A Self-Powered Wearable Motion Sensor For Monitoring Volleyball Skill

In recent years,with the progress and integration of mobile communication,sensors and other technologies,wearable devices have entered people’s daily life,and have a wide range of applications in medical care,human monitoring and other fields.However,the development of wearable devices is restricted by portability,flexibility,sustainable working ability and other factors.Flexible piezoelectric materials can convert mechanical energy into electrical energy through the piezoelectric effect,which can ensure the wearability of wearable devices while solving the power supply demand,and is the emerging development direction of wearable devices.Today,self-powered flexible biosensors have been used to monitor various physiological indicators in daily life in real time,such as blood sugar,body temperature,heart rate and pulse.These self-powered flexible sensors with no external power supply can also be used in the field of motion monitoring.In this thesis,the piezoelectric material is made into a new wearable motion sensor suitable for human wear.The flexible device can fit the human skin comfortably.The piezoelectric material can automatically collect the mechanical energy generated by human motion and further convert it into electrical energy,so that the motion sensor can work independently without external power supply or battery.At the same time,the output piezoelectric signal can be collected and analyzed by external equipment as a reflection of the technical level of spiking in volleyball.This new self-driving scheme overcomes the limitations of traditional video recording and widens the application of piezoelectric materials in the field of motion monitoring.The main research contents of this thesis include:(1)In response to the need to monitor the joint movement of volleyball players,a new type of self-powered wearable flexible motion sensor has been manufactured using a piezoelectric material,polyvinylidene fluoride,which has good flexibility.This enables real-time monitoring of spiking techniques in volleyball sports without external power supply.The sensor is packaged with polydimethylsiloxane,further improving the overall flexibility and being able to fit well with the skin without interfering with normal human movement.The sensor has good sensing performance and can monitor fine mechanical deformation.In a piezoelectric voltage output test with a bend angle of 0-80°,the maximum average output response can reach 120.75%,with excellent discrimination for different angles.In addition,a series of other performance tests have been conducted on the self-powered motion sensor,including the sensor’s response at different bending frequencies,stability during continuous operation,and charging performance.(2)Attach the motion sensor to the surface of the human skin(at the finger joints,elbow joints,and shoulder joints)for experiments,record the piezoelectric signals output by different volunteers during spiking,and verify the actual application effect of the sensor.By observing the sensing data,it is easy to determine whether the spike action is standard(the average response difference between correct and incorrect actions can reach a maximum of 207.79%).Explore other potential applications of sensors,which have great potential in human monitoring fields such as pulse monitoring,respiratory monitoring,and speech recognition.In addition,simple wireless devices can also be powered by the sensor’s charging function to achieve wireless data transmission.