Singularities of Robot Mechanisms

This book presents the singular configurations associated with a robot mechanism, together with robust methods for their computation, interpretation, and avoidance path planning. Having such methods is essential as singularities generally pose problems to the normal operation of a robot, but also determine the workspaces and motion impediments of its underlying mechanical structure. A distinctive feature of this volume is that the methods are applicable to nonredundant mechanisms of general architecture, defined by planar or spatial kinematic chains interconnected in an arbitrary way. Moreover, singularities are interpreted as silhouettes of the configuration space when seen from the input or output spaces. This leads to a powerful image that explains the consequences of traversing singular configurations, and all the rich information that can be extracted from them. The problems are solved by means of effective branch-and-prune and numerical continuation methods that are of independent interest in themselves. The theory can be put into practice as well: a companion web page gives open access to implementations of the algorithms and the corresponding input files. Using them, the reader can gain hands-on experience on the topic, or analyse new mechanisms beyond those examined in the text. Overall, the book contributes new tools for robot design, and constitutes a single reference source of knowledge that is otherwise dispersed in the literature.

Presents mechanism singularities, with powerful numerical methods for their computation and avoidance in the general architecture case, solving two open, long-standing problems of robot kinematics Toolbox of methods for exhaustively computing the singularities, determining accurate workspace maps, and planning safe motion paths between given configurations, for mechanisms of arbitrary architecture A companion web page provides open access to implemented versions of the algorithms, input files for the study cases analyzed, and animated versions of many figures in the book

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Inhalt

Preface.- Notation.- List of Figures.- 1 Introduction.- 1.1 Historical Context.- 1.2 Assumptions and Scope.- 1.3 Reader's Guide.- 2 Singularity Types.- 2.1 Forward and Inverse Singularities.- 2.2 A Geometric Interpretation of Singularities.- 2.3 Lower-level Singularity Types.- 2.4 A Simple Mechanism with All Singularities.- 3 Numerical Computation of Singularity Sets.- 3.1 A Suitable Approach.- 3.2 Formulating the Equations of the Singularity Set.- 3.3 Isolating the Singularity Set.- 3.4 Visualising the Singularity Sets.- 3.5 Case Studies.- 4 Workspace Determination.- 4.1 The Need of a General Method.- 4.2 The Workspace and its Boundaries.- 4.3 Issues of Continuation Methods.- 4.4 Exploiting the Branch-and-Prune Machinery.- 4.5 Case Studies.- 5 Singularity-free Path Planning.- 5.1 Related Work.- 5.2 Formulating the Singularity-free C-space.- 5.3 Exploring the Singularity-free C-space.- 5.4 Case Studies.- 6 Planning with Further Constraints.- 6.1 Wrench-Feasibility Constraints.- 6.2 The Planning Problem.- 6.3 Proofs of the Properties.- 6.4 Case Studies.- 6.5 Details about the Wrench Ellipsoid.- 6.6 Extensions.- 7 Conclusions.- 7.1 Summary of Results.- 7.2 Future Research Directions.- References.- Index.- Author Index.