A piezoelectric array for sensing vibration modal coordinates

Abstract The ability to sense vibration modal coordinates in real time brings much advantage in sensing and controlling structural vibration and acoustic radiation. This paper discusses results from an experiment with a modal coordinate sensor. A modal coordinate sensor for a beam is created from an array of rectangular segments of piezoelectric film. The output voltages of the segments are multiplied by appropriate gains so that the weighted combinations of the outputs approximate the modal coordinates of the beam. The gains are components of a matrix which is obtained from the relationship between the slopes of the beam deflection and the output voltages of the film segments. After numerical simulation, the method is experimentally verified for a beam with simple boundary conditions. The beam is covered with segments of piezoelectric film. The electric current outputs from the segments are linearly combined with weights calculated by the theory. It is shown that this linear 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 addressed. This discretized version of modal sensor shows promising application in structural monitoring and vibration control.