J. Keshavan  J.S. Humbert 《International journal of control》2018,91(3):715-724

This study proposes a novel complete-order nonlinear structure and motion observer for monocular vision systems subjected to significant measurement noise. In contrast with previous studies that assume noise-free measurements, and require prior knowledge of either the relative motion of the camera or scene geometry, the proposed scheme assumes a single component of linear velocity as known. Under a persistency of excitation condition, the observer then relies on filtered estimates of optical flow to yield exponentially convergent estimates of the unknown motion parameters and feature depth that converge to a uniform, ultimate bound in the presence of measurement noise. The unknown linear and angular velocities are assumed to be generated using an imperfectly known model that incorporates a bounded uncertainty, and optical flow estimation is accomplished using a robust differentiator that is based on the sliding-mode technique. Numerical results are used to validate and demonstrate superior observer performance compared to an alternative leading design in the presence of model uncertainty and measurement noise.  相似文献   

    

《Computer Animation and Virtual Worlds》2018,29(3-4)

We cannot not communicate! During our daily lives, we convey information verbally and nonverbally. Most of the affective meaning of a message is transferred with the help of facial expressions, and thereby, when trying to establish a realistic human‐like virtual character, we should pay close attention to the animation. Motion capture is one of the most common techniques, but due to the wide range of expressions humans use, the recording time and data needed are vast. To address this problem, we propose the use of semantic spaces as they help in characterizing and positioning expressions by finding a correlation between them. In this paper, we extend prior research by providing the semantic spaces underlying real videos and motion capture data for a total of 62 conversational expressions. Our results highly correlate with previous work, showing that our new expressions were correctly recognized. Moreover, our results can be used in future work to directly project potential new recordings of these 62 expressions on the found spaces.  相似文献   

    

Sangki Park  Seongcheol Ahn  Jingzhe Sun  Divij Bhatia  Dukhyun Choi  Kap Seung Yang  Jihyun Bae  Jong‐Jin Park 《Advanced functional materials》2019,29(10)

Human joints have respective ranges of motion and joint forces corresponding to each kind of joint; this necessitates considerations of the characteristics of human joints to fabricate wearable strain sensors conformable to the human body, and capable of precisely monitoring complex motions of the human body. In the present study, the “all textile‐based highly stretchable structure” that is capable of precisely sensing motions (folding and rotation) of the human joints (finger, wrist, elbow, spine, and knee) is fabricated by optimizing patterns (straight, blind, and zigzag) of conductive yarns employed as the conductive part of the strain sensor, and several textile substrates (braided elastic fabric, knit fabric, and woven fabric), having preferable elasticity and conformability employed for the fabrication of strain sensors suitable for human joints. In particular, the technology, enabling the prestraining of textile substrate, is exploited to fabricate a strain sensor that is capable of outputting selective signals corresponding to the folding motion of the spinal joint over a predetermined angle of motion, and the gait pattern of the wearer of the sensor, attached to his or her knee joint doing folding and rotational motions, is analyzed.  相似文献   

    

Caihao Deng  Peixiong Gao  Linfeng Lan  Penghui He  Xin Zhao  Wei Zheng  Wangshou Chen  Xizhou Zhong  Yunhui Wu  Lan Liu  Junbiao Peng  Yong Cao 《Advanced functional materials》2019,29(51)

Stretchable/wearable strain sensors are attracting growing interest due to their broad applications in physical and physiological measurements. However, the development of a multifunctional highly stretchable sensor satisfying the requirements of ultrahigh sensitivity (able to distinguish sound frequency) remains a challenge. An ultrasensitive and highly stretchable multifunctional strain sensor with timbre‐recognition ability based on high‐crack‐density vertical graphene (VGr) is fabricated using an ultrasonic peeling (UP) method. It can distinguish frequencies of sounds higher than 2500 Hz. Detailed microscopic examinations reveal that their ultrahigh sensitivity stems from the formation of high‐density nanocracks in the graphitic base layer, which is bridged by the top branched VGr nanowalls. These nanocracks cut the VGr film into a large number of nanopieces, which increase the natural frequency of the sensors, enabling the sensors to distinguish the sound frequency. Demonstrations are presented to highlight the sensors' potential as wearable devices for human physiological signal and timbre detections. This is the first multifunctional highly stretchable strain sensor with timbre‐recognition ability.  相似文献   

    

Dr. Maja Marušič  Dr. Judith Schlagnitweit  Prof. Dr. Katja Petzold 《Chembiochem : a European journal of chemical biology》2019,20(21):2685-2710

An ever-increasing number of functional RNAs require a mechanistic understanding. RNA function relies on changes in its structure, so-called dynamics. To reveal dynamic processes and higher energy structures, new NMR methods have been developed to elucidate these dynamics in RNA with atomic resolution. In this Review, we provide an introduction to dynamics novices and an overview of methods that access most dynamic timescales, from picoseconds to hours. Examples are provided as well as insight into theory, data acquisition and analysis for these different methods. Using this broad spectrum of methodology, unprecedented detail and invisible structures have been obtained and are reviewed here. RNA, though often more complicated and therefore neglected, also provides a great system to study structural changes, as these RNA structural changes are more easily defined—Lego like—than in proteins, hence the numerous revelations of RNA excited states.  相似文献   

    

Qinghua Meng  Zong-yao Sun  Yong Shu  Tingting Liu 《International journal of control》2019,92(4):734-744

The paper presents a lateral motion stability control method for electric vehicle (EV) driven by four in-wheel motors, which considers time-variable vehicle speed and uncertain disturbance caused by external factors. First, an EV lateral motion dynamics tracking control model is presented. Then in order to deal with the uncertain disturbance in the lateral motion model, an almost disturbance decoupling method using sampled-data state feedback is proposed. Third, a sampled-data state feedback controller is constructed based on the state feedback domination approach. The proposed controller can attenuate the disturbances’ effect on the output to an arbitrary degree of accuracy. Simulation and test results under different vehicle speeds show the effectiveness of the control method.  相似文献   

    

Liyun Yang  Ke Lu  Mikael Forsman  Kaj Lindecrantz  Fernando Seoane  Örjan Ekblom 《Ergonomics》2019,62(5):694-705

Work metabolism (WM) can be accurately estimated by oxygen consumption (VO₂), which is commonly assessed by heart rate (HR) in field studies. However, the VO₂–HR relationship is influenced by individual capacity and activity characteristics. The purpose of this study was to evaluate three models for estimating WM compared with indirect calorimetry, during simulated work activities. The techniques were: the HR-Flex model; HR branched model, combining HR with hip-worn accelerometers (ACC); and HR?+?arm-leg ACC model, combining HR with wrist- and thigh-worn ACC. Twelve participants performed five simulated work activities and three submaximal tests. The HR?+?arm-leg ACC model had the overall best performance with limits of agreement (LoA) of ?3.94 and 2.00?mL/min/kg, while the HR-Flex model had ?5.01 and 5.36?mL/min/kg and the branched model, ?6.71 and 1.52?mL/min/kg. In conclusion, the HR?+?arm-leg ACC model should, when feasible, be preferred in wearable systems for WM estimation.

Practitioner Summary: Work with high energy demand can impair employees’ health and life quality. Three models were evaluated for estimating work metabolism during simulated tasks. The model combining heart rate, wrist- and thigh-worn accelerometers showed the best accuracy. This is, when feasible, suggested for wearable systems to assess work metabolism.  相似文献   

    

D. Kasun Prasanga  Kazuki Tanida  Kouhei Ohnishi  Toshiyuki Murakami 《Advanced Robotics》2019,33(15-16):824-839

ABSTRACT

This paper proposes a novel, simultaneous bipedal locomotion method using haptics for remote operation of biped robots. In general, traditional biped walking methods require very high computational power and advanced controllers to perform the required task. However, in this proposed method, a master exoskeleton attached to the human’s lower body is used to obtain the trajectory and haptic information to generate the trajectory of the slave biped robot in real time. Lateral motion of the center of mass of the biped is constrained in this experiment. Also, it is considered that no communication delay is presented in between the two systems in this experiment, and they are not discussed in this paper. Since a direct motion transmission is used in the proposed method, this method is quite straight forward and a simultaneous walking can be realized at the same time with high performance. Also, it does not require an exact dynamic model of the biped or specific method to plan the trajectory. The gait pattern of the biped is directly determined by that of the human. Also, the operator can feel the remote environment through the exoskeleton robot. Results obtained from the experiments validate the proposed method.  相似文献   

    

Yinhong Liao  Zhiyan Wu  Xiaoping Feng 《国际射频与微波计算机辅助工程杂志》2019,29(3)

Moving elements have been widely used in microwave applicators to improve heating uniformity. However, elements in periodic motion can lead to temperature oscillations in the process of heating. In this case, the processed samples are difficult to reach target temperature and the control system may also become unstable. Aiming at overcoming these problems, we investigate the temperature response of the heating process in microwave applicators with elements in periodical motion in this article. By modeling periodical motion as a periodical heat source, the temperature characteristics can be obtained by solving the heat transfer equation with eigenfunction expansions. The results show that the amplitude of temperature oscillations decreases with angular velocity of the element's motion, which is verified by experiments. It means that temperature oscillations can be reduced by increasing the element's velocity, which is helpful to improve the heating performance in microwave applicators.  相似文献   

    

Jing Jia  Geng Tu  Xin Deng  Chuchu Zhao  Wenlong Yi 《Concurrency and Computation》2019,31(10)

In the three‐dimensional human‐computer interaction, the identification of dynamic and static gestures is a very important and challenging work in the field of machine vision, In this paper, we propose a new gesture recognition system. Leap Motion device is a kind of equipment, which is specially used for hand recognition, which can get the feature data to realize the gesture recognition in real time. The system is mainly composed of the following two parts. For static gestures, we use a kind of feature information based on the distance, direction, and bending degree of the fingertip, and bring the support vector machine into the training to realize the static gesture recognition. For dynamic gestures, we use gesture length as a benchmark to reject non‐key gestures and preprocess frames with abnormal gesture sequences. The average recognition rate of static gestures reaches 99.98%, and the recognition rate of dynamic gestures reaches 96.20%. The experimental results show that the algorithm has a good effect on gesture recognition, and it is suitable for the simple interaction between gestures, people and people and daily communication of daily communication barriers.  相似文献