Research On Fabric-based Joint Motion Angle Sensing Technology

The improvement of living material level is accompanied by the acceleration of pace of life and the improvement of working pressure.The sub-health state has aroused widespread concern.People pay close attention to their physical health in daily life.As an important indicator of human body signs,body posture can represent the daily exercise state of human body,and can also reflect the recovery of patients with joint injuries in rehabilitation medicine.The existing human motion sensors often bring the users extra dyskinesia and discomfort in the process of detection.Therefore,fabric-based joint motion sensing technology is studied in this paper.Firstly,in order to reduce the sense of motion obstacle,the fabric-based sensing technology is studied and a fabric-based joint motion angle capacitive sensor is designed.A capacitive sensing mathematical model is established and verified by MATLAB and finite element analysis software ANSYS,and the sensor detection model is also determined.In order to shield external electromagnetic signal and to eliminate the parasitic capacitance of cable,a cascade structure of the fabric capacitive sensor is designed,and the fabrication steps are given.The material type of the conductive textile is determined by the impedance test and the surface evenness evaluation.Through finite element simulations,the optimal dimension of the sensor plate is determined to be 40 mm × 40 mm,and combined with ergonomics,the optimum center distance of two paltes is determined to be 60 mm.Secondly,a fabric-based joint motion angle sensing system architecture based on the capacitive sensor is designed.Capacitance measurement circuit based on capacitive sensing method is designed to achieve joint motion angle detection.Capacitive sensors are susceptible to external electromagnetic signal and parasitic capacitance of the cable.Thus,a drive-following module based on double-shield method is designed.A prototype of fabric-based joint motion angle sensing system is fabricated.After that,a visual software platform of joint motion angle sensing system based on conductive textile is set up with mixed programming of MFC and OpenGL.In order to ensure the reliability of data transmission,a data check protocol is designed.To enhance the visualization effect,the joint motion angle data are displayed in real time in terms of numerical text,graph curve and OpenGL 3D dynamic image.In addition,through the establishment and connection of the database,the storage of data and the function of historical data query are realized.Finally,the experiments and tests of this prototype are carried out.The feasibility of the fabric-based joint motion angle sensing system is verified by shielding effect test and simulated joint flexion and extension motion test.The "capacitance-angle" calibration experiment is carried out by using the sectional calibration method,and the detected capacitance is converted to the elbow or knee joint motion angle.The system is used to detect the motion of the knee and elbow joint in marking time,push-ups,and pull-ups,the good applicability of the system is verified.The experimental results show that the system can be used to detect the daily motion of the human body,and it does not bring extra dyskinesia and discomfort.