Spatiotemporal modulation method for ultrasonic airborne haptic graphic presentation
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 vir-tual 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 simu-lations and planning.Furthermore,science and technology to the good,such as the blind,deaf,and dumb and other spe-cial 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 brings the user a sense of immersion,greatly enhancing 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 noncontact 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 multipoint 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 focus-ing 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 study;it can generate multiple focal points in each modulation period,reduce modulation noise,and enhance haptic synchronization effect while eliminat-ing the directivity between focal points.Method First,data are received for a plurality of focal points that must 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.Given that the ultrasonic emitters 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 calcu-lating the longest emission distance L within the emission range.To achieve the focus of each transmitter transmitting signal at each focal point,the delay time of each transmitter driving signal must be controlled 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.Second,a modulation frequency f0 that can be perceived by the human body is chosen,and all focal points are emitted within the same modulation period T0.Under the assumption that there are I focal points,the modulation period T0 is divided into I equal parts of the time slice(T1～T1),and each focal point occupies a modulation period of T0/I,that is,each focusing time is T0/I.The required modulation frequency signal and rendering signal are generated,and the cycle time of the modulation signals is equally distributed according to the num-ber 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 with 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 con-sumption 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 modu-lation 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.Experimen-tal results show that this method can considerably reduce noise focusing noise and provide stronger feedback force.
万方数据
维普
