impact Torque caused by Joint-Locked Failure of Space Manipulator under External Force

“…During these operations, external force acts on the endeffector of space manipulator. Once joint-locked failure occurs [4], impact torque may occur in joint space and operations space simultaneously, which will bring about damage to manipulator structure and manipulating objects. For purpose of operation completion, the external force acting on the end-effector should be maintained.…”

An Illustration of Generating Robots from Optimal Fault-Tolerant Jacobians

“…These analyses have been performed both on the local properties associated with the manipulator Jacobian [29][30][31][32] as well as the global characteristics such as the resulting workspace following a particular failure [33][34][35][36]. (Clearly both local and global kinematic properties are related, e.g., workspace boundaries correspond to singularities in the Jacobian.)…”