A piezoelectric array for sensing vibration modal coordinates

The ability to sense vibration modal coordinates in real time brings much a dvantage in sensing and controlling structural vibration and acoustic radia tion. This paper discusses results from an experiment with a modal coordina te sensor. A modal coordinate sensor for a beam is created from an array of rectangular segments of piezoelectric film. The output voltages of the seg ments are multiplied by appropriate gains so that the weighted combinations of the outputs approximate the modal coordinates of the beam. The gains ar e components of a matrix which is obtained from the relationship between th e slopes of the beam deflection and the output voltages of the film segment s. After numerical simulation, the method is experimentally verified for a bea m with simple boundary conditions. The beam is covered with segments of pie zoelectric film. The electric current outputs from the segments are linearl y combined with weights calculated by the theory. It is shown that this lin ear combination of segment outputs with correct weights results in a sensor that is sensitive to only a selected vibration mode and filters out other modes. A few problems in laboratory implementation of the sensor are addres sed. This discretized version of modal sensor shows promising application i n structural monitoring and vibration control. (C) 2001 Elsevier Science B. V. All rights reserved.