Research On Noncontact Shape Control Of The Flexible Beam Structure Actuated By Light

As the technical advances,a legion of new intelligent materials emerge in an endless stream.Under the stimulus of the external environment,the shape of the intelligent materials make a change accordingly.Consequently,intelligent materials are widely used in the research and application of actuators.The mainly research objects in current thesis are two kind of intelligent materials,one is PLZT(Pb La Zr Ti)photoelectric ceramic materials,the other is light actived polymers(LAPs).In addition,the applications of these two kinds of intelligent materials in shape control had made a useful exploration in present thesis.In this thesis,the shape control problem of the LAPs is explored firstly.Under irradiation of ultraviolet light at a particular wavelength,the structures of the crosslink polymer networks in LAPs alter.Such structural alterations lead to macroscopical deformation.On this basis,LAPs possesses the potential to be actuators.Owing to this change involving many aspects(such as optics,chemistry and mechanics),a theoretical model is applied to simulate the complicated behavior in this thesis.A three layer hierarchical particle swarm optimizer(HPSO)algorithm is proposed in this thesis to search the appropriate group of LAPs numbers,locations and lengths for non-contact shape control at the same time.In accordance with this proper group,the LAPs slices are arranged on the beam to achieve the objective of shape control.Because the intelligent materials have the driving power,these materials can play the same role as the complicated mechanical transmission system.When ultraviolet light illuminates on a 0-1 polarized PLZT ceramics,the photostrictive effect of PLZT ceramics is due to the comprehensive effect(such as anomalous photovoltaic effect,photothermal effect,pyroelectric effect and thermal expansion effect).To accurate describe the the photostrictive effect of PLZT ceramics,a constitutive model for 0-1 polarized PLZT ceramics with coupled multi-physics field models is developed in present thesis.This thesis also investigated the relation between light and PLZT ceramics temperature,voltage and strain.It is found out that the calculation results are consistent with the experimental results,thus the rationality and validity of the constitutive model is verified.Afterwards we investigate shape control problem based on 0-1 polarized PLZT actuators subject to multi-parameters.In which,a finite element formulation for multiphysics analysis of coupled opto-electro-thermo-mechanical fields in PLZT ceramics is introduced above all.And then,this finite element is applied to stimulate the shape control of cantilever beam and cantilever plate driven by PLZT ceramics.The shape control is optimized via the hierarchical genetic algorithm(HGA).The advantage of hierarchical genetic algorithm is that the locations,quantities and light intensities of PLZT actuators are searched simultaneously.Once the combination of locations,quantities and light intensities is obtained,arrangement of PLZT actuators on beam and plate according to the combination can result in a extremely tiny difference between actuated shape and desired shape.The intelligent materials has a brilliant application prospect in the micro-and nano-scale devices and systems.Thus,in the end part of the article,the mechanical properties of LAPs at micro and nano scale are also studied.Based on the modified couple stress theory,a nonlinear size-dependent model of sandwich micro-beam including an intermediate elastomeric layer and two outer LAPs layers is proposed.The effects of the material length scale parameter,the thickness ratio of intermediate elastomeric layer and LAPs layer,the initial strain in intermediate elastomeric layer and the UV light intensity on the bending curvature of sandwiched micro-beam are demonstrated via numerical simulation.In the wake of developments in the type of LAPs materials,researchers had found that without pre-stretching the Young’s modulus of LAPs would change under the exposure of laser light.In this thesis,on the basis of this special feature,a microstructure-dependent Timoshenko beam theory is applied to prescribe the free vibration of LAPs thin beam for different boundary conditions.