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时佳豪1, 孙士友2, 杨芳雁3, 陈建3(1.吉林大学;2.深圳市腾讯计算机系统有限公司;3.吉林大学通信工程学院)

摘 要
目的 超声波空中触觉反馈技术为虚拟现实、混合现实提供非接触、无约束的触觉体验,是混合现实领域触觉呈现的主要途径。使用传统调制方法对多点图形进行聚焦呈现时,在每个调制周期内只进行单点聚焦,发射阵列的使用率较低,聚焦过程中产生噪声较大。针对现有调制方法的不足之处,提出了一种新型时空调制方法来提高阵列利用率并降低聚焦时产生的噪声。方法 首先,根据所需呈现图形获取多个焦点的位置数据,计算每个焦点聚焦时发射器所需延时时间并进行储存。其次,将调制信号的周期按聚焦点个数进行平均分配,并生成超声发射器驱动信号。最后,将驱动信号发送至延时模块,并在调制信号周期的不同时间片内,将各聚焦点的延时数据送入,实现多点聚焦触觉同步的效果。结果 通过实验对新型调制方法进行测试,在进行占空比为10%和20%的两点聚焦时,相比于传统调制方法,调制噪声分别降低了8.4%和13%,聚焦功耗提高了80%和86%;在进行占空比为10%和20%的四点聚焦时,相比于传统调制方法,调制噪声降低了6.3%和10.1%,聚焦功耗分别提高了60%和100%。在主观图形识别实验中,三角形、矩形、圆形的识别率分别提升了25%、 19%、35%。对比实验结果证明新型调制方法降低了聚焦噪声,提高了阵列利用率以及对呈现图形的识别率。结论 本文所提出的新型时空调制方法有效减小了聚焦噪声,提供了更好的触觉图形反馈效果。
Spatiotemporal modulation method for ultrasonic mid-air haptic graphic presentation

(1.Shenzhen Tencent Computer System Co,Ltd;2.College of Communications Engineering,Jilin University)

Objective With the continuous development of computer vision, human-computer interaction, virtual reality, augmented reality, the visual and auditory interaction field has reached a commercialization level. haptic interaction enables users to perceive the tactile characteristics of virtual graphics, and the integration with visual and audio makes virtual graphics have more physical attributes and enhances the user"s immersive experience. For example, purchasers can realistically feel the texture of online materials, drive a car without having to shift their eyes to distract themselves from some screen operations, shop at home and experience different products, and doctors can remotely perform surgical simulations and planning. Further, science and technology to the good, such as the blind, deaf and dumb and other special groups through the sense of touch can also fully enjoy the "era of map reading", to avoid not seeing and hearing is not capable of using the poor situation. The extensive use of haptic feedback technology will bring the user a sense of immersion, greatly enhance the sense of immersion and the sense of reality, virtual reality, augmented reality, mixed reality and other areas of future research focus direction. Ultrasonic airborne haptic feedback technology provides non-contact and unconstrained haptic experience for virtual reality and mixed reality, and is the main way of haptic presentation in the field of mixed reality. The current ultrasonic haptic feedback devices generally use the method of rapidly and repeatedly moving the ultrasonic focus on a given path when performing multi-point focusing to present an ideal pattern, and only single point focusing is performed in one modulation cycle, with low efficiency of array usage and large noise generated during the focusing process, which affects the user"s sense of experience. To solve the above problems, a novel ultrasonic haptic multi-point synchronous focusing method based on spatiotemporal modulation is proposed in this paper, which can generate multiple focal points in each modulation period, reduce modulation noise and enhance haptic synchronization effect while eliminating the directivity between focal points. Method First of all, data is received for a plurality of focal points that need to be focused, and the focusing information is sent to a calculation module via the top-level module. After receiving the coordinates of the focal points sent by the top-level module, the calculation module calculates the distance S from each ultrasound emitter to the focal point. Since the ultrasonic emitter used are not omnidirectional, the ultrasonic emission Angle has a limit. The maximum effective emission Angle should be considered for calculating the path. A comparison can be made by calculating the longest emission distance L within the emission range. In order to achieve the focus of each transmitter transmitting signal at each focal point, it is necessary to control the delay time of each transmitter driving signal, so that each signal is transmitted at different times, with the farthest emitter emitting ultrasonic waves first, and the nearest emitter emitting ultrasonic waves last, thus ensuring that the ultrasonic waves emitted by each transmitter arrive at the same focus at the same time. The time delay required to focus each focal point is calculated and stored. Secondly, choose a modulation frequency f0 that can be perceived by the human body, and all focal points are emitted within the same modulation period T0. Assuming that there are I focal points, the modulation period T0 is divided into I equal parts of the time slice (T1~TI), and each focal point occupies a modulation period of T0/I, that is, each focusing time is T0/I. Generate the required modulation frequency signal and rendering signal, and distribute the cycle time of the modulation signals equally according to the number of focusing points, to obtain the final ultrasonic transmitter driving signal. Finally, the drive signal is sent to the delay module, which sends the delay data of the previous different focus points in different time slices of the modulation signal cycle to achieve the effect of multipoint focusing haptic synchronization. Result Testing of the new modulation method through experiments showed that compared to traditional modulation methods, the modulation noise decreased by 8.4% and 13% when focusing on two points with duty cycles of 10% and 20%, respectively. However, the focusing power consumption increased by 80% and 86%. When focusing on four points with duty cycles of 10% and 20%, the new modulation method reduced modulation noise by 6.3% and 10.1%, while the focusing power consumption increased by 60% and 100% respectively. In subjective graphic recognition experiments, the recognition rates for triangles, rectangles, and circles increased by 25%, 19%, and 35% respectively. Comparative experimental results demonstrate that the new modulation method reduces focusing noise, enhances array utilization, and improves the recognition rates of presented graphics. Conclusion In this study, we present a novel spatiotemporal modulation method for ultrasonic focused haptics. Experimental results show that this method can significantly reduce noise focusing noise and provide stronger feedback force.