基于时频融合特征的3D空间手写识别

研究基于3D加速度传感器的空间手写识别技术,提出一种基于时频融合特征的分类识别方法。从加速度数据中提取短时能量 (STE)特征及低频分量,经快速傅里叶变换后提取频域特征WPD+FFT,将时域特征STE和频域特征WPD+FFT进行特征融合,利用主成分分析法对其降维,采用支持向量机进行分类识别。实验结果表明,该方法能提高空间手写识别系统的识别率。     

基于隐马尔可夫模型的3D手写识别方法

为实现便捷高效的人机交互,提高交互能力,在基于隐马尔可夫模型(HMM)的基础上,提出了一种新的3D手写识别方法。该方法使用带有三轴加速度传感器的手持设备去采集各种手写数据;使用插值及快速傅里叶变换(FFT)滤波等方法对采集的数据进行预处理;使用隐马尔可夫模型对每个手写动作进行模型训练;使用训练过的手写模型对采集的数据进行手写识别。数据测试结果表明,该方法在手持移动设备上数据分类的准确性可达到84.5%。     

2D representation of facial surfaces for multi-pose 3D face recognition

The increasing availability of 3D facial data offers the potential to overcome the intrinsic difficulties faced by conventional face recognition using 2D images. Instead of extending 2D recognition algorithms for 3D purpose, this letter proposes a novel strategy for 3D face recognition from the perspective of representing each 3D facial surface with a 2D attribute image and taking the advantage of the advances in 2D face recognition. In our approach, each 3D facial surface is mapped homeomorphically onto a 2D lattice, where the value at each site is an attribute that represents the local 3D geometrical or textural properties on the surface, therefore invariant to pose changes. This lattice is then interpolated to generate a 2D attribute image. 3D face recognition can be achieved by applying the traditional 2D face recognition techniques to obtained attribute images. In this study, we chose the pose invariant local mean curvature calculated at each vertex on the 3D facial surface to construct the 2D attribute image and adopted the eigenface algorithm for attribute image recognition. We compared our approach to state-of-the-art 3D face recognition algorithms in the FRGC (Version 2.0), GavabDB and NPU3D database. Our results show that the proposed approach has improved the robustness to head pose variation and can produce more accurate 3D multi-pose face recognition.     

基于三轴加速度传感器的手势识别

针对手势交互中手势信号的相似性和不稳定性,设计实现一种基于三轴加速度传感器的手势识别方案。采用MMA7260加速度传感器采集主手腕的手势动作信号,根据手势加速度信号的特点,进行手势动作数据窗口的自动检测、信号去噪和重采样等预处理,通过提取手势动作的关键特征,构造离散隐马尔可夫模型,实现手势动作识别。实验结果证明该方案的识别精度较高。     

Aligned texture map creation for pose invariant face recognition

In last years, Face recognition based on 3D techniques is an emergent technology which has demonstrated better results than conventional 2D approaches. Using texture (180° multi-view image) and depth maps is supposed to increase the robustness towards the two main challenges in Face Recognition: Pose and illumination. Nevertheless, 3D data should be acquired under highly controlled conditions and in most cases depends on the collaboration of the subject to be recognized. Thus, in applications such as surveillance or control access points, this kind of 3D data may not be available during the recognition process. This leads to a new paradigm using some mixed 2D-3D face recognition systems where 3D data is used in the training but either 2D or 3D information can be used in the recognition depending on the scenario. Following this concept, where only part of the information (partial concept) is used in the recognition, a novel method is presented in this work. This has been called Partial Principal Component Analysis (P²CA) since they fuse the Partial concept with the fundamentals of the well known PCA algorithm. This strategy has been proven to be very robust in pose variation scenarios showing that the 3D training process retains all the spatial information of the face while the 2D picture effectively recovers the face information from the available data. Furthermore, in this work, a novel approach for the automatic creation of 180° aligned cylindrical projected face images using nine different views is presented. These face images are created by using a cylindrical approximation for the real object surface. The alignment is done by applying first a global 2D affine transformation of the image, and afterward a local transformation of the desired face features using a triangle mesh. This local alignment allows a closer look to the feature properties and not the differences. Finally, these aligned face images are used for training a pose invariant face recognition approach (P²CA).     

用块稀疏贝叶斯学习算法重构识别体域网步态模式

针对低功耗体域网步态远程监测终端非稀疏加速度数据重构和步态模式识别性能优化问题,提出了一种基于块稀疏贝叶斯学习的体域网远程步态模式重构识别新方法,该方法基于体域网远程步态监测系统架构和压缩感知框架,在体域网传感节点利用线性稀疏矩阵压缩原始加速度数据,减少传输数据量,降低其功耗,同时在远程终端基于块稀疏贝叶斯学习算法充分利用加速度数据块结构内在相关性,获取加速度数据内在稀疏性,有效提高非稀疏加速度数据重构性能,为准确识别步态模式提供可靠的数据支撑.采用USC-HAD数据库中行走、跑、跳、上楼、下楼五种步态运动的加速度数据验证新方法的有效性,实验结果表明,基于所提算法的加速度数据重构性能明显优于传统压缩感知重构算法性能,使基于支持向量机多步态分类器识别准确率可达98%,显著提高体域网远程步态模式识别性能.所提新方法不仅有效提高非稀疏加速度数据重构和步态模式识别性能,并且也有助于设计低功耗、低成本的体域网加速度数据采集系统,为体域网远程监测步态模式变化提供一个新方法和新思路.     

A time-efficient convolutional neural network model in human activity recognition

Activity recognition represents the task of classifying data derived from different sensor types into one of predefined activity classes. The most popular and beneficial sensors in the area of action recognition are inertial sensors such as accelerometer and gyroscope. Convolutional neural network (CNN) as one of the best deep learning methods has recently attracted much attention to the problem of activity recognition, where 1D kernels capture local dependency over time in a series of observations measured at inertial sensors (3-axis accelerometers and gyroscopes) while in 2D kernels apart from time dependency, dependency between signals from different axes of same sensor and also over different sensors will be considered. Most convolutional neural networks used for recognition task are built using convolution and pooling layers followed by a few number of fully connected layers but large and deep neural networks have high computational costs. In this paper, we propose a new architecture that consists solely of convolutional layers and find that with removing the pooling layers and instead adding strides to convolution layers, the computational time will decrease notably while the model performance will not change or in some cases will even improve. Also both 1D and 2D convolutional neural networks with and without pooling layer will be investigated and their performance will be compared with each other and also with some other hand-crafted feature based methods. The third point that will be discussed in this paper is the impact of applying fast fourier transform (FFT) to inputs before training learning algorithm. It will be shown that this preprocessing will enhance the model performance. Experiments on benchmark datasets demonstrate the high performance of proposed 2D CNN model with no pooling layers.

     

人脸识别:从二维到三维

人脸识别是生物特征识别技术的一个重要方向。虽然目前大部分研究都还只是针对二维人脸图像,但是3D人脸模型包含更丰富的人脸信息,有助于机器对人脸的识别。从二维到三维,人脸识别研究进入了一个新的阶段。从3D人脸数据的获取方式入手,介绍最近提出的一系列3D人脸识别算法,并进行归类。最后提出"有针对性地获取3D人脸模型数据是进行有效识别的基础"这一结论。     

Online motion recognition using an accelerometer in a mobile device

This paper introduces a new method to implement a motion recognition process using a mobile phone fitted with an accelerometer. The data collected from the accelerometer are interpreted by means of a statistical study and machine learning algorithms in order to obtain a classification function. Then, that function is implemented in a mobile phone and online experiments are carried out. Experimental results show that this approach can be used to effectively recognize different human activities with a high-level accuracy.     

Recognition of Actions of Medical Workers on the Basis of Accelerometer Readings with the Use of a Deep Belief Network

This paper analyzes a real set of large-volume medico-statistical data used for the recognition of actions of medical workers on the basis of accelerometer readings at definite moments of time. During the recognition process, a deep belief network was applied to unlabeled data, and then it was supervisedly learned using the error backpropagation method. The obtained results demonstrate higher recognition accuracy in comparison with basic methods. A considerable improvement in medical staff productivity is also achieved.     

Geometry-Based Ensembles: Toward a Structural Characterization of the Classification Boundary

This article introduces a novel binary discriminative learning technique based on the approximation of the non-linear decision boundary by a piece-wise linear smooth additive model. The decision border is geometrically defined by means of the characterizing boundary points - points that belong to the optimal boundary under a certain notion of robustness. Based on these points, a set of locally robust linear classifiers is defined and assembled by means of a Tikhonov regularized optimization procedure in an additive model to create a final lambda-smooth decision rule. As a result, a very simple and robust classifier with a strong geometrical meaning and non-linear behavior is obtained. The simplicity of the method allows its extension to cope with some of nowadays machine learning challenges, such as online learning, large scale learning or parallelization, with linear computational complexity. We validate our approach on the UCI database. Finally, we apply our technique in online and large scale scenarios, and in six real life computer vision and pattern recognition problems: gender recognition, intravascular ultrasound tissue classification, speed traffic sign detection, Chagas' disease severity detection, clef classification and action recognition using a 3D accelerometer data. The results are promising and this paper opens a line of research that deserves further attention.     

一种基于特征增强和决策融合的人体行为识别方法

利用三轴加速度传感器进行人体行为识别一直是传感器数据处理、模式识别领域的研究热点。加速度数据往往存在着多种动作数据难以区分的情况,特别是走、上楼、下楼这3个动作数据非常相似,这给正确识别这3种人体动作带来了较大的难度。提出一种基于特征增强与决策融合的行为识别方法,通过对部分特征值进行增强处理和对多个分类结果进行决策融合来识别走、上楼、下楼这些难以区分的相似动作。实验验证,所提方法可克服由于加速度数据的相似性而导致的动作识别正确率低、识别误差大的情况,有效提高人体行为识别率,且可在实际应用中实时识别人体行为动作。     

基于手机加速度计的地震场景分层识别方法

利用智能手机内置加速度计进行地震场景识别是地震预警研究领域的新热点,现有的利用手机识别地震的方法中,地震模拟场景与真实情形出入较大,且识别方法较为单一。利用地震体验屋模拟出地震场景数据,提出一种两层分类的地震场景识别方法以区分地震场景和不同日常生活场景。该方法中,首先为提出的最大相关系数和（Sum of Maximum Correlation,SMC）特征设置单门限,利用数据周期性排除跑步、步行等人类运动场景,再利用[K]最邻近算法对非周期性运动场景数据进行第二层分类,以正确提取地震场景。实验结果表明,该分层识别方法快速且地震场景和非地震场景识别率均在96%以上。     

基于CNN与双向LSTM的行为识别算法

针对传统行为识别依赖手工提取特征,智能化程度不高,识别精度低的问题,提出一种基于3D骨骼数据的卷积神经网络(CNN)与双向长短期记忆网络(Bi-LSTM)的混合模型。使用3D骨骼数据作为网络输入,CNN提取每个时间步的3D输入数据间的空间特征,Bi-LSTM更深层地提取3D数据序列的时间特征。该混合模型自动提取特征完成分类,实现骨骼数据到识别结果的端对端学习。在UTKinect-Action3D标准数据集上,模型的识别率达到97.5%,在自制Kinect数据集上的准确率达到98.6%,实验结果表明,该网络有效提高了分类准确率,具备可用性和有效性。     

Static and dynamic 3D facial expression recognition: A comprehensive survey

Automatic facial expression recognition constitutes an active research field due to the latest advances in computing technology that make the user's experience a clear priority. The majority of work conducted in this area involves 2D imagery, despite the problems this presents due to inherent pose and illumination variations. In order to deal with these problems, 3D and 4D (dynamic 3D) recordings are increasingly used in expression analysis research. In this paper we survey the recent advances in 3D and 4D facial expression recognition. We discuss developments in 3D facial data acquisition and tracking, and present currently available 3D/4D face databases suitable for 3D/4D facial expressions analysis as well as the existing facial expression recognition systems that exploit either 3D or 4D data in detail. Finally, challenges that have to be addressed if 3D facial expression recognition systems are to become a part of future applications are extensively discussed.     

Multi-scale Conditional Random Fields for first-person activity recognition on elders and disabled patients

We propose a novel pervasive system to recognise human daily activities from a wearable device. The system is designed in a form of reading glasses, named ‘Smart Glasses’, integrating a 3-axis accelerometer and a first-person view camera. Our aim is to classify subject’s activities of daily living (ADLs) based on their vision and head motion data. This ego-activity recognition system not only allows caretakers to track on a specific person (such as disabled patient or elderly people), but also has the potential to remind/warn people with cognitive impairments of hazardous situations. We present the following contributions: a feature extraction method from accelerometer and video; a classification algorithm integrating both locomotive (body motions) and stationary activities (without or with small motions); a novel multi-scale dynamic graphical model for structured classification over time. In this paper, we collect, train and validate our system on two large datasets: 20 h of elder ADLs datasets and 40 h of patient ADLs datasets, containing 12 and 14 different activities separately. The results show that our method efficiently improves the system performance (F-Measure) over conventional classification approaches by an average of 20%–40% up to 84.45%, with an overall accuracy of 90.04% for elders. Furthermore, we also validate our method on 30 patients with different disabilities, achieving an overall accuracy up to 77.07%.     

保角特征结合改进差分进化算法的三维人脸识别

针对三维人脸识别的高复杂度和二维人脸识别无法提供粒状线索的问题,提出一种全自动3D人脸表情识别算法, 该算法主要是提供比2D人脸识别更多的线索,同时降低计算复杂度。首先通过保角映射将3D人脸转化到2D平面,保留了面部变化的线索;然后,提出了基于优化算法的差分进化(DE)算法用于提高识别效率,同时提取最优人脸特征集和分类器参数,加速鲁棒特征(SURF)池描述了所有预期的人脸特征点。在博斯普鲁斯、FRGC v2及自己搜集的人脸数据集上的实验结果表明,本文算法解决了三维人脸识别的高计算复杂度和二维人脸识别的线索低问题,并在不降低识别性能的前提下大大地节约了成本,相比几种较为先进的三维人脸识别算法,本文算法取得了更好的识别效果,有望应用于一些商业人脸识别系统。     

Pose-Robust Facial Expression Recognition Using View-Based 2D $+$ 3D AAM

This paper proposes a pose-robust face tracking and facial expression recognition method using a view-based 2D 3D active appearance model (AAM) that extends the 2D 3D AAM to the view-based approach, where one independent face model is used for a specific view and an appropriate face model is selected for the input face image. Our extension has been conducted in many aspects. First, we use principal component analysis with missing data to construct the 2D 3D AAM due to the missing data in the posed face images. Second, we develop an effective model selection method that directly uses the estimated pose angle from the 2D 3D AAM, which makes face tracking pose-robust and feature extraction for facial expression recognition accurate. Third, we propose a double-layered generalized discriminant analysis (GDA) for facial expression recognition. Experimental results show the following: 1) The face tracking by the view-based 2D 3D AAM, which uses multiple face models with one face model per each view, is more robust to pose change than that by an integrated 2D 3D AAM, which uses an integrated face model for all three views; 2) the double-layered GDA extracts good features for facial expression recognition; and 3) the view-based 2D 3D AAM outperforms other existing models at pose-varying facial expression recognition.     

PCA-based image recombination for multimodal 2D + 3D face recognition

Most of the existing approaches of multimodal 2D + 3D face recognition exploit the 2D and 3D information at the feature or score level. They do not fully benefit from the dependency between modalities. Exploiting this dependency at the early stage is more effective than the later stage. Early fusion data contains richer information about the input biometric than the compressed features or matching scores. We propose an image recombination for face recognition that explores the dependency between modalities at the image level. Facial cues from the 2D and 3D images are recombined into a more independent and discriminating data by finding transformation axes that account for the maximal amount of variances in the images. We also introduce a complete framework of multimodal 2D + 3D face recognition that utilizes the 2D and 3D facial information at the enrollment, image and score levels. Experimental results based on NTU-CSP and Bosphorus 3D face databases show that our face recognition system using image recombination outperforms other face recognition systems based on the pixel- or score-level fusion.