Investigating the use of Symbol Timing Recovery for Medium-Derived Feedback in Nanopositioning Controllers

Τhe 2012 IEEE Multi-conference on Systems and Control, Dubrovnik, Croatia, October 3-5, 2012.

Abstract: Accurate nanopositioning is of significant importance in modern Atomic Force Microscopy (AFM) applications that demand high-speed and ultra-precise probe operation. In such applications, position sensors are mostly used in order to provide the control mechanism with feedback regarding probe movement. It has been shown experimentally that the measurement noise introduced by the positioning sensors significantly impairs the overall system performance. In this work, the use of symbol timing recovery for providing medium-derived velocity feedback in nanopositioning tracking controllers for probe-based storage devices is investigated. Although dedicated storage areas with predefined data sequences are used to provide real-time estimates of the system velocity, the proposed approach can also be applied to systems using non-data aided symbol timing recovery. A complete controller enhanced with timing synchronization feedback was designed and its performance was evaluated. It is shown that this medium-derived velocity estimation can be used as an alternative to the sensor derived position or velocity readings with similar and in some cases superior performance results for a given motion controller. The superiority of the proposed scheme is even more profound when controllers of high-speed nanopositioning are considered, due to the elimination of the position sensor measurement noise, which would corrupt the usually used high-bandwidth closed loop system.

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