Vibration nodes, and the cancellation of poles and zeros by unit-rank modifications to structures

The main focus of this paper is on pole-zero cancellation in structures by unit-rank modifications. The modifications may be achieved by passive stiffnesses or by active control techniques. A review of the classical theory on unit-rank modification is included and new results are obtained to explain the existence of coincident zeros in point and cross receptances. The necessary and sufficient conditions are established for the production of a vibration node by pole-zero cancellation. The classical theory is used to bring about the cancellation of poles and zeros, and numerical examples are used to illustrate the application of the technique. (C) 1999 Academic Press.