Study On Problems For The Electrothermal Drive Used In The Logic Micro-system For Optical Path

Micro drive technology is the key technology to micro,quick and precise development for the logic micro-system for optical path that used for laser ignition.At present,electrostatic drive,piezoelectric drive,electrothermal drive and electromagnetic drive are the common driving methods.Based on Joule heating and thermal expansion effect,electrothermal microactuator is a device that can transfer from electric energy to mechanical energy.The electrothermal microactuator gives access to flexible design,lower driving voltage,larger moment of force and compatibility with circuit,which promises a well development foreground in the logic micro-system for optical path.Now,on the one hand,the miniaturization is gradually required in the development of intelligent ammunition and fuze and the full-electronic fuze is susceptible to electromagnetic interference.On the other hand,three are some problems,such as complex structure,slow response and low reliability under long time voltage.To solve these,theoretical analysis,numerical simulation and experiment test are adopted.The mechanism of the multiphysical field coupling,characteristic of dynamic displacement response,reliability with stochastic fabrication error,double-objective structural optimization and design for electrothermal actuator are studied.According to the research conclusions above,an optical switch with logical control in MOEMS is designed and fabricated.It is based on direct light initiation and owns simple structure,fast response,reliable switch-on and ease of control.(1)With the excitation voltage,the electro-thermal coupling lying in the U&V-shaped electrothermal actuator is studied and an improved Chebyshev spectral method is put forward.Thus,the temperature distribution on the electrothermal actuator is gained.The efficiency of the method is verified by numerical simulation and the change law of the temperature field in the electrothermal actuator is also achieved.Based on this,the thermo-elastic model is established.Therefore,a complete model of the electrothermal actuator is acquired and its dynamic displacement response can be theoretically depicted.Finally,the theoretical model of the electrothermal actuator is demonstrated by finite element model and experiment measurement on static displacement.(2)To further study the dynamic response of U&V–shaped electrothermal microactuator,an efficient method that consists of background difference and canny edge detection algorithm is put forward.By the independently developed high-speed optical measurement system,the feature detection on the images of the transient motion and visualization of test results in the electrothermal actuator are realized.So the transient displacement of the actuator under constant voltage and dynamic response of the actuator under alternating voltages(sine,square and plus one)are obtained.Test results show that the theoretical model can also be used to depict the transient motion of the electrothermal actuator and the characteristic of the motion of the actuator under periodic voltage is analyzed.(3)According to the relationship between design parameters and performance in the U&Vshaped electrothermal actuator,the sensitive design parameters in the electrothermal actuator that is fabricated by deep reactive ion etching(DRIE)technology are analyzed,assigned and measured.Thus,the characteristic and feature values of the error distribution from the sensitive parameters are obtained.Non-intrusive polynomial chaos(NIPCE)models on the displacement,maximum temperature with the stochastic error are built.The results from the models above are validated by monte calor simulation.By simulation,the functional and structural failure probability density of the U&V-shaped electrothermal actuator used in the MOEMS light logic system are gained.The displacement probability density of the U-shaped one is skewed positively distribution,while the displacement probability density of the V-shaped one meet normal distribution.By comparison,the U-shaped one owns better function and hardly has access to structural failure so that it is more suitable for driving in the MOEMS light logic system.The best range of working voltage on the U-shaped electrothermal actuator is finally obtained.(4)Given the load capacity that the U-shaped electrothermal actuator needs to supply to push the fiber in the MOEMS light logic system,its output displacement and force are simutaneously selected to be the objectives for structural optimization.The mathematic model of the double-objective optimization problem is formed.The numerical calculation model on the output force and displacement of the U-shaped electrothermal actuator is established and validated by the experiment.Based on the double-objective numerical calculation model and the independently established automatic simulation platform,the genetic algorithm(GA)and particle swarm optimization(PSO)algorithm are combined together and utilized to solve the optimization problem.Given the fabrication error and optimization results,the reliability design of the U-shaped electrothermal actuator is conducted.(5)Based on optimization results,an switch used for optical path control in MOEMS optical logic system is designed and fabricated.The structural reliability of the switch is tested in the extreme environment of fuze,such as high impact and high rotation speed.Its functions such as self-locking and recoverable capability,are also validated in the static and centrifugal environment,respectively.More,the capability of the switch to push the fiber is also evaluated.Based on the high-speed optical measurement system in part 2,the dynamic response of the locking array and the driving array in the switch is studied.According to the results above,a reasonable voltage wave for logic control is given to improve the response speed of the switch,prominently.By independently establieshed electrical measurement platform,the minimum response time of the switch is only 24 ms.