Energy-saving shape-retainment using two types of piezoelectric actuators

To realize structure systems of future high-precision space observation satellites, smart structure systems which measure and correct their configuration or/and suppress their vibration on obit have been studied. Among sensors and actuators to be used in the smart structure systems, piezoelectric materials are expected to be a good candidate since they have less mechanical parts and high compatibility for space environment. When a shape of a smart space structure is controlled by the piezoelectric actuators attached to its structural element, electric voltage must be continued to be applied to retain a desired shape. To save the amount of electricity usage, a new control method was proposed and its feasibility was examined in the previous papers [Ikeda and Takahashi, Proc. SPIE 8689; Ikeda et al., Trans. JSASS 12 ists29]. In the method the hysteretic behavior of piezoelectric actuators was utilized effectively. The results showed that displacement of a smart beam with a piezoelectric ceramic actuator bonded remained without any voltage applied to the actuators after a pulsed voltage was applied. However, the displacement of the beam overshot a final position. In this paper this overshoot is suppressed. To this end another type of piezoelectric actuator showing almost no hysteretic behavior is bonded on the beam opposing the actuator showing the hysteretic behavior. Result shows that the overshoot can be suppressed by applying a feedback plus feedforward control to the additional actuator while the pulsed voltage is applied to the actuator showing hysteretic behavior.