Multisensor Fusion and Integration
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INTRODUCTION
Sensor is a device that detects or senses the value or changes
of value of the variable being measured. The term sensor some
times is used instead of the term detector, primary element or
transducer.
The fusion of information from sensors with different physical
characteristics, such as light, sound, etc enhances the
understanding of our surroundings and provide the basis for
planning, decision making, and control of autonomous and intelligent
machines.
SENSORS EVOLUTION
A sensor is a device that responds to some external stimuli
and then provides some useful output. With the concept of input and
output, one can begin to understand how sensors play a critical role
in both closed and open loops.
One problem is that sensors have not been specified. In other
words they tend to respond variety of stimuli applied on it without
being able to differentiate one from another. Neverthless, sensors
and sensor technology are necessary ingredients in any control type
application. Without the feedback from the environment that sensors
provide, the system has no data or reference points, and thus no
way of understanding what is right or wrong g with its various
elements.
Sensors are so important in automated manufacturing
particularly in robotics. Automated manufacturing is essentially the
procedure of remo0ving human element as possible from the
manufacturing process.
SENSOR AND SENSOR TECHNOLOGY
IN THE PAST
The earliest example of sensors are not inanimate devices but
living organisms. A more recent example of living organisms used in
the early days of coal mining in the United States and Europe.
Robots must have the ability to sense and discriminate
between objects. They must then be able to pick up these objects,
position them properly and work with them without damaging or
destroying them.
Intelligent system equipped with multiple sensors can interact
with and operate in an unstructured environment without complete
control of a human operator. Due to the fact that the system is
operating in a totally unknown environment, a system may lack of
sufficient knowledge concerning the state of the outside world.
Storing large amounts of data may not be fesible. Considering the
dynamically change world and unforeseen events, it is usually
difficult to know the state of the world.
SENSORS PRINCIPLES
A sensor is defined as a measurement device which can
detect characteristics of an object through some form of interaction
with them.
Sensors can be classified into two categories:
Contact and noncontact. A contact sensor measure the
response of a target to some form of physical contact .this group of
sensors responds to touch, force ,torque,pressure,temperature or
electrical quantities.
A noncontact type sensor measures the response brought by
some form of electromagnetic radiation. This group of sensors
responds to light, x-ray, acoustic, electric or magnetic radiation.
MULTISENSOR INTEGRATION
The diagram represents multisensor integration as being a
composite of basic functions. A group of n sensors provide input to
the integration process. In order for the data from each sensor to be
used for integration, it must first be effectively modelled. A sensor
model represents the uncertainty and error in the data from each
sensor and provides a measure of its quality that can be 7used by
the subsequent integration functions.
After the data from each sensor has been modelled, it can be
integrated into the operation of the system in accord with three
different types of sensory processing: fusion, seperate operation,
and guiding or cueing.
Sensor registration refers to any of the means used to make
data from each sensor commensurate in both its spatial and
temporal dimensions. If the data provided by a sensor is significantly
different from that provided by any other sensors in the system, its
influence on the operation of the sensors might be indirect.