Research On Constitutive Model Of Photostrictive Actuator And Modal Vibration Control Of Plate And Shells

Smart materials can be used as sensors and actuators by laminating on orinserting in space plate and shell structures to realize Smart control, which has beenan important direction in the aerospace field. In contrast to traditional actuators(e.g.,piezoelectric actuators, SMA actuators, electrostrictive actuators.etc.), photostrictiveactuators or actuators actuated by hybrid photovoltaic/piezoelectric actuationmechanism does not require hard-wird connections to control light source. Thus, thecontrol commands will not be influenced by undesirable electric noises. Withoutaccessorial devices and connecting wires, photonic control which conforms to thelightweight trend of space structure has great research value. In this paper, twomethods which are the lanthanum modified lead zirconate titanate (PLZT) with0-3polarization photostrictive laminated smart structure and hybridphtovoltaic/piezoelectric actuation mechanism are proposed respectively to realizevibration control of shell structures. Systematical theoretical research on theestablishment of constitutive model of photostrictive actuator, dynamic model of thephotostrictive laminated plate and shell, actuator configuration theory and controlscheme of actuator are carried out. This research can provide theoretical proof forapplications of this kind of smart structure in the field of space aviation.Constitutive equations defining the photo-induced time dependent strains ofactuator for the two photonic control method are established respectively. In view oflight-electric-thermal-elastic coupling, the photovoltaic effect and photostrictivemechanism of PLZT are studied. Equations are established to define the effect ofgeometric parameters of0-3polarized PLZT (PLZT(0-3)) acuator and light intensityon photo-induced saturated strain and time constant. Constitutive equations definingthe time history response of photo-induced strain for PLZT(0-3) actuator areaccordingly established. The novel hybrid photovoltaic/piezoelectric actuationmechanism is proposed. The ultraviolet light-driven PLZT induced voltages are usedto drive piezoelectric actuator. Based on the equivalent electrical model, equationsare derived to define the actuation strain of piezoelectric acutuator driven byphotovoltage. These two constitutive model are verified by experimentsrespectively.Based on the Hamilton’s principle and composite shell theory, the systematicdynamic model of the photostrictive laminated shell are set up, which can be appliedto shell with different structure types and geometric parameters. Based on the modalexpansion technique, the modal control actions of photostrictive actuator are st udied,which can technically support the design of actuator location and configuration. By specifically configuring the boundary condition of the actuator, askew-quad actuator system inducing multi-DOF non-uniform control forces andcontrol moments is proposed. Based on the variation method, the distributionfunctions of induced forces and moments are calculated. In the case study of opencylindrical shell, control actions of the skew-quad actuator system with differentlocations and sizes are calculated to define the better placement and the size of thenew actuator system. According to the characteristic of one-way actuation of PLZT（0-3） photostrictive actuator, the control schemes of half cycle illumination toeach region of skew-quad actuator system together with the constant light intensitycontrol based on velocity feedback is proposed. Based on the Newmark-β method,the modal control equation is numerically analyzed, and the results show that theshell vibration can be effectively controlled by this proposed control scheme. Thesimulation results of different light intensity show that the increase of light intensitywill increase the response speed of PLZT(0-3) actuator which accordingly improvethe control effectiveness of shell structures.In order to realize photonic independent modal control of smart structure, theshaped orthogonal actuator theory is studied. Electrode shape functions of theactuators are disigned for some typical structures. Independent modal control of thecantilever beam based on the PLZT(0-3) photostrictive actuator and on the hybridphotonic/piezoelectric actuation mechanism is studied respectively. According to thecharacteristic of one-way actuation of PLZT(0-3) photostrictive actuator, theactuation strategy of double side ON/OFF actuation with two light sources for eachregion of shaped orthogonal photostrictive actuator is proposed. In order to realizethe independent modal control of cantilever beam using hybridphotovoltaic/piezoelectric actuation mechanism, orthogonal sensors are designed.The ON/OFF control of positive/negative connection between PLZT andpiezoelectric actuator is used, combining with constant light control algorithm basedon velocity feedback. Dynamic modal control equations of the cantilever beamlaminated with orthogonal actuators based on the two photonic control methods arenumerically simulated respectively. The simulation results show that the orthogonalsensors/actuators designed and control schemes proposed for the two photonicmethod can effectively realize photonic independent modal control of cantileverbeam.Experiments for the actuation srategies of hybrid photovoltaic/piezoelectricactuation mechanism and active independent modal control of beam are carried out.Four actuation srategies are proposed and their feasibility are tested. Experimentalplatform for active beam independent modal control is set up, and the modalorthogonality of orthogonal sensors is tested. The validity of theoretical derivationand evaluation results of shaped photostrictive actuator configuration theory can be verified by the experimental results of different light intensity.