Kinematic, dynamics, and control of a particular micro-motion system
Date
2000
Authors
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Degree Level
Masters
Abstract
In many applications such as chip assembly in the semiconductor industry, cell
manipulation in biotechnology, and surgery automation in medicine, there is a need for
devices which can perform very small motions (less than 100 μm) with very high
positioning accuracy (in the submicron range) and complex trajectories. This range of
motion is known as micro-motion. In this thesis, the research is described concerning
the design of micro-motion systems. A particular interest of this research lies in a
particular system that produces planar micro-motions and has been found useful in
semi-conductor industries.
The general methodology of designing such systems is based on an observation made
by the author. It is not difficult to find that most of the micro-motion systems
commercially available were developed based on the ball-screw and DC-servo or
stepper motor component systems. These systems have their inherent problems, such as
backlash, friction, and assembly errors, which usually call for high precision
manufacturing technologies and, thus, cause high cost. The compliant mechanism
concept, which suggests generating motions based on deformations in a member of
compliant material, was proposed around the 1990s. The compliant mechanism concept
has been used in mechanism design for years; however, it has not been used for systems
with a feedback control need. Therefore, using the compliant mechanism concept for
building micro-motion systems appears to be a promising methodology and worth
studying.
The goal of the research described in this thesis is to develop an understanding of and a
design tool for a particular planar micro-motion system (called the RRR compliant
mechanism) which is constructed based on the compliant mechanism concept. This
system consists of three PZT actuators and a specially shaped member of compliant
material. The structure of this system is symmetrical to the center of the system which
serves as the end-effector of the system to perform two translations and one rotation in a
plane. As a result, the following contributions of this research are described in this
thesis.
A Constant-Jacobian method for kinematic analysis of the RRR compliant mechanism
is developed and verified using the pseudo rigid body model (PRBM) concept. The
result of the kinematic calibration based on this method shows an excellent agreement
with the experimental result. The PRBM concept leads to a lumped model of materially
continuous systems and, hence, to a computationally efficient model.
The finite element analysis of the RRR compliant mechanism, using the ANSYS
program, is performed. In this analysis, mesh is directly generated on a compliant
material, which differs from the lumped approximation procedure associated with
PRBM. This finite element model is a parametric one and is completely determined by
nine parameters. A change in any one of these parameters will update the mesh
automatically. This is very useful for an optimal selection of parameters to achieve
some set of design objectives. The result of the finite element analysis is compared with
those obtained using other methods, including the Constant-Jacobian method and the
experiment, which further confirms that the Constant-Jacobian method is an excellent
method for kinematic analysis in terms of computational efficiency and modeling
accuracy.
A novel dynamic model is further developed based on the Constant-Jacobian
kinematics, the PRBM concept, and other simplification procedures that leave out the
terms of order o(Δl²) and above (Δl=0-12 μm). Consequently, this dynamic model
achieves both computational efficiency and modeling accuracy. This dynamic model is
used for feedback control simulation studies for the RRR compliant mechanism.
***Note: There was a floppy disk with the original thesis***
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Degree
Master of Science (M.Sc.)
Department
Mechanical Engineering
Program
Mechanical Engineering