Design And Experimental Research On Flexible Contacts Of Piezoelectric Hydraulic Amplifying Braille Dot Display

Braille display is an electronic mechanical device designed for the blind that can output in braille,which is also a form of tactile reproduction.It converts text information from a computer into braille and allows a blind person to interact with the computer through the sense of touch.The use of piezoelectric materials to construct braille contacts is promising in the field of braille tactile display.The piezoelectric contact has the advantages of wide frequency range and good resonance performance,but also avoids the disadvantage of small deformation of piezoelectric vibrator,which can reduce the size and increase the output capacity.This paper combines the National Natural Science Foundation of China project "Research on Design Theory and Key Technology of Piezoelectric Driven Gas Flexible Actuator"(51705031)and the Natural Science Fund Project of Jilin Provincial Department of Science and Technology "Research on Design Theory and Key Technology of Piezoelectric Driven Liquid Flexible Braille dot Display"(20200201063JC)research needs,design and manufacture a flexible contact based on piezoelectric hydraulic amplifying braille dot display(hereinafter referred to as "piezoelectric braille contact").The piezoelectric braille contact uses a circular piezoelectric vibrator as the driving force source,and the piezoelectric vibrator displacement is amplified by the system resonance and flow-solid coupling to drive the flexible film to realize the contact display.According to the working principle,a systematic theoretical analysis is carried out on the piezoelectric braille contact,and the structural parameters are optimized.Finally,the feasibility of the piezoelectric braille contact is analyzed.The main contents are as follows:(1)The structural model of circular piezoelectric vibrator is established,and the piezoelectric vibrator vibration deformation problem is analyzed by using Rayleigh-Ritz method,and the modal simulation and frequency domain simulation of the piezoelectric vibrator are carried out by using COMSOL Multiphysics software,and the theory and simulation are verified by output performance test and impedance test.(2)Two different hydraulic amplification structures are proposed,and the best structure is selected by flow-solid coupling simulation and test.The deformation characteristics of flexible films are analyzed by using the large deflection deformation theory,and the film materials are selected by simulation,and the deformation of three kinds of films,PET film,PVC film and rubber film,are tested.(3)Combined with the above analysis,the whole structure of the piezoelectric braille contact was designed,the vibration model of the piezoelectric braille contact system was established,the displacement out amplification ratio formula was derived,and the deformation theory of the piezoelectric vibrator under the action of flow-solid coupling and the deformation theory of the flexible contact were analyzed,and the output performance of the piezoelectric vibrator under the flow-solid coupling state was tested.(4)Based on the theoretical and simulation analysis,the prototype was fabricated and the test platform was built to investigate the effects of the diameter and height of the reservoir cavity,the shape and diameter of the contact hole,the thickness of the rubber film,different liquid media,the size of the piezoelectric vibrator and other parameters on the performance of the piezoelectric braille contact and to determine the best parameters.Finally,a circular piezoelectric vibrator with a metal substrate of27 mm diameter and 0.2 mm thickness and a piezoelectric ceramic of 20 mm diameter and 0.1 mm thickness was selected.At a driving voltage of 170 V and a driving frequency of 282 Hz,the displacement of the flexible contact was 0.402 mm,and the displacement amplification ratio could reach 10.1 times,and the response time of the piezoelectric Braille contact was less than 5 ms at this time.Fingers can feel the obvious contact bump.The above analysis provides a new theoretical and technical reference for the research and development of braille dot displayers.