2.1 Introduction

The sensing system is the network of nerves within the smart structure. Its role is to monitor the state of the structure to determine either loading conditions or the impact of physical deterioration on the structure's performance. Ideally it would be capable of detecting any changes in any part of the structural artefact. However even the biological model to which many of the smart structures advocates aspire focuses its sensory capabilities in specific areas determined through many generations of evolution (Fig. 2.1). The smart structure designer must conduct himself similarly so that concentrating the sensor array in the more vulnerable sections of the structure is an essential part of the sensor system design process. Some combination of intuition and system modelling can set this process in motion but, like nature, evolution must play an important part and learning from one generation to the next of designed artefact probably produces the most significant improvements.

Figure 2.1: The homunculus: a representation of sensor evolution in humane the larger the relative size of a particular area, the more sensitive.

This short overview will concentrate on sensor technology more than sensor system design. At present this is realistic. The system design process focuses on determining sensor location subject to the highest physical strain, to the largest temperature excursions, to the greatest exposure to the vagaries of the elements, or to the greatest vulnerability to chemical attack. As the whole design process becomes more integrated the procedures for incorporating the nervous system will...