Piezoelectric strain rate sensor and actuator designs for active vibration control

Abstract

A series of piezoelectric sensors which measure the strain rate of a structyre directly arc dcvclopcd hy recognizing the fact that'due to the high output irnpedancc nature oS piczoclectric scnsors the measured signal i.; strongly influenced by the impctlancc matching circuit. tlxperimentnl data which verifies thc performance of a local strain ratc sensor is presented. A uniaxial strain ratc sensor which cornplctely eliminates the cross-axis sensitivity is developed, as well as a pure shcar strain rate scnsor which measurcs the in-planc shcar rate. T o achieve rnorc clTcctivc distributed control, a singlc-input singlc-output multi-modc scnsor/actuator dcsign approach is prcscntcd for controlling N > I modes of a bcam type stlucturc which docs not exhibit any o r the spillover phcnomcnon into tlic uncontrolled modes typically fourid in othcr flcxihlc structure vibration control approaches. It is shown that tlic two-mode scnsor/actuator case is capahlc of achieving critical damping for both rnodcs undcr control. 'I'hc pcrformance of this sensor/actuator approach [or controlling rnorc than two modes are also prcscnted. Even though negative vclocity fccdback has traditionally been the primary fccdhack variablc uscd in flexible structure vihration control 11-31, in many cases velocity feedback is closely related to strain ratc control [4-61. Strain gagcs havc bccn used successf~illy Tor strain measurement during the last half century, but scnsors or gagcs that measure the local strain ratc of a structurr directly havc not been avaiiablc. Tratlitionallv,