Triboelectric Joint Sensors And Their Application In Knee Walking Aids

A large number of researchers in China and abroad are currently conducting research on knee assistive devices in order to solve the problems faced by rehabilitated patients or elderly people who have difficulty walking.Knee assistive devices usually consist of a power module and a sensor module,which consume a lot of electrical energy,and therefore the difficulty of improving the endurance of knee assistive devices has been a major challenge.In the last decade,the Triboelectric Nanogenerator(TENG)technology has been rapidly developed and research results have shown that TENG-based sensors are not only stable,sensitive,material-rich and low-cost,but also operate without additional electrical energy(self-powered).The TENG sensor has a very promising application in human motion monitoring.To this end,this thesis designs a TENG-based knee booster device that uses a self-driven triboelectric sensor instead of the active sensor used in conventional knee assistive devices,in order to reduce the energy consumption of the sensor and improve the range of the knee booster device.The specific research work and contents are as follows:Firstly,a TENG-based joint motion sensor is designed.Considering the complexity of human lower limb motion,the joint motion sensor is based on a single electrode mode,using a rotating disc pair structure,with a copper(Cu)electrode set distributed uniformly at intervals on the rotating disc as the positive polarity frictional electric material and using polytetrafluoroethylene(PTFE)as the negative polarity frictional electric material.The detection of joint motion is achieved by establishing a mapping relationship between the frequency of the AC signal and the speed of rotation.Secondly,according to the biomechanical analysis when the human body walks,a knee assist device is designed,which is fixed on the outside of the knee joints of both legs through straps.After designing the signal conditioning circuit,motor control circuit and software,it is possible to collect and process the tiny signals of the friction nanogenerator in an electromagnetic interference environment.Finally,the TENG-based joint motion sensor is implanted into the knee assist device,the experimental results verify that the corresponding mapping relationship between the rotational speed and the AC signal frequency can be established,and the gait information can be detected in real time.Finally,in order to analyse the booster effect of the TENG-based knee booster,a coupled knee joint-booster model was constructed based on Open Sim software,which mainly analysed the changes in joint angle and muscle force during normal walking before and after wearing the knee booster.The simulation results showed that the muscle force of the gastrocnemius and hallux valgus muscles in the lower leg decreased to a certain extent after wearing the knee booster device,indicating that the knee booster device has a certain booster effect,which verifies the application prospect of the frictional electric sensor in the field of joint booster.