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71.
梭车是短壁机械化开采技术的重要运输设备。简要介绍了现有梭车的现状及应用局限,详细阐述了分体梭车的主要设计思路,重点介绍了薄壁分体式机架的结构特征,阐述了分体梭车在模块化卷电缆装置、四象限变频驱动等方面的技术升级,并介绍了分体梭车在国内矿区的应用情况。 相似文献
72.
Alessandro Brumana Luigi Piroddi 《International Journal of Adaptive Control and Signal Processing》2020,34(7):877-900
The problem of real-time frequency estimation of nonstationary multi-harmonic signals is important in many applications. In this paper, we propose a novel multi-frequency tracker based on a state-space representation of the signal with Cartesian filters and the second-order central divided difference filter (CDDF), which improves the performance of the extended Kalman filter (EKF) by using Stirling's interpolation method to approximate the mean and covariance of the state vector. A crucial element of the method is the adaptive scaling of the process noise covariance matrix appearing in the filter equations, as a function of the innovation sequence, which tunes the accuracy-reactivity trade-off of the filter. The proposed solution is evaluated against two approaches from the literature, namely the factorized adaptive notch filter (FANF) and the extended Kalman filter frequency tracker (EKFFT). Several experiments emphasize the estimation accuracy of the proposed method as well as the improved robustness with respect to initial errors and input signal complexity. The presented method appears to be particularly efficient with rapidly varying frequencies, thanks to the update mechanism that adjusts the filter parameters based on the amplitude of the estimation error. 相似文献
73.
Z型变截面折叠机翼作为一种可变体机翼结构,不同的折叠角对机翼稳定性有着重要的影响,因此研究不同折叠角度下的特性参数对机翼动态稳定性有着重要的意义.本文首先设计加工了Z型变截面可折叠机翼结构的实验模型,通过建立与实验模型相匹配的有限元模型,仿真得到不同折叠角度下机翼的前5阶固有频率和振型,针对不同折叠角度下机翼的固有特性,通过扫频实验得到机翼前5阶固有频率和模态振型,以及横向外激励作用下三段翼的频响曲线,对比分析有限元仿真与实验结果,验证结果的可靠性,这将对机翼结构设计以及特性参数的选取提供参考依据. 相似文献
74.
天然气水合物沉积物中的黏土成分显著影响沉积物的电学特性以及水合物饱和度的计算模型。以自主设计开发的复电阻率参数测量装置为实验平台,在20 Hz ~ 100 kHz频率范围内测试了黏土条件下含水合物海沙体系的复电阻率,分析了复电阻率的频散特性、黏土影响以及主导的电极化机制,利用泥质修正Archie公式建立了基于宽频复电阻率的水合物饱和度计算模型。研究结果表明:(1)含水合物海沙体系的复电阻率呈现出显著的频散特性,双电层极化和界面极化分别是20 Hz ~ 1 kHz和1 ~ 100 kHz频段主导的极化机制;(2)黏土颗粒表面的双电层发生形变增强了含水合物沉积物双电层极化作用,提高了复电阻率相角和虚部的绝对值;(3)在20 Hz ~ 100 kHz频率范围内泥质修正Archie公式岩性系数较为稳定,而胶结指数和饱和度指数与测试频率之间的关系在20 Hz ~ 1 kHz和1 ~ 100 kHz频段差异显著,因此应分频段建立水合物饱和度计算模型。本研究为探讨含水合物沉积物的低频电学特性和建立含黏土沉积物中水合物饱和度计算模型提供了新的途径。 相似文献
75.
为了实现电炉厂提产增效的目标,研究了脉冲磁致振荡(PMO)在提高铸坯生产拉速中的应用潜能。结果表明,优化PMO处理参数可以适应生产拉速提高的要求,并改善铸坯的中心偏析和宏观偏析。当连铸拉速提至1.05 m/min,PMO脉冲频率为1.16Kf Hz,峰值电压为1.00KiV处理参数(Kf和Ki分别为仪器的放电频率和电压峰值)时, 铸坯横断面碳偏析指数可控制在1±0.05内;当连铸拉速提至1.15 m/min,PMO脉冲频率为1.28KfHz,峰值电压为1.00KiV处理参数时,铸坯横断面碳偏析指数可控制在1±0.07内。试验证明,在高拉速条件下通过保证单位时间内对钢液施加的脉冲能量可以使连铸坯质量得到有效改善。 相似文献
76.
《Ceramics International》2022,48(16):23428-23435
CaCu3Ti4O12-xwt%BiSbO4 ceramics (CCTO-xwt%BSO, x = 0, 1, 2, 3) were prepared by solid-state reaction method. The microstructure, dielectric properties, varistor properties, photoluminescence properties of CCTO-xwt%BSO ceramics were studied in this work. Results showed that all samples formed CaCu3Ti4O12 (CCTO) single phase. Doping BiSbO4 (BSO) restrained the abnormal grain growth and increased the grain boundary density of ceramics. The introduction of BSO led to the increase of the grain boundary resistance, reducing the dielectric loss and enhancing the temperature stability of dielectric properties. The nonlinear electrical characteristics are enhanced with proper concentration of BSO. And the improved varistor performance with breakdown electric field of ~3.98–34.6 and nonlinear coefficient of ~1.49–2.96 are obtained for CCTO-xwt%BSO samples. In addition, the photoluminescent emission of the samples is enhanced with the addition of appropriate equivalent BSO, showing the potential applications in novel devices with photoluminescent/electrical multifunctional properties. 相似文献
77.
提出了一种基于智能控制的煤层气抽采监测系统。该系统以可编程逻辑控制器为控制中心,通过监测传感器实现对煤层气抽采时的井底流压力、温度等的连续性监测,实现对抽采设备运行转速的调整。实际表明该控制系统能将井底流压力变化范围控制在0.4%范围内,有效提升了煤层气采集的控制精度和采集速度。 相似文献
78.
In this study, the impacts of non‐integer order controller on the stable parameter space of the microgrid (MG) frequency control system with fixed communication time delay are investigated and discussed with the help of the stability boundary locus (SBL) method. This study proposes a non‐integer order controller for the load frequency control (LFC) of the MG systems. To that end, the load frequency model of the MG is formulated and then the characteristic equations of this model are obtained. Then, with the help of this characteristic equation, the stable parameter space of the non‐integer controller is determined with regard to different time delay (τ ) and fractional integral order values (α ) using the SBL method. In order to show the accuracy of the obtained stable parameter space, time domain and generalized modified Mikhailov (GMM) criterion studies are carried out for different values of (τ ) and (α ). According to the results obtained, the areas of stable parameter space according to different α values and τ = 1.6 are calculated as 444.8860 for α = 0.4 , 342.9728 for α = 0.7 , 259.3578 for α = 1 , 216.2541 for α = 1.3 and 159.6826 for α = 1.6 . In addition, the areas of stable parameter space according to different τ values and α = 1.4 are calculated as 784.5222 for τ = 1 , 106.3219 for τ = 2 , 29.6959 for τ = 3 and 11.5946 for τ = 4 . Despite the extreme variability arising from nature of resources that make up the MG, the designed non integer order controller with the values selected within the stable parameter space stably carries out LFC control of the MG. 相似文献
79.
Monopiles and gravity base foundations (GBF) are two of the most commonly used foundations for offshore wind turbines. As resonance can cause damage and even failure of wind turbines, understanding the difference between the dynamic responses of monopiles and GBFs under free vibration is important. However there is little experimental data regarding their natural frequency, especially from model tests carried out at correct stress levels. This paper presents the results of novel monopile and GBF tests using a centrifuge to directly determine the natural frequency (fn) of the foundation-soil system. The natural frequencies of wind turbine monopiles and GBFs in centrifuge models were measured during harmonic loading using a piezo-actuator, with the results confirming that soil-structure interaction must be considered to obtain the system’s natural frequency as this frequency reduces substantially from fixed-base values. These results will contribute in preventing resonance induced damage in wind-turbines. 相似文献
80.
Gurumurthy Komanapalli Rajeshwari Pandey Neeta Pandey 《International Journal of Circuit Theory and Applications》2019,47(5):666-685
The objective of this brief is to introduce four new structures of electronically tunable sinusoidal oscillators (SOs) designed using operational transresistance amplifier (OTRA). Each of the proposed SO consists of forward path derived from a generic structure along with one/two OTRA-based resistive gain stages or differentiator in its feedback path. All the proposed SOs enjoy independent tuning of the frequency of oscillation (FO) through resistors without affecting the condition of oscillation (CO). Further, all topologies are found to exhibit low fo sensitivities at all frequencies with respect to circuit parameters, and the second topology is capable of achieving very low frequencies (VLFs) using less RC component spread and provides linear tuning too. The fourth circuit provides quadrature output. The proposed SOs have been successfully implemented and verified in 180-nm CMOS technology node using ADE (analog design environment) tool Cadence Virtuoso. Both prelayout and postlayout simulation results have been included. To assess the oscillator prefabrication performances, Monte Carlo and process-voltage-temperature (PVT) analyses have been performed. The total harmonic distortion (THD) is observed to be less than 3.5%. 相似文献