Tactile Rendering System Based On Bidirectional Friction Control

Tactile rendering is able to express the surface characteristics of virtual objects, which enhance the fidelity of virtual reality systems, and become the research focus in human computer interaction. Among several tactile rendering methods, friction control based technology can realize continuous and fine tactile rendering system, which becomes a more promising method. While the squeeze film effect based tactile rendering method can realize tactile stimulation by reducing friction between operator’s fingers and the contact surface. Electrovibration based tactile rendering method employs electrostatic force to increase friction. Electromagnetic actuation can create both attracting and repelling forces, which can also be utilized to transmit tactile information. This thesis presents a novel tactile rendering method through combining squeeze film effect, electrovibration effect and electromagnetic actuation. Based on the method, we expanded a more extensive friction control and a bidirectional friction control based tactile rendering system.Firstly, the principle of electrovibration, squeeze film effect and electromagnetic actuation are presented. Then we analyzed the relationship of the size of the plate and the vibration characteristics of plate by using the finite element analysis software for squeeze film effect, and we also do research on the influencing factors of electrostatic force for electrovibration, including the amplitude of voltage and the thickness of insulating layer. What’s more, the influence of electromagnetic force on the tactile rendering system is analyzed.Secondly, based on the theoretical analysis of bidirectional friction control based tactile rendering method, the bidirectional friction control based tactile rendering system is designed in this thesis. The system consists of tactile rendering panel module, central control module based on ARM Coretex-M4 microprocessor TM4C1294, piezoelectric ceramic driver module, electrode array driver module, electromagnet driver module, finger position detection module based on linear sensor TSL1410 R and power supply module. Piezoelectric ceramic driver module is used to provide squeeze film effect, electrode array driver module is used to provide electrovibration, electromagnet driver module is used to provide electromagnetic force control signal. This paper presents the implementation of the system including the production of tactile panel, and the design work of software of system.To verify the proposed method, several experiments have been carried out based on the prototype tactile rendering system, which include several experiments of perception threshold and cognition of graphics. Experiments of perception threshold include experiment of vibration characteristics of tactile plate, experiment of the sensory threshold of human finger to the friction coefficient based on bidirectional friction control, experiment of the sensing frequency range on the electrode array excitation voltage, experiment of the perception of difference of friction coefficients, experiment of threshold on two-dimensional spatial perception. Perception experiments of graphics include cognition of simple graphics and cognition of complex graphics. The experiment results show that the proposed system is able to achieve finer tactile perception and wider controllable friction coefficients than tactile rendering method based on traditional friction control, and the perceived success rate can reach 80% in the perception experiments of complex graphics.Based on the prototype tactile rendering system, this thesis does research on the perception of human fingerwhich improve the traditional tactile rendering methods based on friction control.