Experimental evaluation of a two degree of freedom capacitive MEMS sensor for velocity measurements

Abstract

This paper presents the experimental tests carried out on a novel two-degrees-of-freedom capacitive MEMS sensor. The sensor comprises an internal feedback loop, which produces a sky-hook damping effect on the principal seismic mass of the transducer so that the output of the sensor is proportional to the base velocity over a low audio frequency range. The four frequency response functions that characterise the dynamic response of the MEMS block have been measured and used to simulate the closed loop response of the transducer. The off-line test shows that, at low audio frequencies between about 100 Hz and 1 kHz, the spectrum of the sensor output signal is proportional to the base velocity. Moreover at frequencies above the fundamental resonance frequency of the transducer, the output signal shows a -90° phase lag with reference to the base velocity. These two properties are of great interest for the implementation of vibration control systems using feedback loops with collocated sensor and actuator transducers. © 2011 Published by Elsevier Ltd.