A review of experimental techniques in modal testing

Digital vibration control and analysis equipment has had a dramatic impact on structural dynamic testing. Previously, many tests or analyses were impractical if not impossible. This paper reviews current applications of digital equipment to the identification of structural dynamic characteristics including modal testing. The applications presented will cover the following input excitations; pure random, pseudorandom, periodic random, impact (hammer), swept sine, and shaped transient. The resulting transfer functions will be discussed. The effects of using different measurements for the reference signal will be discussed and illustrated. Most of the structures used in the examples will be communication satellites built by the Space and Communications Group of Hughes Aircraft Company.