Sensor Technologies - Artificial Human Sensors: Science and Applications - page 86

should also dependent on an individual's subjective characteristic qualities, be-
haviours and habit.
4.4.2 Sensing and Gathering Information
Sensing and gathering information from the world around us is regarded as a ma-
jor step when collecting and organising data and a fundamental cornerstone in
building the communication and interaction of intelligent systems, normally re-
ferred to as the intelligent human computer interaction. The expectation increases
rapidly when using the aim of the phrase - intelligence behaviour (or intelligent
systems). The often huge amount of gathered information that is needed requires
a strategy, that in some adequate manner does not make use of any intelligent
behaviour, when obtaining the required amount of data by fusing single sensing
modalities into a multiple fusion information model. The desired depth of in-
formation is gained from the use of different physical, chemical and biological
principles, that cover different information spaces to generate time related data
that may have individual specificity, i.e., range, accuracy, resolution and reliability.
Therefore, the strategy to properly fuse the sensed information, often from various
sources and complex environmental properties, is focussed on the concept to pro-
duce the required, specific and indeed the expected amount of information in the
available time. When dealing with a human related sensor system, the ultimate
challenge is to design an active system to collect the most effective information
and to provide an interactive communication process in a reasonable time scale.
Techniques for fusion of multi-sensor data are drawn from a diverse set
of more traditional disciplines including digital signal processing, statistical
estimation, control theory, artificial intelligence, and classical numerical methods,
Llinas (1997). The characteristics of the mentioned, commonly used techniques
have to be merged with the specified requirements needed to find a generalised
sensor fusion solution for context-related applications. More details, and further
reading can be found in Wu (2003).
4.4.2.1 INDIRECT SENSOR PRINCIPLE
Within the field of traditional sensor technologies, there are several differ-
ent operational principles of sensing. In principle, the most frequently used
technology is a common sensor technique that exhibits an indirect operational
sensing element. The sensor property may indirectly use known physical, chemi-
cal or biological properties to convert the measured parameter into a more appli-
cable and often used physical quantity before further data processing occurs, as
illustrated in Fig. 4.2.
An excellent illustration of an indirect measurement is the well-known
detection principle based on piezoelectric quartz crystal micro-balanced
technology (QCM) used in biosensor applications, Rogers (1998). A resonant fre-
quency, which is measured from a quartz crystal and changes output frequency
as a linear function of the mass of a target substance deposited on the crystal's