Access and Positioning Control of Precise Single-Deck Dual-Axes Air-Bearing Motion Stage
Date Issued
2016
Date
2016
Author(s)
Huang, Wei-Lun
Abstract
This thesis proposes a novel control framework, “Access and Positioning control”, which is designed to solve problems caused while switching between speed and position control. For example, since the bandwidth of speed and position controller are not consistent, switching between these controllers may induce unnecessary vibration. Moreover, for the best performance, the switching timing is hard to determine. “Access and Positioning control” focus on boosting the fluency of motion and shortening the time which it takes for the stage to arrive the demanded target. The proposed method also makes the control parameters adjust easily. The system is a dual-axes air-bearing motion stage system consists of linear motors. For simplicity, in this thesis the complex system is decoupled to three single input single output (SISO) systems. Since the system is unstable, the closed-loop system identification is required. To compensate the inadequate parts of mathematical models from SISO identification, the multiple input multiple output (MIMO) system identification is utilized after the controller is designed. In pure speed or position control, the Luenberger observer is installed to estimate the states, which is not able to be measured by sensor for the state feedback control to stabilize the system. In order to deal with the steady state error, an integrator control is implemented. The overall control structure is based on the Robust and Optimal control to calculate the constant control gains in CSD, restricting the H-infinite norm of the system in a specific range. Performances of both speed and position control are important, thus a simple control strategy which applies the speed control first and switch to position control when the stage is near the designed target. This method is named “Speed and Position Switching Control”. On the other hand, the “Access and Positioning Control” includes the reference speed and position for input signals together so switching between two control methods is not necessary. The performance of speed and accuracy can be controlled simultaneously. The experimental results confirm that for “Access and Positioning Control”, it takes lesser time to arrive the demanded target even the maximum speed is lower than the “Speed and Position Switching Control” since the fluency of motion is raised.
Subjects
air-bearing stage
linear motor
robust control
H∞ control
point-to-point motion control
Type
thesis
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