monitoring systems in the manufacturing
environment because of recent developments and trends in
machining technology and machine tool design (high speed machining
and hard turning, for example). In-process sensors play a significant
role in assisting manufacturing systems in producing products
at a cost affordable to the mass consumer market. In-process sensors
are used to generate control signals to improve both the control and
productivity of manufacturing systems. For example, acoustic emission
sensors are used in many precision metal cutting processes to monitor
the degree of tool wear, chip formation, surface features, etc., and
in precision grinding, acoustic emission sensors are used to detect both
the near approach of the grinding wheel to the work surface, and the
initial wheel contact with the work52. In particular, in-process sensors
are needed in precision manufacturing systems, because human
oversight of the manufacturing process is inadequate to achieve the
performance levels necessary in precision manufacturing processes.
In the precision grinding example just mentioned, stock removal can
be just a few tens of microns, and a human operator has a poor ability
to monitor and control material removal in this regime.