Research On Stress Relaxation Characteristics And Compensation Methods Of Flexible Strain Sensor Based On 3D Graphene Foam

With the rapid development of polymer conductive materials and new sensor technologies in the field of intelligent detection and biomimetic robots,flexible large strain sensors made of highly stretchable materials have gradually become a research hotspot.Compared with traditional strain sensors,flexible strain sensors have a larger strain range and better flexibility,and have great potential for development.In the previous research of our group,a flexible strain sensor based on three-dimensional graphene foam was proposed to solve the task of long-term strain detection.However,graphene foam sensitive components and flexible packaging substrates have obvious stress relaxation phenomena.When the monitored object maintains a fixed deformation,the output resistance of the flexible strain sensor based on graphene foam will continue to decrease due to the stress relaxation characteristics.This "resistance relaxation" phenomenon makes the flexible strain sensor unable to be directly used in the field of long-term monitoring.Aiming at the stress relaxation problem of the three-dimensional graphene foam flexible strain sensor,this paper proposes a stress relaxation compensation model of the flexible strain sensor to solve the stress relaxation problem of the graphene foam flexible strain sensor in long-term monitoring.The core of the compensation model is based on the prediction algorithm of support vector machine(SVM).The model can distinguish the realtime strain state of the monitored object through the output buffer and detection result of the flexible strain sensor.At the same time,the model makes correct output compensation based on the stress relaxation characteristic mechanism of viscoelastic materials.By establishing a compensation algorithm model,the graphene foam-based flexible strain sensor can overcome the influence of stress relaxation characteristics and is competent for long-term strain monitoring tasks.The research content of this paper mainly includes:(1)Preparation of flexible strain sensors based on three-dimensional graphene foam,analysis and testing of the static and relaxation properties of flexible strain sensors;(2)Research on the viscoelastic theoretical characteristics of flexible strain sensors,and establish a stress relaxation model Fit the curve,compare and analyze the stress relaxation characteristics of the sensor prepared in this article,and explain the possibility of making late compensation;(3)Design the compensation algorithm to meet the needs of long-term monitoring problems,and evaluate the model compensation effect;(4)Design a resistance measurement circuit suitable for the flexible strain sensor prepared in this article,and can interact with the host computer.The research results show that the graphene foam-based flexible strain sensor designed in this paper has a size of 25 mm×8 mm×5 mm,and can detect strains in the range of 0%-20%,with a sensitivity coefficient of GF up to 16,and every 1% change in strain resistance5.08 K(?).After explaining the reasons for the stress relaxation phenomenon,a compensation method based on the SVM prediction algorithm is designed,which can cope with the stress relaxation under long-term monitoring problems.In the simulation experiment,the results before and after compensation are compared.If the compensation algorithm is used for calibration,the error is reduced by 3.51 times,especially the compensation error in the stretching process only accounts for 11.7% of the total error.Finally,according to the resistance value of the three-dimensional graphene foam/PDMS sensor,a resistance measurement circuit was designed and implemented,which can measure the resistance of56197 (?)-153228 (?) with a resolution of 3 (?).This paper proposes a preliminary solution to the problem that the flexible strain sensor with stress relaxation phenomenon cannot be used for long-term monitoring tasks.The stress relaxation compensation algorithm proposed in this paper can solve the same type of compensation problems.Viscoelasticity is a common feature of flexible composite materials.Any sensor with stress relaxation phenomenon can be tried using the compensation method in this paper to expand the application of flexible strain sensors in the future.The field provides method support.