A novel sensorless control method for brushless DC motor

The authors present the theory and implementation of a novel sensorless control method for the interior permanent magnet (IPM) brushless DC motor (BLDCM). The proposed new sensorless technique can accurately detect the zero-cross point (ZCP) of back electromotive force (BEMF), which is based on a comparison of the terminal voltage of the un conducting phase during the first and second part of a pulse width modulation (PWM) cycle. Compared with the conventional BEMF sensorless approach, the proposed new sensorless method solves the problem of the sensorless BLDCM drives at very low speeds. Experimental results confirm the validity of the new method.     

Sensored and sensorless speed control methods for brushless doubly fed reluctance motors

The study considers aspects of scalar V/f control, vector control and direct torque (and flux) control (DTC) of the brushless doubly fed reluctance machine (BDFRM) as a promising cost-effective alternative to the existing technological solutions for applications with restricted variable speed capability such as large pumps and wind turbine generators. Apart from providing a comprehensive literature review and analysis of these control methods, the development and results of experimental verification, of an angular velocity observerbased DTC scheme for sensorless speed control of the BDFRM which, unlike most of the other DTC-concept applications, can perform well down to zero supply frequency of the inverter-fed winding, have also been presented in the study     

A new measuring method to detect the emissions of metal working fluid mist

During metal machining the rotating machine tool or grinding wheel is generating fine droplets and vapor which can cause occupational health problems. A new continuous measuring method was developed to detect both droplets and vapor of metalworking fluid mist and to provide information about the droplet size distribution. According to this method, an air sample of the metalworking fluid mist is segregated by impactors of different cut sizes, carried out in several successive passes. In each pass the droplets that are not collected in the impactor are fed into an evaporator that immediately evaporates all droplets, and subsequently the sample is analyzed in-line by a Flame Ionization Detector (FID). By subtraction of the value measured at the respectively next smaller fraction, the oil amount of the metalworking fluid mist found in a certain droplet size range is obtained. The metalworking fluid mist is thus segregated according to the droplet size, and a definite cut size between droplet and vapor can be defined, below which we can say "vapor". This method was calibrated with Di-2-Ethylhexyl-Sebacat (DEHS) as equivalence substance for further measurements applied on various metalworking fluids.     

Initial rotor position estimation and sensorless direct torque control of surface-mounted permanent magnet synchronous motors considering saturation saliency

For a practical direct torque-controlled (DTC) permanent magnet synchronous motor (PMSM) drive system, the information of the initial rotor position, which is usually obtained by a mechanical position sensor, is essential for starting under the full load. To avoid the disadvantages of using mechanical position sensors, great efforts have been made on the development of sensorless control schemes. An initial rotor position estimation strategy is presented for a DTC PMSM drive based on a nonlinear model of PMSM incorporating both structural and saturation saliencies. In the new scheme, specially designed high-voltage pulses are applied to amplify the saturation saliencies. The peak currents corresponding to the voltage pulses are used, in combination with the inductance patterns, to determine the d-axis position and the polarity of the rotor. The presented initial rotor position identification strategy has been implemented in a sensorless DTC drive for a surface-mounted PMSM. Experiments are conducted to confirm the effectiveness of the method and the performance of the drive system.     

基于参数辨识的永磁同步电机自校正速度控制方法

针对永磁同步电机伺服系统的机械参数经常发生变化的情况,提出了一种通过辨识转动惯量和摩擦系数实现速度控制器系数自校正的方法.辨识转动惯量和摩擦系数采用的是根据波波夫超稳定理论设计的一种转动惯量和摩擦系数的模型参考辨识算法.辨识中引入了负载转矩观测器的观测值,使辨识算法不需要附加条件.参数辨识的结果用于速度控制器的校正.通过实验分析了速度环采用比例积分(PI)控制器时控制器的系数不等于理论计算值的问题,得出了一种简单的控制器系数自校正规律--比例系数和转动惯量成正比,且积分系数和摩擦系数也成正比.这种方法能够根据机械参数的变化校正控制器,提高速度控制的性能.仿真结果证明了参数辨识方法和控制器系数校正规律的有效性.     

一种滤除衰减简谐振动信号中奇异点的新方法

提出了将带有奇异点的衰减简谐振动信号成分转换成简谐信号 ,再用畸点衰减法滤除奇异点的新思想。在分析衰减简谐振动信号与简谐信号幅值特性的基础上 ,发展了通过在衰减简谐振动信号中乘以逆衰减因子 ,将衰减简谐振动信号成分变换成简谐信号的新方法。对仿真和实测信号的应用研究表明 ,所提新方法切实可行且精度较高 ,能满足工程实际需要。     

随焊旋转冲击控制焊接变形新方法

提出了旋转冲击控制应力变形的新方法,并研制了一套旋转冲击装置.工作时通过电锤带动装配在其上的压杆施加旋转冲击作用于焊缝及焊趾部位,使其延展产生拉伸塑性应变来抵消焊接过程产生的残余压缩塑性应变,从而有效的控制了工件的焊接变形.应用所研制的装置,对2A12T4铝合金进行控制焊接变形的试验,发现旋转冲击可以起到减小焊后工件中残余变形、细化焊缝晶粒、提高强度的作用.     

微透镜列阵浮雕深度控制的新方法

在对材料光刻阈值特性进行研究的基础上,提出了一种可有效克服材料非线性特性影响,提高微透镜浮雕深度的新方法——基底曝光法。在曝光之前,对抗蚀剂整体施加一定量的曝光,提升抗蚀剂刻蚀基面。该方法可制作出面形均方根误差小于3%的微透镜阵列。     

A new method of accurate polarization measurement on isobaric analog resonance to detect parity non-conservation effect

For the study of parity mixing in the compound states, a method to measure the longitudinal analyzing power A_z of the isobaric analog resonance (IAR) as a function of energy in the proton elastic scattering is discussed. A thick target is used and energy loss of the protons in the target is utilized to measure the energy dependence. The energy resolution is presented and the sources of the systematic errors in A_z are discussed together with the way of their elimination. The method has been shown to be quite efficient for deriving both the transverse and the longitudinal analyzing powers. The measurement of A_z for the s-wave IAR at E_cm=5.86 MeV in ⁹⁰Zr(p,p) and the analysis to derive PNC matrix elements are described.     

储纬器电机无位置传感器的全速域控制方法研究

针对储纬器电机无位置传感器的调速控制问题,采用脉振高频注入法与扩展反电动势法相结合的控制策略,研究了一种全速域下的无位置传感器矢量控制方法。在电机静止时,利用电机凸极特性,采用高频注入法配合极性判断准确估计初始位置并使电机速度闭环启动。当运行至中速时,估计算法切换为扩展反电动势法估计转子位置与速度。在加减速过程速度切换区间采用滞环切换策略。通过实验验证了所提出的控制策略在全速域下电机矢量控制的可行性,且满足储纬器电机配合织机的工作要求。     

A new method to detect gamma ray extensive air showers which directly measures angles and identifies muons

We describe an extensive air shower array (GRAND™) ⁷ which is currently under construction. It is dedicated to recording ultrahigh energy (UHE) gamma rays from stellar point sources by measuring the angle of charged secondaries with proportional wire chamber tracking detectors. This new method is designed to give 0.25° angular resolution for the primary gamma direction with 100 detected secondary electrons. These same tracking detectors make possible a new, inexpensive detector for muons thereby enabling the rejection of muon-rich hadronic shower background.     

A new approach to detect and size closed cracks by ultrasonics

The effect of a crack on time-of-flight of shear waves (4.5 MHz) polarized in perpendicular (t ) and parallel (t ) directions to the crack surface, propagating parallel to the direction of crack growth is investigated. The first and second back-wall echoes are used instead of the weak crack-tip echo for the measurement of time-of-flight. The measurement is made for fatigue cracks grown by different loading histories in ferritic steel (pressure vessel steel A533B-1) under the condition of no loading. The normalized time-of-flight (t –t )/t at the crack position is found to change proportionally as the ratio of crack depth to specimen width increases. The change is mainly due to the effect of plastic deformation occurring around the crack ont . It is shown that the depth of tightly closed fatigue crack in austenitic stainless steel (AISI 304) also can be evaluated under the condition of no loading by using this relationship.     

Update-based evolution control: A new fitness approximation method for evolutionary algorithms

Evolutionary algorithms are robust optimization methods that have been used in many engineering applications. However, real-world fitness evaluations can be computationally expensive, so it may be necessary to estimate the fitness with an approximate model. This article reviews design and analysis of computer experiments (DACE) as an approximation method that combines a global polynomial with a local Gaussian model to estimate continuous fitness functions. The article incorporates DACE in various evolutionary algorithms, to test unconstrained and constrained benchmarks, both with and without fitness function evaluation noise. The article also introduces a new evolution control strategy called update-based control that estimates the fitness of certain individuals of each generation based on the exact fitness values of other individuals during that same generation. The results show that update-based evolution control outperforms other strategies on noise-free, noisy, constrained and unconstrained benchmarks. The results also show that update-based evolution control can compensate for fitness evaluation noise.     

一种基于Chord的完全分布式克隆TPM检测方案

针对直接匿名验证(DAA)协议中使用可变名字基时检测克隆可信平台模块(TPM)存在的困难,在保持TPM高匿名度的前提下,提出了一种基于Chord的完全分布式克隆TPM检测方案.将访问服务的TPM映射到Chord覆盖层中,在不依赖可信第三方(TTP)参与的情况下实现了对克隆TPM的有效检测.以服从泊松分布的TPM访问规律和服从负指数分布的服务时间为模型,对该方案和已有方案的性能进行了分析与仿真,结果表明该方案具有高检测率和零虚警率等特性.该检测方案思想可以在不增加额外开销的情况下部署到基于分布式哈希表(DHT)的完全分布式系统中.     

A digital method for the determination of the magneticcharacteristic of variable reluctance motors

A digital method is proposed for the measurement of the magnetic flux, starting from the digital integration of the induced electromotive force (EMF). The method features sensitivity and accuracy greater than, or at least as high as, that of other methods, and is applied to the determination of the flux-linkage-versus-current diagrams of a variable-reluctance (VR) motor. Two different methods are proposed to determine flux variations in the motor magnetic circuit, and the results of the experimental work carried out on a typical 4-kW switched reluctance (SR) motor, show that the methods are in good agreement. The methods allow quicker and more accurate determination of the flux-linkage characteristics than other proposed methods, and allow the measurement of flux-linkage values for any value of the excitation current and of the rotor position. For this reason, the methods are useful for the determination of flux-linkage characteristics to be used in the analytical prediction of VR motor performance     

A new method for quality control of zinc pyritione pharmaceutical and cosmetic forms

A simple high-performance liquid chromatographic (HPLC) method was developed to determine zinc pyritione in pharmaceutical and cosmetic products. Reversed-phase chromatography was conducted using a C₁₈ column with an isocratic mobile phase consisting of a suitable mixture of methanol, acetonitrile, and water (30:2.5:20). The effluent was monitored on a ultraviolet (UV) detector at 243 nm. The method was validated following International Conference on Harmonisation (ICH) suggestions and proved accurate, precise, and specific.     

A hybrid method of analysis of low-speed linear induction motors

A current-excited low-speed solid-iron secondary single-sided linear induction motor (SLIM) with aluminum reaction rail is considered, A hybrid method of analysis consisting of field analysis in conjunction with the multilayer transfer-matrix concept with adjustment of secondary iron permeability to match the tangential magnetizing field in each layer is developed. It is shown that this method gives valuable information on permeability and flux penetration in secondary iron. Computed thrusts are in good agreement with test results.     

一种精确的医学细胞图像边缘检测法

细胞边缘检测是进行细胞形态分析的基础,其检测结果直接影响病情分析和诊断的结果。传统的边缘检测算子由于受噪声影响比较大,无法检测细胞可靠的边缘位置,因而不宜应用于细胞形态分析。提出一种用迭代算法求图像分割最佳阈值和运用数学形态学的腐蚀算法实现轮廓提取相结合的细胞图像边缘精确检测算法,并给出仿真实例。与传统的边缘检测算子Laplacian-Gauss算子、Sobel算子相比较,该算法具有检测精度高和抗干扰能力强的优点。