Research On Human Walking Energy Collection And Plantar Pressure Sensing Technology

Since the beginning of the 21th century,with the rapid development and improvement of science and technology and people's living standards,wearable devices based on micro-computing technology,wireless sensor technology,and microelectronic technology have gradually entered people's lives.At present,wearable devices are developing towards function integration,miniaturization,and comfort.However,with the rapid development of wearable devices,there is no substantial upgrade in energy supply.The traditional battery-powered method is still used.The short life of chemical batteries requires frequent replacement or charging,and long-term power supply requires large batteries,which is undoubtedly a shackle of the development of wearable devices.And it is also one of the biggest problems faced by the convenience and miniaturization of wearable devices.At the same time,the human body can generate a large amount of energy in daily exercise.Collecting and applying human energy to the energy supply of wearable devices has become an effective means to solve this problem.In this paper,an energy harvesting device applied to the plantar energy harvesting was proposed.Using the piezoresistive properties of the conductive polymer composite material made by mixing carbon nanotubes and silicone rubber,it was able to detect plantar pressure of people under different motion states.The research work of this article mainly includes:(1)Summarizing the development status of human energy harvesting technology,introduces electromagnetic,electrostatic,triboelectric human energy harvesting technology.Sort out the working principle of multiple types of flexible pressure sensors and the current research status at home and abroad.And summarize the current development and research status of human foot pressure detection technology.(2)By studying the movement of the front and hind feet and the stress characteristics of the soles during walking,a plantar energy harvesting device based on the frictional electrification effect was designed to realize energy harvesting in the front and back of the foot.The hind foot adopts a round tube sandwich structure.A metal copper film is embedded in the hollow part of the silicone round tube.The shape of the silicone round tube is used to effectively increase the friction area.At the same time,the elastic recovery ability of the silicone round tube avoids the additional designing of rebound structure.The forefoot uses surface-treated silicone rubber material and copper as friction materials to effectively improve the output capacity of the harvester.Through the mechanical theory analysis and the use of COMSOL Multiphysics simulation software,the mechanical characteristics and electrical working principle of the triboelectric energy harvester of the composite structure are analyzed,and the quantitative relationship between pressure and friction contact area is obtained.And by optimizing the design of different materials and different tube lengths,the output capacity of the energy harvesting device is improved.(3)On the basis of theory and simulation,an energy harvesting device capable of harvesting the energy generated by the foot of the human body while walking was produced,and the output of the friction energy harvester under different motion states of the human body was measured.The maximum open circuit voltage of the forefoot and hind foot energy harvesting structure can reach 202 V and 290 V,and the maximum output power reaches 138 ?W and 580 ?W,respectively.In order to further characterize the ability of the friction energy harvester as an energy supply,during the walking process,the charging time of 900 s can charge 88?F capacitor to 2.5V.(4)Conductive polymer materials are made by mixing carbon nanotubes and silicone rubber in different proportions.The resistivity of the material is experimentally measured,and the relationship between the ratio of carbon nanotubes and the resistance of the composite material is obtained.Selecting the optimal ratio of 0.04wt% to make a conductive polymer material with piezoresistive effect,and using this material to make a flexible piezoresistive sensor,and through experiments showed that the sensor's pressure detection ability which shows the ability of the sensor to apply to plantar pressure detection.(5)According to the pressure detection capability of the obtained sensor,a hardware circuit capable of detecting the pressure of the plantar zone is designed,which can perform conditioning,AD acquisition and wireless transmission on the piezoresistive signal.