压电片位置对功率超声复合换能器共振频率的影响

研究了压电片位置对功率超声复合换能器机械共振频率的影响,给出了在不同情况下二者之间的关系曲线图。为设计和研究不同频率的夹心换能器提供了依据。     

含曲线裂纹的压电材料反平面应变问题

用复函数的Faber级数展开方法 ,通过求解Hilbert问题研究了含任意曲线裂纹的压电材料反平面应变问题 ,获得了问题的解析解和场强度因子。结果表明 ,当边界上仅受应力和电位移载荷作用时 ,应力场与电位移载荷无关 ,电位移场与应力载荷无关。算例中分别给出了圆弧裂纹的强度因子和椭圆弧裂纹问题的无量纲强度因子。     

旋转柔性梁的振动控制仿真及实验探讨

在综合比较已有文献所建立的刚体-柔性附件耦合系统动力学模型的基础上,以微元法为根据提出对旋转柔性梁运动方程中各项的理解,澄清了某些文献中模糊的认识。利用位置正反馈控制律,对旋转耦合系统中柔性梁的振动控制进行了数值仿真。并进一步利用压电陶瓷作为传感器和致动器,从实验上探讨旋转柔性梁的振动控制并给出了初步的实验结果及分析。     

陀螺振荡误差对方位对准的影响

通过对实验数据的研究发现,光纤陀螺仪测量的角速率中存在一部分低频振荡误差,此种误差会影响惯性导航系统初始对准的稳定性。为了抑制陀螺振荡误差所产生的影响,从频域角度对罗经法对准系统的频率特性进行了研究,分析了不同频率的陀螺振荡性误差对方位对准的影响形式。最终提出了抑制陀螺低频振荡误差的罗经法对准参数设计方案。经过理论分析以及半实物仿真,结果表明,按此种方法设计出的系统能够有效地抑制陀螺振荡性误差对方位对准所产生的影响。     

光纤激光陀螺的实验研究

分析了光纤激光陀螺系统的工作原理和基本构成,采用单向泵浦光纤复合谐振腔结构的光学系统设计方案,通过调整光学系统结构参数,实现了窄线宽单模激光输出. 在此基础上实现双向功率匹配,并最终获得稳定的角速率旋转电压信号. 结果表明,该实验装置具有可行性,通过转台实验测得光纤激光陀螺的灵敏度为0.02°/s.     

An in-pipe micro robot actuated by piezoelectric bimorphs

A novel in-pipe micro robot providing stable and accurate locomotion inside a tubular structure with diameters ranging from 16 mm to 18 mm is presented in this paper. Driven by impulsive voltages, deflections of the piezoelectric bimorphs are generated and then converted into translational locomotion by the principle of the Impact Drive Mechanism （IDM）. Theoretical analysis of the proposed system is performed based on a simplified mechanical model. Then dynamic simulations of the dynamic behavior are performed. Finally, an experiment is conducted to investigate the moving ability of this device. The results demonstrate that a maximum translational velocity of 3.5 mm/s can be obtained under an im- pulsive driving voltage with peak value at 50 V and frequency of 1100 Hz. Both theoretical analysis and experimental trials prove that the principle of IDM actuated by piezoelectric bimorphs is feasible and robust for achieving accurate locomotion of the micro robot in pipes with diameters of less than 20 mm.     

20MHz超声聚焦换能器的设计及其应用

为提高工业超声显微镜的成像分辨率,需要用高灵敏度的超声聚焦换能器.本文对研制的聚焦换能器的等效电路进行了理论分析,利用Matlab软件,数值模拟了聚焦换能器沿轴线方向辐射的脉冲聚焦声场,讨论了聚焦换能器的脉冲声场特性.采用特殊工艺研制压电晶片,用环氧树脂和钨粉的混合物作背衬,由此研制的主频为20 MHz宽带窄脉冲有源自聚焦换能器,在实际检测中回波仅有一个波形,缺陷的成像分辨率达0.4 mm.     

BNT-BKT-BiCrO3压电陶瓷的压电性能和退极化温度

采用传统陶瓷制备方法,制备了一种新型无铅压电陶瓷材料(1-x-y)Bi0·5Na0·5TiO3-xBi0·5K0·5TiO3-yBiCrO3(简写为BNT-BKT-BC-x/y).研究了该体系陶瓷微观结构、压电性能和退极化温度的变化规律.结果表明:除x=0·18、y=0·025的组成析出第2相外,其他组成陶瓷均能够形成纯钙钛矿固溶体,陶瓷三方、四方共存的准同型相界(MPB)成分范围为x=0·18~0·21,y=0~0·02.在准同型相界成分附近该体系陶瓷压电性能达到最大值:d33=168pC·N-1,kp=0·326.采用平面机电耦合系数kp和极化相位角θmax与温度的关系确定的退极化温度基本相同,陶瓷的退极化温度随BC含量的增加一直降低,随BKT含量的增加先降低后升高.     

音叉式硅微机械振动陀螺仪的粘滞阻尼研究

粘滞阻尼的研究对硅微机械振动陀螺仪的设计至关重要。而品质因数的大小反映了阻尼特性。本文首先理论分析了硅微型机构振动陀螺仪粘滞阻尼的耗能,然后根据耗能分析给出了驱动结构和敏感结构的品质因数。     

Ferroelectric and piezoelectric properties of novel relaxor ferroelectric single crystals PMNT

Relaxor ferroelectric single crystals PMNT with the size of 40 mm×80 mm have been grown by a modified Bridgman method and their ferroelectric and piezoelectric properties have been characterized.The properties varied with the compositions and cut types.On the (001) cut,PMNT76/24 single crystals exhibited a dielectric constant of about 3 400,a dielectric loss of tan＜0.7%,a piezoelectric constant d33 of 980 pC/N,an electromechanical coupling factor kt of 0.55 and Tc of about 110℃.Whereas the properties of PMNT67/33 single crystals on (001) cut were better: ε of about 5 300,tanδ＜0.6%,d33 up to 3 000 pC/N,kt 0.64,k33 0.93 and Tc of about 150℃.The piezoelectric properties on other cuts such as (110) and (111) were much lower than those on the (001) cut.The rhombohedral PMNT crystals grown by this method showed more excellent piezoelectric properties than those grown by high temperature solution method and higher value of kt than the rhombohedral PZNT single crystals.It has also been found that the fluctuation in ferroelectric and piezoelectric properties was related to such factors as composition uniformity and poling degree.