Research On Driving Signal Synthesis Technology Of Electrostatic Force Tactile Representation

Based on the principle of electrostatic induction, electrostatic force tactile representation can reproduce different surface tactile properties by changing the pressure and friction of the interface between finger and tactile representation panel, which plays an important role in the field of human computer interaction and virtual reality. The present study on electrostatic force tactile representation is focused on tactile representation devices and image tactile rendering algorithm, but the study on the mechanism of electrostatic force tactile representation and the quantitative characterization of tactile electrostatic force is lacking. In this paper, we research the principle of electrostatic force tactile representation, system modeling and the driving signal synthesis technology, and we complete the synthesis of driving signal on the DSP platform. We built a platform for the measurement of tactile electrostatic force, and research the quantitative relationship between tactile electrostatic force and driving signal objectively by the actual measurement of tactile electrostatic force, so we can achieve the synthesis of tactile electrostatic force through the synthesis of driving signal. The research work in this paper can provide a reference for the theoretical research and the related product development of electrostatic force tactile representation.(1) Based on the system architecture and basic principle of electrostatic force tactile representation, we build an equivalent system model of electrostatic force tactile representation considering the bioelectric property of finger skin. The quantitative relationship between tactile electrostatic force and driving signal was obtained by the analysis of system model utilizing electrostatic field theory and circuit principle.(2) The driving signal synthesis scheme of electrostatic force tactile representation was designed based on the analysis of the principle and structure of DDS(Direct Digital Frequency Synthesis). The phase accumulator and waveform ROM table are accomplished in the master chip DSP. An analog step waveform is generated after the digital to analog converter, and the waveform is smoothed through a low pass filter. The high magnitude driving signal of electrostatic force tactile representation is generated through the amplitude amplification. The driving signal synthesis hardware circuit of electrostatic force tactile representation is accomplished based on the scheme considering electromagnetic compatibility and signal integrity.(3) The waveform synthesis and serial communication program are developed on the basis of driving signal synthesis hardware circuit of electrostatic force tactile representation. The frequency control word is decided according to the frequency of driving signal and the sample frequency, and the periodic waveform phase is achieved through accumulating phase control word by the phase accumulator. The amplitude of waveform is obtained through the waveform ROM table according to the periodic waveform phase, and the waveform amplitude is sent to the digital-to-analog converter in the sample frequency by DSP to generate the driving signal. The amplitude and frequency of waveform can be set by the serial communication program, and the digital modulation method and program of modulation waveform is presented. The driving signal parameter setting software of PC is developed, and we test the driving signal generated by the circuit we design.(4) A electrostatic force measurement device is constructed to measure the electrostatic force exerted on finger under the condition of different driving signal. The transient state response and steady state response are researched through the simulation of system model considering the bioelectric property of finger skin and the measurement of electrostatic force. The validity of the equivalent system model of electrostatic force tactile representation is verified through the quantitative relationship between electrostatic force and the frequency and amplitude of driving signal. The impact of the duty ratio and polarity of pulse driving signal on electrostatic force is researched and the low power design scheme of the parameter of pulse signal is given. Moreover, the impact of amplitude-modulated signal on electrostatic force is also researched.The main contributions and innovations of this paper are as follows:(1) The equivalent system model of electrostatic force tactile representation is established, which provides a solution for calculating the electrostatic force. The electrostatic force measurement platform is set up, which provide a solution for the measurement of electrostatic force between finger and tactile representation panel.(2) The quantitative relationship between electrostatic force and driving signal is analyzed, and the synthesis of tactile force is achieved by the synthesis of driving signal.(3) The driving signal synthesis scheme of electrostatic force tactile representation is designed, and hardware circuit and software program is implemented, and the driving signal synthesis of electrostatic force tactile representation is implemented.The work of this paper provides a scheme for the electrostatic force tactile representation system analysis, driving signal synthesis and tactile electrostatic force synthesis, which has certain theoretical and practical reference value.