From the viewpoint of the utilization of space environment, much more enlargement of space structures, such as a space antenna or a solar cell of satellites, has been expected to improve the performance of those structures. Space structures are required to be lightweight due to weight limitation in rocket launches, and lightweight materials such as CFRP are used in those structures. Enlargement of space structures leads to the highly flexible space structures which are weak from the aspect of vibrations. Since vibrations are hard to decrease in the space environment of high vacuum, it is important to suppress these vibrations. The vibration suppression or control study using piezoelectric materials has been carried out widely during recent years.
Piezoelectric materials which are embedded in or bonded to an aerospace structure have been used for active, passive, and semi-active vibration suppression. Synchronized switch damping (SSD) is one of semi-active methods. In this method, a resistive or inductive circuit shunted to piezoelectric devices is switched synchronously with the structure motion in order to enhance its inherent passive vibration damping. Since no energy is supplied to the total system, the system is always stable and doesnft require any bulky power amplifier unlike the active method. Furthermore, the semi-active method can give better vibration suppression than the passive method, because of its efficient mechanical energy dissipation performance.
Recently, synchronized switch damping on voltage sources (SSDV) technique was proposed for increasing the damping effect of semi-active methods. SSDV is most effective among the SSD techniques, but it requires external power systems for constant voltage sources. Therefore, this paper adopts the energy-harvesting techniques using piezoelectric device to enhance the performance of semi-active method, in stead of constant voltage sources of SSDV. This harvesting technique exploits the property of piezoelectric vibration-to-electricity converters, and requires no external voltage source. A vibration suppression experiment of CFRP cantilever beam is carried out to verify the validity of the present method. It is shown that the proposed vibration control system is effective for vibration suppression as well as SSDV technique. It is also shown that the system requires more than a threshold lower limit power of energy-harvesting to achieve stable control effect.
edited by Nobutaka TAKAYANAGI