Space
structures are expected to be larger for high performance such as ISS and
ETS-VIII.
Additionally, they are required to be lightweight for reducing transportation
cost in rocket launch,
and therefore lightweight composite materials, such as CFRP, have been used in
space structures. These large and lightweight structures tend to be highly
flexible, and then external forces caused by thermal impulse and attitude
control can induce the slowly-damped vibration easily in space environment of
highly vacuum and low gravity. Therefore, this vibration may cause the
degradation of structural performance and the failure of equipments. For this
reason, space structures are required to be structural healthiness and
durability, with low cost of maintenance in the space environment. The vibration
suppression systems using smart materials equipped the ability of sensing and
actuation are effective and the vibration suppression or control study has been
carried out widely during recent years.
Composites
implanted optical fibers, strain gauges or piezoelectric materials are proposed
as sensors. The other hand, shape memory alloys (SMA) and piezoelectric
materials are proposed as actuators. Among them, piezoelectric materials, such
as PZT and PVDF, produce an electric field due to deformation and they undergo
deformation subjected to an electric field. They have advantages of
rapid-response and highly energy effective performance.
In addition to their high manufacturability and lightweight, they can be
easily attached on or imbedded into structures, therefore, piezoelectric
materials are popular for vibration control systems. Recently, piezoelectric
fibers have newly been developed as flexible and high-performance actuators. The
failure strain is larger than that of traditional piezoceramics, and
piezoelectric fiber composites have been able to produce large strain.
In
vibration measurement and control of structures modeled as a multi
degree-of-freedom system, it is effective to use modal coordinates by
decomposing a complex vibration problem into some independent vibration modes.
The modal sensor and modal actuator systems allow an independent modal space
control.
This
paper presents the vibration control of CFRP plates based on modal sensors and
actuators. Especially, in this research, the advantages of piezoelectric fibers
that have their high performance and anisotropy are focused through numerical
simulations and experiments.
edited by Osamu AKIBA