Spiking Neural Network Robot Tactile Object Recognition Method with Regularization Constraints
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摘要: 拓展触觉感知能力是智能机器人未来发展的重要方向之一,决定着机器人的应用场景范围。由触觉传感器采集的数据是机器人完成触觉感知任务基础,但触觉数据具有复杂的时空性。脉冲神经网络具有丰富的时空动力学特征和契合硬件的事件驱动性,能更好地处理时空信息和应用于人工智能芯片给机器人带来更高能效。该文针对脉冲神经网络神经元脉冲活动离散性导致网络训练过程反向传播失效的问题,从智能触觉机器人动态系统角度,引入脉冲活动近似函数使脉冲神经网络反向传播梯度下降法有效;针对触觉脉冲数据量少导致的过拟合问题,融合正则化方法加以缓解;最后,提出具有正则化约束的脉冲神经网络机器人触觉物体识别(Spiking neural network Tactile dropout, SnnTd; Spiking neural network Tactile dropout-l2-cosine annealing, SnnTdlc)算法。相较于经典方法TactileSGNet, Grid-based CNN, MLP和GCN, SnnTd正则化方法触觉物体识别率在EvTouch-Containers数据集上比最好方法TactileSGNet提升了5.00%,SnnTdlc正则化方法触觉物体识别率在EvTouch-Objects数据集上比最好方法TactileSGNet提升了3.16%。Abstract: It is important for the future development of intelligent robots to expand tactile perception ability, which determines the scope of application scenarios for robots. Tactile data collected by tactile sensors are the basis of robotics work, but these data have complex spatio-temporal properties. Spiking neural network has rich spatio-temporal dynamics and event-driven nature. It can better process spatio-temporal information and be applied to artificial intelligence chips to bring higher energy efficiency to robots. To solve the problem of backpropagation failure in the network training process caused by the discreteness of neuron spike activity in the spiking neural network, from the perspective of the dynamic system of the intelligent robot, the spiking activity approximation function is introduced to make the spiking neural network back-propagation gradient descent method effective. The over-fitting problem caused by the small amount of tactile data is alleviated by the regularization methods. Finally, the spiking neural network robot tactile object recognition algorithm SnnTd and SnnTdlc with regularization constraints are proposed. Compared with the classical methods TactileSGNet, Grid-based CNN, MLP and GCN, the SnnTd method tactile object recognition rate is improved by 5.00% over the best method TactileSGNet on EvTouch-Containers dataset, and the SnnTdlc method tactile object recognition rate is improved by 3.16% over the best method TactileSGNet on EvTouch-Objects dataset.
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算法1 具有L2正则化约束的脉冲神经网络机器人
触觉物体识别算法相关参数:学习率${\mu _t}$, 网络参数$w$和$b$,时间步长$T$,触觉脉冲数
据$S = \left\{ {{S_1},{S_2},\cdots,{S_T}} \right\}$,目标输出
$R = \left\{ {{R_1},{R_2},\cdots,{R_T}} \right\}$,权重衰减参数$\sigma $,损失函数
$L = L(R,S) + \dfrac{\sigma }{2}{\left\| w \right\|^2}$初始化:$w$,$b$,空列表$K = \{ \} $ for ${\rm{Epoch}} = 1,2, \cdots ,N$: for $t = 1,2, \cdots ,T$: (1) 输入${S_t}$到脉冲神经网络,获得输出脉冲${K_t}$,将${K_t}$添
加到$K$;end (2) 计算损失$L = L(R,S) + \dfrac{\sigma }{2}{\left\| w \right\|^2}$; (3) 计算 $\dfrac{{\partial \left(L + \dfrac{\sigma }{2}{{\left\| w \right\|}^2}\right)}}{{\partial w}} = \displaystyle\sum\nolimits_{t = 1}^T {\dfrac{{\partial L}}{{\partial P_t^n}}E_t^{n - 1}} + \sigma w$,
$\dfrac{{\partial (L + \dfrac{\sigma }{2}{{\left\| w \right\|}^2})}}{{\partial b}} = \displaystyle\sum\nolimits_{t = 1}^T {\dfrac{{\partial L}}{{\partial P_t^n}}} $;(4) 根据Adam优化算法进行更新; (5) 通过余弦退火算法更新学习率${\mu _t}$; (6) 更新参数$w$,$b$; end 表 1 超参数设置表
参数 值 参数 值 Epochs 100 宽度系数$a$ 0.5 初始学习率${\rm{lr}}$ 1×10–3 dropout1 0.2 学习率衰减因子$\alpha $ 0.1 dropout2 0.5 学习率衰减代数${\rm{lrEpochs}}$ 40 动量${\beta _1}$ 0.9 余弦退火最小学习率${{\rm{lr}}_{ {\text{min} } } }$ 5×10–6 均方根传播${\beta _2}$ 0.999 膜电位阈值${P_{{\text{TH}}}}$ 0.5 权重衰减$\sigma $ 0.01 表 2 EvTouch-Containers数据集实验结果
模型 方法 Acc(%) TrainingLoss TestLoss Dropout L2 Cosine Annealing SnnT 66.00±0.86 2.13±0.04 1.03±0.01 SnnTd √ 69.17±1.18 2.61±0.01 1.04±0.01 SnnTl √ 68.33±1.11 2.13±0.02 1.02±0.01 SnnTc √ 67.17±1.58 1.96±0.01 1.03±0.01 SnnTdl √ √ 66.33±1.32 2.67±0.01 1.04±0.01 SnnTdc √ √ 66.17±0.81 2.45±0.01 1.03±0.01 SnnTlc √ √ 67.17±1.37 2.01±0.01 1.02±0.01 SnnTdlc √ √ √ 67.33±0.86 2.51±0.01 1.04±0.01 表 3 EvTouch-Objects数据集实验结果
模型 方法 Acc(%) TrainingLoss TestLoss Dropout L2 Cosine Annealing SnnT 89.17±0.36 1.60±0.01 1.13±0.01 SnnTd √ 90.63±0.59 2.34±0.01 1.20±0.01 SnnTl √ 89.31±0.88 1.71±0.02 1.14±0.01 SnnTc √ 89.10±0.57 1.48±0.01 1.12±0.01 SnnTdl √ √ 90.90±0.39 2.38±0.01 1.20±0.01 SnnTdc √ √ 90.49±0.33 2.17±0.01 1.18±0.01 SnnTlc √ √ 89.86±0.67 1.58±0.02 1.12±0.01 SnnTdlc √ √ √ 91.04±0.39 2.22±0.01 1.18±0.01 表 4 SnnTdlc模型与经典方法在两个数据集下Acc的实验结果(%)
模型 EvTouch-Containers EvTouch-Objects TactileSGNet 64.17±2.75 89.44±0.55 Grid-based CNN 60.17±2.78 88.40±1.14 MLP 58.83±2.49 85.97±0.85 GCN 58.83±2.84 85.14±1.51 SnnTd 69.17±1.18 90.63±0.59 SnnTdlc 67.33±0.86 91.04±0.39 -
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