| Tactile rendering can not only provide information of virtual objects such as texture,roughness and temperature,but also merge with visual and auditory channels to enhance the reality and presence of human-computer interaction.Therefore,it has become a research hotspot in the field of human-computer interaction.Compared with other tactile rendering methods such as vibration tactile and electrical stimulation tactile,the tactile rendering method based on the squeeze film effect and electrovibration effect can achieve more extensive friction control,and realize the rendering of complex images,which can combine with intelligent terminals to generate more touch applications.Therefore,it has broad research significance.In this paper,a tactile rendering system with a large area and a wide range of friction is designed and implemented,and a modeling method based on tactile perception of image information is developed.In this paper,the principle of controlling the friction in tactile rendering is firstly analyzed theoretically based squeeze film and electrovibration effect.In order to obtain the optimal tactile rendering performance,the finite element method is used to optimize the tactile rendering device based squeeze film effect.And a method based the amplitude average and standard deviation is proposed to evaluate the vibration of the plate.Based on this method,the factors influencing the amplitude of the plate are analyzed,including the thickness ratio of the plate to the piezoelectric ceramic,the Young modulus ratio,the resonance frequency of the system,and the piezoelectric ceramic layout on the plate.Secondly,based on the theoretical analysis,this paper designs and implements the overall scheme of the tactile rendering system merging the squeeze film effect and the electrovibration effect.The system consists of an integrated tactile rendering plate,excitation signal generation module for squeeze film effect,excitation signal generation module for electrovibration effect,finger position tracking module,central control module based STM32F429 and system power supply module.Based on the hardware platform,the system driver software is designed,which includes the generation software of excitation signal for electrovibration effect,the generation software of excitation signal for squeeze film effect,the LCD display module and the finger position tracking module.Based on the SFS(Shape From shading)algorithm,the relationship between information of image depth and tactile perception level is established,and a haptic rendering modeling algorithm for image information was implemented.In order to verify the effectiveness of the system and to study the image-based tactile perception,the experiments of the discriminating coefficient of friction coefficient,simple pattern sensing experiment,simple texture sensing experiment and complex texture image sensing experiment are carried out.The experimental results show that tactile rendering system based electrovibration effect can be distinguished with four levels of frictional force,and tactile rendering of squeeze effect can be distinguished with three levels of frictional force,which can achieve wide control of friction(friction increase and decrease);The accuracy of simple pattern recognition is over 95%,which has a better tactile perception;The accuracy of simple texture recognition is 91.25%,which means the texture information is perceived correctly,but the detail of texture is weaker to sense;And the perceived success rate of complex texture is between 60% and 80%,and the experimental data verify that the tactile rendering system based on squeeze film and electrovibration effect has a wider range control of friction,which can be widely applied in intelligent terminals.The tactile rendering system developed in this paper can effectively render the information of virtual objects and is of great significance to the further development of tactile rendering technology. |
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