Research On Potostrictive Characteristics Of PLZT And Active Control Of Photostrictive Laminated Thin Shells Of Revolution

The thin shell of revolution is widely used in the aviation, aerospace, civilian and national defense industries. The shape control and vibration control of thin revolution shell structure has always been difficult and important item of the system design and engineering application. By using smart materials to give effective actuation for the purpose of achieving vibration suppression has been a favored way. The smart material activated by electric or magnetic signals can induce electromagnetic noise because of complex accessorial devices and connecting wires.The new smart material, lanthanum modified lead zirconate titanate (PLZT), can transform the light energy to the mechanical energy without electromagnetic noise. PLZT is suitable for the non-contact actuation and remote control in the space environment. In this paper, based on the research of the photostrictive characteristics of PLZT ceramics, the active vibration control of the photostrictive laminated thin shell of revolution is studied, which can provide the theoretical base for engineering applications of photostrictive laminated smart structure.The photostrictive effect of PLZT with multi-energy field coupling is researched in this paper. Photostrictive mechanism with LED-UV illumination is revealed here.Based on the equivalent electrical model of the PLZT ceramics, the effect of the light intensity, aspect ratio and the thickness of the PLZT ceramics on the photostrictive strain are researched. And the new photostrictive mathematic model of PLZT ceramics with illumination is established. The mathematic model is validated through the photostrictive static experiments. Residual strain light off is studied; the expression of the residual strain and the relationship of the darkness time constant and the illumination time constant are presented.The configuration and actuation characteristic of photostrictive actuator made of PLZT are studied, and photodeformation characteristic of 0-1 polarized, 0-3 polarized, bimorph and multi-patch combination configuration is analyzed respectively. Based on the laminated method with controlled structure, actuation force and moment of different configurations are deduced. Actuator's actuation strategies are investigated and two actuation strategies, ON/OFF actuation with a single light source and double side ON/OFF actuation with two light sources, are presented. The applicability of photostrictive actuators are analyzed, the 0-1 polarized photostrictive actuator is chosen for active control of thin revolution shell.Governing equations of photostrictive laminated open cylindrical shell, open spherical thin shell and paraboloidal thin shell are presented based on the Love equations of elastic shell. In order to transform the governing equation of photostrictive laminated thin revolution shell from physical space into mode space which can achieve modes decoupling, mode shape functions of open spherical thin shell and paraboloidal thin shell with free boundary conditions are obtained using membrane theory. Modal control equations of photostrictive laminated these three shells are deduced using modal expansion method, and corresponding modal control factor expressions are given. Using the modal control factor, modal control analysis of the photostrictive laminated these three thin shells of revolution are implemented, which can provide the theory for actuator configuration.In order to realize the closed-loop control of the photostrictive laminated thin shell, research on the active vibration control scheme of the photostrictive laminated thin shell is carried out. Based on the active control characteristic analysis for the photostrictive laminated smart structure, suitable illumination scheme for the photostrictive laminated thin shell structure is presented, together with the constant light intensity control and the variable light intensity control algorithm based on velocity proportional feedback. Active control scheme for the photostrictive laminated thin shell structure is obtained through combining the illumination scheme and the control algorithm. Dynamic numerical analysis of the modal control equation of the photostrictive laminated thin shells under the closed-loop control is carried out using Newmark-βmethod. Taking the photostrictive laminated paraboloidal thin shell for example, active vibration control simulation analysis for the 1st and 2nd mode is carried out. Simulation results show that the constant light intensity control is better than the variable light intensity control, and the control effect is affected by the actuator configuration under the same control algorithm.In order to verify the correctness of the theory analysis and the effectivity of the active control scheme, active vibration control experiment is carried out by taking the photostrictive laminated paraboloidal thin shell for an instance. The experiment platform is set up. Natural frequency testing and analysis of the paraboloidal thin shell with two kinds of free boundary conditions are carried out. Actuation characteristic experiment, ON/OFF control experiment and active control experiment for the photostrictive laminated paraboloidal thin shell are carried out. Test results show that photostrictive actuator can give active control force to the paraboloidal shell and restrain the low order mode vibration of the photostrictive laminated paraboloidal shell. Thus the active vibration control scheme for the photostrictive laminated thin shell of revolution is effective.