Quantification of Environmental Compensation Strategies for Guided Wave Structural Health Monitoring

The level of post-subtraction noise due to benign structural features limits the sensitivity that guided wave structural health monitoring systems can achieve. Subtraction of reference signals without compensation leads to unacceptably high post-subtraction noise in the presence of modest environmental changes, and in particular temperature. Hence some form of compensation is necessary. In this paper, various compensation strategies are investigated and their performance quantified. Factors such as the length of time-window considered, sensor variations and inhomogeneous temperature variations are also addressed. It is concluded that the best performance that can currently be achieved is by (a) obtaining the best matched signal from an ensemble of multiple reference signals recorded at different temperatures and (b) fine tuning this signal by numerically stretching or compressing it.