Thermo-Piezoelectric-Mechanical Coupling Analysis And Control Of A Novel Flexible Nano-Manipulator Based On Piezoelectric Thin Sheet Actuators

With the rapid development of micro-electromechanical systems and nanoscale science technologies,intelligent micro/nano-actuators,compliant mechanisms and detection devices,as the main components of micro/nano-motion stages or systems,have been greatly improved in terms of the stroke,function,accuracy,dynamic characteristics and intelligence to achieve its strategic leading position in many related high-technology industries and interdisciplinary frontier fields,such as the high-end equipment manufacturing,biomedicine,optical communication,aerospace.However,the previous micro-motion stages or systems composed of the piezoelectric stack actuators or voice coil motors and compliant mechanismes have many disadvantages,such as large overall size,high-cost,large assembly error,poor static/dynamic performance,which greatly limit the development and application of micro/nano-motion stages or systems in the fields of the ultra/high-precision processing,super-resolution micro-imaging,micro/nano-manipulation,space optical communication,remote sensing and measurement,etc,where more stringent precision and performance have been required.A three degrees-of-freedom flexible nano-manipulator driven by uniformly distributed piezoelectric thin sheet actuators was proposed to achieve the requirements of the micro/nano-electromechanical systems with a more compact size,lower cost,larger stroke in the multi-disciplinary and multi-field,to provide a feasible and effective scheme for many limited application scenarios of the micro/nano-motion servo stages or systems,such as some traditional micro-motion stages,micro/nano-manipulators or fast steering mirrors.Meanwhile,the scientific laws of how the piezoelectric thin sheet actuator achieves the excellent static/dynamic characteristics of the flexible piezoelectric thin sheet nano-manipulator through complex and precise coupling with energy(such as electrical energy and thermal energy)were mainly studied.The main research work of this paper was illustrated as follows:First of all,the improved deflection output model and the improved thermo-piezoelectric coupling deflection output model of the unimorph/bimorph piezoelectric thin sheet actuator under the action of thermal/electrical field and thermo-electric compound field were established,respectively,where the thermo-piezoelectric coupling effect caused by the change of electric field and temperature field,as well as the influence of internal transverse strain on the bending characteristics of micro-actuators,were considered.In addition,the simulations and experiments of piezoelectric thin sheet actuators under the action of thermal/electrical load and thermo-electric load were conducted,respectively.And the structure size change on its output characteristics was further studied.Meanwhile,the equivalent area moment of inertia of the unimorph piezoelectric thin sheet micro-actuator was solved,and the optimal thickness ratio of maximum deflection output was also determined,which provided guidance and theoretical basis for the design optimization and analysis of piezoelectric micro-actuators.Secondly,a novel three degrees-of-freedom flexible piezoelectric thin sheet nano-manipulator driven by uniformly distributed piezoelectric thin sheet actuators was proposed with a more compact size,lower cost,larger stroke,where the thermo-piezoelectric-mechanical coupling static model of the nano-manipulator including the structural dimension parameters was established by the compliance matrix method.Then,a detection method of the flexible piezoelectric nano-manipulator using two position sensitive devices(PSD)was adopted to verify the validity and accuracy of the modeling method and mathematical model under the thermal/electric load and thermo-electric load,respectively.Furthermore,the structural size of the nano-manipulator change on its output stroke and natural frequency was further studied,and the three degrees-of-freedom range of the center point of the flexible piezoelectric nano-manipulator under the limited voltage was also determined,which provided theoretical support and guidance for the design and optimization of the flexible piezoelectric nano-manipulator.Thirdly,based on the analysis of the thermo-piezoelectric-mechanical coupling effect of the flexible piezoelectric nano-manipulator,the conversion relationships between the equivalent deformation of each piezoelectric thin sheet actuator and the nano-manipulator outputs were solved.Then,the flexible piezoelectric nano-manipulator with distributed-parameter characteristics was transformed into an equivalent spring-mass-damping lumped-parameter system,and the thermo-piezoelectric-mechanical coupling dynamic model of the flexible piezoelectric thin sheet nano-manipulator,based on Lagrange equation of the second kind,was finally established,which could be applied in the feedback control research.Furthermore,the validity and accuracy of the established dynamic model were verified by the simulations and experiments.Finally,based on the established improved static deflection model of unimorph piezoelectric thin sheet actuators,the thermo-electric conversion coefficient which could convert the thermal load to the equivalent electric load was obtained,and the deflection output error of each unimorph piezoelectric thin sheet actuator of the flexible piezoelectric nano-manipulator caused by the temperature change was compensated.Then the high-precision position and attitude decoupling servo control scheme of three degrees-of-freedom of the flexible piezoelectric nano-manipulator in the thermo-electric field was achieved by using the sliding mode control method based on the extended state observer.