On adaptive robot systems for manufacturing applications
Date
2002
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Doctoral
Abstract
System adaptability is very important to current manufacturing practices due to frequent
changes in the customer needs. Two basic concepts that can be employed to achieve
system adaptability are flexible systems and modular systems. Flexible systems are fixed
integral systems with some adjustable components. Adjustable components have limited
ranges of parameter changes that can be made, thus restricting the adaptability of systems.
Modular systems are composed of a set of pre-existing modules. Usually, the parameters
of modules in modular systems are fixed, and thus increased system adaptability is
realized only by increasing the number of modules. Increasing the number of modules
could result in higher costs, poor positioning accuracy, and low system stiffness in the
context of manufacturing applications. In this thesis, a new idea was formulated: a
combination of the flexible system and modular system concepts. Systems developed
based on this new idea are called adaptive systems. This thesis is focused on adaptive
robot systems.
An adaptive robot system is such that adaptive components or adjustable parameters are
introduced upon the modular architecture of a robot system. This implies that there are
two levels to achieve system adaptability: the level where a set of modules is
appropriately assembled and the level where adjustable components or parameters are
specified. Four main contributions were developed in this thesis study.
First, a General Architecture of Modular Robots (GAMR) was developed. The starting
point was to define the architecture of adaptive robot systems to have as many
configuration variations as possible. A novel application of the Axiomatic Design
Theory (ADT) was applied to GAMR development. It was found that GAMR was the
one with the most coverage, and with a judicious definition of adjustable parameters.
Second, a system called Automatic Kinematic and Dynamic Analysis (AKDA) was
developed. This system was a foundation for synthesis of adaptive robot configurations.
In comparison with the existing approach, the proposed approach has achieved
systemization, generality, flexibility, and completeness. Third, this thesis research has
developed a finding that in modular system design, simultaneous consideration of both
kinematic and dynamic behaviors is a necessary step, owing to a strong coupling
between design variables and system behaviors. Based on this finding, a method for
simultaneous consideration of type synthesis, number synthesis, and dimension synthesis
was developed. Fourth, an adaptive modular Parallel Kinematic Machine (PKM) was
developed to demonstrate the benefits of adaptive robot systems in parallel kinematic
machines, which have found many applications in machine tool industries. In this
architecture, actuators and limbs were modularized, while the platforms were adjustable
in such a way that both the joint positions and orientations on the platforms can be
changed.
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Degree
Doctor of Philosophy (Ph.D.)
Department
Mechanical Engineering
Program
Mechanical Engineering