Navigation by vibration: Effects of vibrotactile feedback on a navigation task

In the background of spatial orientation in a navigation task, this study investigated the effect of frequency, duration and amplitude of vibrotactile feedback when it provided primary information modality. Multiple levels of each parameter were designed for an experiment conducted with 18 participants. Their performance was evaluated via number of errors, task completion time, annoyance level, and user preference. Result showed that medium level of frequency and duration was more preferred and can produce better performance. However, optimal amplitude level varied by individuals and also interacted with frequency. The paper summarized a set of design guidelines, which could be used to the design of future user interface with vibrotactile feedback. The study should provide great empirical data and meaningful insight for the design of vibrotactile feedback for future applications.Relevance to industryThe paper evaluated the vibrotactile interfaces and summarized a set of design guidelines, which could help to speed up the commercialization and industrial application of vibrotactile user interface.     

Reduction of electrotactile perception threshold using subthreshold vibrotactile stimuli

Electrotactile Perception Threshold (EPT) is critical for designing electrotactile displays, which is the minimum amplitude of an electrical stimulus that can be perceived. A significant concern in electrotactile displays is skin irritation and burns due to prolonged electrical stimulus with high amplitude. This study aims to propose a method for reducing the EPT using a background stimulation with a vibrotactile display at subthreshold: 90% of the Vibration Perception Threshold (VPT) at 235 Hz. A psychophysical experiment was conducted to measure EPT at the middle of the left forearm with and without the vibrotactile display using the staircase method. A reduction of 3 to 5% in EPT was observed, which can be further enhanced with varying study parameters. In addition, the comfort and safety aspects of the user’s assessment have been analyzed. Electrotactile stimulations have a higher Steven’s power exponent (1.51). Hence a reduced threshold (although it’s only 3 to 5%) would be perceptually significant and advantageous for sensory substitution and rehabilitation (vision, auditory, and gustatory).     

Tactile display and vibrotactile pattern recognition on the torso

A wirelessly controlled tactile display has been designed, fabricated and tested for use as a navigation aid. The display comprises a 4 × 4 array of vibrating motors that is mounted on a waist band and stimulates the skin across the lower back. Three types of electromechanical actuators were evaluated for use in the display; based on their mechanical performance and power requirements, two of these motors were then used to fabricate tactile displays. The performance of the displays and the wireless tactile control units was assessed experimentally by having subjects identify which of eight possible vibrotactile patterns was presented to the lower back. The results indicated that subjects could recognize the vibrotactile patterns with almost perfect accuracy and that there was no difference between the two types of motor used for the displays. Moreover, the ability to recognize the pattern of vibrotactile stimulation was superior on the back as compared to the forearm. A further experiment confirmed that the tactile display can be used as a navigation aid outdoors and that the vibrotactile patterns presented can be interpreted as directional or instructional cues with almost perfect accuracy.     

Presentation of Surface Height Profiles Based on Frequency Modulation at Constant Amplitude Using Vibrotactile Elements

This study attempted to observe what effects the frequency modulation of vibration elements produce in representing a tactile shape. Tactile shapes were modulated based on frequency difference at constant amplitude through a tactile feedback array of 30 (5 × 6) pins, which stimulated the finger pad. Experiment I showed that participants feel height changes when modulating frequency. In Experiment II, the participants were asked to discriminate three basic tactile shape patterns, which were generated with different frequencies at constant amplitude. Experiment II proved that spatial height information can be represented by modulating temporal information. In Experiment III, the frequency modulation method was applied to the tactile mouse system. Dynamic frequency modulation at passive touch can be used to transmit tactile height pattern information to the user of the mouse pointer for more practical application. The results showed that the participants were able to discern eight predefined shapes with an accuracy of 98.4% upon passive touch.     

Wearable vibrotactile systems for virtual contact and information display

This paper presents a development history of a wearable, scalable vibrotactile stimulus delivery system. This history has followed a path from desktop-based, fully wired systems, through hybrid approaches consisting of a wireless connection from the host computer to a body-worn control box and wires to each tactor, to a completely wireless system employing Bluetooth technology to connect directly from the host to each individual tactor unit. Applications for such a system include delivering vibrotactile contact cues to users of virtual environments, providing directional cues in order to increase situational awareness in both real and virtual environments, and for general information display in wearable contexts. Through empirical study, we show that even a simple configuration, such as eight tactors arrayed around the torso, can be effective in increasing situational awareness in a building-clearing task, compared to users who perform the same task without the added cues.     

巴克豪森励磁检测传感器设计与仿真分析

针对铁磁性材料设计了一种基于巴克豪森效应的励磁检测传感器装置.为了验证所设计的励磁检测传感器中励磁装置的可行性,利用有限元电磁场仿真分析软件Ansoft对磁化器部分进行了有限元仿真,并分析了不同激励条件下的试样磁化效果.通过仿真结果可以得出:磁化装置符合设计要求,能够对试件进行有效的励磁;通过不同参数下的仿真结果得到,励磁电流幅值以及频率是影响励磁效果的关键因素,并且对于特定分析点,随着励磁电流的幅值减小以及频率的增加,试件磁感应强度基本呈现减小的变化趋势.     

Cursor orientation and computer screen positioning movements

Implicit directional cues in arrowhead cursors could influence positioning of a cursor on the screen of the computer. Performance during cursor placement may benefit from compatibilities between cursor orientation and direction of movement. Arrowheads could also elicit illusory processes that may affect judgments of (a) the distances on the screen or (b) the location of the point of the arrowhead. To address the impact of the cursor's orientation on its positioning, we had 12 participants move cursors (crosshairs, leftward, or rightward arrow) leftward or rightward to targets (near, far) on a computer screen. Movement amplitude was more important than cursor orientation for initiation of rightward movements, whereas cursor orientation affected the duration of leftward movements and movements to farther targets. Arrowhead orientation contributed to the greater overshooting of far targets. There was little evidence that compatibility of orientation and direction of movement assisted response initiation or execution, and there was little indication that arrowhead cursors led to illusory effects that influenced cursor placement. Arrowhead cursors can provide irrelevant stimulus dimensions that distract users. This work can be applied to the design of cursors in graphical user interfaces. The use of orientation-neutral cursors or cursors whose stimulus dimensions are more relevant is recommended.     

移动无线传感器网络系统在n-Rayleigh信道下的性能分析

在n￣Rayleigh信道下,研究了使用选择合并( SC)接收的移动无线传感器网络系统的平均符号误码率( ASEP )和信道容量。基于矩生成函数( MGF)方法,推导了系统采用相干检测的相移键控调制( PSK),正交幅度调制( QAM),脉冲幅度调制(PAM)等数字调制方式的ASEP的精确表达式。同时,也得到了系统信道容量的精确表达式。然后对不同条件下的ASEP和信道容量性能做了数值仿真,理论分析结果与仿真结果相吻合,验证了理论分析结果的正确性。仿真结果表明：随着分集支路数的增加,系统的ASEP和信道容量性能得到了很好的改善,当使用QPSK调制,信噪比为16 dB时,分集支路数L＝1,系统的误码率是6×10－2,信道容量是4(bit/s)/Hz;分集支路数L＝2,系统的误码率是1×10－2,信道容量是5.1(bit/s)/Hz;分集支路数L＝3,系统的误码率是2×10－3,信道容量是5.8(bit/s)/Hz。     

A wearable system for mobility improvement of visually impaired people

Degradation of the visual system can lead to a dramatic reduction of mobility by limiting a person to his sense of touch and hearing. This paper presents the development of an obstacle detection system for visually impaired people. While moving in his environment the user is alerted to close obstacles in range. The system we propose detects an obstacle surrounding the user by using a multi-sonar system and sending appropriate vibrotactile feedback. The system aims at increasing the mobility of visually impaired people by offering new sensing abilities.     

含间隙限位约束梁结构频响特征的实验研究

本文用实验的方法研究了含间隙限位约束梁结构的频响特征,同时与仿真计算结果进行了对比,验证了实验结果的正确性.实验研究了间隙距离大小和外激励幅值大小的变化对含间隙限位约束梁结构的第一阶频响特征的影响,实验结果表明随着间隙距离逐渐缩小和外激励幅值不断增大,结构频率逐渐增大,跳跃区间逐渐加大,结构出现明显的变硬特征.通过理论定性分析也可得知,间隙的存在使得系统的动力学控制方程中的刚度增加,从而使其频率发生变化.     

Helping older pedestrians navigate in the city: comparisons of visual,auditory and haptic guidance instructions in a virtual environment

Preserving older pedestrians’ navigation skills in urban environments is a challenge for maintaining their quality of life. However, existing aids do not take into account older people’s perceptual and cognitive declines nor their user experience, and they call upon sensory modalities that are already used during walking. The present study was aimed at comparing different guidance instructions using visual, auditory, and haptic feedback in order to identify the most efficient and best accepted one(s). Sixteen middle-age (non-retired) adults, 21 younger-old (young-retired) adults, and 21 older-old (old-retired) adults performed a navigation task in a virtual environment. The task was performed with visual feedback (directional arrows superimposed on the visual scenes), auditory feedback (sounds in the left/right ear), haptic feedback (vibrotactile information delivered by a wristband), combinations of different types of sensory feedback, or a paper map. The results showed that older people benefited from the sensory guidance instructions, as compared to the paper map. Visual and auditory feedbacks were associated with better performance and user experience than haptic feedback or the paper map, and the benefits were the greatest among the older-old participants, even though the paper-map familiarity was appreciated. Several recommendations for designing pedestrian navigation aids are proposed.     

基于DSP的悬浮转子微陀螺数字幅度解调

在悬浮转子微陀螺中输出的角度检测信号为一经过幅度调制的调幅波形,为了使用数字信号处理器(DSP)读取调制波形中的低频有用信号,需要开发一种数字解调系统。介绍了一种能应用于悬浮转子微陀螺信号检测的基于DSP的数字滤波自相关算法及其实现,使用D/A和异步串行口将解调所得信号输出。使用经低频调制的20 kHz载波信号进行了实验。实验结果表明:该系统可响应的低频角度变化为25Hz,能够满足悬浮转子陀螺信号检测和后续控制的要求。     

The differential effect of vibrotactile and auditory cues on visual spatial attention

Previous research has shown that the presentation of spatially predictive auditory and vibrotactile warning signals can facilitate driver responses to driving events seen through the windscreen or rearview mirror. The present study investigated whether this facilitation reflects the priming of the appropriate response (i.e. braking vs. accelerating) or an attentional cuing effect (i.e. a perceptual benefit that facilitates subsequent behavioural responding). In the experiments reported here, participants had to discriminate the colour of a number plate (red vs. blue) following the presentation of either spatially predictive vibrotactile (experiment 1) or auditory (experiment 2) warning signals that indicated the likely location (front or back) of the visual target, while simultaneously performing a highly attention-demanding rapid serial visual presentation task. Numberplate discrimination performance was facilitated following the presentation of valid auditory cues, but not following the presentation of equally informative vibrotactile cues. The use of an orthogonal spatial cuing design enabled with us to rule out of a potential response priming account of these data. The results suggest that whilst directional congruency between a warning signal and a target event may be sufficient to facilitate performance due to the priming of the appropriate response, attentional facilitation effects may also require the co-location of the cue and target within the same functional region of space.     

The differential effect of vibrotactile and auditory cues on visual spatial attention

Previous research has shown that the presentation of spatially predictive auditory and vibrotactile warning signals can facilitate driver responses to driving events seen through the windscreen or rearview mirror. The present study investigated whether this facilitation reflects the priming of the appropriate response (i.e. braking vs. accelerating) or an attentional cuing effect (i.e. a perceptual benefit that facilitates subsequent behavioural responding). In the experiments reported here, participants had to discriminate the colour of a number plate (red vs. blue) following the presentation of either spatially predictive vibrotactile (experiment 1) or auditory (experiment 2) warning signals that indicated the likely location (front or back) of the visual target, while simultaneously performing a highly attention-demanding rapid serial visual presentation task. Numberplate discrimination performance was facilitated following the presentation of valid auditory cues, but not following the presentation of equally informative vibrotactile cues. The use of an orthogonal spatial cuing design enabled with us to rule out of a potential response priming account of these data. The results suggest that whilst directional congruency between a warning signal and a target event may be sufficient to facilitate performance due to the priming of the appropriate response, attentional facilitation effects may also require the co-location of the cue and target within the same functional region of space.     

Theoretical analysis and experimental study for nonlinear hybrid piezoelectric and electromagnetic energy harvester

A nonlinear hybrid piezoelectric (PE) and electromagnetic (EM) energy harvester is proposed, and its working model is established. Then the vibration response, output power, voltage and current of nonlinear hybrid energy harvester subjected to harmonic excitation are derived by the method of harmonic balance, and their normalized forms are obtained by the defined dimensionless parameters. Through numerical simulation and experimental test, the effects of nonlinear factor, load resistance, excitation frequency and the excitation acceleration on amplitude and electrical performances of hybrid energy harvester are studied, which shows that the numerical results are in agreement with that of experimental tests. Furthermore, it can be concluded that the bigger nonlinear factor, the lower resonant frequency; moreover, there is an optimal nonlinear factor that make the harvester output the maximum power. In addition, the output power of nonlinear hybrid energy harvester reaches the maximum at the optimal loads of PE and EM elements, which can be altered by the excitation acceleration. Meanwhile, the resonant frequency corresponding to the maximum power rises firstly and then falls with PE load enhancing, while it rises with EM load decreasing; furthermore, the frequency lowers with the acceleration increasing. Besides, the larger acceleration is, the bigger power output and the wider 3 dB bandwidth are. Compared with performances of linear hybrid energy harvester, the designed nonlinear energy harvester not only can reduce the resonant frequency and enlarger the bandwidth but also improve the output power.     

A novel prediction model based on hierarchical characteristic of web site

Internet has developed in a rapid way in the recent 10 years,and the information of web site has also been increasing fast. Predicting web user’s behavior becomes a crucial issue following the purposes like increasing the user’s browsing speed efficiently, decreasing the user’s latency as well as possible and reducing the loading of web server. In this paper, we propose an efficient prediction model, two-level prediction model (TLPM), using a novel aspect of natural hierarchical property from web log data. TLPM can decrease the size of candidate set of web pages and increase the speed of predicting with adequate accuracy. The experiment results prove that TLPM can highly enhance the performance of prediction when the number of web pages is increasing.     

基于弓网电弧检测系统的电弧电流分析

基于弓网放电机理,提取电弧发生时刻放电特征量—(250±10)nm波段的紫外光,作为在线检测目标,研制出了一种非接触式紫外弓网电弧检测系统。利用该检测系统对广州地铁二号线弓网电弧现象,进行现场检测,利用经验模态分解(EMD)方法筛除电弧电流的趋势信号,对处理后的电流信号进行分析,结果表明:电弧的发生导致牵引电流中0~50 Hz谐波幅值明显增加。     

单脉冲雷达合并通道定向接收机建模

对一种在单脉冲雷达中采用的以调相信号的频率压缩和合并通道中压缩信号的限幅为基础的通道合并定向接收机(角度鉴别器)进行了分析，建立了这种定向接收机在三通道幅相特性不平衡时的仿真用模型，应用这一模型可以分析接收机非线性、通道间耦合、和差通道幅相特性的不平衡等对单脉冲雷达定向特性的影响。     

Bit error rate reduction for circular ultrawideband antenna by dynamic differential evolution

The dynamic differential evolution (DDE) is used to synthesize the radiation pattern of the directional circular arc array to minimize the bit error rate (BER) performance in indoor ultrawideband (UWB) communication system. Using the impulse response of multipath channel, the BER performance of the synthesized antenna pattern on binary pulse amplitude modulation system can be calculated. Based on the topography of the circular antenna array and the BER formula, the array pattern synthesis problem can be reformulated into an optimization problem and solved by the DDE algorithm. The novelties of our approach are not only choosing BER as the object function instead of sidelobe level of the antenna pattern but also considering the antenna feed length effect of each array element. The strong point of the DDE algorithm is that it can find out the solution even if the performance index cannot be formulated by simple equations. Simulation results show that the synthesized antenna array pattern is effective to focus maximum gain to the line of site path which scales as the number of array elements. In other words, the receiver can increase the received signal energy to noise ratio. The synthesized array pattern also can mitigate severe multipath fading in complex propagation environment. As a result, the BER can be reduced substantially in indoor UWB communication system. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.