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摘要: 为提高回声状态网络对于时间序列预测问题的处理能力, 本文提出了一种延迟深度回声状态网络构造方法.该方法将多个子神经元池顺序连接, 每两个相邻的子神经元池之间嵌入了一个滞后环节.由于滞后环节的存在,该网络可将长时记忆任务转化为一系列短时记忆任务, 从而简化长时依赖问题的求解, 同时降低神经元池的构建难度.实验表明, 该网络具有强大的短时记忆容量, 对初始参数有较好的鲁棒性, 对时间序列预测问题的处理能力也比常规回声状态网络有显著提高.Abstract: To improve the prediction ability of echo state network (ESN) on time series problems, this paper proposes a delayed deep ESN (DDESN) constructing method. In this scheme, multiple sub-reservoirs are connected one by one in sequence, and time delay modules are inserted between every two adjacent sub-reservoirs. The DDESN can transfer a long-term memory task into a series of short-term memory tasks because of the existence of the delay links. It simplifles the solution to long-term dependent task and reduces the di–culty of building a reservoir. Experimental results show that the proposed DDESN has stronger short-term memory capacity, better robustness to randomly initialized parameters, and higher performance on solving time series tasks than a standard ESN.
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Key words:
- Artiflcial neural networks /
- echo state network /
- deep learning /
- short-term memory capacity /
- time series prediction
1) 本文责任编委 刘青山 -
表 1 ESN及DDESN参数设置
Table 1 Parameters settings for ESN and DDESN
Model $n$ $N^i$ $D^i$ $\rho^i$ $MC_{\max}$ ESN 1 100 0 0.95 31.08 DDESN$_2$ 2 50 0 $\sim$ 100 0.95 54.02 DDESN$_5$ 5 20 0 $\sim$ 50 0.95 62.07 表 2 参数设置
Table 2 Parameter settings
表 3 Mackey-Glass预测性能
Table 3 Prediction performance for Mackey-Glass
Task ESN D & S ESN DDESN $\mathrm{NRMSE}_{84}$ 0.140 0.031 5$.81\times10^{-3}$ NRMSE120 0.220 0.049 0.010 表 4 不同ESN模型的性能比较(MSO任务)
Table 4 Performance comparison of different ESN models (MSO tasks)
Task DDESN Balanced ESN[19] Evolutionary[27] D & S ESN[22] Evolino[28] MSO$_2$ $3.95\times10^{-8}$ $2.51\times10^{-12}$ $3.92\times10^{-8}$ $3.02\times10^{-9}$ $4.15\times10^{-3}$ MSO$_5$ $6.84\times10^{-7}$ $1.06\times10^{-6}$ $2.54\times10^{-2}$ $8.21\times10^{-5}$ $0.166$ MSO$_8$ $6.89\times10^{-6}$ $2.73\times10^{-4}$ $4.96\times10^{-3}$ $-$ $-$ MSO$_{12}$ $1.50\times10^{-4}$ $-$ $-$ $-$ $-$ 表 5 DDESN的鲁棒性测试结果
Table 5 Robustness testing results of DDESN
Task NARMA MSO$_{2}$ MSO$_{5}$ MSO$_{8}$ MSO$_{12}$ M-G$_{30}$ 最大NRMSE 0.2369 $7.03\times 10^{-5}$ $4.44\times 10^{-3}$ $6.33\times 10^{-2}$ $3.10\times 10^{-3}$ 0.0874 最小NRMSE 0.1968 $3.95\times 10^{-8}$ $6.84\times 10^{-7}$ $5.17\times 10^{-6}$ $1.50\times 10^{-4}$ 0.0058 平均NRMSE 0.2151 $1.06\times 10^{-6}$ $1.42\times 10^{-4}$ $7.17\times 10^{-4}$ $6.44\times 10^{-4}$ 0.0224 NRMSE标准差 0.0089 $7.03\times 10^{-6}$ $7.17\times 10^{-4}$ $6.31\times 10^{-3}$ $4.41\times 10^{-4}$ 0.0130 -
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