基于梯形算子的AFM驱动器非对称迟滞性校正

原子力显微镜(AFM)通常采用压电陶瓷(PZT)作为驱动器以实现纳米尺度的观测和操作。然而,PZT自身的迟滞非线性会对AFM观测质量和操作精度产生很大影响。基于Prandtl-Ishlinskii(PI)模型的前馈控制方法可对PZT的迟滞非线性进行补偿,但传统PI模型无法消除PZT的非对称迟滞性的影响。针对这个问题,提出一种基于梯形算子的非对称迟滞模型,并可用系统辨识方法获取逆模型参数,该方法可有效实现具有非对称迟滞特性驱动器的前馈补偿控制。AFM系统实验证明,该模型可有效减小非对称迟滞性导致的建模误差,基于该模型的前馈迟滞补偿控制可有效提高AFM的扫描成像质量。     

称重传感器误差标定装置托盘提升装置设计

基于CATIA虚拟样机技术对称重传感器误差标定装置进行参数化建模设计和虚拟装配。考虑到装置主要承力部件如果刚度、强度、挠度达不到使用要求,易发生弯曲变形甚至疲劳断裂等现象。因此有必要运用有限元分析软件ANSYS对装置主要承力部件进行强度刚度校合。其分析结果表明:托盘的提升装置设计合理,没有发生干涉现象;机构刚度好,所承受荷载大,提升运动过程平稳。分析结论为称重传感器误差标定装置在设计和选用过程中提供了理论依据,具有指导作用。     

无标样聚甲氧基二甲醚校正因子的测定

聚甲氧基二甲醚是一种理想的新型柴油添加剂。针对聚甲氧基二甲醚组分缺少标样的问题,研究采用气相色谱技术,依据质量守恒原理测定并计算了不同聚合度聚甲氧基二甲醚组分的质量校正因子,以实现各组分含量的准确定量分析。根据反应过程的CH2O守恒及混合过程的质量守恒,对质量校正因子的准确性进行了验证,应用该校正因子计算所得到的质量相对误差小于4%。用此方法测定的校正因子准确度高于有效碳数估算法所得校正因子。该测定方法操作简单,可满足企业生产及实验室研究中聚甲氧基二甲醚产物的定量分析要求。     

基于自动力觉传感器力控策略的遥控焊接虚拟环境标定

利用T形管试件,采用自动力觉传感器力控策略的遥控焊接虚拟环境标定法来降低试件虚拟环境标定的误差。该方法主要通过自动力觉传感器直角系切面轮廓线的力控策略和轨迹跟踪最小二乘拟合算法、试件标定算法,实现对试件表面接触点空间坐标的精确定位和试件的虚拟环境标定。实验证明,该方法可以大大提高虚拟环境标定的精度,满足大多数遥控焊接接触的要求。     

A novel approach of accurately evaluating residual stress and microstructure of welded electrical steels

In the present research work the determination of residual stress distribution in welded non-oriented electrical steel samples is discussed. Tungsten inert gas was used for the welding method. Residual stress was directly determined through deformation measurements and appropriate math calculations. Two methods were used: the magnetic, non-destructive method of Barkhausen noise and the semi-destructive method of X-ray diffraction. In order to evaluate the accuracy and reliability of the magnetic method applied, the steel samples were subjected to both compressive and tensile stresses and the magnetic noise values were correlated to residual stress values through an appropriate calibration curve. The results were then verified by the XRD method and were further evaluated by examining the microstructure and the mechanical properties of the as received and welded samples through scanning electron microscopy and hardness measurements, respectively. It was found that the deviation between the two methods was within acceptable limits, thus implying potential applicability of the MBN method in non-destructive testing of materials.     

变压器供电系统电动机启动电压降计算

简介与变压器供电系统电机启动电压计算有关的参数和概念;运用"功率法"和"阻抗法"对工程案例进行计算;对工程设计中常遇到的问题进行讨论。     

电流互感器的选择及应用(Ⅲ)

文章对电流互感器的作用、构造、原理及技术性能进行介绍,并对它的选择及应用进行了详细描述。     

Separation of isotope C using high-performance structured packing

A special high-performance structured packing, PACK-¹³C, with the surface area high as 1135 m² m⁻³ was developed, and the first stable isotope ¹³C pilot-scale plant using structured packing was designed and constructed by carbon monoxide cryogenic distillation, which has run smoothly over 6 months. The height and inner diameter of the distillation column were respectively, 20 m and 45 mm and the height of packing bed was 18 m. The column was well insulated by vacuum multilayer insulation and the total heat leakage of the column was less than 30 W. When the F-factor changes from 0.18 to 0.90 ms⁻¹ (kg m⁻³)^1/2, the numbers of theoretical plates per meter decreases from 30 to 20, the pressure drop is less than 25 Pa for each theoretical plate, the dynamic liquid holdup is between 11% and 21%, and the pilot-scale plant produces 2.1 g 15% isotope ¹³C each day. The fluid mechanical and mass transfer empirical equations were developed according to the experimental data of PACK-¹³C. The PACK-¹³C structured packing exhibits very high performances in isotope separation efficiency and operational flexibility, which is far superior to the traditional random packing. PACK-¹³C is a perfect packing to serve in ¹³C separation to increase productivity and reduce consumption.     

一种新的差压式流量计标定方法

针对目前差压式流量计标定方法计算公式复杂,实流测量误差较大,为提高精度仍需实测校验的问题,经过对标定方法的研究,提出了广义流出系数的概念,根据流量和差压开方的比例关系,提出的新方法标定时无需经过流量公式计算,仅需一次实流校验即可标定流量计。该方法标定精度比传统法高出3~5倍,简化了标定方法,提高了测量精度。