Position-aware activity recognition with wearable devices

Reliable human activity recognition with wearable devices enables the development of human-centric pervasive applications. We aim to develop a robust wearable-based activity recognition system for real life situations where the device position is up to the user or where a user is unable to collect initial training data. Consequently, in this work we focus on the problem of recognizing the on-body position of the wearable device ensued by comprehensive experiments concerning subject-specific and cross-subjects activity recognition approaches that rely on acceleration data. We introduce a device localization method that predicts the on-body position with an F-measure of 89% and a cross-subjects activity recognition approach that considers common physical characteristics. In this context, we present a real world data set that has been collected from 15 participants for 8 common activities where they carried 7 wearable devices in different on-body positions. Our results show that the detection of the device position consistently improves the result of activity recognition for common activities. Regarding cross-subjects models, we identified the waist as the most suitable device location at which the acceleration patterns for the same activity across several people are most similar. In this context, our results provide evidence for the reliability of physical characteristics based cross-subjects models.     

Robust least squares twin support vector machine for human activity recognition

Human activity recognition is an active area of research in Computer Vision. One of the challenges of activity recognition system is the presence of noise between related activity classes along with high training and testing time complexity of the system. In this paper, we address these problems by introducing a Robust Least Squares Twin Support Vector Machine (RLS-TWSVM) algorithm. RLS-TWSVM handles the heteroscedastic noise and outliers present in activity recognition framework. Incremental RLS-TWSVM is proposed to speed up the training phase. Further, we introduce the hierarchical approach with RLS-TWSVM to deal with multi-category activity recognition problem. Computational comparisons of our proposed approach on four well-known activity recognition datasets along with real world machine learning benchmark datasets have been carried out. Experimental results show that our method is not only fast but, yields significantly better generalization performance and is robust in order to handle heteroscedastic noise and outliers.     

A lightweight deep learning with feature weighting for activity recognition

With the development of deep learning, numerous models have been proposed for human activity recognition to achieve state-of-the-art recognition on wearable sensor data. Despite the improved accuracy achieved by previous deep learning models, activity recognition remains a challenge. This challenge is often attributed to the complexity of some specific activity patterns. Existing deep learning models proposed to address this have often recorded high overall recognition accuracy, while low recall and precision are often recorded on some individual activities due to the complexity of their patterns. Some existing models that have focused on tackling these issues are always bulky and complex. Since most embedded systems have resource constraints in terms of their processor, memory and battery capacity, it is paramount to propose efficient lightweight activity recognition models that require limited resources consumption, and still capable of achieving state-of-the-art recognition of activities, with high individual recall and precision. This research proposes a high performance, low footprint deep learning model with a squeeze and excitation block to address this challenge. The squeeze and excitation block consist of a global average-pooling layer and two fully connected layers, which were placed to extract the flattened features in the model, with best-fit reduction ratios in the squeeze and excitation block. The squeeze and excitation block served as channel-wise attention, which adjusted the weight of each channel to build more robust representations, which enabled our network to become more responsive to essential features while suppressing less important ones. By using the best-fit reduction ratio in the squeeze and excitation block, the parameters of the fully connected layer were reduced, which helped the model increase responsiveness to essential features. Experiments on three publicly available datasets (PAMAP2, WISDM, and UCI-HAR) showed that the proposed model outperformed existing state-of-the-art with fewer parameters and increased the recall and precision of some individual activities compared to the baseline, and the existing models.     

Multi-sensor information fusion based on machine learning for real applications in human activity recognition: State-of-the-art and research challenges

This paper firstly introduces common wearable sensors, smart wearable devices and the key application areas. Since multi-sensor is defined by the presence of more than one model or channel, e.g. visual, audio, environmental and physiological signals. Hence, the fusion methods of multi-modality and multi-location sensors are proposed. Despite it has been contributed several works reviewing the stateoftheart on information fusion or deep learning, all of them only tackled one aspect of the sensor fusion applications, which leads to a lack of comprehensive understanding about it. Therefore, we propose using a more holistic approach in order to provide a more suitable starting point from which to develop a full understanding of the fusion methods of wearable sensors. Specifically, this review attempts to provide a more comprehensive survey of the most important aspects of multi-sensor applications for human activity recognition, including those recently added to the field for unsupervised learning and transfer learning. Finally, the open research issues that need further research and improvement are identified and discussed.     

支持向量机在模式识别中的核函数特性分析

支持向量机是20世纪90年代中期发展起来的一种机器学习技术,与传统人工神经网络不同之处在于前者基于结构风险最小化原理,后者基于经验风险最小化原理。支持向量机不仅结构简单,而且技术性能尤其是泛化能力与BP神经网络相比有明显提高。讨论了支持向量机的分类原理,并用多项式函数、径向基函数和感知机函数等3种核函数作为内积回旋,分别以平面点集分类、手写体汉字识别及双螺旋线识别为例,在不同的结构参数下进行了仿真实验,并对3种核函数的分类特性进行了对比分析,给出了在不同模式识别问题中3种核函数的选择条件。     

支持向量机算法用于拮抗药化合物活性的模式识别

试用新近提出的，特别适合于小样本多变量训练集的支持向量机（support vector machine,简称SVM）算法于复杂药物分子设计。对一批26个处理化疗或放疗呕吐拮抗药的候选化合物筛选数据用留一法判别SVM的预报能力。结果表明：与人工神经网络，最近邻法（KNN），Fisher法相比，SVM算法可以提供误报率更低的数学模型。     

液晶字符识别的CNN和SVM组合分类器

针对仪表液晶显示字符识别问题,提出一种结合了卷积神经网络(CNN)和支持向量机(SVM)的字符识别方法.分别采用具有并联结构的CNN模型和基于梯度方向直方图(HOG)特征的SVM方法构建基本分类器,当2个分类器的结果存在冲突时,利用CNN的softmax输出最大值判决最终结果,当其大于设定阈值时采用CNN分类器的结果,...     

Face recognition based on extreme learning machine

Extreme learning machine (ELM) is an efficient learning algorithm for generalized single hidden layer feedforward networks (SLFNs), which performs well in both regression and classification applications. It has recently been shown that from the optimization point of view ELM and support vector machine (SVM) are equivalent but ELM has less stringent optimization constraints. Due to the mild optimization constraints ELM can be easy of implementation and usually obtains better generalization performance. In this paper we study the performance of the one-against-all (OAA) and one-against-one (OAO) ELM for classification in multi-label face recognition applications. The performance is verified through four benchmarking face image data sets.     

基于支持向量机方法的中文组织机构名的识别

在应用基本的支持向量机算法的基础上,提出了一种分步递增式学习的方法,利用主动学习的策略对训练样本进行选择,逐步增大提交给学习器训练样本的规模,以提高学习器的识别精度.实验表明,采用主动学习策略的支持向量机算法是有效的,在实验中,中文机构名识别的正确率和召回率分别达到了81.7%和86.8%.     

Dynamic action recognition based on dynemes and Extreme Learning Machine

In this paper, we propose a novel method that performs dynamic action classification by exploiting the effectiveness of the Extreme Learning Machine (ELM) algorithm for single hidden layer feedforward neural networks training. It involves data grouping and ELM based data projection in multiple levels. Given a test action instance, a neural network is trained by using labeled action instances forming the groups that reside to the test sample’s neighborhood. The action instances involved in this procedure are, subsequently, mapped to a new feature space, determined by the trained network outputs. This procedure is performed multiple times, which are determined by the test action instance at hand, until only a single class is retained. Experimental results denote the effectiveness of the dynamic classification approach, compared to the static one, as well as the effectiveness of the ELM in the proposed dynamic classification setting.     

Integration of discriminative and generative models for activity recognition in smart homes

Activity recognition in smart homes enables the remote monitoring of elderly and patients. In healthcare systems, reliability of a recognition model is of high importance. Limited amount of training data and imbalanced number of activity instances result in over-fitting thus making recognition models inconsistent. In this paper, we propose an activity recognition approach that integrates the distance minimization (DM) and probability estimation (PE) approaches to improve the reliability of recognitions. DM uses distances of instances from the mean representation of each activity class for label assignment. DM is useful in avoiding decision biasing towards the activity class with majority instances; however, DM can result in over-fitting. PE on the other hand has good generalization abilities. PE measures the probability of correct assignments from the obtained distances, while it requires a large amount of data for training. We apply data oversampling to improve the representation of classes with less number of instances. Support vector machine (SVM) is applied to combine the outputs of both DM and PE, since SVM performs better with imbalanced data and further improves the generalization ability of the approach. The proposed approach is evaluated using five publicly available smart home datasets. The results demonstrate better performance of the proposed approach compared to the state-of-the-art activity recognition approaches.     

考虑性别差异基于SVM的说话人识别研究

说话人识别是目前身份认证及人工智能领域研究的一个热点,解决说话人识别问题具有重要的理论价值和深远的实用意义.基于语音鲜明个性特征和显著的性别差异,提出了一种考虑性别差异的说话人识别方法,并采用SVM分类器进行训练和测试.先对SVM分类器分别进行性别识别训练和同性集合内个体识别的分类训练,建立起相应的支持向量集合,以此为基础,先后进行说话人的性别识别测试和个体识别测试.实验结果表明,该方法可以有效提高闭集说话人识别系统的性能.     

The Opportunity challenge: A benchmark database for on-body sensor-based activity recognition

There is a growing interest on using ambient and wearable sensors for human activity recognition, fostered by several application domains and wider availability of sensing technologies. This has triggered increasing attention on the development of robust machine learning techniques that exploits multimodal sensor setups. However, unlike other applications, there are no established benchmarking problems for this field. As a matter of fact, methods are usually tested on custom datasets acquired in very specific experimental setups. Furthermore, data is seldom shared between different groups. Our goal is to address this issue by introducing a versatile human activity dataset recorded in a sensor-rich environment. This database was the basis of an open challenge on activity recognition. We report here the outcome of this challenge, as well as baseline performance using different classification techniques. We expect this benchmarking database will motivate other researchers to replicate and outperform the presented results, thus contributing to further advances in the state-of-the-art of activity recognition methods.     

An efficient feature selection method for mobile devices with application to activity recognition

This paper presents a feature selection method for data classification, which combines a model-based variable selection technique and a fast two-stage subset selection algorithm. The relationship between a specified (and complete) set of candidate features and the class label is modeled using a non-linear full regression model which is linear-in-the-parameters. The performance of a sub-model measured by the sum of the squared-errors (SSE) is used to score the informativeness of the subset of features involved in the sub-model. The two-stage subset selection algorithm approaches a solution sub-model with the SSE being locally minimized. The features involved in the solution sub-model are selected as inputs to support vector machines (SVMs) for classification. The memory requirement of this algorithm is independent of the number of training patterns. This property makes this method suitable for applications executed in mobile devices where physical RAM memory is very limited.An application was developed for activity recognition, which implements the proposed feature selection algorithm and an SVM training procedure. Experiments are carried out with the application running on a PDA for human activity recognition using accelerometer data. A comparison with an information gain-based feature selection method demonstrates the effectiveness and efficiency of the proposed algorithm.     

基于支持向量机和小波分析的说话人识别

为解决说话人识别问题,提出了一种基于支持向量机和小波分析的识别方法以及其框架模型,即将小波分析应用于信号预处理,并以此为基础,利用其奇异点检测原理将语音信号和噪声分离,实现语音增强,最终基于样本进行训练和测试,采用SVM实现说话人的分类识别.     

用于回归的临近支持向量机

将临近支持向量分类杌应用在回归问题上,提出临近支持向量回归机,给出线性与非线性情况下的回归函数,该方法比支持向量回归机(svR)问题减少了参数和一半变量,比最小二乘支持向量回归机(LSSVMR)求解公式更加简单,且核函数不需要满足Mercer条件.数值实验结果表明,与SVR和LSSVMR相比,该方法的学习速度更快,且泛化能力较之不相上下.     

基于支持向量机的尿液细胞图像识别分类研究

为提高尿液细胞进行识别分类的效果,分析和比较了在RGB和HIS两种不同色彩坐标系统下使用支持向量机对尿液细胞进行识别分类的效果,分析和比较了使用色彩特征参数与空间特征参数进行综合识别分类尿液细胞的效果,提出使用网格搜索交叉验证法对支持向量机的参数进行优化.实验结果表明,提出的HSI颜色参数、空间参数、网格搜索交叉验证优化选择参数相结合的方法在尿液细胞识别分类中效果良好.     

疲劳驾驶面部表情识别算法

针对疲劳驾驶的六种表情 ,提出几何规范化结合 Gabor滤波提取表情特征 ,使用支持向量机对疲劳驾驶的面部表情分类识别的系统。首先对视频图像预处理进行几何规范化 ,利用二维 Gabor核函数构造最优滤波器 48个,获取 48个面部表情特征点 ,最后利用支持向量机进行面部表情分类识别。实验结果表明径向基函数的 SVM性能最好。     

基于sEMG的行走步态非均匀特性及其对识别的影响

人体生理特性和运动特性是影响步态识别的重要因素。利用实验采集的下肢表面肌电信号,首先对肌电信号进行小波消噪及特征提取,然后构造支持向量机分类器进行分类与识别,并针对步态周期数据的非均匀性（非等时性）特性进行了详细讨论。结果表明,即使在匀速行走条件下,人体步态周期仍然存在一定的非均匀特性,且这一特点会影响步态识别的准确性。这对于进一步研究步态稳定性和步态识别率等具有一定的参考价值。