Research On The Influence Of Finger Moisture On Electrostatic Tactile Display Effect Of Mobile Terminal

With the increasing intelligence of smartphones and tablet Personal Computers,mobile terminals with tactile representation become an inevitable trend in development of technology.Electrostatic representation is one of the effective ways to display tactile feedback on mobile terminals.It changes the friction between the finger and the screen by applying a driving signal to the screen to display different tactile sensations to the users.Electrostatic tactile representation devices are fast,low-power and real-time,making them the most promising solution for tactile representation on mobile devices.The current electrostatic tactile representation devices are prone to failure when the finger skin has a higher moisture.In order to solve this problem,we must study the mechanism of the effect of the finger moisture on electrostatic tactile representation.The existing electrostatic tactile representation mechanism is mainly focused on the contact process of the finger in its natural state and screen.It develops the study from two aspects of electrostatic field and equivalent circuit,and on the basis of which many rendering methods and evaluation methods are derived,and has made some progress.However,research on the effect of finger moisture on electrostatic tactile representation has yet to be further developed,and there is a lack of systematic conclusions and data on the effect of finger moisture on electrostatic tactile representation.To address the above problems,this paper analyses the electroadhesion mechanism of contact of finger skin and screen in wet condition,and investigates the quantitative relationship between relative dielectric constant of the contact gap between the finger skin and screen and the electric field strength.On this basis,the effect of driving signal parameters and screen parameters on the electroadhesion is analyzed,and the finger moisture is introduced into the existing rendering methods to provide a reference for solving the problem of the effect of moisture of finger skin on the electrostatic tactile representation.The main work and novelties of this paper are as follows:(1)Analyzing the quantitative relationship between relative dielectric constant of the contact gap between the finger skin and screen and the electric field strength to complete the description of the existing electroadhesion mechanisms.The principle of tactile representation of electroadhesion is analyzed in terms of the charge distribution between finger skin and screen,the electric field strength generated by the charge and the mechanism of electrostatic attraction.On the basis of Persson's basic theory of electroadhesion,relative dielectric constant of the contact gap between the finger skin and screen is introduced,and the quantitative relationship relative dielectric constant of the contact gap between the finger skin and screen and the electric field strength is investigated,improving the equivalent model of the electroadhesion effect between finger skin and screen.On this basis,the effects of finger skin parameters,screen parameters and driving signal parameters on the electroadhesion effect are systematically analyzed.(2)Analyzing the effect of finger moisture on the impedance between the finger skin and the screen and the force applied to the finger.The reasons for the influence of finger moisture on the effect of electrostatic tactile reproduction were clarified by the measured data.Developing experiments for measuring the impedance of the gap layer at different moisture levels.A constant value resistor was connected in series between the human body and the earth terminal during interaction between the finger skin and the electrostatic tactile representation device.The voltage and current between the finger and the screen is calculated by measuring the output voltage of the drive circuit and the voltage of the constant resistor as finger slides across the screen,and the nature of the impedance between the finger skin and the screen are analysed in the form of lissajous figures,and the impedance amplitude between the finger skin and the screen according to Ohm's law is calculated.In addition,we measured the tangential between the finger and the screen,friction and electrostatic forces at different moisture levels.It was concluded that when the moisture of the finger skin increases,the impedance and the force between the finger skin and the screen decrease,which is the main reason for the failure of the device.(3)The relative permittivity of intercontact material,which represents finger moisture,is introduced into the existing rendering methods.It is proved that the moisture adaptability of electrostatic tactile reproducing device can be modified by rendering method within a certain moisture range.The method first extracts the image grey-scale features,establishes the mapping relationship between finger moisture and the relative dielectric constant of the contact gap between the finger skin and screen,and the mapping relationship between the relative dielectric constant and the driving signal amplitude parameters,and determines amplitude of driving signal by the combination of moisture of finger skin and force,and provides a reference for solving the problem of the effect of moisture of finger skin on the electrostatic tactile representation.The experiment of tactile perception intensity verifies that in a certain moisture range,the method proposed in this paper can improve the problem of electrostatic tactile reproduction failure.