Design, Analysis and Control of a Novel Triaxial Elastomeric Bearing Positioning Stage

• Main Authors: Yu-ChengChen, 陳昱丞
• Other Authors: Kuo-Shen Chen
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/2k66a2

碩士 === 國立成功大學 === 機械工程學系 === 105 === Positioning stage plays an important role in precision metrology and manufacturing systems. One key application is the fast steering mirrors, which mainly comprised of a rotational positioning stage and they have been widely used in laser manufacturing related applications. In this thesis, a novel 3-DoF translational and rotational positioning stage is designed and realized. It consists of two rotational DoF for guiding the laser path in manufacturing and one translational DoF for compensating the focusing error caused by lens curvature variation due to temperature changes. This stage utilizes elastomeric bearing for providing anisotropic stiffness and has the advantages of size miniaturization and structurally simple design. The stage is driven by three voice coil motors and the resulted displacements are measured by three capacitive displacement sensors. In order to establish the system dynamics, the rubber stiffness is also characterized in different loading manners by both simulation and experiment using a biaxial material testing system and a high strain compression testing system. The characterized hyperelastic behavior is then modelled via Arruda-Boyce model, for subsequent finite element simulation. Based on these stiffness characterization and additional vibrational analyses, a 3-DOF stage dynamics model is developed and is validated using the FE simulations. The models of three positioning axes and coupling effect are established by kinematics and system identification using both including step and swept sine responses. The PID controllers are designed based on loop transmission shaping method and simulated by MATLAB/Simulink. Furthermore, in order to suppress the coupling effect, different compensators are also added in control system. The controllers are implemented in NI cRIO with LabVIEW FPGA program for positioning control experiments. By the step and sinusoidal tracking control experiment, the achieved positioning precision are 84nm, 5.4μrad and 1.9μrad and bandwidths are 80Hz, 62Hz and 54Hz in Y-, θX- and θZ-axis, respectively. The strokes can be up to ±159μm and ±5mrad in translational and rotational axis, respectively. In summary, this research successfully develops a tri-axial positioning stage and realize PID controller with decoupled compensators to eliminate the coupled effect. Compared to two DoF fast steering mirror, the translational DoF in this stage can compensate the focusing error in laser manufacturing. On the other hand, this stage is designed based on elatomeric bearing characterization, and the results of material testing and finite element analysis can be taken as reference for mechanical desing in the future.