Electrostatic Haptic Display And Interaction For Mobile Terminals

Haptic display builds a new channel for communication between humans and the virtual world and pushes the communication to a new stage with the integration of three interaction dimensions: hearing,vision,and touch.It brings a new sense of immersion and realism to humans,and it is the hotspot of current human-computer interaction studies.With the continuous improvement of the intelligent level of mobile phones and tablets,mobile terminals with haptic feedback are an inevitable trend of technological development.Using various electrical signals,electrostatic haptic display controls the electrostatic friction between the finger and the touchscreen in real-time to produce various haptic effects.The electrostatic haptic display could produce rich haptic effects while not interfering with the visual display and having low power consumption.Currently,it is the most promising haptic solution for mobile terminals.To promote industrial applications of electrostatic haptic display technology for mobile terminals,three aspects of the technology must be studied: reliability of haptic display devices,the realism of rendering algorithms,and the design of the haptic interactive interface.The current electrostatic haptic rendering algorithm mainly uses the amplitude parameter of the excitation signal,which limits the dimension of the haptic rendering,while the use of other parameters such as frequency and waveform of the excitation signal needs to be deeply explored.The design of the haptic interface of mobile terminals must depend on how the haptic display is used in an application and how it influences the accuracy and efficiency of interaction.For single-finger operations such as panning and clicking,such research topics have made significant progress,but not for two-finger operations such as zooming.Current electrostatic haptic display technology for mobile terminals is mainly through bare finger interaction,so the perceived haptic effect could be more affected by individual differences and environmental factors,and it could cause discomfort or even numbness in situations that require long-term using like writing and painting.Pen-based interaction has become one of the standard interaction models for tablets and smartphones.It is an alternative to bare-finger interaction which has the potential to solve these problems,but the technology of pen-based electrostatic haptic display is still blank.In this thesis,two types of electrostatic haptic display devices for mobile terminals are developed,namely bare-finger type and stylus type.Texture and geometric shape rendering,two-finger operation,pen-based interaction,pen and actuator combination methods,and the performance evaluation of them are studied based on the developed devices.This thesis aims to provide a reference for future applications of electrostatic haptic display technology on mobile terminals.The innovations are as follows:(1)With regard to electrostatic force rendering of image texture and geometry,a texture rendering algorithm based on amplitude-frequency parameter and a geometric shape rendering algorithm based on Weber Fechner theorem are proposed,which can improve the reality of image texture rendering and haptic identification of geometric shape.The image texture rendering method uses the Roberts operator to extract the gradient information from the image,and establishes the logarithmic mapping model between the frequency parameter of the sinusoidal excitation signal and the soft hardness of the object,and establishes the logarithmic mapping model between the amplitude parameter and the geometric height of the object.The dimension of excitation signal parameters is expanded.The result of a haptic perception experiment with 10 users and 10 images shows that the satisfaction of the proposed method is 26% higher than that of the traditional method.The geometric shape rendering method uses a 120 Hz sine wave as the excitation signal and uses the Weber Fechner model to map the gradient parameters of geometric shape to construct the haptic excitation signal with greater dynamic change under unit gradient.The result of a haptic perception experiment with 10 users and 3 geometric shapes shows that the satisfaction of the proposed method is 36% higher than that of the haptic rendering algorithm using a linear model.(2)With regard to methods and performance of applying electrostatic force haptic rendering on two-finger scaling operation,the mapping model between the target position and haptic feedback force,and the mapping model between operation process and haptic feedback force is established.It is proved that the scheme based on the target position is optimal and meets the Fitts' Law and Meyer's law and significantly improves the interactive efficiency and accuracy.The results of the comparative experiment of 12 users show that compared to the scheme without haptic feedback,the completion time and operation error of the scheme based on target position is reduced by 27.59% and 22.08%,respectively,and the completion time and operation error of the scheme based on the operation process is reduced by 9.61% and 12.24% respectively.Regression analysis results show that the correlation coefficient of Fitts' Law and Meyer's law based on the target location scheme is greater than 0.9.(3)In order to realize haptic display for writing and painting on mobile terminals,the method of implementing electrostatic force haptic rendering technology into the pen structure is proposed,and a new device is developed with such a method.With this device,the accuracy of trajectory interaction and the satisfaction of drawing interaction is improved.The result of a comparison experiment of steering tasks and tracking tasks with 12 users shows that the interactive accuracy of the electrostatic pen scheme is better than that of the electrostatic bare-finger scheme and that of the pen vibration scheme,and the operation error is reduced by 13.04% and 3.08% respectively.A texture haptic perception experiment of writing,painting with 6 users shows that an electrostatic pen scheme can enhance immersion and realism.(4)In order to solve the problem that electrostatic pen device can not provide haptic feedback for click operation,one haptic pen representation method based on the combination of electrostatic force and the linear actuator is proposed,and a new device is developed based on such method which significantly improves the interactive efficiency of the electrostatic haptic pen.The result of a click-and-slide interactive operation comparison experiment with 12 users shows that the completion time of the electrostatic force and linear actuator combination scheme is 14.58% shorter than that of the electrostatic force the only scheme.