This paper presents a method for designing excitations for the purpose of enhancing the detectability of damage. The field of structural health monitoring (SHM) seeks to assess the integrity of structures for the primary purpose of moving from time-based maintenance to a more cost effective condition-based maintenance strategy. Consequently, most approaches to SHM are nondestructive in nature. One common nondestructive approach is known as vibration-based SHM. In this approach, a structure is instrumented with an array of sensors at various locations. The structure is then excited and its dynamic response recorded. This response is then interrogated to extract features that are correlated with damage. A survey of the SHM literature [1], [2], reveals that a great deal of attention has been paid to the data interrogation portion of the SHM process, with almost no attention paid to the excitation design. This focus is quite understandable in many applications where only ambient excitation is available, such as most civil engineering applications. However there are many applications where the excitation is selectable (e.g., most wave propogation approaches to SHM), and, indeed, where proper excitation selection is essential. As a simple example, consider a beam or column with a crack that is nominally closed due to a preload. If the provided excitation is not sufficient to open and close the crack, the detectability of the crack in the measured output will be severely limited.
Cost-Effective Condition Monitoring for Wind Turbines