Development Of A Self-powered Smart Safety Belt For Driving Status Monitoring

The energy crisis and the traffic crisis are the two common problems in the world today.Using high-tech energy-saving measures to achieving intelligent driving has gradually become the best solution for the problems.On one hand,triboelectric nanogenerators(TENG)are widely used as self-powered sensors,since they can convert mechanical energy into electrical energy and the the electronic signals are correlated with the magnitude of external stimuli.On the other hand,driving status monitoring is especially helpful in preventing driving accidents and ensuring the safety of the drivers.Based on this,this thesis proposes a self-powered smart safety belt based on triboelectric generators,which is used to monitor the driving status of the driver,and prevent dangerous behaviors such as fatigue driving and aggressive driving.Firstly,a new configuration of triboelectric generator with three friction layers is proposed,and its theoretical model as TENG is established.Then,two kinds of composite TENGs,namely auxetic and arch-shaped TENGs,are designed and fabricateded,which are used for axial stretching and longitudinal compression sensing,respectively.The working principles of those TENGs are thoroughly investigated.The auxetic PU foam is selected as the intermediate polarity friction layer,and a fabrication process of triaxial compression and heating is adopted to achieve auxetic properties of the foam.For the friction layer PTFE film,the surface of the PTFE film is roughened and modified by inductively coupled plasma(ICP)dry etching to form a dense and uniform micro-nano structure,which enhances the electrical performance output.Then,the electrical properties of the TENGs are studied on a tensile and compression test platform.The open circuit voltage of the cylindrical TENG increases as the tensile strain increases,and open circuit voltage of 6.98 V is achieved for 100%tensile strain,the response time is 52ms,and the gauge factor in the strain range of 40%~100%reaches0.89V/cm~2.For the arch-shaped TENG,the open-circuit voltage increases as the device is further pressed,reaching 12.06V when the displacement is 2.5mm,and the response time is28ms.There is a highly linear correlation between open-circuit voltage and displacement when the displacement is?2.5mm,and the gauge factor reaches 47.2V/cm~3.For both sensors,the output is stable and maintains excellent stability in the case of a cyclic test of50,000 cycles.Finally,the auxetic TENG sensor is integrated to abdomen location of the horizontal strip in the safety belt,which can accurately capture the frequency,amplitude and waveform stability of the driver's breathing,and the driver's forward displacement of up to 100mm can be measured due to the capability of large strain measurements.The arch-shaped composite TENGs arrays are integrated to shoulder and waist locations of the diagonal strip in the safety belt,and the turning directions and angles of the driver can be determined based on the voltage distribution countour map of the sensor arrays.The innovations of this study are as follows:Firstly,a new configuration of composite TENG is proposed,so that the same friction layer in a single device has both positive and negative polarities;Secondly,the advantages of auxetic materials and TENGs are leveraged simultaneously through the fabrication of the auxetic TENG sensor;Thirdly,the TENGs are used in driving status monitoring,and the performances of the self-powered smart safety belts are successfully demonstated.