Design, simulation and fabrication of a MEMS based levitated platform for laser scanner applications

Kaya, Onurcan
This thesis presents design, simulation and fabrication of a MEMS based levitated platform for laser scanner applications. Electrostatic detection and actuation are utilized for levitation of the platform. There are a number of laser scanners presented in the literature for several applications. All of the scanners in the literature are based on a mechanically suspended structure, which redirects a light source. Mechanical connection of those structures limits the maximum achievable scan range. This work represents a levitated platform for laser scanner applications. The main motivation behind the proposed structure is to achieve 360 degrees of scan range. Designed structure consists of two stators and a rotor. There are sets of actuation and sense electrode structures defined on each stator. Mathematical models for actuation and detection mechanisms for levitation are derived. Equations of motion of the rotor are obtained using mass-spring-damper model. Damping and stiffness acting on the rotor are modeled using squeeze film and slide film damping models. A capacitive readout circuitry is designed to convert rotor motion to voltage signals for each 5 axes. To achieve stable levitation of the rotor, closed loop controllers are designed for each of 5 axes. For controller design, nonlinear and coupled equations of motions of rotor are decoupled and linearized around the nominal position of rotor. Following that, root locus design techniques are utilized to determine controller parameters. Since damping and stiffness acting on the rotor highly depends on ambient pressure, controllers are designed for both in air and in vacuum operation conditions. Robustness of designed controllers are verified by Simulink simulations, which utilizes nonlinear and coupled equations of motions. Noise generated by the controller and sense electronics are modeled. Equivalent voltage noise is calculated and its effect on position of rotor along 5 axes is discussed. Fabrication of the proposed structure is performed. Stator structures are manufactured from a 6 layer Printed Circuit Board (PCB). Rotor, on the other hand, is fabricated using a SOI wafer. Rotor has a radius of 11300 μm and a thickness of 80 μm. Two stators are aligned with respect to each other by using bearing-balls with a diameter of 0.5 mm.


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Citation Formats
O. Kaya, “Design, simulation and fabrication of a MEMS based levitated platform for laser scanner applications,” M.S. - Master of Science, Middle East Technical University, 2017.