EEMD+BiGRU组合模型在短时交通流量预测中的应用

针对城市交通流随机波动性强、数据中含噪声多导致预测精度下降的问题,提出一种基于集合经验模态分解(ensemble empirical mode decomposition,EEMD)和双向门控循环单元(bidirectional gated recurrent unit,BiGRU)的组合交通流量预测模型,有效地提升了短时交通流预测的精度。模型利用EEMD算法对原始数据进行分解,根据分解所得的本征模函数(intrinsic mode function,IMF)分量绘制噪声能量图谱,去除分量中的噪声,并将去噪后的IMF分量作为BiGRU网络的输入进行训练,再将训练所得的结果进行重构加和,得到最终的预测结果。实验结果表明,未舍弃含有噪声的IMF分量进行重构的预测结果,相比于参考文献中提出的EMD+LSTM模型、LSTM模型和EEMD+LSTM模型,其平均绝对百分误差分别优化了42.36%、61.82%和30.95%;舍弃含有噪声的IMF分量后进行重构的预测结果,其平均绝对百分误差相比于将全部IMF分量进行重构优化了56.62%。

基于经验模态分解和长短期记忆神经网络的短期交通流量预测

交通流量预测作为智能交通的重要一环,所要处理的交通数据具有非线性、周期性和随机性的特点,导致在数据预测时,不稳定的交通流量数据依赖于长期数据范围,且由于一些外部因素使得原始数常包含一些噪声,可能导致预测性能的进一步下降。针对上述问题提出了一种能够去噪且能处理长时依赖的预测算法——EMD-LSTM。首先,通过经验模态分解(EMD)算法将交通时序数据中的不同尺度分量逐级分解出来,生成一系列具有相同特征尺度的本征模函数,从而去除一定的噪声影响;然后,借助长短期记忆(LSTM)神经网络解决数据的长期依赖问题,从而使所提算法在长时间视野预测方面表现更为突出。对实际数据集进行短期预测的实验结果表明,EMD-LSTM的平均绝对误差(MAE)比LSTM低了1.91632,平均绝对百分误差(MAPE)比LSTM降低了4.64545个百分点,可见所提出的混合模型使预测准确性得到显著提高,能够有效解决交通数据的问题。

基于EMD-LSTM神经网络的交通流量预测模型

针对城市交通流序列非线性、周期性、随机性以及原始数据常还包含一些噪声的特点,为了提高交通流量预测精度,本文提出了一种能够去噪且能处理长时依赖问题的组合预测算法--EMD-LSTM。首先,通过经验模态分解(EMD)算法将交通时序数据中不同尺度分量逐级分解出来,生成一系列具有相同特征尺度的本征模函数,从而去除一定噪声影响;再利用长短期记忆(LSTM)神经网络解决数据的长期依赖问题,进一步提升预测精度。实验结果表明,EMD-LSTM组合模型在整体的交通流量预测和早高峰晚高峰交通流量预测中均取得了较好的结果。其中,在整体的交通流量预测中,EMD-LSTM组合预测模型的均方根误差(RMSE)比LSTM减少了5.325,平均绝对误差(MAE)比LSTM减少了3.942,平均绝对百分比误差(MAPE)比LSTM降低了5.61个百分点。

Real-time road traffic states estimation based on kernel-KNN matching of road traffic spatial characteristics

The accurate estimation of road traffic states can provide decision making for travelers and traffic managers. In this work,an algorithm based on kernel-k nearest neighbor(KNN) matching of road traffic spatial characteristics is presented to estimate road traffic states. Firstly, the representative road traffic state data were extracted to establish the reference sequences of road traffic running characteristics(RSRTRC). Secondly, the spatial road traffic state data sequence was selected and the kernel function was constructed, with which the spatial road traffic data sequence could be mapped into a high dimensional feature space. Thirdly, the referenced and current spatial road traffic data sequences were extracted and the Euclidean distances in the feature space between them were obtained. Finally, the road traffic states were estimated from weighted averages of the selected k road traffic states, which corresponded to the nearest Euclidean distances. Several typical links in Beijing were adopted for case studies. The final results of the experiments show that the accuracy of this algorithm for estimating speed and volume is 95.27% and 91.32% respectively, which prove that this road traffic states estimation approach based on kernel-KNN matching of road traffic spatial characteristics is feasible and can achieve a high accuracy.