Workspace analysis and design improvement of a carotid flow measurement system

Heart and cerebrovascular diseases such as arteriosclerosis and myocardial ischemia dysfunction are currently among the main causes of death in developed countries. Recently, wave intensity (WI), which is an index used to obtain the force of cardiac contraction, has been investigated as a method for early-stage diagnosis of the above-mentioned diseases. Nevertheless, experimental tests have proven that the manual measurements of WI by means of commercial ultrasonic diagnostic systems require too much time and can be affected by the operator's skills. For this purpose, the introduction of robotic-assisted technology has advantages in terms of repetitiveness and accuracy of the measurement procedure. Therefore, at Waseda University, the development of a carotid blood flow measurement system has been proposed to support doctors while using ultrasound diagnostic equipment to measure the WI. This robotic system is composed of a serial robot with a wrist having a six-degree-of-freedom (6-DOF) parallel mechanism. The main focus is to obtain a suitable workspace performance of the 6-DOF parallel mechanism wrist. In this paper, a workspace analysis is carried out on a wrist prototype built for the Waseda-Tokyo Women's Medical Aloka Blood Flow Measurement System No.1 Refined (WTA-1R). Then, mechanical design enhancements are proposed and validated to provide a suitable workspace performance both as reachable workspace and dexterity, and a refined prototype WTA-1RII has been built.     

铰链间隙对6自由度并联机床刀具位姿的影响分析

为了评价6自由度交叉杆型并联机床中铰链间隙对刀具空间位置与姿态(简称位姿)的影响,提出了一种"分解、求交"方法,确定铰链间隙引起刀具平台位姿的可达空间,进而分析铰链间隙对刀具位姿的影响。基于旋量理论,采用指数坐标法推导了该机床各支链的正向运动学指数式解析表达式,并分别求取单支链单独约束下铰链间隙引起刀具平台的可达空间。对6个空间进行求交处理,获得6支链同时约束下的可达空间,即为间隙引起的误差空间。实验结果证明了该"分解、求交"方法的正确性和有效性。     

Design of a contact probe with high positioning accuracy for plasmonic lithography

Plasmonic lithography with a contact probe records nano-meter scale features and has high-throughput owing to its capability to scan in contact mode. The probe is commonly based on a micrometer-scale cantilever, which leads to the tip-positioning problem due to force-deflection that induces lateral tip displacement. We propose a geometrically modified probe to achieve high positioning accuracy. Contrary to a conventional cantilever-tip probe, we designed a "circular probe" with arc-shaped arms that hold the tip in the center. The mechanism is based on the "fixed-fixed beam" concept in material mechanics. To confirm its positioning accuracy, we used a finite element method (FEM) to calculate the tip displacement for a circular probe and compared the results with those using a conventional cantilever-tip probe. The probe was designed considering a silicon-based micro-fabrication process. The designed probe has a square outline boundary with a length of 50 μm, four arms, and a pyramidal tip with a height of 5 μm. The ratio of the lateral tip displacement to the vertical deflection was evaluated to indicate the accuracy of the probe. The probe has higher positioning accuracy by a factor of 10(3) and 10 in its approach mode and scan mode, respectively, compared with a cantilever-tip probe. We expect that the probe is suitable for the applications that require high positioning accuracy, such as nanolithography in contact mode and applications based on multiple-probe arrays.     

X-Y精密定位平台的敏感函数逆前馈补偿控制

针对音圈电机驱动的X-Y定位平台中稳态误差导致的系统定位精度较低的问题,提出了基于敏感函数逆的前馈补偿控制方法。首先,采用频域辨识方法建立了系统模型,基于终值定理推导出系统扰动和稳态误差的关系,并由此设计了敏感函数的逆模型来补偿扰动对稳态误差的影响,从而提高系统精密定位性能。最后,在搭建的音圈电机驱动X-Y定位平台上进行了不同运动行程的实验研究。实验结果表明:在行程为10μm,最大加速度为6mm/s2的微定位运动条件下,补偿后的定位误差可由2μm降低到0.2μm;在行程为10mm,最大加速度为6m/s2的宏定位运动条件下,定位误差可由2μm降低到0.4μm。实验结果验证了本方法的有效性,为后续高精密伺服系统的研制提供了重要参考和设计依据。     

基于DSP控制器的精锻机器人控制系统设计

通过分析精锻工艺过程对控制系统的硬件和软件需求,开发了具有开放式结构的精锻机器人控制系统。系统采用PC4-DSP为核心的运动控制器开放式结构模式,以DSP为核心,位置伺服控制方式,构建硬件平台,软件设计采用模块化和多线程技术,通过调用运动控制卡的动态链接库,设计了具有良好实时响应的运动控制程序,满足运行速度要求。软件设计界面直观友好,操作方便。调试结果表明,该系统重复定位精度达到2mm,满足设计要求。     

复杂坏境下基于SINS/UWB的容错组合定位技术研究

针对超宽带无线定位系统在复杂坏境中出现的定位数据丢失以及粗大误差等导致SINS/UWB组合系统定位精度下降的问题,提出了一种基于超宽带定位系统容错判断的组合定位方法。首先根据捷联惯导测量值进行基于中值滤波的运动载体静止状态检测,进而利用最小二乘法实现静止状态下捷联惯导量测偏差矫正;然后在建立SINS/UWB组合定位模型的基础上,引入决策树容错判断机制,对超宽带定位系统在复杂环境中由于信号干扰以及非视距导致的测量数据丢失以及粗大定位误差进行实时评估,进而应用卡尔曼滤波算法,实现容错组合定位系统的构建。在搭建的SINS/UWB组合定位实验平台中进行模型验证,结果表明容错组合定位系统能够有效检测出UWB定位系统出现的定位数据丢失以及粗大定位误差,并且在UWB粗大误差状态持续6 s的情况下,容错组合定位系统仍然能够保持较高的定位精度。     

Ultrasound-guided prostate percutaneous intervention robot system and calibration by informative particle swarm optimization

Applying a robot system in ultrasound-guided percutaneous intervention is an effective approach for prostate cancer diagnosis and treatment. The limited space for robot manipulation restricts structure volume and motion. In this paper, an 8-degree-of-freedom robot system is proposed for ultrasound probe manipulation, needle positioning, and needle insertion. A novel parallel structure is employed in the robot system for space saving, structural rigidity, and collision avoidance. The particle swarm optimization method based on informative value is proposed for kinematic parameter identification to calibrate the parallel structure accurately. The method identifies parameters in the modified kinematic model stepwise according to parameter discernibility. Verification experiments prove that the robot system can realize motions needed in targeting. By applying the calibration method, a reasonable, reliable forward kinematic model is built, and the average errors can be limited to 0.963 and 1.846 mm for insertion point and target point, respectively.     

Compact maglev stage system for nanometer-scale positioning

Semiconductor manufacturing systems and ultra-precise machine tools now require nanometer-scale positioning accuracy. To improve positioning accuracy, it is efficient to support the top table with a noncontact guide system to prevent guide friction and heat transfer from the lower table or base. A magnetic levitation (maglev) stage can accomplish ultra-precise positioning accuracy with six-degrees-of-freedom (6DOF) control even in vacuum conditions. However, if the gravity of the levitated table is supported by the thrust of a linear motor, heat generation from the motor coil dramatically increases. In addition, a larger motor is required, which causes the moving mass to increase and the mechanical response to deteriorate. We aimed to develop a compact maglev stage for which the levitated mass is less than 1 kg and that is dramatically more lightweight than existing maglev stages. This compact feature was enabled by our newly proposed gravity compensation system with repellent force and a planar motor structure. The developed stage system also has long strokes, specifically 200 mm in the X and Y-directions on a horizontal plane. We designed a maglev stage with the following design concepts to create its compact structure: (1) Reduce top-table mass to minimize the motor dimensions and enable a light weight and high responsiveness. (2) Measure the top-table position from the base to eliminate positioning error and isolate vibrations of the coarse stage. (3) Install a motor in a symmetrical layout in view from the Z-axis to enable the same driving characteristics between the X and Y axes. The results of the performance evaluation showed that the developed maglev stage system with a compact structure with 0.81 kg levitated mass has ±10 nm positioning stability.     

The long-range scanning stage: a novel platform for scanned-probe microscopy

This paper describes a magnetically suspended six degree-of-freedom precision motion control stage with a horizontal positioning noise of less than 0.6 nm three sigma. The vertical positioning noise is less than 2.2 nm three sigma. The stage utilizes four levitation linear motors to suspend and servo the moving element (platen) throughout its 25 mm × 25 mm × 0.1 mm range of travel. Position feedback is provided by three plane mirror interferometers and three capacitance probes. The suspended platen (12 kg mass) is floated in oil to enhance the stage’s disturbance rejection and to reduce power dissipation in the actuators. The stage has been designed to achieve a positioning accuracy of 10 nm and is used to position samples beneath a scanned probe microscope. The ultimate purpose of this measuring machine is to provide a means of measuring submicron-scale features with nanometer-scale accuracy. The technology can easily be scaled to larger travels, with accuracy limited primarily by the wavelength instability of the HeNe light source. This article gives an overview of the LORS project, emphasizing the system error terms, tolerancing, and experimental results.     

在机测量线激光传感器安装位姿的全局标定

针对三轴数控机床激光测头安装位姿误差造成测量误差且不易调整和校准的问题,提出了一种在机测量线激光传感器安装位姿标定方法。建立了线激光在机测量系统的数学模型,通过机床运动带动线激光测头对标定基准点的空间位置进行测量,基于手眼标定原理给出了关于测头安装位姿参数的线性求解算法,完成了对测头安装误差的全局标定。考虑了机床定位误差对于标定结果精度的影响,采用蒙特卡洛模拟进行了误差分析。采用半径为35 mm的圆孔进行测量验证,实验结果表明,标定后圆孔测量误差为0.051 6 mm,测量精度提高了约96%,实验结果验证了该标定方法的有效性和可行性。     

基于无线传感器网络自校正定位算法

节点定位是无线传感器网络的重要应用之一,为了抑制实际应用中各种环境因素对无线传感器节点精度的影响,提出了一种基于误差校正的定位算法。通过基于粒子群优化算法的粒子群优化-接收信号强度指示算法(par-ticle swarm optimization-received signal strength indication,简称PSO-RSSI算法)将未知节点收到信标节点一定数量的存在偏差的链路质量指示值进行优化,实现对误差的补偿。将链路质量指示值转化为接收信号强度指示值,从而得到距离。实验结果表明,该算法可提高定位精度,具有普遍应用价值。     

工业坐标测量机器人定位误差补偿技术

由通用工业机器人和视觉传感器组成的柔性坐标测量系统是视觉检测技术在工业在线测量领域的重要应用。工业机器人的机械结构和控制过程复杂,因此其定位误差成为影响系统测量精度的最主要因素,但可以通过修正连杆参数的方式加以补偿。以MD-H运动学模型为基础,建立机器人工具中心点(Tool center point,TCP)的基于相对定位精度的定位误差补偿模型,避免坐标在不同坐标系转换过程中产生精度损失。对与机器人测量姿态有关的柔度误差进行针对性补偿,通过建立柔性关节的弹性扭簧模型,将柔度误差分解为外加负载柔度误差和机械臂自重柔度误差分别进行补偿。标定过程中使用激光跟踪仪作为外部高精度测量设备,只需在单点测量模式下就能实现对TCP的三维坐标采集,大大简化数据采集过程。经过补偿后,标定点处的方均根误差由之前的1.230 2 mm降至0.428 8 mm,验证点处的则由0.723 6 mm降至0.505 4 mm。     

Study on compound ultra-precision alignment technique

A nano-displacement measurement system with duo-gratings is analyzed by using optics theory,a mathematic model for the system is established,and the characteristic of laser Moirésignals is studied through CAD simulation.To improve signal sensitivity and positioning accuracy,two methods of precision positioning are brought forward：differential Moirépositioning method and modified Moirépositioning method.A compound control system for precision positioning is set up by combining these 2 Moiréalignment methods,in which the modified Moiréalignment technique is used for coarse alignment and the differential Moiréalignment technique is used for fine alignment,and the system obtains positioning accuracy of±10 nm in±500μm positioning range with shot response time.     

一种用于引线键合视觉定位的图像质量评估方法

引线键合机视觉定位的精度受到采集图像质量的影响,当采集图片的质量较差时,会导致定位精度发生较大的缺失。为了解决这个问题,将基于生成对抗网络的图片质量评估方案引入到引线键合机视觉系统中,作为引线键合机的“第三方监督者”对视觉系统采集到的图片质量进行实时监督,保证采集到的图片质量符合视觉定位需求,进而保障生产过程中引线键合的视觉定位精度。     

Performance Comparison of Algorithms for Estimating the Strain of Soft Tissue from Ultrasound

Abstract

A specially designed device is used to link ultrasound and force transducers by mounting them in series. The combined transducers can simultaneously sense the deformation and compression force in the soft tissue. In this system, the method for obtaining the exact strain of the soft tissue during compression is very important. In this paper, six different algorithms to estimate the strain of the tissue are compared: Normalized Correlation (NC), Direct Correlation (DC), Sum Absolute Differences (SAD), Sum Squared Differences (SSD), Hybrid‐sign Correlation (HC), and Maximum algorithm. In order to evaluate the results of the six algorithms, a calibration system is setup in which the grating transducer and ultrasound sensor are connected in series. The strain of the soft tissue analyzed by six methods is compared. The results show that the estimating accuracy of tissue strain by the NC, DC, and SSD algorithms are completely the same, and there is no distinct difference in estimating accuracy between the SAD and NC (or DC and SSD) algorithms (α=0.05). The standard deviation and maximal deviation of the delay time obtained by the HC and Maximum algorithms is unstable, and the delay time estimated by these two algorithms also shows false peaks. The time to run the SAD algorithm is more than the time to run the DC and SSD algorithms (α=0.05), while there is no distinct difference in the time to run the DC and SSD algorithms. For systems with limited hardware resources, the DC and SSD algorithms are suitable.     

基于ZigBee技术的患者定位系统的研究与实现

从分析信号强度作为场景特征统计的数据所表现数据特征入手,进行Zigbee信号测距的可行性分析。结合系统要求选择指纹法定位方案,优化了测距方程。提出一种参考节点组网布局方案,确定最优参考点间距,大大消除了环境因数的影响提高位置指纹的匹配效率和准确度,进而大幅提高定位精度。     

数控车床回转刀架结构与转位精度

本文主要介绍了两种回转刀架(中国大连机床厂和意大利巴鲁法迪公司)的结构构成、性能、工作原理及它们在工作中所需转角和时间等方面的比较。进一步分析了其有关转位精度的粗定位精度与回转分度的转动惯量的克服。为今后设计或选用数控回转刀架提供借鉴。     

Bearing diagnosis using proximity probe and accelerometer

Employing multiple sensors that generate different physical parameters from the measured system to monitor its health increases the diagnosis reliability. In the present work, bearing diagnosis capabilities of proximity probes are explored by exploiting its advantages and alleviating its shortcomings using appropriate signal processing of the raw time domain data. A Time Synchronous Averaging based method is proposed for processing of the data acquired by proximity probes and its benefit is illustrated on test bearings. Simultaneous synchronous data is acquired with the help of proximity probes and accelerometer during a life test as the defect is naturally induced and progressed with time. The proximity probe is shown to perform better diagnosis for inner race defect compared to accelerometer due to a direct transmission path for this defect. The use of proximity probe can effectively supplement the information from accelerometer and improve the accuracy of bearing diagnosis.     

基于iGPS的煤巷狭长空间中掘进机绝对定位精度研究

为解决目前掘进机定位方法中存在的非坐标化测量、自动化程度低、易被障碍物遮挡等问题,提出一种基于室内定位系统的掘进机定位方法。该方法将激光接收器安装在掘进机机身固定位置处,通过测量激光接收器在发射站坐标系下的三维坐标,实现对掘进机的绝对定位。基于随机误差建模理论推导双发射站坐标测量的误差传导公式;针对目前室内定位系统绝对测量精度检测方法在狭长空间应用中的局限性,结合测量精度理论分析结果,提出一种适用于狭长空间的绝对测量精度检测方法。实验数据表明,双发射站测量系统在1.2m间距下,发射站与掘进机相距17m时Y轴定位精度优于10cm,X、Z轴定位精度优于2cm。