Robust metrology procedures for modular robotic systems using indoor GPS coordinate measuring system

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Date

2004

Authors

Kang, Seong Ho

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Abstract

An OAS or a modular reconfigurable system is a collection of individual link and joint modules with standardized interfaces that can be reconfigured on demand into different geometries ranging from mobile platforms and 6 degrees of freedom (DOF) manipulator arms to 40 DOF manufacturing robotic cells. Such systems will allow flexible manufacturing, rapid repair, and upgrade, but these benefits have yet to be realized. A significant barrier is the presence of error between the ideal frame and the actual frame. While the repeatability of a typical robot can be 0.005", its accuracy may not be better than 0.1" due to configuration, load, model error, etc. Teaching or calibrating a robotic device is, therefore, required in industries to improve its accuracy for high-value added precision operations. The associated costs are extremely high. This fact trumps other modular technology benefits. Robot metrology is a solution to overcome these problems by increasing the absolute pose accuracy in the same order of magnitude as its repeatability. Despite the advancement of traditional metrology techniques, System Metrology for Monolithic Systems (SMMS) has proven to be too cumbersome, costly, and time-consuming for practical usage on modular systems. These obstacles suggest a strong need for a new look at robot metrology. Robust Metrology for Modular Systems (RMMS) (the metrology of robots that are composed of modules) is much more tractable, as a consequence of the reduced number of parameters in each module addressed by this metrology approach. In this dissertation, a highly advanced interface called ‘RRG Interface’ has been introduced. An advanced metrology system has been developed including a coordinate measuring system based on a state-of-the-art technology called “indoor GPS (Global Positioning System)” and a fully automatic loading mechanism with pure force generating capability. A hand-held probe called the ‘3D Probe’ has been developed. The impact of nonlinear compliance is examined. Based on the developed optimal measuring strategies, the metrology system has been applied to OAS metrologies and experimental results are presented. Kinematic modeling formulations are presented including geometric and compliance parameters. The performance of a 6 DOF modular system is predicted and a 22 time improvement over the best industrial practice has been made.

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