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1.
    
为预测与评估多维视觉编码对飞行员信息辨识的影响,在大量已有单维视觉编码研究的基础上,采用元分析和综合绩效法对显示界面上的多维视觉编码进行归一量化,结合G1法所确定的权重系数并运用模糊加权平均算子,建立了一种新的显示界面多维视觉编码综合评价数学模型.为了验证模型的效度,对波音和空客界面进行了综合评价,据此设计出优化界面,采用22名被试在不同显示界面下开展仪表监视实验,并采用了主观评价法、任务绩效评价法和生理评价法(包括眼动追踪测量和心电图时域指标测量)3种方法记录实验数据.综合测评结果表明:模型的理论预测值与多种实验方法测量结果显著相关,优化界面更利于被试完成信息辨识任务.显示界面多维视觉编码综合评价模型的提出对指导飞机驾驶舱显示界面的设计具有一定的参考价值.  相似文献   

2.
  总被引:1,自引:0,他引:1  
为满足毫米级微型涡轮发动机性能设计需求,提出了一种毫米级微型涡轮发动机性能仿真模型。该模型采用考虑低雷诺数效应和传热效应的微型涡轮发动机叶轮特性,并将热平衡方程纳入该发动机性能仿真模型的共同工作方程组。通过与静子结构热网络方程组的耦合求解,实现了微型涡轮发动机特性和部件传热的动态模拟。以典型毫米级微型涡轮发动机为对象建立了仿真算例,研究了启动过程中发动机内部参数的变化规律。结果表明:毫米级微型涡轮发动机转动惯量对其加速性能影响微小,非稳态传热效应是影响其过渡态特性的主要因素。发动机转子和静子部件达到热响应时间存在显著差异,导致发动机启动过程的工作线呈现多拐点的现象。  相似文献   

3.
    
针对非线性系统领域具有更广泛意义的线参数多项式组合模型,提出一种非线性多项式模型结构辨识和参数辨识一体化算法。该算法将结构辨识中基于贡献项的择优过程与基于冗余项的劣汰过程结合。在择优过程中,根据输出向量投影残差下降的最大化,采用基于输出向量残差化的递归改进Gram-Schmidt(RMGS)算法,在向量空间的全集中择优,并允许部分冗余非模型项选入。在劣汰过程中,为平等对待正交化向量的贡献,采用基于改进正交化次序的模型结构劣汰策略,在优选集合里逐个删除对实际输出贡献相对较小的结构项,以系统完备性指标为约束,确认结构与参数。2类典型非线性多项式模型辨识仿真算例对比验证了算法的有效性。  相似文献   

4.
    
基于修理延迟下单部件三状态(工作、修理延迟、修理)可修系统的更新模型,提出了带有故障小修的三状态(工作、故障小修、修理)更新模型。运用简捷的方法把更新方程化为微分方程得到其解析表达式。结果显示模型的变化使得稳态可用度提升。使用一套波动理论,其中包括基础的波动定义和相关的波动判定引理。依此给出了瞬时可用度波动产生的条件。通过固定故障率,分析修复率对瞬时可用度波动的影响。同时结合实际背景,提供了抑制波动的方法,即控制平均修理时间小于平均故障时间的1/4。仿真结果与理论相一致。  相似文献   

5.
    
为进一步提升星群协同的系统容量,考虑在卫星星群上配置阵列天线的传输模式.分析了最大化容量时下行链路的信道条件,给出了系统容量最大化的实现方式,探索了系统参数对信道容量的影响,发现信道容量随地面天线间距成周期性变化,其周期与卫星数目成反比、与地面天线阵列相对于东西方向的夹角的余弦成反比、与相邻卫星之间的角间距成反比.在多卫星多天线环境下,发现信道容量曲线的包络同样随地面天线间距成周期性变化,提出并通过仿真验证了多卫星多天线环境下减小地面天线间距和降低测控精确度要求的地面天线排布方案.  相似文献   

6.
    
针对现代飞艇控制中动力学模型不确定性带来的系统建模和参数辨识工作较为复杂的问题,提出了一种基于自适应建模和在线学习机制的控制策略。设计了一种在分析实际运动的基础上建立飞艇控制马尔可夫决策过程(MDP)模型的方法,具有自适应性。采用Q-Learning算法进行在线学习并利用小脑模型关节控制器(CMAC)神经网络对动作值函数进行泛化加速。对本文方法进行仿真并与经过参数整定的PID控制器对比,验证了该控制策略的有效性。结果表明,在线学习过程能够在数小时内收敛,通过自适应方法建立的MDP模型能够满足常见飞艇控制任务的需求。本文所提控制器能够获得与PID控制器精度相当且更为智能的控制效果。  相似文献   

7.
    
工业机器人在使用过程中,由于末端负载的变化导致机械振动,因此需要识别机器人末端负载去调整相应的控制参数来保证其具有良好的运动表现.提出一种基于伺服电机输出力矩,不需要额外传感器的机器人负载识别方法.根据机器人静力学模型,计算出静止状态下末端空载和负载情况下的输出力矩差异,由此得到负载计算模型.对埃夫特的QH165机器人进行了试验,在工作空间内随机选择10个测量点,在末端空载和负载的情况下读取电机输出的力矩,计算得到末端负载.结果表明:识别的负载与已知负载相同,试验表明该方法的可行性.  相似文献   

8.
  总被引:2,自引:0,他引:2  
基于改进高斯法(IGM)和遗传算法(GA)的混合优化算法,为解决空间拦截轨道燃料消耗和转移时间的综合最优问题,提出一种空间拦截轨道设计方法.首先,引入牛顿-拉夫逊迭代法对原始高斯法进行改进,解决原始高斯法在解算空间拦截轨道时收敛速度慢、转移角范围小等问题;接着,给出并证明改进高斯法迭代方程有唯一解的充分必要条件.当给定初始轨道参数时,用此条件判断可否用椭圆轨道进行转移;然后给出转移时间,最大脉冲速度等约束条件,对编码方式进行改进,给出混合优化算法的计算步骤;最后以空间拦截轨道优化问题为例,进行仿真分析.仿真结果表明,与传统优化算法相比,混合优化算法收敛的遗传代数少,耗时短,能够较好地运用于空间拦截轨道的设计.  相似文献   

9.
    
针对丘陵山区耕地小型无人机航拍图像(低空遥感图像)中的尺度变化、几何畸变、图像重叠等问题,提出了基于双特征的丘陵山区耕地低空遥感图像配准算法。该算法鉴于丘陵山区耕地背景环境复杂、光照因素等影响,采用尺度不变特征SURF算法提取了遥感图像的特征点,并构建了能够稳健描述航拍图像几何特征的双特征描述子;在此基础上,以高斯混合模型(GMM)为核心,结合2个单一特征差异描述子(基于欧氏距离的全局特征和基于和向量的局部特征)构造的双特征描述子,得到了能够同时通过2种特征进行对应关系评估的双特征有限混合模型(DFMM),并通过再生核希尔伯特空间(RKHS),基于高斯径向基函数(GRBF)对待配准图像进行了全局与局部结构双约束的空间变换更新。为了验证本文算法的可行性及其性能,采用小型无人机航拍的丘陵山区坡耕地多视角遥感图像开展了实验,将本文算法与SIFT、SURF、CPD、AGMReg、GLMDTPS及PRGLS进行了比较。实验结果表明,本文算法不仅在不同坡度的坡耕地航拍图像多视角配准过程中,均具有较好的鲁棒性,也适用于部分复杂地形小型无人机航拍的多视角遥感图像配准。  相似文献   

10.
    
为了找到一种获得K-π相移的有效方法,并从格点计算得到的能级中获取K*介子的性质,首先使用手征幺正理论研究了有限体积中的P波K-π相互作用.这种方法曾在无限空间中成功地应用于计算K-π相移.然后用这种方法计算得到作为立方体盒子尺寸和π介子质量的函数的P波K-π散射振幅的能级;并计算了K-π散射的相移以及基于该结果的K*介子的物理性质.最后,为了和格点量子色动力学(QCD)计算结果进行比较,又在π介子取非物理质量时计算得到了K*介子的能级.比较表明:文中方法与格点QCD得到的结果基本一致.当介子能量为266 Me V时,本文方法得到的两个能级分别为924.0 Me V和1 483.0 Me V,其结果与格点QCD得到的915.6 Me V和1 522.3 Me V的两个能级符合得很好.  相似文献   

11.
This paper presents the results of the numerical calculations thermosphere/ionosphere parameters which were executed with using of the Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP)and comparison of these results with empirically-based model IRI-2001. Model GSM TIP was developed in West Department of IZMIRAN and solves self-consistently the time-dependent, 3-D coupled equations of the momentum, energy and continuity for neutral particles (O2, N2, O), ions (O+, H+), molecular ions (M+) and electrons and largescale eletric field of the dynamo and magnetospheric origin in the range of height from 80 km to 15 Earth’s radii. The empirically derived IRI model describes the E and F regions of the ionosphere in terms of location, time, solar activity and season. Its output provides a global specification not only of Ne but also on the ion and electron temperatures and the ion composition. These two models represent a unique set of capabilities that reflect major differences in along with a substantial approaches of the first-principles model and global database model for the mapping ionosphere parameters. We focus on global distribution of the Ne, Ti, Te and TEC for the one moment UT and fixed altitudes: 110 km, hmF2, 300 km and 1000 km. The calculations were executed with using of GSM TIP and IRI models for August 1999, moderate solar activity and quiet geomagnetic conditions. Results present as the global differences between the IRI and GSM TIP models predictions. The discrepancies between model results are discussed.  相似文献   

12.
径向圆跳动误差的最小二乘评定数学模型和微机数据处理   总被引:2,自引:1,他引:2  
用传统的测量方法只能得到被测零件的径向圆跳动误差的近似值。为了得到该项误差的准确值,需要研究新的测量方法。建立了径向圆跳动误差最小二乘评定数学模型,并编制了高级语言数据处理程序。在万能工具显微镜上获得了采样数据,给出了计算结果。  相似文献   

13.
A Joss–Waldvogel impact type disdrometer was installed at four different locations in the Indian peninsula during various periods from 2001 till date. The data are analysed to study the nature of rain drop size distribution (DSD) in this region. Out of the three well known distributions that describe DSD, namely, the Marshall–Palmer, Gamma and Lognormal, it has been found that Lognormal distribution fits the DSD in this region better than the other ones. Lognormal distributions for different rain rates were then derived by fitting the lognormal function to the data using a curve fitting software. Then the variation of fit parameters with rain rate was evaluated. Incorporating these variations, into the Lognormal distribution, an empirical equation that describes the DSD in this region for different rain rates was derived. Then this equation was tested with sample data from each of these stations. The data used for validation were not used for fitting lognormal equation to derive the fit parameters. The correlation between the DSD measured and derived using the empirical model was found to be quite good (0.9) except in some cases where the coefficient dropped to 0.75. The empirical model can be updated when more data are available.  相似文献   

14.
The most frequently used mapping function for converting slant total electron content (STEC) to vertical total electron content (VTEC) uses a simplified ionospheric single layer model in satellite based augmentation system (SBAS). Aiming at ionospheric single layer model altitude variation, we analyzed the statistical characteristic of mapping function in systemic approach particular for the region of China, and then experimental mapping function was proposed. The experimental mapping function is used in SBAS ionospheric correction and the precision of vertical correction is compared with standard mapping function. The results show that conversion factor errors depend on latitude, time and elevation, experimental mapping function is helpful to the vertical TEC estimation and may improve the precision of SBAS ionospheric refraction correction especially for the low latitude region of China.  相似文献   

15.
There are remarkable ionospheric discrepancies between space-borne (COSMIC) measurements and ground-based (ionosonde) observations, the discrepancies could decrease the accuracies of the ionospheric model developed by multi-source data seriously. To reduce the discrepancies between two observational systems, the peak frequency (foF2) and peak height (hmF2) derived from the COSMIC and ionosonde data are used to develop the ionospheric models by an artificial neural network (ANN) method, respectively. The averaged root-mean-square errors (RMSEs) of COSPF (COSMIC peak frequency model), COSPH (COSMIC peak height model), IONOPF (Ionosonde peak frequency model) and IONOPH (Ionosonde peak height model) are 0.58 MHz, 19.59 km, 0.92 MHz and 23.40 km, respectively. The results indicate that the discrepancies between these models are dependent on universal time, geographic latitude and seasons. The peak frequencies measured by COSMIC are generally larger than ionosonde’s observations in the nighttime or middle-latitudes with the amplitude of lower than 25%, while the averaged peak height derived from COSMIC is smaller than ionosonde’s data in the polar regions. The differences between ANN-based maps and references show that the discrepancies between two ionospheric detecting techniques are proportional to the intensity of solar radiation. Besides, a new method based on the ANN technique is proposed to reduce the discrepancies for improving ionospheric models developed by multiple measurements, the results indicate that the RMSEs of ANN models optimized by the method are 14–25% lower than the models without the application of the method. Furthermore, the ionospheric model built by the multiple measurements with the application of the method is more powerful in capturing the ionospheric dynamic physics features, such as equatorial ionization, Weddell Sea, mid-latitude summer nighttime and winter anomalies. In conclusion, the new method is significant in improving the accuracy and physical characteristics of an ionospheric model based on multi-source observations.  相似文献   

16.
Monthly median values of foF2, hmF2 and M(3000)F2 parameters, with hourly time interval resolution for the diurnal variation, obtained with DPS-4 digisonde observations at Hainan (19.4°N, 109.0°E) are used to study the low latitude ionospheric variation behavior. The observational results are compared with the International Reference Ionospheric Model (IRI) predictions. The time period coverage of the data used for the present study is from March 2002 to February 2005. Our present study showed that: (1) In general, IRI predictions using CCIR and URSI coefficients follow well the diurnal and seasonal variation patterns of the experimental values of foF2. However, CCIR foF2 and URSI foF2 IRI predictions systematically underestimate the observed results during most time period of the day, with the percentage difference ΔfoF2 (%) values changing between about −5% and −25%, whereas for a few hours around pre-sunrise, the IRI predictions generally overestimate the observational ones with ΔfoF2 (%) sometimes reaching as large as ∼30%. The agreement between the IRI results and the observational ones is better for the year 2002 than for the other years. The best agreement between the IRI results and the observational ones is obtained in summer when using URSI coefficients, with the seasonal average values of ΔfoF2 (%) being within the limits of ±10%. (2) In general, the IRI predicted hmF2 values using CCIR M(3000)F2 option shows a poor agreement with the observational results. However, when using the measured M(3000)F2 as input, the diurnal variation pattern of hmF2 given by IRI2001 has a much better agreement with the observational one with the detailed fine structures including the pre-sunrise and post-sunset peaks reproduced reasonably well. The agreement between the IRI predicted hmF2 values using CCIR M(30,000)F2 option and the observational ones is worst for the afternoon to post-midnight hours for the high solar activity year 2002. During daytime hours the agreement between the hmF2 values obtained with CCIR M(30,000)F2 option and the observational ones is best for summer season. The discrepancy between the observational hmF2 and that obtained with CCIR M(30,000)F2 option stem from the CCIR M(3000)F2 model, which does not produce the small scale structures observed in the measured M(3000)F2.  相似文献   

17.
The temporal and seasonal variations of Total Electron Content (TEC) are studied at Agra (Geographic Lat. 27.17°N, Long. 78.89°E, Dip: 41.4°), India, which is in the equatorial anomaly region, for a period of 12 months from 01 January to 31 December, 2007 using a Global Positioning System (GPS) receiver. The mean TEC values show a minimum at 0500 h LT (LT = UT + 5.5 h) and a peak value at about 1400 h LT. The lowest TEC values are observed in winter whereas largest values are observed in equinox and summer. Anomalous variations are found during the period of magnetic disturbances. These results are compared with the TEC derived from IRI-2007 using three different options of topside electron density, NeQuick, IRI01-corr, and IRI-2001. A good agreement is found between the TEC obtained at Agra and those derived from IRI models.  相似文献   

18.
Bottom side electron density profiles for two stations at the southern crest of the Equatorial Ionization Anomaly (EIA), São José dos Campos (23.1°S, 314.5°E, dip latitude 19.8°S; Brazil) and Tucumán (26.9°S, 294.6°E, dip latitude 14.0°S; Argentina), located at similar latitude and separated by only 20° in longitude, have been compared during equinoctial, winter and summer months under low (year 2008, minimum of the solar cycle 23/24) and high solar activity (years 2013–2014, maximum of the solar cycle 24) conditions. An analysis of parameters describing the bottom side part of the electron density profile, namely the peak electron density NmF2, the height hmF2 at which it is reached, the thickness parameter B0 and the shape parameter B1, is carried out. Further, a comparison of bottom side profiles and F-layer parameters with the corresponding outputs of IRI-2012 and NeQuick2 models is also reported. The variations of NmF2 at both stations reveal the absence of semi-annual anomaly for low solar activity (LSA), evidencing the anomalous activity of the last solar minimum, while those related to hmF2 show an uplift of the ionosphere for high solar activity (HSA). As expected, the EIA is particularly visible at both stations during equinox for HSA, when its strength is at maximum in the South American sector. Despite the similar latitude of the two stations upon the southern crest of the EIA, the anomaly effect is more pronounced at Tucumán than at São José dos Campos. The differences encountered between these very close stations suggest that in this sector relevant longitudinal-dependent variations could occur, with the longitudinal gradient of the Equatorial Electrojet that plays a key role to explain such differences together with the 5.8° separation in dip latitude between the two ionosondes. Furthermore at Tucumán, the daily peak value of NmF2 around 21:00 LT during equinox for HSA is in temporal coincidence with an impulsive enhancement of hmF2, showing a kind of “elastic rebound” under the action of the EIA. IRI-2012 and NeQuick2 bottom side profiles show significant deviations from ionosonde observations. In particular, both models provide a clear underestimation of the EIA strength at both stations, with more pronounced differences for Tucumán. Large discrepancies are obtained for the parameter hmF2 for HSA during daytime at São José dos Campos, where clear underestimations made by both models are observed. The shape parameter B0 is quite well described by the IRI-2012 model, with very good agreement in particular during equinox for both stations for both LSA and HSA. On the contrary, the two models show poor agreements with ionosonde data concerning the shape parameter B1.  相似文献   

19.
A new set of data obtained at low solar activity from Ilorin, Nigeria (geog. latitude 8.5°N, geog longitude, 4.6°E, dip 4.1°S) is used to validate the IRI 2001 model at low solar activity. The results show in general a good agreement between model and observed B0 at night but an over estimation during daytime. The overestimation is greatest during the morning period (0600LT–1000LT). The model prediction for B1 is fairly good at night and during the day. A dependence of B0 on solar zenith angle χ is observed during the daytime. A formulation of the form B0 = A[cos(χ)n] is therefore proposed. Values of the constants n and A were determined for the period of low solar activity for this station.  相似文献   

20.
The main challenge in real-time precise point positioning (PPP) is that the data outages or large time lags in receiving precise orbit and clock corrections greatly degrade the continuity and real-time performance of PPP positioning. To solve this problem, instead of directly predicting orbit and clock corrections in previous researches, this paper presents an alternative approach of generating combined corrections including orbit error, satellite clock and receiver-related error with broadcast ephemeris. Using ambiguities and satellite fractional-cycle biases (FCBs) of previous epoch and the short-term predicted tropospheric delay through linear extrapolation model (LEM), combined corrections at current epoch are retrieved and weighted with multiple reference stations, and further broadcast to user for continuous enhanced positioning during outages of orbit and clock corrections. To validate the proposed method, two reference station network with different inter-station distance from National Geodetic Survey (NGS) network are used for experiments with six different time lags (i.e., 5 s, 10 s, 15 s, 30 s, 45 s and 60 s), and one set of data collected by unmanned aerial vehicle (UAV) is also used. The performance of LEM is investigated, and the troposphere prediction accuracy of low elevation (e.g., 10–20degrees) satellites has been improved by 44.1% to 79.0%. The average accuracy of combined corrections before and after LEM is used is improved by 12.5% to 77.3%. Without LEM, an accuracy of 2–3 cm can be maintained only in case of small time lags, while the accuracies with LEM are all better than 2 cm in case of different time lags. The performance of simulated kinematic PPP at user end is assessed in terms of positioning accuracy and epoch fix rate. In case of different time lags, after LEM is used, the average accuracy in horizontal direction is better than 3 cm, and the accuracy in up direction is better than 5 cm. At the same time, the epoch fix rate has also increased to varying degrees. The results of the UAV data show that in real kinematic environment, the proposed method can still maintain a positioning accuracy of several centimeters in case of 20 s time lag.  相似文献   

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