Design of a linear piezomotor with ultra-high stiffness andnanoprecision

An ultra-stiff nanoprecision linear piezomotor was recently designed for grinding application. This piezomotor consists of three high-voltage piezoelectric actuators integrated by a monolithic flexure frame. This monolithic frame was designed to have multiple functions such as protecting and pre-loading three piezoelectric actuators and withstanding all the shearing forces during operation. The monolithic frame as a motion mechanism eliminates the backlash problem. The stiffness distributions in certain directions over the frame were designed using the finite-element method     

Using a Walking Piezo Actuator to Drive and Control a High-Precision Stage

Piezoelectric actuators are commonly used for micropositioning systems at nanometer resolution. Increasing demands regarding the speed and accuracy are inducing the need for new actuators and new drive principles. A nonresonant piezoelectric actuator is used to drive a stage with 1-DOF through four piezoelectric drive legs. In order to improve the positioning accuracy of the stage, a new drive principle and control strategy for the walking piezomotor are proposed in this paper. The proposed drive principle results in overlapping tip trajectories of the drive legs, resulting in a continuous and smooth drive movement. Gain scheduling feedback in combination with feedforward control further improves the performance of the stage. With the developed drive principle and control strategy, the piezomotor is able to drive the stage at constant velocities between 100 nm/s and 1 $mu$m/s with a tracking error below the encoder resolution of 5 nm. Constant velocities up to 2 mm/s are performed with tracking errors below 400 nm. Point-to-point movements between 5 nm and the complete stroke of the stage are performed with a final static error below the encoder resolution.      

The design and characterization of a novel piezoelectric transducer-based linear motor

Before microminiature robots can be realized, new direct drive micromotor systems must be developed. In this research, a linear motor system for a miniature jumping robot was desired. However, current systems must display better force/torque characteristics than is currently available. This paper deals with the design, construction, and testing, of a macro-scale, unidirectional, direct drive linear piezomotor that operates like an inchworm. It uses a parallel arrangement of unimorph piezoelectric transducers, in conjunction with passive mechanical latches, to perform work on a coil spring. Experimental results showed that the linear piezomotor achieved a maximum no-load velocity of 161 mm/s, and a blocked force of 14 N, at a drive signal frequency of 100 Hz. Thereafter, back slip in the latch assembly restricted the forward motion. Based on the results obtained with the macro-level linear piezomotor, it is concluded that smaller direct drive piezomotor designs based on unimorph piezoelectric transducers are achievable. System scalability will be addressed in a future publication.     

尺蠖型压电驱动器结构及其特性

由于微纳米级精密定位技术在原位测试、精密光学、超精加工等领域的作用无可替代,因此具有精密定位功能的各种新型驱动器受到国内外学者的广泛关注,其中尺蠖型压电驱动器的研究尤为活跃。该类驱动器定位精度高,结构紧凑,输出力大,运动稳定,具备较大工作行程的同时拥有较高的运动分辨率,在各类驱动器中综合优势明显。首先,介绍了尺蠖型压电驱动器的原理和关键部件;其次,对直线型、旋转型和一体型三类代表性尺蠖驱动器的研究进展进行了总结和归纳,分析了各自的主要结构、动作原理、性能特点和适用场合。结果表明,实用性问题是未来研究重点,可从构型设计、控制系统、补偿算法以及温度控制等方面加以改进。     

压电谐波电机位移放大机构的设计

压电谐波电机是一种基于谐波传动原理的新型低速电机，它由压电波发生器、柔轮、刚轮等组成。压电波发生器由八组以上压电驱动器及弹性铰链位移放大机构组合而成。该文在研究了杠杆、三角、压曲三种位移放大原理后，根据这三种放大原理设计出压电谐波电机的弹性铰链一体化位移放大机构。分析了影响放大机构性能的因素。介绍了放大机构的制造方法。     

压电谐波电机承载能力的研究

以保证柔轮与刚轮的正常啮合为条件,引入计算径向变形量系数,设计径向变形量系数以及允许位移损失系数,通过确定位移放大机构输出端允许位移损失量或柔轮的实际径向变形量,计算压电谐波电机承载能力。建立了压电谐波电机承载能力的设计准则,是包括压电驱动器驱动能力选择以及其他结构尺寸设计与校核的主要依据。其输出扭矩与压电驱动器与位移放大机构的刚度成正比,与柔轮变形力、轮齿啮合角以及摩擦系数成反比。克服了基于压电驱动器最大驱动能力建立压电谐波电机输出扭矩方法的缺陷。该模型也可用于采用超磁致伸缩等其他驱动器的谐波电机承载能力的计算。设计计算表明,相对于一般原动机,压电谐波电机能提供较大的输出扭矩。     

Engineering and performance of a contactless linear slider based on superconducting magnetic levitation for precision positioning

In this paper, a contactless linear slider for precision positioning able to operate in cryogenic environments is presented. The device, based on superconducting magnetic levitation, does not present contact between the slider (composed of a permanent magnet) and the guideline (made of high-temperature superconducting disks) of the mechanism, thereby avoiding any tribological problems. Moreover, the slider is self-stable and the superconductors provide inherent guidance to the permanent magnet in the sliding DoF due to the high translational symmetry of the magnetic field that leads to low power consumption. A sub-micrometre resolution and a symmetric stroke over ±9 mm have been demonstrated at cryogenic temperatures. In addition, a set of design rules for this kind of mechanism has been proposed and experimentally validated. These rules demonstrate that the performance of the device can be tuned just by modifying some geometrical parameters of the mechanism. In this way, the sensitivity and stiffness, resolution, angular run outs and power consumption can be adjusted for different applications and requirements.     

星载SAR功能结构一体化天线技术研究

提出了新型低剖面合成口径雷达(SAR)有源相控阵天线设计方法———多功能结构一体化天线技术,采用高密度互联、新型功能材料等进行模块化、轻量化的系统级集成设计,将系统功能与天线结构相结合,大幅减小了SAR天线的体积,增大了内部可用空间;同时,有效去除天线寄生质量及各分系统间的重复质量。对SAR天线进行了一体化设计验证,结果表明天线性能、结构承载及热控的指标满足要求,多功能结构一体化设计方法对大型有源相控阵天线系统的结构设计有实际指导意义。     

高体份SiC/Al复合材料空间相机框架的拓扑优化设计

为了提高空间相机在力/热双重环境条件下的系统稳定性,同时能够实现系统的轻量化目标,在某型空间相机的研制过程中选用了具有高比刚度和热稳定性的高体份SiC/Al复合材料。采用整体式框架结构,将基于变密度法的连续体结构拓扑优化方法应用到相机框架结构的初始设计中,通过设定相应的约束条件和目标函数,进行迭代求解,得到了相机框架分别在X、Y、Z三个方向重力作用下的结构拓扑优化结果,结合工艺要求,最终确定了空间相机框架的设计方案。通过与对比方案比较发现,经过拓扑优化所得到的框架结构在结构刚度及轻量化率上都有明显提高,实现了空间相机框架高刚度、轻量化的设计目标。     

基于线阵CCD的激光FPC加工定位方法研究

为在FPC激光柔性加工系统中对FPC板进行精确定位,本文提出了一种基于线阵CCD的精确定位方法。首先阐明了线阵CCD的工作原理和激光FPC加工过程的定位原理。然后分析了采集数据的处理方式,并给出了定位操作的流程。最后通过计算相对坐标实现了线阵CCD定位,总结出了该定位方法具有定位精度高、操作灵活、视场大等优点。     

A charge-coupled area image sensor and frame store

A two-dimensional three-phase charge-coupled array with 128 × 106 elements, that can serve either as a solid-state image sensor or as an analog serial memory, has been built. As an image sensor the device has been operated successfully in the frame transfer mode to yield 120 frames/s with 64 × 106 resolution elements. By using the whole array as an image sensor, pictures with 128 × 106 resolution elements have been obtained at 15 frames/s with tolerable smearing. In the memory mode the device can store a whole analog frame as produced by a companion device, or 13 568 bits of digital information. But for the latter application defect-free devices are mandatory. The design of the device, the various modes of operation, the quality of the results, some typical defects, and some further applications are discussed.     

A systematic procedure for the design of piezoelectric inchworm precision positioners

Design equations are developed and integrated into a computerized design tool in order to facilitate the creation of inchworm piezoelectric based positioners. Fundamental to the development of the design tool is the piezoelectric actuator and motor frame stiffness interaction and its influence on positioner performance. A generalized motor frame configuration for each of the motor subsystems is presented and used to generate key initial positioner frame geometry. An inchworm precision positioner is implemented based on the generalized motor frame and the computerized design tool and it is shown experimentally and through finite-element analysis that the design approach is effective for precision positioner design. The prototype of the inchworm positioner developed is shown to have a stiffness in the direction of motion of 88 N//spl mu/m, a maximum thrust of 150 N and a traversing speed of up to 20 mm/s.     

大型平板微波天线伺服俯仰系统工程设计

针对大型平板微波天线俯仰系统进行工程研究,设计了一种强度高、质量轻的桁架结构作为天线背架。根据指标要求建立数学模型,将整个运动过程通过准确的力学计算进行力矩分配,从而选定电机、减速机等结构要件;通过对关键结构件的有限元仿真及高功率微波环境下的电磁兼容性设计,进一步保证整个俯仰系统可靠工作。通过实验验证,承载负载总重达到2 t左右,角速度最高可达10°/s,可以完成0°~70°俯仰运动,定位精确度优于0.1°。实测平板微波天线各项参数均能达到设计要求,微波测试方向图形态良好,波束指向满足要求。     

基于RFID的轨道车辆实时定位系统设计

为了使目前轨道车辆运行效率提高,采用射频识别RFID技术对轨道车辆的物理位置进行实时监测的方法,提出一种利用RFID技术对轨道车辆进行实时定位的系统,并介绍该实时定位系统的设计方案、组成及工作原理,主要包括RFID标签安置、RFID读写及与后台服务器通信等技术。系统运行性能结果表明利用RFID技术对轨道车辆进行实时定位具有精度高、环境适用性强等优点,在地铁和企业厂段的轨道车辆实时定位中具有良好的应用前景。     

基于主动光学的大口径反射镜硬点定位技术

大口径望远镜主镜、副镜等反射镜相对于其镜室的位置和方向靠硬点来保证,它是主动光学系统的关键组成部分,对提高望远镜的成像质量和安全防护性能具有重要的作用。本文全面地概述了大口径反射镜不同类型硬点定位的结构及工作原理,并详细介绍了E-ELT、VLT、VISTA、LSST望远镜中的硬点定位技术,它们是不同类型硬点定位的典型代表。最后,总结了大口径反射镜硬点定位的发展趋势,指出六杆硬点定位最有应用前景,并深入地论述了其结构特点及关键技术,提出了一系列提高其定位精度、轴向刚度及安全可靠性的方法。     

Improved digital/analogue conversion technique using currentsplitting in lateral bipolar transistors

Describes the use of multiple collector lateral bipolar transistors as precision current splitting elements suitable for use in high resolution monolithic D/A convertor design. Multiple collector structures result in better overall linearity and smaller chip area than previously suggested techniques. A six-bit convertor implemented on a linear bipolar semicustom array is used to demonstrate the advantages of this technique     

Analytical stiffness estimation for short flexures

Accurate stiffness determination is critical for flexures used in high accuracy positioning—such as inchworm^® piezomotors—because stiffness significantly affects the positioner’s response time, resonant frequency and range of motion. The flexures are often short beams while the standard formulae for stiffness are for long, slender beams based only on bending stress and can over predict the stiffness of the short flexures. An improved model for a single, short beam is presented which incorporates shear stress and a comparison to FEA results shows almost exact agreement. A study of a more complex flexure showed that simple stiffness models were inaccurate because of end effects in the supporting structure. Development of a multi-section analytical model to include the end effects is presented in this paper and again a comparison to FEA results shows sufficient accuracy to be used in design to quickly optimize the positioner’s performance.     

Control of a 2-DOF ultrasonic piezomotor stage for grommet insertion

The treatment of a common disease called “Otitis Media with Effusion (OME)” involves the surgeon inserting a grommet in the eardrum to bypass the Eustachian tube for draining fluid when medication fails. In this paper, a novel device for myringotomy and grommet insertion is first designed and introduced. Due to the advantages of high precision and fast response, a 2-DOF ultrasonic piezomotor (USM) stage is chosen to provide the motion sequences of the device, especially a precise path tracking during the grommet insertion. This paper briefly presents the mechanical design of the device and the configuration and control of the 2-DOF USM stage. The model of the USM consisting of a linear and nonlinear term is built. A PID controller is used as the main controller and tuned with the help of LQR technique. Since there are nonlinear dynamics caused by friction and hysteresis existing in the system, a nonlinear compensation including a sign function and sliding mode control is designed to reject the nonlinearity. Moreover, a decoupling controller is designed to eliminate the coupling effects between the two USM stages. The experimental results show that the LQR-assisted PID controller with compensation can achieve very good system performance and the decoupling controller can further improve the performance.     

合成孔径无源定位性能分析与参数设计

合成孔径无源定位中，为获得高的2维分辨率，需要长的合成孔径，但斜距历程的多项式近似会带来距离定位的误差。针对此问题，该文分析了合成孔径定位中距离误差的影响因素，给出了定位误差的近似表达式，同时分析了距离和方位分辨率的影响因素，给出了分辨率的分析方法。在此基础上，综合考虑定位精度和分辨率的约束条件，给出了合成孔径长度参数的优化方法。仿真结果验证了方法的有效性。     

贴片机x-y运动横梁结构设计研究

高速、高精度是贴片机的主要特征。在框架式贴片机中,横梁的质量与刚度是决定整机速度和精度的主要因素。横梁的结构形式、与传动机构的连接方式、材料等都直接影响横梁的质量与刚度值。通过综合分析传动机构与横梁不同连接方式的利弊,从中选择能够满足设计要求的连接方式。在此基础上,对横梁结构进行数值仿真分析与优化,从而达到了降低横梁质量、提高刚度的设计目的。