Control of Microcantilevers Using a Stand-alone FPGA-Processor Platform

Abstract

In magnetic resonance force microscopy (MRFM), feedback control of the microcan- tilever is often needed to reduce the effective Q value. But because the natural frequency of the microcantilver is of order 10 KHz, this controller can be challenging to implement. Early MRFM experiments at the University of Washington used a field programmable gate array (FPGA) controller that worked well, but was expensive and time consuming to design, implement and maintain. However, there exist computing solutions that can perform the necessary functions of the earlier controller, for which program development and mainte- nance is less complex. This master's thesis explores the implementation of a single board platform (SBP) with a real-time processor and programmable FPGA to control the micro- cantilever. Two separate control methods were tested in this project: conventional and heterodyne control. The resulting data shows that this device is sufficient for control of the microcantilever when using either control method. Additionally, heterodyne control is advantageous, largely because it eliminates the need for many additional instruments, such as a lockin amplifier and spectrum analyzer. Therefore, with the combination of a SBP and the heterodyne control method, the separate instruments needed in our MRFM experiment have been reduced by half. Moreover, the cost of the SBP is a fraction of the combined cost of the equipment it has replaced. Finally, because SBPs are often programmed in common languages such as LabVIEW, the expertise required for program development and maintenance is substantially reduced.