A microcontroller-based variable voltage variable frequency sinusoidal power source with a novel PWM generation strategy

The present paper describes the development of a low cost, microcontroller-based variable voltage variable frequency sinusoidal power source, which is the demand of the day for various applications. The power source is developed using MOSFET H-bridge inverter and with a stand alone LCD display system. The design methodology proposes to utilize a novel concept of generating sinusoidal pulse width modulation signals for the driver circuit of the inverter. The system proposes to incorporate a ROM-based LUT within the power source itself for the sinusoidal signal generation with enhanced stability. This low cost, yet accurate power source has been successfully developed for wide range of voltage commands (30-80 V rms) and frequency commands (40-70 Hz), and their real-life performances in voltage wave generation were also found to be quite satisfactory.     

Efficient estimation of generator instability characteristics in the time domain

This paper considers the problem of determining the true (nonsampling) variance of the Allan parameter-the main frequency instability characteristic of frequency generators, synthesizer, and standards in the time domain. The variables influencing the efficiency of estimating the parameter are determined and compared in magnitude. For frequency fluctuations with flicker noise power-law power spectral density, the parameter estimate accuracy is most significantly affected by the variance of the estimated average frequency—the quantity included in the Allan parameter and defining the quality of averaging over a finite time interval.     

A megavolt frequency generator pulses with an FWHM duration of 30 ns

A generator of a pulse voltage with an amplitude of up to 1 MV based on a ten-stage voltage multiplier is described. The generator contains a control panel, a unit for periodical triggering of spark gaps in the generator stages, and a rectifier outputting a voltage of ± 50 kV for charging capacitors in stages. The generator has an output discharge capacitance of 500 pF, a stored energy of 250 J, a self-inductance of <0.7 μH, a guaranteed service life of 10⁵ charging-discharging cycles, a rise time of the first voltage half-wave of 15 ns at a load of 200 pF, and a repetition rate of 1 Hz. To reduce the self-inductance of the source, insulating housings of capacitors and spark gaps are used in its layout.     

可调频旋磁激励式压电发电机的设计与试验

为提高旋转式压电发电机的安全性与有效带宽,提出一种可调频旋磁激励式压电发电机,并从理论、仿真与试验三个方面对发电机的工作特性进行了研究。建立了压电梁在端部外载荷作用下的刚度/频率偏移模型,并通过仿真获得了刚度、动磁铁数量对发电机响应特性的影响规律。结果表明,压电梁刚度随端部拉/压力的增大而线性增大/减小,固有频率相应地提高且趋于平缓/降低且速率增大,而动磁铁数量将影响发电机的谐振峰数量与放大比。在此基础上进行了相关试验,试验表明,压电梁受拉伸/压缩都将提高发电机的固有频率并降低输出电压幅值,且受压时减幅更大;此外,动磁铁数量除仿真中影响因素外对发电机的固有频率也具有一定影响;通过改变动磁铁数量与调节量,实现了发电机固有频率在39.2～112Hz内的调整,最大频率偏移为185.7%。     

A pulsed generator of X-ray bremsstrahlung with a high peak exposure rate

A new pulsed generator of X-ray bremsstrahlung based on an inductive energy storage and a plasma opening switch is described. The radiation parameters are as follows: the peak exposure rate is as high as 5 × 10⁹ R/s, and the dose is as high as 800 R.     

从光电容积图中提取脉搏率、呼吸率和心率的新方法

光电容积描记图(PPG)是一种利用光学技术无创检测人体心血管脉搏波的方法。PPG信号来源于MIMIC数据库,它含有许多生理信息。本文提出了将集合经验模态分解(EEMD)、倒谱、快速傅里叶变化和过零点检测相结合的方法,从PPG中可靠地估算脉搏率(PR)、心率(HR)和呼吸频率(RR)。首先,将PPG信号通过EEMD分解为有限个固有模态函数(IMF)。因为EEMD有自适应滤波特性,所以估算不同的生理参数时,可以用不同的IMF分量来重构信号。其次,估算脉搏率时,舍去低频含有伪迹的IMF,再通过过零点检测可以得到瞬时脉搏率。然后,估算心率时,用1 Hz~1.67 Hz(60次/分钟~100次/分钟)的IMF来重构信号,再求倒谱,选取反映心脏活动的频带来得到心率。最后,估算呼吸率时,用0.05 Hz~0.75 Hz(3次/分钟~45次/分钟)的IMF来重构信号,然后对呼吸信号求快速傅里叶变化得到频谱图,寻找频谱图中的峰值得到呼吸率。对来自MIMIC数据库的53个成人PPG信号进行了仿真。仿真结果表明使用该综合信号处理方法提取的生理参数与实际生理参数一致,且该方法有运算量小,精确度高的优点(误差不超过1.17%)。     

基于Hilbert谱的心率变异信号时频分析方法

心率变异性(heart rate variability,HRV)信号的频域分析方法是用来表征自主神经调控信息的基本方法。为了评估自主神经系统功能及对心血管活动的影响,提出一种基于Hilbert时频谱的HRV信号的时频特征提取和分析的新方法。对HRV信号进行希尔伯特-黄变换(Hilbert-Huang transform,HHT)以获得HRV信号Hilbert时频谱,依据短时程HRV信号的线性频域分析指标,得到不同生理频带的Hilbert能量棒形图,提取总能量、各生理频带的能量和其归一化能量以及生理频段的能量比值作为评价心率变异性的时频特征。对MIT-BIH数据库的年轻人、老年人样本和健康人、心衰病人样本的HRV信号分析表明,基于Hilbert谱的时频特征的区分性能好,有较清晰的生理意义,能反映人的生理病理变化,为短时程HRV信号分析提供了一种有效方法。     

Measurement of heart rate variability and stress evaluation by using microwave reflectometric vital signal sensing

In this paper, we present two robust signal processing techniques for stress evaluation using a microwave reflectometric cardiopulmonary sensing instrument. These techniques enable the heart rate variability (HRV) to be recovered from measurements of body-surface dynamic motion, which is subsequently used for the stress evaluation. Specifically, two novel elements are introduced: one is a reconfiguration of the HRV from the cross-correlation function between a measurement signal and a template signal which is constructed by averaging periodic component over a measurement time. The other is a reconstruction of the HRV from the time variation of the heartbeat frequency; this is evaluated by a repetition of the maximum entropy method. These two signal processing techniques accomplish the reconstruction of the HRV, though they are completely different algorithms. For validations of our model, an experimental setup is presented and several sets of experimental data are analyzed using the two proposed signal processing techniques, which are subsequently used for the stress evaluation. The results presented herein are consistent with electrocardiogram data.     

A compact high-voltage pulse generator with opening insulated-gate bipolar transistor switch and a high pulse repetition rate

A small-size high-voltage (～20 kV) microsecond pulse generator, which is based on a pulse transformer and loaded into a reactor with a pulse corona discharge, is described. Insulated-gate bipolar transistors (IGBTs) that form the switch are used in the low-voltage circuit of the generator. When the switch is open, voltage pulses with an amplitude of up to 1000 V are created across it and, hence, across the primary winding of the transformer. The pulse repetition rate of the generator is ～20000 pulses/s.     

A novel compact repetitive frequency voltage booster based on magnetic switches and Fitch generator

In this paper, a novel repetitive frequency voltage booster (named repetitive Fitch booster by the authors) based on magnetic switches and Fitch generators is proposed. The principle of operation is to charge capacitors in parallel when magnetic switches (MSs) are unsaturated and reverse voltage polarity of every other capacitor when MSs saturate. With the principle, circuit topology of a 4-stage repetitive Fitch booster (RFB) is presented. Simulation as well as experiment shows its feasibility in boosting voltage and compressing rise-time. In simulation, the input voltage of 100 V is boosted to 372 V, while test stand yields output voltage with frequency of 1 kHz, amplitude of 19 kV with each capacitor charged to about 5.6 kV, and rise-time compression from 7.3 μs to 700 ns. Meanwhile, calculations show that the 4-stage RFB effectively reduces core volume by about half, from 1093.5 cm(3) to 585.2 cm(3). Furthermore, design rules are proposed so that topologies of RFBs with stages other than four can be conveniently derived. As an example, an 8-stage RFB is proposed and verified with circuit simulation, which shows an output voltage of 759 V with the input voltage of 100 V.     

一种基于频域整形的滑模变结构控制器设计

为避免未建模误差对系统性能的影响,本文采用滑模面的频域整形方法提出了一种基于Ｈ∞理论设计滑模面的变结构控制器,并将它运用到一泵控马达伺服系统中,并给出仿真结果。     

一种基于MATLAB的控制系统频域分析方法

提出一种新型的应用FFT（快速付立叶变换）实现控制系统信号频域分析的方法,结合MATLAB强大的运算功能简单快速地得到控制系统信号的频谱,从而实现系统的频域分析与控制.     

重复轨迹运动迭代学习控制的频域分析

应用频域分析方法讨论了一类闭环迭代学习算法的收敛条件和性能,指出其比Arimoto开环迭代学习算法具有明显的优越性,并在讨论迭代收敛条件的基础上给出了闭环迭代学习算法的频域设计方法.     

The sensitivity analysis of yaw rate for a front wheel steering vehicle: In the frequency domain

In this paper, the sensitivity analysis of yaw rate for a front wheel steering vehicle is performed in the frequency domain. A two degree of freedom system is used to represent a simple vehicle model in order to derive the system transfer function. The transfer function is defined between a steering angle input and a yaw rate output. This model shows the simplest lateral dynamic effect and is useful for understanding of the dynamic characteristics and control aspect of the target system. Vehicle mass, inertia, cornering stiffiness, and wheel base are selected as design variables. Sensitivity functions of the transfer function with repect to design variables are derived, and the results show that the response of the yaw rate always has stable minimum phase characteristics. The objective of this paper is the proposition of a base for re-design and new-design of the vehicle by checking the yaw rate variations with respect to the design variable change in the frequency domain. Finally, dominant design variables can be selected based on the sensitivity analysis.     

A frequency domain method for the measurement of nonlinearity in heterodyne interferometry

This paper presents a method for the measurement of nonlinearity in heterodyne interferometry which utilizes the frequency spectrum of the output of the photodetector for the direct measurement of the magnitudes of the first and second harmonic nonlinearities. The underlying theory and the experimental technique are discussed. Results showing the application of this technique for the determination of the influence of the azimuthal alignments of the polarization beamsplitter, the analyzer and measurement retroreflector are presented. The applicability of the technique to the in situ optimization of an interferometer system is demonstrated. It is shown that using this technique an interferometer system can be optimized to reduce the first-harmonic nonlinearity to below 0.5 nm p-p and the second harmonic nonlinearity to 2 nm p-p. This method is contrasted with other methods and the advantages conferred by the elimination of an external reference and the phase measuring electronics are highlighted.     

变速恒频轴带发电机组监控系统的研制

针对传统的船舶混合推进系统中存在效率低、污染高、工作模式单一、监控麻烦等问题,将变速恒频轴带发电机组系统应用于新型混合推进系统,在传统的轴带发电机和船舶微电网间添加了一个四象限变频器,对新型混合推进系统在不同工作模式下的系统性能进行了研究;同时设计了一个监控系统,采用TMS320F28335作为控制芯片,与底层控制器之间采用CAN总线通信,与上层的船舶综合信息管理平台之间采用Profibus总线通信,显示部分采用液晶模块,完成了系统实时控制、状态参数在线监测及命令数据传输等功能.实验结果表明,新型混合推进系统能够在不同模式工作下稳定工作,降低了燃油成本和污染,提高了系统的工作效率;监控系统的人机界面良好,操作方便快捷,通信稳定可靠,适合工业现场应用.     

A compact semiconductor opening swith-based generator with a 300-kV output voltage and up to 2-kHz pulse repetition rate

A compact generator with a semiconductor opening switch (SOS-diode) shaping across resistive load pulses with an amplitude of up to 300 kV, duration of 30–50 ns, and a 300-Hz pulse repetition under uninterrupted operation and up to 2 kHz in a 30-s burst mode is described. The generator contains a thyristor charging device, magnetic compressor, and inductive storage with a semiconductor opening swith based on SOS-diodes. The average output power at a maximum pulse repetition rate and a 250kV-voltage is 16 kW. The overall dimensions of the generator are 0.85×0.65×0.42 m, the weight is about 115 kg.     

High-accuracy displacement metrology and control using a dual Fabry-Perot cavity with an optical frequency comb generator

A displacement metrology and control system using an optical frequency comb generator and a dual Fabry-Perot cavity is developed with sub-nm accuracy. The optical frequency comb generator has expanded the displacement measurement range and the dual cavity system has suppressed the environmental fluctuation. We evaluated the absolute uncertainty of the developed displacement measurement system to be approximately 190 pm for the displacement of 14 μm and the accurate displacement control using a phase-locked loop was demonstrated with a resolution of approximately 24 pm.     

∑-△A/DC频谱补偿的研究

∑-△DC的数字滤波通常使用SINC^3滤波器，该滤波器通带内带宽很窄，对于较高频率的信号衰减过大，严重限制∑-△A/DC的应用。本文研究两种频谱补偿的方法，以改善∑-△A/DC带宽，并以心电信号为例给出频谱补偿后的结果。     

Σ-ΔA/DC频谱补偿的研究

Σ -ΔA/DC的数字滤波通常使用SINC3滤波器 ,该滤波器通带内带宽很窄 ,对于较高频率的信号衰减过大 ,严重限制Σ -ΔA/DC的应用。本文研究两种频谱补偿的方法 ,以改善Σ -ΔA/DC带宽 ,并以心电信号为例给出频谱补偿后的结果