Thin thickness measurements by means of a wavelet transform-based method

A non-invasive method for thin thickness measurements of multilayer structures is presented herein. This measurement method uses the wavelet transform for the analysis and processing of the ultrasonic signal received from the structure under test. The wavelet transform also shows itself to be a powerful tool for the detection of partially overlapping echoes in a noisy environment. This paper first describes the basic idea underlying the measurement method and then a procedure, set up by the authors, and suitable for the validation of the method when a standard multilayer structure to be used as a reference is not available, is presented and discussed. Finally, measurements of the thicknesses of actual multilayer structures and, in particular, of structures in the ophthalmic and microelectronic technology field, are carried out.     

On the accuracy of high impulse voltage measurements

Measurements and tests on solid dielectrics with lightning or switching impulses have received considerable attention because they are concerned in the optimal design of internal insulation for high voltage apparatus. Accuracy of measurements relating to the above phenomena is generally deemed very important. In this paper a model is proposed and an investigation is attempted regarding the accuracy of such measurements. The results are confirmed through laboratory measurements. According to the results presented, the value of the grounding resistance is a crucial parameter that affects measurement accuracy; it must never exceed the value of 0.5 Ω.     

Heat capacity measurements by means of thermal relaxation method in medium temperature range

The thermal relaxation method is used to measure heat capacities of small samples in the temperature range around room temperature. The calorimeter is designed to measure under heat exchange gas and a steplike excess heat is applied to the sample by irradiation from a lamp.     

A microinterferometric method for analysis of rotation-symmetric refractive-index gradients in intact objects

A new method for measuring refractive-index gradients in rotation-symmetric objects is described. Interference micrographs of intact objects, with the symmetry axis perpendicular to the optical axis of the microscope, are used to obtain a phase-shift profile, which is converted into a refractive-index profile by a computer program. The conversion calculations are based on iterative approximations of the gradient slope in a number of presumed shells in the object. The method is fast, convenient and yields highly accurate results even when only a small number of phase shift values can be obtained. The new method is especially advantageous for analysing many invertebrate eyes but it can also be used for measuring manufactured graded-index optical fibres.     

Increasing of accuracy of angular measurements by using hybrid photoelectric converters

The basis sources and methods of reducing the errors of incremental photoelectric digital converters for angular measurements are analyzed. A method of constructing hybrid photoelectric converters that increase the accuracy of angular measurements is proposed. The result is achieved by simultaneous measurements of the turning angle and current radial deflections of the converter shaft axis.     

Wear estimation of turbine blades by means of X-ray thickness measurements

A method for estimating the wear of blade edges by means of X-ray thickness measurements is suggested.     

Enhancing positioning accuracy of CNC machine tools by means of direct measurement of deformation

The positioning accuracy of computer numerical control (CNC) machine tools is mainly limited by the manufacturing accuracy of their linear and circular motion axes and by the long-term dimensional stability of their structures. Maximizing this accuracy can prove to be a particularly challenging task, especially for large-sized systems. In fact, heat-induced deformations, long-period deformation of foundations and the manufacturing process itself, these all cause time-dependent structural deformations of the machine body, which are difficult to model and to predict. The usual approach is a model-based prediction of structural deformations, which is followed by a compensation of positioning errors at CNC level. This approach is often limited by the complexity of the problem from both geometrical (system geometry can be very complex and it can vary in time) and physical (it is difficult to model and consider any possible load type and loading condition) point of view. As a consequence, only limited success has been achieved in active error compensation based on the modelling of the relationship between the generalized dynamic loads and the structural deformation field. This paper illustrates a different approach in active error compensation, which exploits a new measurement system able to provide real-time measurement of the displacement field of a given structural component, without any model about its dynamic/thermal structural behavior.     

Vortex flowmeter with enhanced accuracy and reliability by means of sensor fusion and self-validation

Due to the complementary qualities of the principles of vortex frequency estimation and vortex time of flight estimation they are ideally suited for an effective sensor fusion within flow measurement. A flow meter which combines the results of the two individual systems in an intelligent manner was built and beside theoretical considerations the performance of the fused system is demonstrated by a variety of measurements. In comparison with conventional vortex meters which only use the vortex frequency to estimate the flow rate, the measuring range can be extended by a factor of 8–10 and the accuracy of the system as well as the robustness to disturbances like a second fluid phase or depositions on the bluff body are strongly increased.     

用划线方法确定曲轴的回转中心

曲轴毛坯锻造过程中由于压机异常、模具异常等因素影响造成曲轴毛坯成型偏离设计成型状态;曲轴锻造需要加热、曲轴热处理(调质)也需要加热,在加热过程再到冷却过程有应力的释放,当应力释放时曲柄销开档有不同程度的张开,由于应力分布不是均匀的所以各曲柄销的张开程度也不同造成曲轴弯曲;如不重新确定曲轴的回转中心,在后期加工过程中很容易使产品不合格,甚至可能会造成曲轴报废;为避免企业造成重大经济损失,划线确定曲轴的回转中心是必要的。     

On the dimensional accuracy of deep drawing products by hydroforming processes

In the hydroforming process the punch deforms the blank to its final shape by moving against a controllable fluid-pressure in a pre-determined path. The present work exhibits the fact that the final geometry of the product (mainly the wall thickness variations) depends on the overall history by which the fluid pressure-path is operated during the drawing process. In addition, other phenomena akin to hydroforming processes have been observed, e.g. the shift in the location of the rupture site (if it occurs) from near the bottom of the product to near its lip and the (slight) variation in the final length of the product. In order to explain these occurrences a detailed numerical stress analysis is offered, featured by an ad-hoc “finite difference” scheme. It differs from previous solutions by admitting changes in the thickness of the blank and still accounting for the blank/tool interfacial friction and the out-of-plane curvature of the product. The material behavior of the blank includes exponential strain hardening, normal anisotropy and initial strain. The experiments shown here were carried out on aluminum sheets with a specially built hydroforming machine.     

Spatiotemporal temperature fluctuation measurements by means of a fast swept Langmuir probe array

Stationary Langmuir probe measurements of ion saturation current and floating potential in a plasma cannot give direct information on density and plasma potential fluctuations in the presence of temperature fluctuations. This problem can be avoided if the probe bias voltage is continuously swept faster than the fluctuation time scale, recording the current-voltage characteristic. This article reports the development of a spatiotemporal highly resolving Langmuir probe array with 15 fast swept tips, operating in the strongly magnetized, collisionless edge plasma of the Wendelstein 7-AS stellarator [Plasma Phys. Controlled Fusion 31, 1579 (1989)]. The probe tips are aligned in the poloidal direction, the tip spacing is 2 mm, and the sweeping frequency is 1.4 MHz. Current and voltage data are sampled with 50 MHz. The high bandwidth of the measurement is achieved by placing miniaturized differential amplifiers close to the probe tips in order to do an impedance transform. The surface-mounting technology and an additional inverse feedback module are utilized, allowing for an input voltage range of +/-100 V, and a common mode rejection rate of 55 dB at 4 MHz, which is sufficient to resolve the nonlinear probe characteristic. For the evaluation of the data, a fit model for stationary probes is employed and found adequate. Changes of the plasma parameters during one voltage sweep are taken into account by a linear interpolation of the fit parameters. Spatio-temporal fluctuation data gained by a fast swept Langmuir probe array, which can be relevant for the turbulent radial transport of particles and energy, are presented.     

利用AutoLISP提高绘图效率的方法

在AutoCAD中,给出了常用基本图形(如矩形、多边形、圆等)的绘制命令,利用它们可快速而方便地完成绘图。但是在我们的实际工作中,所要绘制的图形是千变万化的,不同的行业具有不同的基本几何图形,为此,可利用AutoLISP为这些图形编制程序,以提高绘图效率。这里通过几个简单的例子,说明了该方法。     

利用AutoCAD快速确定装备质心位置的方法

论述了利用AutoCAD Inquiry工具条中的有关命令快速计算装备质心的方法,举例说明了整个计算过程,并阐述了在计算质心时应注意的问题。     

Improving disturbance rejection of PI controllers by means of the magnitude optimum method

The magnitude optimum (MO) method provides a relatively fast and nonoscillatory closed-loop tracking response for a large class of process models frequently encountered in the process and chemical industries. However, the deficiency of the method is poor disturbance rejection when controlling low-order processes. In this paper, the MO criterion is modified in order to optimize disturbance rejection performance, while the tracking performance has been improved by an integral set-point filtering PI controller structure. The new tuning rules, referred to as the disturbance rejection magnitude optimum (DRMO) method, were applied to several different two-degrees-of-freedom PI controllers. The DRMO method has also been tested on several different representatives of process models. The results of experiments have shown that the proposed tuning method with the integral set-point filtering PI controller is quite efficient in improving disturbance rejection performance, while retaining tracking performance comparable to the original MO method.     

Improving disturbance rejection of PID controllers by means of the magnitude optimum method

The magnitude optimum (MO) method provides a relatively fast and non-oscillatory closed-loop tracking response for a large class of process models frequently encountered in the process and chemical industries. However, the deficiency of the method is poor disturbance rejection performance of some processes. In this paper, disturbance rejection performance of the PID controller is improved by applying the“disturbance rejection magnitude optimum” (DRMO) optimisation method, while the tracking performance has been improved by a set-point weighting and set-point filtering PID controller structure. The DRMO tuning method requires numerical optimisation for the calculation of PID controller parameters. The method was applied to two different 2-degrees-of-freedom PID controllers and has been tested on several different representatives of process models and one laboratory set-up. A comparison with some other tuning methods has shown that the proposed tuning method, with a set-point filtering PID controller, is quite efficient in improving disturbance rejection performance, while retaining tracking performance comparable with the original MO method.     

利用过零式固态继电器实现功率调整的方法

提出了一种基于微处理器和利用固态继电器实现交流功率连续调整的方法.文中给出了具体的硬件控制电路、软件算法及详尽的程序清单.该方法已成功的应用于蒸汽锅炉加热功率控制.     

保证夹具装配精度的加工方法

在生产制造过程中,各种类型夹具制造的难点主要反映在如何保证装配精度上。笔者根据多年的生产实践,总结出了一些常见类型夹具的加工工艺方法,这些方法能有效地解决夹具在生产实际中遇到的困难,从而保证夹具的装配精度:具有较高的实用价值。     

Experimental study on the sensitivity and accuracy of electric potential local flow measurements

A measuring system based on potential difference probes is presented which makes possible the determination of very small values of the velocity in liquid metal flows. The resolution limit, the size of the sensor, and the induction of the static measuring field have always been a compromise. These opposite demands were countered with state of the art analog instrumentation, and by meticulously avoiding potential sources of error such as induced noise and thermoelectricity. The present paper instances the flow driven by a rotating magnetic field, in which the scaling of velocity versus strength of the driving electromagnetic force was examined. Measurements of the transition from a Stokes regime to a laminar boundary layer regime demonstrate the improvement in velocity resolution by about two orders of magnitude.     

冷却床模型的有限元建模技术

介绍了冷却床模型的有限元建模技术。对所建立的有限元模型 ,用 SAP5计算了前五阶固有频率 ,与实验对照表明 ,有限元建模是正确的