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《现代制造工程》2017,(4)
混合威布尔分布常用于拟合多失效模式的设备寿命数据,但由于该分布的形式复杂且参数众多,其参数估计较为困难。针对该问题,在对布谷鸟搜索(Cuckoo Search,CS)算法的步长比例和寄主鸟发现概率改进的基础上,提出基于改进CS的混合威布尔分布最优化参数估计方法。该方法以最小化残差平方和为目标,建立参数估计优化模型,并通过改进的CS算法进行参数寻优。案例以飞机挡风玻璃寿命数据为对象,采用CS算法以及3种改进的CS算法分别对两重两参数威布尔分布进行2 000次参数估计,对比分析各算法的寻优结果表明:融合步长比例改进和寄主鸟发现概率改进的CS算法的参数估计精度较高,估计结果较可靠。 相似文献
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为了提升故障诊断模型在数据不平衡场景下的性能,提出一种基于贝叶斯优化的自动不平衡故障诊断方法.首先,构建了一种分层多模型的参数空间,探索重采样和分类器的算法组合选择和超参数优化;然后,使用基于树形结构Parzen估计器(TPE)的贝叶斯优化器进行模型的训练与优化,得到参数空间中最优的算法组合和超参数配置;最后使用最优配置模型在测试集上进行结果评估.将所提方法应用于UCI(university of California Irvine)不平衡标准数据集和滚动轴承数据集.实验通过设置多个不平衡比,对优化后的模型分类效果进行检验,并与传统的随机搜索方法进行对比.结果表明,所提方法更好地提升了模型在不平衡故障数据上的分类能力,且优化过程更加高效. 相似文献
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基于优化理论的原理和特点,结合可靠性试验数据分布参数的估计方法——回归分析法和极大似然函数法,提出一种新的优化估计方法。通过一组具体的试验数据,论述威布尔分布的3个分布参数的优化估计过程。应用表明这种方法简单实用,求得的分布参数估计值更加精确合理。 相似文献
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最佳无偏整体估计方法 总被引:9,自引:3,他引:9
提出一种最佳无偏整体估计方法,给出整体参数的估计量及其协方差公式,建立正态分布、Weibull分布和极值分布等位置-尺度分布族的点估计与区间估计。传统的回归分析只适用于正态分布和完全数据,最佳无偏整体估计方法则将回归分析推广到工程中常见的位置-尺度分布族和截尾数据的情况。该方法可以将不同条件(状态)下的试验数据作为一个整体进行统计推断,能够全面开发利用不同条件下试验数据之间的横向信息,使其可利用的信息量远远大于只能分别在各自条件下对试验数据进行处理的传统最佳线性无偏估计方法。最佳无偏整体估计方法对一种条件下只有一个失效数据的情况也能进行分析,传统最佳线性无偏估计方法则要求在一种条件下有较多的失效数据,因此前者具有小样本性质;并且前者的参数估计量是所有条件下顺序统计量的线性函数,后者的参数估计量只是一种条件下顺序统计量的线性函数,所以前者的参数估计量具有更好的正态分布特性。大量Monte Carlo模拟和工程应用表明,在试样数相同的情况下,文中方法比传统方法具有更高的精度,而在精度相同的情况下,则可节省大量试样。 相似文献
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Seungjin Yoo Cheol-Gyu Park Seung-Han You 《Journal of Mechanical Science and Technology》2018,32(9):4045-4056
This paper presents a systematic method for estimating the inertial parameters of an excavator. The method utilizes dynamic excavator models with the pressure and displacement measurements of the hydraulic actuators. Provided that the geometrical parameters of the mechanical linkages are obtained with relatively high accuracy, the dynamic model is factored into the unknown inertial parameter vector and the known kinematic matrix. The contribution of each inertial parameter on the actuator force under the specific motion is explored through a dynamic sensitivity analysis. The results are then used to investigate various properties of the inertial parameters and categorize them into identifiable, unrelated to dynamics, and known parameter groups, according to numerical properties of the kinematic matrix. Then the identifiable inertial parameters are estimated sequentially, and the guideline for the optimal excavator position at each estimation step is suggested in order to minimize estimation error. The practicality of this method is demonstrated via data acquired using an actual hydraulic excavator. 相似文献
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提出了极值超出量服从广义Pareto分布的载荷谱外推方法。将所提方法运用到汽车用户典型路面载荷谱的外推中,分别拟合了形状参数为零和不为零的广义Pareto分布函数,对比分析了不同形状参数的分布函数对载荷谱外推结果的影响。将外推前后的载荷谱、采集载荷谱分别从幅值域和频率域进行了对比分析,研究结果表明:基于广义Pareto分布函数形状参数为零的载荷谱外推方法可得到偏于保守的外推结果;基于广义Pareto分布函数形状参数不为零的外推方法得到的外推载荷谱幅值比采集载荷谱幅值偏大。 相似文献
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Jong-Won Kim Seungmin Jung Jinuk Kim Jongwon Kim TaeWon Seo 《Journal of Mechanical Science and Technology》2014,28(8):3103-3111
The workspace, working velocity, excavating force, and load capacity of a hydraulic excavator play critical roles in the performance of the excavator for various tasks. This paper presents an optimal design of the front linkage of an excavator to maximize the performances of several indices simultaneously. A multi-objective function is defined to increase the excavator’s workspace, working velocity, excavating force, and load capacity simultaneously. The workspace is defined by using four geometrical indices and the working velocity is defined by the amount of time needed to perform one cycle composed of digging and dumping. The excavating force consists of two forces, and the load capacity is defined by using the minimum values of three types with specific operations. A total of 10 indices define objective function with each weight, and pin-points of the front linkage are the design parameters, including joint positions of links and hydraulic actuators. A two-step optimization procedure is considered based on a new method called the hybrid Taguchi-random coordinate search algorithm. The results indicate a 3.43% increase in performance relative to the initial design parameters of a commercial excavator. More specifically, the excavator’s workspace, working velocity, excavating force, and load capacity increase by 5.55%, 0.14%, 5.46%, and 0.33%, respectively. These improved design parameters can be applied to next generation excavators. 相似文献
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《Mechanical Systems and Signal Processing》2007,21(1):4-23
The structural parameter estimation problem based on measured modal data is often formulated as a weighted least-squares problem in which modal residuals measuring the fit between experimental and model predicted modal properties are build up into a single weighted residuals metric using weighting factors. Standard optimisation techniques are then used to find the optimal values of the structural parameters that minimise the weighted residuals metric. Due to model error and measurement noise, the results of the optimisation are affected by the values assumed for the weighting factors. In this work, the parameter estimation problem is first formulated as a multi-objective identification problem for which all Pareto optimal structural parameter values are obtained, corresponding to all possible values of the weights. A Bayesian statistical framework is then used to rationally select the optimal values of the weights based on the measured modal data. It is shown that the optimal weight value for a group of modal properties is asymptotically, for large number of measured data, inversely proportional to the optimal value of the residuals of the modal group. A computationally efficient algorithm is proposed for simultaneously obtaining the optimal weight values and the corresponding optimal values of the structural parameters. The proposed framework is illustrated using simulated data from a multi-dof spring–mass chain structure. In particular, compared to conventional parameter estimation techniques that are based on pre-selected values of the weights, it is demonstrated that the optimal parameter values estimated by the proposed methodology are insensitive to large model errors or bad measured modal data. 相似文献
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针对我国机车车辆现行检修制度中可能存在的过修、欠修问题,提出了一种综合图解法和改进人工蜂群(ABC)算法的机车车辆关键零部件可靠性模型拟合方法,对三参数威布尔分布进行参数估计并确立三参数威布尔可靠性模型。首先利用图解法求得三参数威布尔分布参数的初始估计值以及ABC算法的搜索空间,随后运用改进ABC算法进行迭代计算以获得较优的参数估计值,最后将可靠性模型拟合方法与最小二乘法以及概率加权矩法进行分析比较。研究结果表明,提出的可靠性模型拟合方法能够较为准确地确定三参数威布尔可靠性模型。以该模型为基础对机车车辆关键零部件进行可靠性指标计算,为决策人员确定机车车辆最佳维修周期和改进检修规程提供了科学依据。 相似文献
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为了解决混合动力挖掘机电回转系统中超级电容储能容量配置较大、价格昂贵的问题,提高整个驱动系统的性价比,提出了一种将超级电容应用于混合动力挖掘机电回转系统的功率匹配策略,并在此基础上将超级电容储能系统的性价比作为储能容量的优化目标。运用遗传算法对建立的系统数学模型进行容量优化配置。最后通过搭建系统的MATLAB模型进行了仿真验证,并对优化前后参数进行了对比。结果表明,该优化模型提高了混合动力挖掘机回转驱动系统的性价比,对于混合动力挖掘机电回转系统中超级电容容量的配置有一定的参考作用。 相似文献
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针对求解步行式挖掘机最大作业范围参数问题,建立了整机的运动学模型和稳定性力学模型,提出了一种求解步行式挖掘机最大作业范围及其最大挖掘力参数的优化模型,采用网格法对其求解,计算结果表明,该优化方法简单、可靠,为确定步行式挖掘机作业性能参数提供了理论依据. 相似文献
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为兼顾电能质量信号分析的类型识别与参数估计需要,设计一种最优化多分辨率快速S变换(OMFST),用于电能质量信号识别与参数估计。首先,分析不同时-频分辨率下时间-幅值曲线与频率-幅值曲线中,扰动起、止处峭度与扰动参数估计误差间的关系;之后,根据离差最大化法,确定不同频率范围内最优窗宽调整因子,并通过3次样条插值法进行拟合,自适应调整不同扰动信号识别和参数估计所需最优窗宽;然后,针对扰动信号基频与扰动所在的中、高频频域范围进行OMFST处理;最后,从原始信号、原始信号傅里叶谱和OMFST变换结果中提取5条特征,构建基于模糊决策树的扰动分类器,识别13种电能质量信号,并估计电能质量信号参数。仿真实验和实测数据分析表明,新方法能够满足电能质量复合扰动参数估计需要,参数估计误差低于广义S变换等方法,同时保留了良好的分类能力。 相似文献
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The hydraulic excavator energy-saving research mainly embodies the following three measures: to improve the performance of diesel engine and hydraulic component, to improve the hydraulic system, and to improve the power matching of diesel-hydraulic system-actuator. Although the above measures have certain energy-saving effect, but because the hydraulic excavator load changes frequently and fluctuates dramatically, so the diesel engine often works in high-speed and light load condition, and the fuel consumption is higher. Therefore, in order to improve the economy of diesel engine in light load, and reduce the fuel consumption of hydraulic excavator, energy management concept is proposed based on diesel engine cylinder deactivation technology. By comparing the universal characteristic under diesel normal and deactivated cylinder condition, the mechanism that fuel consumption can be reduced significantly by adopting cylinder deactivation technology under part of loads condition can be clarified. The simulation models for hydraulic system and diesel engine are established by using AMESim software, and fuel combustion consumption by using cylinder-deactivation-technology is studied through digital simulation approach. In this way, the zone of cylinder deactivation is specified. The testing system for the excavator with this technology is set up based on simulated results, and the results show that the diesel engine can still work at high efficiency with part of loads after adopting this technology; fuel consumption is dropped down to 11% and 13% under economic and heavy-load mode respectively under the condition of driving requirements. The research provides references to the energy-saving study of the hydraulic excavators. 相似文献