Modeling and control of power flow in a double-beam system

The vibrational power flow in a double-beam system is investigated theoretically and experimentally in this paper. A novel large displacement piezoelectric actuator assembly, comprising two curved THUNDER actuators, is used to connect the two beams and provide both passive and active isolation at the same time. A simulation model is proposed to describe the coupled mechanical and electrical properties of the new actuator assembly. Modal expansion approach is used to study the power transmissions between the two beams which are mechanically and electrically coupled via the actuator mounts. The effectiveness of both active and passive isolation has been investigated. The optimal control voltage for each actuator is obtained by minimizing the time-averaged power transmitted into the receiver beam. Results show a significant reduction in vibration power transmission. A correlation between the control effort and the mode shapes to be controlled is shown to exist.     

Hybrid inversion method for equivalent electric charge of thunder cloud based on multi-station atmospheric electric field

This article proposes the hybrid method to inverse the equivalent electric charge of thunder cloud based on the data of multi-station atmospheric electric field. Firstly,the method combines the genetic algorithm( GA) and New ton method through the mosaic hybrid structure. In addition,the thunder cloud equivalent charge is inversed based on the forw ard modeling results by giving the parameters of the thunder cloud charge structure. Then an ideal model is built to examine the performance compared to the nonlinear least squares method. Finally,a typical thunderstorms process in Nanjing is analyzed by Genetic-New ton algorithm with the help of weather radar. The results show the proposed method has the strong global searching capability so that the problem of initial value selection can be solved effectively,as well as gets the better inversion results. Furthermore,the mosaic hybrid structure can absorb the advantages of tw o algorithms better,and the inversion position is consistent with the strongest radar echo.The inversion results find the upper negative charge is small and can be ignored,w hich means the triple-polarity charge structure is relatively scientific,w hich could give some references to the research like lightning forecasting,location tracking.     

THUNDER元件热机电耦合动力学分析

针对THUNDER型压电驱动器这一类特殊结构形式,提出一种包含4个位移节点,8个温度节点和2个电势节点的热机电耦合混合有限元模型,并基于虚功原理推导了热机电耦合有限元方程。针对物理属性截然不同的冷却阶段、再极化阶段和驱动阶段开展了动力学研究,并利用初始位移这一变量将它们有机地联结起来;系统地分析了该类驱动器的热机电耦合问题。数值算例表明:该混合有限元模型具有良好的计算精度;THUNDER型压电驱动器的驱动性能与其制造过程密切相关,且其驱动位移与外载荷的凹曲线关系使其具有良好的综合驱动性能;在实际应用中,当温度发生变化时,热应变对驱动性能具有重大影响,而焦电效应的影响相对较小但仍十分明显,体现出对THUNDER型压电驱动器开展热机电耦合动力学研究的重要性。