2
1 Introduction
possess sensors that enable the determination or monitoring of the system states
or characteristics”, and the adaptive structures “possess actuators that enable the
alteration of system states or characteristics in a controlled manner”. The sensory
structures have sensors, but possess no actuators. Conversely, the adaptive structure
possess actuators, but does not have sensors. Later, higher level structures, controlled
structures, were defined as those with both sensors and actuators that are connected
into a feedback architecture. In the third level structures, active structures were proposed and used frequently in the literature. It was defined as a subset of controlled
structures with the sensors and actuators highly integrated into a host structure as one
object [16]. In the literature, the structures named smart structures or intelligent structures are mostly referred to active structures. The highest level, intelligent structures,
was defined as those where sensors and actuators are highly integrated into a feedback
architecture which also includes control logic and electronics [16, 17]. Additionally,
Rogers [18] defined intelligent material systems in biological engineering point of
view as “those with intelligence and life features integrated in the micro-structure of
the material system to reduce mass and energy and produce adaptive functionality”.
1.2 History of Smart Structures
The concept of smart structures or intelligent structures was initiated in 1950s. In the
1970s, Claus [19] of Virginia Institute of Technology embedded optical fiber sensors
into carbon fiber-reinforced composites, which made the structures have ability to
sense stress and fracture damage. This is the first experiment of smart structures,
called adaptive structures at that time.
From 1980s, various programs of smart structures were launched by United States
government. For example, the United States carried out the research on active control
of structural vibration of B-1 aircraft’s panel, and then studied the vibration of F/A-18
aircraft’s vertical tail [20, 21]. In 1984, the U.S. Army Scientific Research Bureau
sponsored the research of rotorcraft technology. One year later, the U.S. government
launched the research plan of smart structures, requiring the spacecraft to be adaptive.
After the catastrophic fracture accident of Boeing 737 aircraft on April 28, 1988,
the United States Congress realized that the aircraft should have a self diagnosis
and timely prediction system to avoid similar accidents of aircraft in service. The
congress forced the aircraft company to complete the smart aircraft concept design
within three years.
During 1990s, various programs of smart structures were launched by United
States, Europe, and Asia. In the United States, the fundamental research activities
were carried out by the Department of Defense funding agencies, e.g. the Army
Research Office (ARO), the Office of Naval Research (ONR), and the Air Force Office
of Scientific Research (AFOSR), whereas the applications-oriented research activities were carried out by the Defense Advanced Research Project Agency (DARPA).
Therefore, most of the early research programs in smart structures were first initiated
by ARO and then supplemented by DARPA. The early major programs focused on
smart structures are as follows.
1 Introduction
possess sensors that enable the determination or monitoring of the system states
or characteristics”, and the adaptive structures “possess actuators that enable the
alteration of system states or characteristics in a controlled manner”. The sensory
structures have sensors, but possess no actuators. Conversely, the adaptive structure
possess actuators, but does not have sensors. Later, higher level structures, controlled
structures, were defined as those with both sensors and actuators that are connected
into a feedback architecture. In the third level structures, active structures were proposed and used frequently in the literature. It was defined as a subset of controlled
structures with the sensors and actuators highly integrated into a host structure as one
object [16]. In the literature, the structures named smart structures or intelligent structures are mostly referred to active structures. The highest level, intelligent structures,
was defined as those where sensors and actuators are highly integrated into a feedback
architecture which also includes control logic and electronics [16, 17]. Additionally,
Rogers [18] defined intelligent material systems in biological engineering point of
view as “those with intelligence and life features integrated in the micro-structure of
the material system to reduce mass and energy and produce adaptive functionality”.
1.2 History of Smart Structures
The concept of smart structures or intelligent structures was initiated in 1950s. In the
1970s, Claus [19] of Virginia Institute of Technology embedded optical fiber sensors
into carbon fiber-reinforced composites, which made the structures have ability to
sense stress and fracture damage. This is the first experiment of smart structures,
called adaptive structures at that time.
From 1980s, various programs of smart structures were launched by United States
government. For example, the United States carried out the research on active control
of structural vibration of B-1 aircraft’s panel, and then studied the vibration of F/A-18
aircraft’s vertical tail [20, 21]. In 1984, the U.S. Army Scientific Research Bureau
sponsored the research of rotorcraft technology. One year later, the U.S. government
launched the research plan of smart structures, requiring the spacecraft to be adaptive.
After the catastrophic fracture accident of Boeing 737 aircraft on April 28, 1988,
the United States Congress realized that the aircraft should have a self diagnosis
and timely prediction system to avoid similar accidents of aircraft in service. The
congress forced the aircraft company to complete the smart aircraft concept design
within three years.
During 1990s, various programs of smart structures were launched by United
States, Europe, and Asia. In the United States, the fundamental research activities
were carried out by the Department of Defense funding agencies, e.g. the Army
Research Office (ARO), the Office of Naval Research (ONR), and the Air Force Office
of Scientific Research (AFOSR), whereas the applications-oriented research activities were carried out by the Defense Advanced Research Project Agency (DARPA).
Therefore, most of the early research programs in smart structures were first initiated
by ARO and then supplemented by DARPA. The early major programs focused on
smart structures are as follows.