| Measuring human motions is beneficial to rehabilitation, training or exercises. Motion capture system, which consists of cameras, accelerometers, and flexible electrogoniometers has been used to monitor human motion. Although this system is capable of accurate measurements, its portability and obscurability is poor and not convenient to use. And also, the sensors in current motion capturing system are rigid or inelastic, if they are fixed on the cloth, it will make people uncomfortable. In order to develop a wearable system to monitor limb movement, the strain sensors which use flexible conductive fabric have been widely studied. Currently, due to the characteristics of large deformation under stretching, the knitting fabric has been used as strain sensor mostly. However, the curling and knockover of knitting fabric, the signal stability as a sensor is relatively poor. Relatively, the woven structure is stable than knitting structure, so that their signal as strain sensor may be more stable.To obtain both the stability of signal and good deformation, this paper used the C/SP woven fabric as substrate material and the pyrrole(Py) monomer as raw material to produce the polypyrrole(PPy) conductive woven fabric by in-situ chemical polymerization. And then, their resistance properties, electromechanical properties and electrical impedance properties are studied, and the performance of the conductive fabric used in upper limb motion monitoring is evaluated. Finally, it discussed the resistance change mechanism of the conductive fabric. Specifically, the research content follows as:(1)PPy conductive woven fabric was prepared by in-situ polymerization, and its resistance stability was tested. The result showed that the resistance increases with the time which the fabric is exposed to the atmosphere. On the other hand, the PPy has good adhesion strength with the fabric substance, and the washing process didn’t lead to significant PPy flakes on fabric surface. The conductive fabric was exposed to atmosphere, and the resistance was tested every 48 hour of 33 days. The test results showed that the resistance increased about 40% after 33 days. On the other hand, with reference to GB/T3921-2008 and GB/T12490-2014,the washability of the conductive fabric is tested. The results showed that there has no significant loss PPy flakes on fabric surface after 4h washing. But the undoping reaction between solvent and PPy makes the resistance increase after washing.(2)The electromechanical performance and electrical impedance of PPy conductive woven fabric under uniaxial tensile were tested. The results showed that the resistance inversely changes with fabric strain below a range of tensile strain, an increase of stretching velocity will lead to a decreasing strain sensitivity and an increasing hysteresis. However, there is no significant inductance effect, and its dynamic response has good reproducibility.On the basis of the customized repeatedly tensile device, the developed conductive woven fabric was stretched at the speed of 1mm/s, and the Agilent 39470 data acquisition device is used to record the real-time resistance of fabric. It was observed that the resistance of PPy conductive plain woven fabric(whether filament fabric or spun yarn fabrics) decreases during stretching, and increases with the elastic return to the original state.The electromechanical performance under different stretch velocity has been tested, The sensitivity of PPy conductive plain woven fabric reach 3.711 at 10% strain rate and 1mm/s stretch velocity. Meanwhile, the repeatability error of stretching process is 8.7%,the maximum hysteresis error is 9.5%, and the linear correlation coefficient is 0.9741. However, with the increasing of the tensile speed, the strain sensitivity decreases, the repeatability of stretching process increases, and the hysteresis error increased.On the other hand, the PPy conductive woven fabric exhibits pure resistance under dynamic stretching deformation. And it is almost not influenced by the scanning frequency and mechanical frequency, which ensures the accuracy of the signal of sensor.(3)For PPy-coated conductive woven fabric’s tensile and bending mode, this paper used the assembly method step-by-step proved the resistance change mechanism of PPy conductive woven by in-situ polymerization. The result showed that the resistance change of PPy conductive woven fabric comes from the contact resistance between warp and weft yarns.In order to explain the resistance change mechanism of PPy conductive woven fabric under tensile, experiments were designed to test the factors which affect PPy conductive woven fabric resistance one by one, including yarn resistance, the contact resistance between the weft and warp yarns and the contact between parallel yarns. The result showed that all of these affect the resistance, but the main factor is the interlace contact resistance between the weft and warp yarns.(4) Explore the feasibility and testing methods of PPy conductive woven fabric used as sensors monitoring the upper limb motion. The result showed that PPy conductive woven fabric can be used as the core sensing element to monitor the state of upper limb motion, the conductive fabric can be imbedded into clothing by sewn mode.This study designed a sensing system, which composted of the Bluetooth data acquisition module as a signal acquisition and PPy conductive fabric as core sensing element to monitor human upper limb movement, including the quasi-static and dynamic movement. The results showed that the resistance change reflects the bending angle of the upper arm, and the resistance changes with the angle is almost linear. And also, it reflects the dynamic movement of the upper limb, such as trends and frequency, including bending and rotational motion. Repeatability trials showed that the test procedures is highly repeatable, but with increasing testing times will cause a decreasing sensitivity.Therefore, this study demonstrated that the PPy-coated conductive stretch woven fabric is appropriate as a strain sensor to test body motion. However, the stability of electrical properties under environment is not good, and there is hysteresis in resistance changes process. In order to obtain an accurate excitation-response conversion function, all of their change rules need to be further studied. |
PDF Full Text Request