Mass sensing utilizing sensorless self-excitation of piezoelectric device
We propose a method to produce the self-excitation in an oscillator actuated by a piezoelectric devise without sensor. In general, the positive feedback with respect to the velocity of an oscillator, which is a cantilever in this study, can produce the self-excitation. Considering the electrical dynamics of the piezoelectric device for the self-excitation, the entire system can be regarded as a third order system. Then, utilizing a coupling effect between the mechanical and electrical systems through the piezoelectric effect, we can produce the self-excitation without the velocity information of the oscillator, namely, by sensorless. We drive the piezoelectric device by the current consisting of the proportional to the linear combination of the voltage across the terminals of the piezoelectric device and its differential voltage signal: the coefficients of the linear coupled signal correspond to the feedback gains. Appropriate feedback gains can locate the eigenvalues at the set of one negative real root and a pair of conjugate complex roots with a positive real part, and the self-excitation can be produced. To confirm the validity of the proposed method, we demonstrated experiments of the sensorless self-excitation and showed the efficiency on the mass sensing using a macrocantilever with the piezoelectric device.