（反应）模晶生长法制备NBT-6BT织构陶瓷的研究

以熔盐法合成的片状SrTiO3，Bi4Ti3O12为种晶，分别采用模晶生长法（TGG）和反应模晶生长发（RTGG）制备了具有〈001〉取向的0．94（Na1/2Bi1／2）TiO3-0．06BaTiO3（NBT-6BT）织构陶瓷。研究了不同种晶选择、流延和热处理工艺参数对陶瓷织构化程度、显微结构和压电性能的影响。结果表明，RTGG制备的织构陶瓷比TGG的在结构和性能等方面都具有优势，且用该方法以Bi4Ti3O12为种晶，制备出了高密度（f≥96％）、高织构度（F≈95％）、高性能（d33≈241pC／N）的NBT-6BT无铅压电陶瓷。     

无铅压电陶瓷的研究进展

在压电陶瓷领域，无铅压电陶瓷从环保的角度考虑越来越引起人们的注意。本文主要综述了以BNT为基的3类无铅压电陶瓷体系。它们都是很好的无铅压电陶瓷的侯选材料，其中BNBT－6，BNTN－3和BNST－2的机电耦合常数K33分别为0．55，0．43，而且具有较高的频率常数和较小的介电系数，适用于众多高频超声换能检测领域以及压电致动装置等方面，所以作为无铅压电陶瓷它们是很有潜力的。     

铜掺杂对(Na0.5K0.5)NbO3无铅压电陶瓷性能的影响

采用传统固相反应法对(Na0.5K0.5)NbO3压电陶瓷进行铜掺杂改性研究。使用SEM、XRD并结合常规压电陶瓷性能测试手段对该体系的显微结构、压电性能等进行表征。研究结果表明:CuO的掺入使材料出现“硬化”现象,即材料的压电系数d33、平面机电耦合系数Kp和介电损耗tanδ下降了,机械品质因子Qm大大提高;CuO掺入量在1%mol时各项性能最佳。另外,从SEM图片中可以看出:(Na0.5K0.5)NbO3压电陶瓷材料的平均晶粒尺寸随着CuO掺入量的增加明显变大。这表明CuO有烧结助熔作用,能降低烧成温度。     

锰掺杂对PNW-PMS-PZT压电陶瓷结构和性能的影响

采用传统陶瓷工艺制备了Pb(Ni1/2W1/2)O3-Pb(Mn1/3Sb2/3)O3-Pb(Ti，Zr)O3-xMnO2压电陶瓷，分析了经1150℃烧结2h制备的陶瓷样品的相结构组成。实验结果表明：所有陶瓷样品均为钙钛矿相，未发现其它晶相。随着锰掺杂量的增加，陶瓷晶粒逐渐长大。研究了不同剂量的锰掺杂对压电陶瓷介电和压电性能的影响。结果表明：随着锰掺杂量的增加，材料逐渐变“硬”，当MnO2掺杂量少于0．2％(按质量计，下同)时，相对介电常数εr、压电常数d33和机械品质因数Qm逐渐增加，介电损耗tanδ减小；当MnO2掺杂量多于0．2％时，εr、d33和Qm逐渐降低，tanδ增加。随着锰掺杂量的增加，机电耦合系数kp和Curie温度θc逐渐减小。MnO2掺杂量为0．2％的压电陶瓷适合制作大功率压电陶瓷变压器。其压电性能为：εr=2138，tanδ=0．0058，kp=0．613，Qm=1275，d33=380pC／N和θc=205℃。     

Tactile display with tangential and normal skin displacement for robot-assisted surgery

This paper proposes a tactile display providing both shear and normal feedback to the fingertip for generating three-axis tactile feedback during teleoperation of a surgical robot. The display is composed of five balloons actuated by controlling the pneumatic pressure. The implemented display is 18?mm?×?18?mm?×?15?mm. This size is suitable for mounting the display onto the master controls of a surgical robot. The maximum normal and shear displacements are 2 and 1.3?mm, respectively. The proposed tactile display may provide perceivable stimuli to a human finger pad in all five directions: normal, distal, proximal, radial, and ulnar. This paper also reports on the results of psychophysical measurement of the minimum perceivable movement of the developed tactile display for each of the five directions.     

Development of large-scale stacked-type electrostatic actuators for use as artificial muscles

Electrostatic actuators have the advantages of light weight, flexibility, and high energy efficiency, which make them suitable for use as artificial muscles. However, a traditional electrostatic actuator cannot generate long strokes and a high force density at the same time because such actuator would excessively widen the gap between the electrodes because of its structure. This paper presents a newly developed large-scale stacked-type electrostatic actuator (LSEA) intended for use as an artificial muscle for robots. LSEA is a multi-stacked electrostatic actuator that can be linearly contracted by the application of a voltage. It has a unique structure that prevents overextension of the gap between the electrodes. It can therefore generate a large force. The spring characteristics and the relationship between the contractive force and the stroke were experimentally determined. The findings showed that LSEA prevents the overextension of the gap between the electrodes and has a high contraction ratio that is equivalent to that of a mammalian skeletal muscle.     

硅酸镓镧结构的新型压电晶体的研究进展

新型压电晶体La3Ga5SiO14因其低声速、零温度切向和良好的高温稳定性受到关注，但是昂贵的Ga2O3原料阻碍了它的工业应用。通过离子置换可获得具有langasite结构的多种新型压电晶体。综述介绍了置换La，Ga，Si形成的新型压电晶体的最新研究进展，比较分析了不同晶体的优势及其存在的问题。在这些新晶体中，由于Sr3Ga2Ge4O14（SGG)具有熔点较低、性能较高的综合优势，它有可能成为新一代表面波器件的重要候选材料。与提拉法相比，采用增蜗密封的下降法生长SGG单晶；可以显著提高晶体产率，降低成本。     

A virtual actuator and sensor approach for fault tolerant control of LPV systems

In this paper, a fault tolerant control (FTC) strategy using virtual actuators and sensors for linear parameter varying (LPV) systems is proposed. The main idea of this FTC method, initially developed for LTI systems, is to reconfigure the control loop such that the nominal controller could still be used without need of retuning it. The plant with the faulty actuator/sensor is modified adding the virtual actuator/sensor block that masks the actuator/sensor fault. The suggested technique is an active FTC strategy that reconfigures the virtual actuator/sensor on-line taking into account faults and operating point changes. The stability of the reconfigured control loop is guaranteed if the faulty plant is stabilizable/detectable. The LPV virtual actuator/sensor is designed using polytopic LPV techniques and linear matrix inequalities (LMIs). A two-tank system simulator is used to assess the performance of the proposed method. In particular, it is shown that the application of the proposed technique results in an improvement, in terms of performance, with respect to the LTI counterpart.     

基于N步不变集的时滞切换系统的饱和控制

构造离散时滞切换系统的不变集,提出基于N步不变集的切换控制器设计方法,估计执行器饱和非线性的吸引域范围。首先,考虑时滞的影响,选取依赖于时滞的Lyapunov函数,构造时滞切换系统的不变集,并将其表达为若干个椭球集的凸组合,椭球集的个数与时滞常数相关。其次,在系统的前N个采样时刻,分别施加不同的饱和约束,求解得到一组椭球集,椭球集的个数与常数N相关,而每一步计算得到的椭球集均为时滞切换系统的不变集。再将N个不变集用一组凸包系数拟合,即可获取较大的吸引域估计。最后,在满足平均驻留时间约束的条件下设计切换律,并设计状态反馈控制器,保证闭环系统渐近稳定。控制器的求解转化为线性矩阵不等式的可行性问题。仿真结果验证了所提方法的可行性和有效性。     

压电作动器的动态迟滞建模与H∞鲁棒控制

压电作动器具有率相关动态迟滞非线性特性,给传统建模和控制技术提出了挑战.本文针对压电作动器,提出了一种基于Bouc-Wen的Hammerstein率相关迟滞非线性模型,其中Bouc-Wen模型和线性动态模块分别用于描述系统的静态迟滞非线性特性和率相关特性.同时,构造了一个基于Bouc-Wen模型的迟滞补偿器,将迟滞补偿器与被控对象串联使系统线性化;并建立了不确定性系统模型,提出了一种H∞鲁棒跟踪控制方案,可以实现给定频率范围内单频率和复合频率参考信号的良好跟踪.实验结果表明,所建动态模型具有良好的泛化能力,跟踪控制相对误差小于8%,证明了所提出方法的有效性.