Jo Sumin, Sun Wookyung, Kim Bokyung, Kim Sunhee, Park Junhee, Shin Hyungsoon
Department of Electronic and Electrical Engineering, Ewha Womans University, Seoul 03760, Korea.
Department of System Semiconductor Engineering, Sangmyung University, Cheonan 31066, Korea.
Micromachines (Basel). 2019 Jun 8;10(6):384. doi: 10.3390/mi10060384.
Memristor devices are considered to have the potential to implement unsupervised learning, especially spike timing-dependent plasticity (STDP), in the field of neuromorphic hardware research. In this study, a neuromorphic hardware system for multilayer unsupervised learning was designed, and unsupervised learning was performed with a memristor neural network. We showed that the nonlinear characteristic memristor neural network can be trained by unsupervised learning only with the correlation between inputs and outputs. Moreover, a method to train nonlinear memristor devices in a supervised manner, named guide training, was devised. Memristor devices have a nonlinear characteristic, which makes implementing machine learning algorithms, such as backpropagation, difficult. The guide-training algorithm devised in this paper updates the synaptic weights by only using the correlations between inputs and outputs, and therefore, neither complex mathematical formulas nor computations are required during the training. Thus, it is considered appropriate to train a nonlinear memristor neural network. All training and inference simulations were performed using the designed neuromorphic hardware system. With the system and memristor neural network, the image classification was successfully done using both the Hebbian unsupervised training and guide supervised training methods.
在神经形态硬件研究领域,忆阻器器件被认为具有实现无监督学习的潜力,尤其是基于脉冲时间依赖可塑性(STDP)的无监督学习。在本研究中,设计了一种用于多层无监督学习的神经形态硬件系统,并使用忆阻器神经网络进行了无监督学习。我们表明,非线性忆阻器神经网络仅通过输入与输出之间的相关性即可进行无监督学习训练。此外,还设计了一种以监督方式训练非线性忆阻器器件的方法,称为引导训练。忆阻器器件具有非线性特性,这使得诸如反向传播等机器学习算法的实现变得困难。本文设计的引导训练算法仅通过使用输入与输出之间的相关性来更新突触权重,因此,在训练过程中既不需要复杂的数学公式也不需要计算。因此,它被认为适合训练非线性忆阻器神经网络。所有训练和推理模拟均使用所设计的神经形态硬件系统进行。利用该系统和忆阻器神经网络,通过赫布型无监督训练和引导监督训练方法成功完成了图像分类。