Application of field programmable analog arrays (FPAAs) to fast scanning probe microscopy

Field Programmable Analog Arrays (FPAA);Atomic Force Microscope;Nanopositioning System;Scanner;Robust Control;Q-control;Scanning Probe Microscope;High-bandwidth

Baranwal, Mayank ; Salapaka ; Srinivasa M.

关键词: Field Programmable Analog Arrays (FPAA);    Atomic Force Microscope;    Nanopositioning System;    Scanner;    Robust Control;    Q-control;    Scanning Probe Microscope;    High-bandwidth;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/50658/Mayank_Baranwal.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

For a long time, signal processing used to be accomplished by microprocessors and DSPs (Digital Signal Processors). The advent of reconfigurable computing devices, such as Complex Programmable Logic Devices (CPLDs) and Field Programmable Gate Arrays (FPGAs) has given a new dimension to signal processing applications by not only allowing users to customize the hardware to suit the specific requirements but also making high speed applications a possibility, too. More recently, Field Programmable Analog Arrays (FPAAs) have emerged as interesting alternatives to most signal processing based applications. Even though the use of FPAA devices is still limited due to small number of suppliers, a growing interest in using FPAAs for various engineering applications is expected. In this thesis, we exploit the FPAAs to demonstrate their usefulness and ease of implementation in developing fast and robust controllers for an Atomic Force Microscope (AFM) unit.Atomic Force Microscopes (AFMs) are getting faster. However, video-rate imaging still remains a big challenge to the AFM community. Therefore AFMs are required to have very fast nanopositioning systems. However, high-bandwidth requirement on the positioning system poses fundamental limitations on the image resolution. The resolution of an image depends on the controller’s capabilities to attenuate the measurement noises. Tools from robust control theory are employed to not only quantify the measurement noises and parametric uncertainties, but also synthesize the controllers in an optimal setting.However, implementation of such controllers require electronics that can support high-bandwidth operations. Field Programmable Analog Arrays (FPAAs), which have bandwidth up to 400 kHz, have been employed to demonstrate not only the direct implementation of these controllers in terms of transfer functions, but also high-bandwidth tracking performance, too, when compared to most other commercially available Digital Signal Processors (DSPs). A significant improvement in the closed-loop bandwidth (∼ 500Hz) has been demonstrated. A part of the work is dedicated to the Q-control of microcantilevers. Since, cantilevers are second-order flexible structures with high resonant frequencies (∼ 50kHz) , Q-control of cantilevers requires estimating velocity at resonant frequencies. High-bandwidth advantage of FPAAs can be exploited to achieve the desired Q-control.