This paper develops an approach for the health monitoring of a smart structures with multiple embedded sensing and actuation capability. For such a structure the consideration of failure consequences is an important component of any real application. The approach developed here is an integrated control and monitoring procedure whereby the sensors, which are assumed to be distributed spatially across the structure, are processed by a set of spatial modal filters which automatically track the modal coordinates of desired, specified modes, and similarly track changes in modal characteristics such as modal frequency, damping, and mode shape. The adaptive modal filter is formulated and applied to tr:a.ck the time varying behavior of specified modes, thereby indicating in some general sense, the health of the structural system. The adaptive modal filter is insensitive to failures or calibration shifts in individual sensors and will automatically ignore failed sensors. It can also be used to detect disturbances entering the system as well as to identify failed actuator locations. A modal controller based on these estimates is then able to adapt to a changing structure and in addition is insensitive to failures in the sensors and actuators. Both the tl1eory and experimental results from a test structure is discussed.
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