Servo and System Design for Generating Sub-Micron-Grating on a Roller
Date Issued
2009
Date
2009
Author(s)
Huang, Chen-Wei
Abstract
In this thesis, we designed and implemented a complex servo system for stitching interference grating patterns on a roller surface. The proposed system included two sub-systems: a “roller positioning system,” which includes a high-accuracy linear motor stage and its controller, and a precision system that is composed of a high-bandwidth and high-precision three-axis PZT stage, a high-precision three-axis manual positioning stage, and a high-resolution DC motor rotary. According to our control strategy, the manual stage would adjust to an adequate position before the roller is put on the positioning system, and then the control program written in Visual C++ environment will transmit and receive the data. The linear motor stage is responsible for the long stroke motion of the roller, and for compensating the positioning error through the PID controller. The posture of roller tilt is compensated by a PZT stage, and then the roller is rotated by a DC rotary motor. The exposure will begin when the positioning procedure was completed. The functions and concepts of the roller positioning system will be discussed in the thesis.nother important sub-system is the measurement system, which includes two measurement instruments. The first is a high-bandwidth and high-accuracy laser interferometer system responsible of measuring the position along X-axis. Second is a set of laser displacement sensors for measuring the roller tilt posture. o obtain the characteristics of the roller positioning system, the system architecture was identified with different simulating methods inside the MATLAB Toolbox. After some tedious estimating and comparing, the simulation result with PEM method in the state-space form can obtain the best system model. The other estimating models with different sets of input/output under the same condition turned out to be not repeatable. It means that there are some uncertainties inside the system, such as jitter phenomenon. We have thus proposed a jitter measurement procedure and simulation model based on the reference system model from the identification. uring the measurement, the digital output signal of linear motor stage was recorded by the oscilloscope for a long period and it showed the variations of sampling frequency and proved the jitter phenomenon exists. The concept of the simulation model is based on the random generated dynamic sampling periods and the bound of frequency variations. In this thesis, we avoided the complicated and unobservable method to estimate the system output directly in the consideration of the different order of jitter severity, and introduced a quantification index for rough estimation of the direct relation between system output and jitter phenomenon. inally, the results show that the feasibility of this simulation model and verify the quantification index can effectively represent the influences of jitter on the system output. They also prove that the general system identification procedure applied on the jitter-affected system did not represent the actual system characteristics.
Subjects
interference lithography
interference fringe stitching
roller positioning
jitter measurement and simulation
servo system
large area periodic microstructures
RIL
Type
thesis
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