Abstract
A procedure is developed to detect sensor failures in flexible structures by means of observers designed at the modal level. Estimates of the modal coordinates generated by the modal observers are used to estimate the system output at the sensor’s locations. These estimates of the system output are then compared with the sensors’ measurements to detect failure. It is shown that, when the observer gains are properly selected, failure of a certain sensor primarily affects the estimate of that sensor, and it affects the estimates of the operational sensors much less. This makes it possible to detect multiple sensor failures. Because the observers are designed for each mode individually, one can obtain closed-form expressions for the observer poles, making the failure detection procedure applicable to high-order systems.