Sensitivity Enhancement for Damage Detection in Linear Systems using Optimal Feedback Auxiliary Signals and System Augmentation

摘要

Recently, a sensitivity enhancement technique for damage detection using eigenstructure assignment has been extended from linear to nonlinear systems. Nonlinearities have been accounted for by forming (higher dimensional) augmented systems, which are designed for each trajectory of the nonlinear system, and are characterized by a specific forcing that ensures that the augmented systems follow that trajectory (when projected onto the original, lower dimensional space). The use of system augmentation for damage detection has several benefits beyond its ability to handle nonlinearities. For example, sensitivity can be increased compared to existing linear techniques through nonlinear feedback auxiliary signals because the constraint that the system is stable during its interrogation has to be applied only to the linearized closed loop system, while the augmented linear system does not have that constraint. In this work, the various benefits of nonlinear feedback auxiliary signals are explored for damage detection in linear systems. System augmentation is used in a linear system because a nonlinear controller is employed to enhance sensitivity. In addition to the increased sensitivity, fewer controller actuator points and sensors are required compared to existing linear techniques due to the efficient use of added (augmented) equations. Numerical simulations for a linear mass-spring and a linear mass-spring-damper system are used to validate the approach and discuss the effects of noise.