Microcantilever Sensor via Second Order Sliding Mode Control
J. English, Y. Shtessel, M. Yegnaraman and M. George
University of Alabama in Huntsville, US
microcantilever sensor, sliding mode control
Improved sensor measurements using second-order sliding mode control of a mass sensor based on a microcantilever is considered. The microcantilever-based mass sensor detects mass loading via deflections in nanometer scale. The polymer-coated cantilever is exposed to a chemical species, where the polymer layer attracts molecules of interest, which deposit on the microcantilever structure. Hence, mass loading in the structure occurs, modulating the resonant frequency, which, being measured, gives a tool for the mass loading computation. Resonant frequency measurements often suffer from low accuracy due to insufficient sensitivity of a microcantilever quality factor to the mass loading.
In order to improve the accuracy of measurement the alternative method based on higher order sliding mode control is developed and presented in this work. The problem is reduced to a time varying parameter identification in microcantilever sensors that is addressed via higher order sliding mode control, in particular a super twist controller. The mass loading is estimated with a very high accuracy in a current time based on the control function, which is actuated by an electrostatic devise and is measuring accessible. The numerical example illustrates the effectiveness (accuracy improvement) of the loading mass estimation based on the microcantilever sensor stabilized by slding mode control.
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Nanotech 2006 Conference Program Abstract