An investigation of programmable compliance during robot/environment interactions

Pike, Darryl Scott (1994) An investigation of programmable compliance during robot/environment interactions. Masters thesis, Memorial University of Newfoundland.

[English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (18MB) [English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. (Original Version)

Abstract

This thesis explores the effects of changing the effective damping and stiffness coefficients on the dynamic operating characteristics of a single degree of freedom direct-drive robot during "making" contact with a rigid environment. Altering these two coefficients ultimately implies changing the compliance of the robot/environment interaction. Since the compliance is changed dynamically and in real-time, the approach is referred to as Active Compliance. The thesis provides insight into the fundamental contact dynamics of a single robotic link such that the results can be used to describe the dynamics of more complex multi-degree of freedom manipulator architectures. -- Active compliance requires real-time control of the damping and stiffness characteristics and is fundamentally a dynamic force control scheme allowing the robot to conform to the natural constraints imposed by the environment. To investigate this interaction in this thesis a software simulation program and a single degree of freedom direct-drive robot arm are developed. The thesis also clearly defines five distinct phases associated with the process of making contact. These contact phases are generic and apply to both mobile and fixed robots. -- This study highlighted the following conclusions (1) Both mobile and fixed robots can benefit from controlled active compliance, (2) Altering these coefficients in real-time during the contact process is achievable, (3) The distance from the environment is not a necessary piece of information for contact under a force controlled contact scheme, (4) Compliance can be implemented based on a force constraint imposed upon the robot and the environment, (5) Sensors provide control information and must be strategically selected and mounted, (6) Ideal Damping and Stiffness laws are developed and proven functional, (7) Friction is a significant impedance factor which effects all aspects of the contact cycle.

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