Parametric hidden Markov models for gesture recognition

A method for the representation, recognition, and interpretation of parameterized gesture is presented. By parameterized gesture we mean gestures that exhibit a systematic spatial variation; one example is a point gesture where the relevant parameter is the two-dimensional direction. Our approach is to extend the standard hidden Markov model method of gesture recognition by including a global parametric variation in the output probabilities of the HMM states. Using a linear model of dependence, we formulate an expectation-maximization (EM) method for training the parametric HMM. During testing, a similar EM algorithm simultaneously maximizes the output likelihood of the PHMM for the given sequence and estimates the quantifying parameters. Using visually derived and directly measured three-dimensional hand position measurements as input, we present results that demonstrate the recognition superiority of the PHMM over standard HMM techniques, as well as greater robustness in parameter estimation with respect to noise in the input features. Finally, we extend the PHMM to handle arbitrary smooth (nonlinear) dependencies. The nonlinear formulation requires the use of a generalized expectation-maximization (GEM) algorithm for both training and the simultaneous recognition of the gesture and estimation of the value of the parameter. We present results on a pointing gesture, where the nonlinear approach permits the natural spherical coordinate parameterization of pointing direction     

基于OpenCV的摄像头动态手势轨迹识别及其应用

利用OpenCV计算机视觉库在vs2008平台上设计了一个基于实时摄像头的集动态手势检测、动态手势跟踪、动态手势轨迹识别的应用.首先,该应用基于静止的背景更新,利用背景差分检测运动手势,再结合颜色直方图的粒子滤波进行动态手势跟踪,最后利用隐马尔可夫模型(HMM)进行运动轨迹识别.在运动检测部分结合了背景差分图与通过颜色直方图获得的反投影图,达到比较满意的实时运动检测效果;在运动手势跟踪部分,改进的颜色直方图的粒子跟踪能够在经过类肤色人脸的干扰后迅速地找回运动手势,基本达到了跟踪的要求,但是同时对于HMM识别轨迹时需要的运动轨迹序列采集造成了影响;在识别轨迹部分,HMM的训练达到了识别的要求,但是识别的效果主要取决于实时运动轨迹序列的采集工作与采集方法的优化.     

一种基于嵌入式系统实时交互的手势识别方法*

提出了一种在单摄像头条件下基于嵌入式系统的手势识别方法。通过拟合手势图的外接多边形,找出其所对应的手势缺陷图,并建立手势与手势缺陷图的一一映射,利用手势缺陷图的特征来匹配和识别不同的手势。算法还将手势的跟踪与识别有机地统一起来,通过预测下一帧中手势出现的粗略位置大大降低识别步骤的计算量。该算法在实际应用的嵌入式平台下,能快速、准确地实现手势的识别,能够满足实时人机交互的要求。     

Untethered gesture acquisition and recognition for virtual world manipulation

Humans use a combination of gesture and speech to interact with objects and usually do so more naturally without holding a device or pointer. We present a system that incorporates user body-pose estimation, gesture recognition and speech recognition for interaction in virtual reality environments. We describe a vision-based method for tracking the pose of a user in real time and introduce a technique that provides parameterized gesture recognition. More precisely, we train a support vector classifier to model the boundary of the space of possible gestures, and train Hidden Markov Models (HMM) on specific gestures. Given a sequence, we can find the start and end of various gestures using a support vector classifier, and find gesture likelihoods and parameters with a HMM. A multimodal recognition process is performed using rank-order fusion to merge speech and vision hypotheses. Finally we describe the use of our multimodal framework in a virtual world application that allows users to interact using gestures and speech.     

Tracking hand rotation and various grasping gestures from an IR camera using extended cylindrical manifold embedding

This paper presents a new approach for tracking hand rotation and various grasping gestures through an infrared camera. For the complexity and ambiguity of an observed hand shape, it is difficult to simultaneously estimate hand configuration and orientation from a silhouette image of a grasping hand gesture. This paper proposes a dynamic shape model for hand grasping gestures using cylindrical manifold embedding to analyze variations of hand shape in different hand configurations between two key hand poses and in simultaneous circular view change by hand rotation. An arbitrary hand shape between two key hand poses from any view can be generated using a cylindrical manifold embedding point after learning nonlinear generative models from the embedding space to the corresponding hand shape observed. The cylindrical manifold embedding model is extended to various grasping gestures by decomposing multiple cylindrical manifold embeddings through grasping style analysis. Grasping hand gestures with simultaneous hand rotation are tracked using particle filters on the manifold space with grasping style estimation. Experimental results for synthetic and real data indicate that the proposed model can accurately track various grasping gestures with hand rotation. The proposed approach may be applied to advanced user interfaces in dark environments by using images beyond the visible spectrum.     

Visual recognition of pointing gestures for human–robot interaction

In this paper, we present an approach for recognizing pointing gestures in the context of human–robot interaction. In order to obtain input features for gesture recognition, we perform visual tracking of head, hands and head orientation. Given the images provided by a calibrated stereo camera, color and disparity information are integrated into a multi-hypothesis tracking framework in order to find the 3D-positions of the respective body parts. Based on the hands’ motion, an HMM-based classifier is trained to detect pointing gestures. We show experimentally that the gesture recognition performance can be improved significantly by using information about head orientation as an additional feature. Our system aims at applications in the field of human–robot interaction, where it is important to do run-on recognition in real-time, to allow for robot egomotion and not to rely on manual initialization.     

Motion estimation based on optical flow and an artificial neural network (ANN)

Motion estimation provides an attractive alternative to cumbersome interface devices for human-computer interaction (HCI). Worthy of note is that the visual recognition of hand gestures can help to achieve an easy and natural interaction between human and computer. The interfaces of HCI and other virtual reality systems depend on accurate, real-time hand and fingertip tracking for an association between real objects and the corresponding digital information. However, they are expensive, and complicated operations can make them troublesome. We are developing a real-time, view-based gesture recognition system. The optical flow is estimated and segmented into motion fragments. Using an artificial neural network (ANN), the system can compute and estimate the motions of gestures. Compared with traditional approaches, theoretical and experimental results show that this method has simpler hardware and algorithms, but is more effective. It can be used in moving object recognition systems for understanding human body languages.     

Tracking,recognition, and distance detection of hand gestures for a 3‐D interactive display

Abstract— This study proposes an interactive system for displays, the technologies of which consists of three main parts: hand‐gesture tracking, recognition, and depth measurement. The proposed interactive system can be applied to a general 3‐D display. In this interactive system, for hand‐gesture tracking, Haar‐like features are employed to detect a specific hand gesture to start tracking, while the mean‐shift algorithm and Kalman filter are adopted for fast tracking. First, for recognizing hand gestures, a principal component analysis (PCA) algorithm is used to localize colored areas of skin, and then hand gestures are identified by comparison with a prepared database. Second, a simple optical system is set up with an infrared laser source and a grid mask in order to project a proposed horizontal stripe pattern. Third, the projected patterns are deciphered to extract the depth information using the Hough‐transform algorithm. The system containing hand‐gesture localization, recognition, and associated depth detection (the distance between the display and the hand), was included in a prototype of an interactive display. Demonstration of rotation recognition of a finger‐pointing hand gesture was successful by using the algorithm of radar‐like scanning.     

基于HMM方法的动态手势识别技术的改进

为了提高基于HMM方法的动态手势识别的效率和准确性,针对HMM方法在训练手势中计算的高复杂性,提出了一种HMM算法和动态规划的算法相结合的方法,对HMM算法中的训练阶段进行了改进,增强了人机交互的准确性与实时性。     

A probabilistic model for state sequence analysis in hidden Markov model for hand gesture recognition

The role of gesture recognition is significant in areas like human‐computer interaction, sign language, virtual reality, machine vision, etc. Among various gestures of the human body, hand gestures play a major role to communicate nonverbally with the computer. As the hand gesture is a continuous pattern with respect to time, the hidden Markov model (HMM) is found to be the most suitable pattern recognition tool, which can be modeled using the hand gesture parameters. The HMM considers the speeded up robust feature features of hand gesture and uses them to train and test the system. Conventionally, the Viterbi algorithm has been used for training process in HMM by discovering the shortest decoded path in the state diagram. The recursiveness of the Viterbi algorithm leads to computational complexity during the execution process. In order to reduce the complexity, the state sequence analysis approach is proposed for training the hand gesture model, which provides a better recognition rate and accuracy than that of the Viterbi algorithm. The performance of the proposed approach is explored in the context of pattern recognition with the Cambridge hand gesture data set.     

Neural recognition of human pointing gestures in real images

We present a neural network based system for the visual recognition of human hand pointing gestures from stereo pairs of video camera images. The accuracy of the current system allows to estimate the pointing target to an accuracy of 2 cm in a workspace area of 50×50 cm. The system consists of several neural networks that perform the tasks of image segmentation, estimation of hand location, estimation of 3D-pointing direction and necessary coordinate transforms. Drawing heavily on the use of learning algorithms, the functions of all network modules were created from data examples only.     

融合关节旋转特征和指尖距离特征的手势识别

作为人机交互的重要方式,手势交互和识别由于其具有的高自由度而成为计算机图形学、虚拟现实与人机交互等领域的研究热点.传统直接提取手势轮廓或手部关节点位置信息的手势识别方法,其提取的特征通常难以准确表示手势之间的区别.针对手势识别中不同手势具有的高自由度以及由于手势图像分辨率低、背景杂乱、手被遮挡、手指形状尺寸不同、个体差异性导致手势特征表示不准确等问题,本文提出了一种新的融合关节旋转特征和指尖距离特征的手势特征表示与手势识别方法.首先从手势深度图中利用手部模板并将手部看成链段结构提取手部20个关节点的3D位置信息;然后利用手部关节点位置信息提取四元数关节旋转特征和指尖距离特征,该表示构成了手势特征的内在表示;最后利用一对一支持向量机对手势进行有效识别分类.本文不仅提出了一种新的手势特征表示与提取方法,该表示融合了关节旋转信息和指尖距离特征;而且从理论上证明了该特征表示能唯一地表征手势关节点的位置信息;同时提出了基于一对一SVM多分类策略进行手势分类与识别.对ASTAR静态手势深度图数据集中8类中国数字手势和21类美国字母手势数据集分别进行了实验验证,其分类识别准确率分别为99.71%和85.24%.实验结果表明,本文提出的基于关节旋转特征和指尖距离特征的融合特征能很好地表示不同手势的几何特征,能准确地表征静态手势并进行手势识别.     

一种面向实时交互的变形手势跟踪方法

变形手势跟踪是基于视觉的人机交互研究中的一项重要内容.单摄像头条件下,提出一种新颖的变形手势实时跟踪方法.利用一组2D手势模型替代高维度的3D手模型.首先利用贝叶斯分类器对静态手势进行识别,然后对图像进行手指和指尖定位,通过将图像特征与识别结果进行匹配,实现了跟踪过程的自动初始化.提出将K-means聚类算法与粒子滤波相结合,用于解决多手指跟踪问题中手指互相干扰的问题.跟踪过程中进行跟踪状态检测,实现了自动恢复跟踪及手势模型更新.实验结果表明,该方法可以实现对变形手势快速、准确的连续跟踪,能够满足基于视觉的实时人机交互的要求.     

图像识别的静态手势识别与动态跟踪系统设计

本文研究了图像手势识别和增强现实技术,设计了可以进行静态手势识别和动态跟踪的系统,通过提前录入不同手势,利用皮肤颜色对图像进行OSTU自适应阈值划分,建立二值化图像,与已知的手势进行匹配,以得到手势结果。实验结果表明,准确率达到96.8%,识别速度达到0.55 s。动态跟踪利用检测每帧图像中手部的位置进行定位和捕捉,图像捕捉帧数达到28帧/s,对手势静态识别和动态跟踪实现了人机之间的良好交互。     

Recognition of dynamic hand gestures

This paper is concerned with the problem of recognition of dynamic hand gestures. We have considered gestures which are sequences of distinct hand poses. In these gestures hand poses can undergo motion and discrete changes. However, continuous deformations of the hand shapes are not permitted. We have developed a recognition engine which can reliably recognize these gestures despite individual variations. The engine also has the ability to detect start and end of gesture sequences in an automated fashion. The recognition strategy uses a combination of static shape recognition (performed using contour discriminant analysis), Kalman filter based hand tracking and a HMM based temporal characterization scheme. The system is fairly robust to background clutter and uses skin color for static shape recognition and tracking. A real time implementation on standard hardware is developed. Experimental results establish the effectiveness of the approach.     

Two-handed gesture recognition and fusion with speech to command a robot

Assistance is currently a pivotal research area in robotics, with huge societal potential. Since assistant robots directly interact with people, finding natural and easy-to-use user interfaces is of fundamental importance. This paper describes a flexible multimodal interface based on speech and gesture modalities in order to control our mobile robot named Jido. The vision system uses a stereo head mounted on a pan-tilt unit and a bank of collaborative particle filters devoted to the upper human body extremities to track and recognize pointing/symbolic mono but also bi-manual gestures. Such framework constitutes our first contribution, as it is shown, to give proper handling of natural artifacts (self-occlusion, camera out of view field, hand deformation) when performing 3D gestures using one or the other hand even both. A speech recognition and understanding system based on the Julius engine is also developed and embedded in order to process deictic and anaphoric utterances. The second contribution deals with a probabilistic and multi-hypothesis interpreter framework to fuse results from speech and gesture components. Such interpreter is shown to improve the classification rates of multimodal commands compared to using either modality alone. Finally, we report on successful live experiments in human-centered settings. Results are reported in the context of an interactive manipulation task, where users specify local motion commands to Jido and perform safe object exchanges.     

基于视线跟踪和手势识别的人机交互

提出一种新的基于视线跟踪和手势识别的交互方式用于远距离操作计算机。系统通过摄像头采集用户的图像,利用图像识别算法检测人眼和手指的位置,由人眼和指尖的连线确定用户指向屏幕的位置,通过判别用户手势的变化实现各种操作,达到人机交互的目的。实验结果表明,该交互方式可以较好地定位屏幕和判断用户的操作,实现自然、友好的远距离人机交互。     

Simulating a Smartboard by Real-Time Gesture Detection in Lecture Videos

Gesture plays an important role for recognizing lecture activities in video content analysis. In this paper, we propose a real-time gesture detection algorithm by integrating cues from visual, speech and electronic slides. In contrast to the conventional “complete gesture” recognition, we emphasize detection by the prediction from “incomplete gesture”. Specifically, intentional gestures are predicted by the modified hidden Markov model (HMM) which can recognize incomplete gestures before the whole gesture paths are observed. The multimodal correspondence between speech and gesture is exploited to increase the accuracy and responsiveness of gesture detection. In lecture presentation, this algorithm enables the on-the-fly editing of lecture slides by simulating appropriate camera motion to highlight the intention and flow of lecturing. We develop a real-time application, namely simulated smartboard, and demonstrate the feasibility of our prediction algorithm using hand gesture and laser pen with simple setup without involving expensive hardware.      

Gesture Spotting and Recognition for Human–Robot Interaction

Visual interpretation of gestures can be useful in accomplishing natural human-robot interaction (HRI). Previous HRI research focused on issues such as hand gestures, sign language, and command gesture recognition. Automatic recognition of whole-body gestures is required in order for HRI to operate naturally. This presents a challenging problem, because describing and modeling meaningful gesture patterns from whole-body gestures is a complex task. This paper presents a new method for recognition of whole-body key gestures in HRI. A human subject is first described by a set of features, encoding the angular relationship between a dozen body parts in 3-D. A feature vector is then mapped to a codeword of hidden Markov models. In order to spot key gestures accurately, a sophisticated method of designing a transition gesture model is proposed. To reduce the states of the transition gesture model, model reduction which merges similar states based on data-dependent statistics and relative entropy is used. The experimental results demonstrate that the proposed method can be efficient and effective in HRI, for automatic recognition of whole-body key gestures from motion sequences     

Enabling Multimodal Human–Robot Interaction for the Karlsruhe Humanoid Robot

In this paper, we present our work in building technologies for natural multimodal human-robot interaction. We present our systems for spontaneous speech recognition, multimodal dialogue processing, and visual perception of a user, which includes localization, tracking, and identification of the user, recognition of pointing gestures, as well as the recognition of a person's head orientation. Each of the components is described in the paper and experimental results are presented. We also present several experiments on multimodal human-robot interaction, such as interaction using speech and gestures, the automatic determination of the addressee during human-human-robot interaction, as well on interactive learning of dialogue strategies. The work and the components presented here constitute the core building blocks for audiovisual perception of humans and multimodal human-robot interaction used for the humanoid robot developed within the German research project (Sonderforschungsbereich) on humanoid cooperative robots.