Application of Unscented Kalman Filters, Wavelet Packet Transforms and Feedback Control to Monitoring and Compensate Damaged Aircraft Structures

摘要

In this paper a scheme for monitoring and control of an aircraft structure isproposed based on based on nonlinear state estimation employing parametricallyinsensitive or sensitive unscented Kalman filters followed by the deployment of astructural controller to compensate for the damage. The measurements are obtainedfrom accelerometers, strain measurements from fiber Bragg sensors and from awavelet packet transform (WPT) filter of the acoustic emission. The WPT filterreveals the structure of the deterministic signal by acting a de-noising filter. By preprocessingthe WPT and reconstituting the acoustic emission, all other contributions tothe emission signal including the emission due to crack initiation is filtered out. Theremaining signal can be considered to be purely a function of the crack propagationphase. Fiber Bragg grating sensors (FBGS) are used to locate regions of maximumstrain.On detecting the damage in a region of maximum strain it is shown that it ispossible to deploy a structural controller to compensate for the damage. The structuralcontroller may be considered to be a compliance controller providing for thepossibility of actively stiffening the damaged structure and also increasing the fracturetoughness. However to be able implement such a controller it is required that a shapememory alloy (SMA) wires are embedded within the structure. The stiffening of thestructure is facilitated by heating the wire so as to transform the wire from a martensitephase to an austenite phase.