| With the development of science and technology,a variety of electronic devices are constantly updated.There are more and more intelligent applications with the rise of 5G and AI,which need a large number of sensors to collect information.As a device based on contact electrification and electrostatic induction,the triboelectric nanogenerator（TENG）provides an efficient way to convert mechanical energy into electrical energy.Compared with traditional piezoelectric or piezoresistive sensors,TENG sensors have attracted much attention due to advantages of self-powered and simple structure,but less research has been done on TENG output signal acquisition circuits.Here,a single-electrode mode TENG has been designed by studying structure and electrical characteristics of the self-powered TENG device.Based on the single-electrode mode TENG,a smart keyboard system that can be applied to the human keystroke dynamics has been designed.The system framework involves design and application of multiple parts,including modeling and simulation,conditioning circuits,acquisition and control circuits,and host computer design.The main contents and innovation are as follows:（1）A single-electrode mode TENG was designed and its working mechanism was analyzed.The friction layer was polytetrafluoroethylene（PTFE）film,and the electrode was copper tape.Compared with the vertical contact separated button,there was no space restriction between the device and the fingers of human,only a wire to output electrical signals.And no specific support rebound structure was required to maintain the separation distance,which conformed to actual human keystroke behavior.（2）The TENG keyboard was performed electrical measurement initially and the simulation model was customized.Firstly,the equivalent model of contact TENG was analyzed,and the equivalent model of contact TENG was deduced by its control equation.It was composed of an ideal AC source and a variable capacitor in series.Then the relationship betweenOC–x andTENG–x could be obtained based on the numerical calculation of the finite element method（FEM）.Since no TENG simulation model in the simulation software,a new dedicated TENG simulation model was built through the modeling syntax,and the simulation results were consistent.（3）Three conditioning circuit design schemes（voltage follower,negative feedback integral amplification,and capacitance conditioning circuit）were proposed to condition the output signal of TENG keyboard.Then,the pre-customized TENG simulation model was used to simulate the design of the conditioning circuit.The simulation results of three conditioning circuits could achieve the effect of signal voltage reduction.However,the voltage follower conditioning circuit couldn’t obtain the ideal output in the subsequent experimental measurements.It was found that the output current of the TENG keyboard was too weak,but the experimental measurement of negative feedback integral amplifier circuit and the capacitor conditioning circuit had a high consistency with the simulation results,and the conditioning of the output voltage was successfully realized.Besides,the noise effect of the TENG keyboard after connected the capacitor conditioning circuit was relatively small than connected the negative feedback integral amplifier circuit,so the capacitor conditioning circuit was selected in this article.（4）The core components of TENG output signal acquisition system was designed.The acquisition control circuit was designed with FPGA,design explanation and simulation verification of communication module,conversion module and instruction module were carried out.On the basis of the acquisition circuit system,the subsequent TENG keyboard numeric key function was realized.And the TENG keyboard output signal was analyzed.Moreover,the method of setting and using the threshold voltage for edge detection was proposed to realize corresponding function.The acquisition system based on this FPGA was flexible and various,and the corresponding module functions could be set or modified according to different functional requirements.（5）On the above basis,a complete TENG keyboard output signal acquisition system was formed by writing the upper computer with MATLAB.Finally,in the actual system test,the function of the number keys of the TENG keyboard was successfully realized.The application of designed TENG keyboard system in the field of human intelligent recognition was investigated by the research on keystroke dynamics,machine learning related intelligent recognition algorithms. |
