Remaining useful life(RUL)prediction is one of the most crucial components in prognostics and health management(PHM)of aero-engines.This paper proposes an RUL prediction method of aero-engines considering the randomne...Remaining useful life(RUL)prediction is one of the most crucial components in prognostics and health management(PHM)of aero-engines.This paper proposes an RUL prediction method of aero-engines considering the randomness of failure threshold.Firstly,a random-coefficient regression(RCR)model is used to model the degradation process of aeroengines.Then,the RUL distribution based on fixed failure threshold is derived.The prior parameters of the degradation model are calculated by a two-step maximum likelihood estimation(MLE)method and the random coefficient is updated in real time under the Bayesian framework.The failure threshold in this paper is defined by the actual degradation process of aeroengines.After that,a expectation maximization(EM)algorithm is proposed to estimate the underlying failure threshold of aeroengines.In addition,the conditional probability is used to satisfy the limitation of failure threshold.Then,based on above results,an analytical expression of RUL distribution of aero-engines based on the RCR model considering random failure threshold(RFT)is derived in a closed-form.Finally,a case study of turbofan engine is used to demonstrate the effectiveness and superiority of the RUL prediction method and the parameters estimation method of failure threshold proposed.展开更多
针对过程复杂且结构未知的对象,在保证模型有效性的前提下,根据数据信息构建简单模型来简化控制器的求解是亟待解决的问题。以受控自回归模型为例,提出一种基于修正最小角回归算法的稀疏辨识方法。首先将系统模型转化为过参数化的高维...针对过程复杂且结构未知的对象,在保证模型有效性的前提下,根据数据信息构建简单模型来简化控制器的求解是亟待解决的问题。以受控自回归模型为例,提出一种基于修正最小角回归算法的稀疏辨识方法。首先将系统模型转化为过参数化的高维稀疏模型,然后将最小角回归算法用于稀疏系统辨识,并提出绝对角度停止准则,使算法经过少量的迭代即可获得模型的稀疏参数估计,并同时获得有效的时滞和阶次估计。结合辨识得到的受控自回归模型,引入一种基于指定相位点频率和增益的比例-积分-微分(proportional integral derivative,PID)控制器。数值仿真和平衡机器人的姿态控制仿真表明,该稀疏辨识算法在低数据量下具有较高的辨识精度,建立的模型具有较好的泛化性能,控制器具有良好的控制效果。展开更多
锂电池健康状态(state of health, SOH)的退化过程在一定程度上是一个非平稳随机过程,使得当前多数点估计机器学习方法在实际应用中受到限制。基于贝叶斯理论的高斯过程回归(Gaussian process regression,GPR),因可输出估计结果的不确定...锂电池健康状态(state of health, SOH)的退化过程在一定程度上是一个非平稳随机过程,使得当前多数点估计机器学习方法在实际应用中受到限制。基于贝叶斯理论的高斯过程回归(Gaussian process regression,GPR),因可输出估计结果的不确定性,近年来在锂电池SOH区间估计中得到广泛应用。然而,GPR的性能很大程度上取决于其核函数的选择,当前研究多凭借经验选用固定单一核函数,无法适应不同的数据集。为此,本文提出一种基于自适应最优组合核函数GPR的锂电池SOH区间估计方法。该方法首先从电池充放电数据中提取出多个健康因子(health factor, HF),并采用皮尔森相关系数法优选出6个与SOH高度相关的健康因子作为模型的输入。然后,在当前常用的7个核函数集合上,通过两两随机组合构造新的组合核函数,并利用交叉验证自适应优选出最优组合核函数。采用3个不同数据集对所提方法进行了验证,结果表明:本文方法具有出色的SOH区间估计性能。在3个公开数据集上,平均区间宽度指标在0.0509以内,平均区间分数大于-0.0004,均方根误差小于0.0181。展开更多
锂电池健康状态(state of health,SOH)的在线估计是锂电池管理系统中必不可少的一部分。大部分基于数据驱动的锂电池SOH估计方法由于计算量较大,难以在锂电池管理系统微控制器中在线使用。因此,文中提出基于新型健康特征的锂电池SOH快...锂电池健康状态(state of health,SOH)的在线估计是锂电池管理系统中必不可少的一部分。大部分基于数据驱动的锂电池SOH估计方法由于计算量较大,难以在锂电池管理系统微控制器中在线使用。因此,文中提出基于新型健康特征的锂电池SOH快速估计方法。首先,分析锂电池的充电数据,基于已有的锂电池恒流充电过程的等压升时间(time interval of an equal charging voltage difference,TIECVD)健康特征,构建一个同充电电压起点、同充电时间间隔的健康特征。其次,文中提出基于新型健康特征和多元线性回归(multiple linear regression,MLR)的锂电池SOH快速估计方法。然后,通过对牛津锂电池老化数据集和美国国家航空航天局锂电池随机使用数据集进行分析,以0.01 V步长遍历恒流充电电压区间,以皮尔逊相关系数最大为目标,确定锂电池最优的起始电压。最后,考虑不同充电时间间隔,利用最小二乘(ordinary least squares,OLS)回归分析方法,确定锂电池最优充电时间间隔参数。使用2个数据集划分的训练集建立MLR模型,使用2个数据集划分的验证集对文中方法进行验证。实验结果表明,文中基于新型健康特征方法可极大缩减计算量,并且可以在保障预测精度的前提下实现锂电池SOH的快速估计。展开更多
Urban air pollution has brought great troubles to physical and mental health,economic development,environmental protection,and other aspects.Predicting the changes and trends of air pollution can provide a scientific ...Urban air pollution has brought great troubles to physical and mental health,economic development,environmental protection,and other aspects.Predicting the changes and trends of air pollution can provide a scientific basis for governance and prevention efforts.In this paper,we propose an interval prediction method that considers the spatio-temporal characteristic information of PM_(2.5)signals from multiple stations.K-nearest neighbor(KNN)algorithm interpolates the lost signals in the process of collection,transmission,and storage to ensure the continuity of data.Graph generative network(GGN)is used to process time-series meteorological data with complex structures.The graph U-Nets framework is introduced into the GGN model to enhance its controllability to the graph generation process,which is beneficial to improve the efficiency and robustness of the model.In addition,sparse Bayesian regression is incorporated to improve the dimensional disaster defect of traditional kernel density estimation(KDE)interval prediction.With the support of sparse strategy,sparse Bayesian regression kernel density estimation(SBR-KDE)is very efficient in processing high-dimensional large-scale data.The PM_(2.5)data of spring,summer,autumn,and winter from 34 air quality monitoring sites in Beijing verified the accuracy,generalization,and superiority of the proposed model in interval prediction.展开更多
光伏发电在能源领域中具有重要地位。为了准确量化光伏发电功率的不确定性和波动范围,并提高区间预测的综合性能,提出了一种基于特征挖掘与改进TCN-BiGRU的光伏功率区间概率预测方法。首先,利用最大信息系数和符号传递熵因果分析,对气...光伏发电在能源领域中具有重要地位。为了准确量化光伏发电功率的不确定性和波动范围,并提高区间预测的综合性能,提出了一种基于特征挖掘与改进TCN-BiGRU的光伏功率区间概率预测方法。首先,利用最大信息系数和符号传递熵因果分析,对气象特征进行筛选,剔除冗余信息,并构造全球水平辐射趋势特征、季节性特征和天气聚类特征以提供更多有效信息。随后,结合时间模式注意力机制和分位数回归方法对TCN-BiGRU模型进行改进,构建组合模型进行区间预测。最后,采用散度度量半极差优化经验带宽选择的核密度估计(kernel density estimation,KDE)方法生成概率预测结果。通过真实光伏电站数据进行分析,验证了所提方法在光伏功率区间概率预测中具有较高的可靠性和适用性。展开更多
基金supported by the National Natural Science Foundation of China(61703410,61873175,62073336,61873273,61773386,61922-089)the Basic Research Plan of Shaanxi Natural Science Foundation of China(2022JM-376).
文摘Remaining useful life(RUL)prediction is one of the most crucial components in prognostics and health management(PHM)of aero-engines.This paper proposes an RUL prediction method of aero-engines considering the randomness of failure threshold.Firstly,a random-coefficient regression(RCR)model is used to model the degradation process of aeroengines.Then,the RUL distribution based on fixed failure threshold is derived.The prior parameters of the degradation model are calculated by a two-step maximum likelihood estimation(MLE)method and the random coefficient is updated in real time under the Bayesian framework.The failure threshold in this paper is defined by the actual degradation process of aeroengines.After that,a expectation maximization(EM)algorithm is proposed to estimate the underlying failure threshold of aeroengines.In addition,the conditional probability is used to satisfy the limitation of failure threshold.Then,based on above results,an analytical expression of RUL distribution of aero-engines based on the RCR model considering random failure threshold(RFT)is derived in a closed-form.Finally,a case study of turbofan engine is used to demonstrate the effectiveness and superiority of the RUL prediction method and the parameters estimation method of failure threshold proposed.
基金Supported by National High Technology Research and Development Program of China （863 Program） （2006AA040308）, National Natural Science Foundation of China （60736021）, and the National Creative Research Groups Science Foundation of China （60721062）
文摘针对过程复杂且结构未知的对象,在保证模型有效性的前提下,根据数据信息构建简单模型来简化控制器的求解是亟待解决的问题。以受控自回归模型为例,提出一种基于修正最小角回归算法的稀疏辨识方法。首先将系统模型转化为过参数化的高维稀疏模型,然后将最小角回归算法用于稀疏系统辨识,并提出绝对角度停止准则,使算法经过少量的迭代即可获得模型的稀疏参数估计,并同时获得有效的时滞和阶次估计。结合辨识得到的受控自回归模型,引入一种基于指定相位点频率和增益的比例-积分-微分(proportional integral derivative,PID)控制器。数值仿真和平衡机器人的姿态控制仿真表明,该稀疏辨识算法在低数据量下具有较高的辨识精度,建立的模型具有较好的泛化性能,控制器具有良好的控制效果。
文摘锂电池健康状态(state of health, SOH)的退化过程在一定程度上是一个非平稳随机过程,使得当前多数点估计机器学习方法在实际应用中受到限制。基于贝叶斯理论的高斯过程回归(Gaussian process regression,GPR),因可输出估计结果的不确定性,近年来在锂电池SOH区间估计中得到广泛应用。然而,GPR的性能很大程度上取决于其核函数的选择,当前研究多凭借经验选用固定单一核函数,无法适应不同的数据集。为此,本文提出一种基于自适应最优组合核函数GPR的锂电池SOH区间估计方法。该方法首先从电池充放电数据中提取出多个健康因子(health factor, HF),并采用皮尔森相关系数法优选出6个与SOH高度相关的健康因子作为模型的输入。然后,在当前常用的7个核函数集合上,通过两两随机组合构造新的组合核函数,并利用交叉验证自适应优选出最优组合核函数。采用3个不同数据集对所提方法进行了验证,结果表明:本文方法具有出色的SOH区间估计性能。在3个公开数据集上,平均区间宽度指标在0.0509以内,平均区间分数大于-0.0004,均方根误差小于0.0181。
文摘锂电池健康状态(state of health,SOH)的在线估计是锂电池管理系统中必不可少的一部分。大部分基于数据驱动的锂电池SOH估计方法由于计算量较大,难以在锂电池管理系统微控制器中在线使用。因此,文中提出基于新型健康特征的锂电池SOH快速估计方法。首先,分析锂电池的充电数据,基于已有的锂电池恒流充电过程的等压升时间(time interval of an equal charging voltage difference,TIECVD)健康特征,构建一个同充电电压起点、同充电时间间隔的健康特征。其次,文中提出基于新型健康特征和多元线性回归(multiple linear regression,MLR)的锂电池SOH快速估计方法。然后,通过对牛津锂电池老化数据集和美国国家航空航天局锂电池随机使用数据集进行分析,以0.01 V步长遍历恒流充电电压区间,以皮尔逊相关系数最大为目标,确定锂电池最优的起始电压。最后,考虑不同充电时间间隔,利用最小二乘(ordinary least squares,OLS)回归分析方法,确定锂电池最优充电时间间隔参数。使用2个数据集划分的训练集建立MLR模型,使用2个数据集划分的验证集对文中方法进行验证。实验结果表明,文中基于新型健康特征方法可极大缩减计算量,并且可以在保障预测精度的前提下实现锂电池SOH的快速估计。
基金Project(2020YFC2008605)supported by the National Key Research and Development Project of ChinaProject(52072412)supported by the National Natural Science Foundation of ChinaProject(2021JJ30359)supported by the Natural Science Foundation of Hunan Province,China。
文摘Urban air pollution has brought great troubles to physical and mental health,economic development,environmental protection,and other aspects.Predicting the changes and trends of air pollution can provide a scientific basis for governance and prevention efforts.In this paper,we propose an interval prediction method that considers the spatio-temporal characteristic information of PM_(2.5)signals from multiple stations.K-nearest neighbor(KNN)algorithm interpolates the lost signals in the process of collection,transmission,and storage to ensure the continuity of data.Graph generative network(GGN)is used to process time-series meteorological data with complex structures.The graph U-Nets framework is introduced into the GGN model to enhance its controllability to the graph generation process,which is beneficial to improve the efficiency and robustness of the model.In addition,sparse Bayesian regression is incorporated to improve the dimensional disaster defect of traditional kernel density estimation(KDE)interval prediction.With the support of sparse strategy,sparse Bayesian regression kernel density estimation(SBR-KDE)is very efficient in processing high-dimensional large-scale data.The PM_(2.5)data of spring,summer,autumn,and winter from 34 air quality monitoring sites in Beijing verified the accuracy,generalization,and superiority of the proposed model in interval prediction.
文摘光伏发电在能源领域中具有重要地位。为了准确量化光伏发电功率的不确定性和波动范围,并提高区间预测的综合性能,提出了一种基于特征挖掘与改进TCN-BiGRU的光伏功率区间概率预测方法。首先,利用最大信息系数和符号传递熵因果分析,对气象特征进行筛选,剔除冗余信息,并构造全球水平辐射趋势特征、季节性特征和天气聚类特征以提供更多有效信息。随后,结合时间模式注意力机制和分位数回归方法对TCN-BiGRU模型进行改进,构建组合模型进行区间预测。最后,采用散度度量半极差优化经验带宽选择的核密度估计(kernel density estimation,KDE)方法生成概率预测结果。通过真实光伏电站数据进行分析,验证了所提方法在光伏功率区间概率预测中具有较高的可靠性和适用性。
