An equivalent circuit analysis of support wires for a flexurally vibrating piezoelectric bar gyroscope

Abstract

The effects of support wires on the operation of flexurally vibrating piezoelectric bar gyroscopes were investigated by the equivalent circuit method and the results were analyzed to delineate design guidelines for the support wires. Composite bar resonators which consist of an elastic metal bar with piezoelectric ceramic plates attached to its surfaces were supported with fine metallic wires bent at 90° and welded to the bar. Because the double-resonant modes of the bar resonators have no common nodal points, these modes may couple mechanically with each other via the support wires. As a consequence, a leakage output may be induced in bar gyroscopes. Furthermore, the antiresonance of the support wires can induce a spurious vibration. When the support wires are represented by a type T equivalent circuit, parallel elements of the circuit represent coupling between double-resonant modes and series elements represent the shift in double-resonant frequency of the bar resonators. By analyzing the circuit in detail, the relationship between the excitation frequency and dimensions of the support wires was determined quantitatively. More specifically, the dimensions of the support wires were determined for a condition where one of the parallel elements is null and the other parallel element and the series element are infinity. © 1997 Scripta Technica, Inc. Electron Comm Jpn Pt 3, 80(8): 75–86, 1997