Research On Rendering Methods Of Pen-based Vibrotactile Feedback Techniques

The stylus,as one of important input devices for mobile terminal,can be,can provide more naturally,accurately and fluently user experience in writing and drawing compared with fingers,however,generally are lack of haptic feedback.Pen-based haptic feedback technology enables the users not only to see the screen,but also to use the stylus to feel the physical attributes such as the outline,shape,texture and hardness of the objects on the screen,to feel the interaction dynamics such as collision and friction with the virtual objects,to broaden the perception dimensions,increase the interaction efficiency and enhance the user experience,which can be widely used in education,medical treatment and games,virtual reality,online shopping and other fields.With the popularity of mobile terminals in the above fields,the application of pen-based haptic feedback technology in mobile terminals is an inevitable trend.There are two problems to be solved pen-based haptic feedback technology.One is the selection of haptic feedback mode and the design of device,which is the premise and guarantee of high-quality tactile rendering effect.The difficulty is that the device needs to meet the characteristics of miniaturization,low power consumption and low delay.The other is the establishment of pen-based haptic feedback technology method,including the establishment of haptic feedback model and the output of haptic feedback,which is the key to generate realistic haptic experience.The difficulty is to ensure that the rendered haptic feedback is similar to the real haptic feedback.Currently,haptic feedback rendering mainly relies on mechanical structure and vibration motor.There are three main methods for of pen-based haptic rendering,which are synthesis computing rendering method,image-based rendering method and datadriven rendering method.The method of synthesis computing is based on 3d modeling of the texture surface,and the output feedback is obtained by calculating the contact state between the finger and the texture surface.The image-based method generates corresponding haptic feedback according to the features of different positions of the image,but it cannot be guaranteed to be similar to the real haptic feedback.The actual measurement of real haptic feedback and the establishment of feedback model based on data-driven method can produce haptic feedback close to the real,but the generated haptic feedback signal can only recover the vibration spectrum feature,the temporal periodicity feature is lost,resulting in the lack of the sense of reality of haptic feedback.To solve the above problems,this paper designs a pen-based vibrotactile feedback system and proposes a pen-based vibrotactile rendering method based on actual measurement,which can recover the periodic characteristics in time domain.The main contents and innovations are as follows:(1)A pen-based vibrotactile rendering method of texture based on actual measurement is proposed.This method consists of three parts: vibrotactile feedback data measurement,feedback model building,electrical signal mapping and generation.In the first part,a texture tactile feedback data acquisition system is used to measure the acceleration data generated by the pen and six representative real textures under different interactive conditions based on the two key parameters of speed and normal force which affect haptic perception as interactive conditions;in the second part,according to the recorded data,for each of textures establishes the mapping relationship among speed,normal force and acceleration data,and stores the mapping relationship in the form of look-up table;the third part uses signal reconstruction method to generate virtual acceleration data according to the texture selected by users and the speed and normal force conditions of interaction between pen and mobile terminal,and linearly maps it to electrical signal,driving linear motor to generate phase According to the vibration signal,real-time tactile rendering of virtual texture is realized.(2)A pen vibration tactile feedback system with small size,portability,strong compatibility and low time delay is built.The hardware part of the system consists of tablet,pressure sensitive stylus,power amplifier and linear vibration motor.The software part is based on C + + programming language.The system can capture the speed and pressure state of the stylus in real time,calculate the haptic feedback signal,synthesize the vibration feedback signal according to the rendering method,and present the interactive interface,which provides a platform for the accomplishment of the vibrotactile rendering method proposed in this paper.At the same time,its low delay characteristics can provide a guarantee for high-quality real-time tactile rendering.(3)The realism of the vibrotactile rendering effect of the proposed method is evaluated.By comparing the method proposed in this paper with the other two international advanced methods,it is verified that the method proposed in this paper can better recover the time-domain periodic features of tactile signals,and the user experiment proves that better recovery of the time-domain periodic features can bring higher reality.User experiments include the comparison of rendering vibrotactile feedback and real vibrotactile feedback,and the recognition of texture based on rendering tactile feedback.At the same time,it analyzes the advantages and limitations of the proposed method,as well as its applicable conditions.