Soft Sensor For Displacement Detection Based On Silicone Elastomer: Design And Experiments

Over the years, the demands for motion sensing of the human body are increasingly urgent for Health and Fitness, human-computer interaction, and so on. At the same time demand is higher and higher. To capture the human body which is a soft structure with many degrees of freedom, requiring a measurement technology capable of reliable and precise, soft and flexible, environmental suitability, and feel better. But accelerometers/gyros systems, camera systems, and piezo-resistive systems can't fulfill all functional requirements. In contrast, soft sensor based on dielectric elastomer(DE) are ideal for these requirements with great potential. Dielectric elastomer sensors(DES) like a soft capacitor. The shape of DES is changed by external force, the capacitance will changed correspond ingly. Based on this principle, DES can be made in stretch mode, pressure mode, shear mode, touch mode, and so on. In this paper, DES will be researched in stretch mode.Firstly, fabrication process of soft sensors is introduced. Silicones is used as material of DES, because silicones are available in variety of hardness, fast response, and many degrees of design freedom. In this paper, three kinds of cured process are present for different types of silicones. System design is researched including moulds, materials, tools and process. In order to produce the flexible electrodes meeting performance requirements, preparation method of polymer-carbon conductive composite is introduced. Through many times of optimization design, mechanical object of soft sensor is designed successfully.Then, soft sensor electromechanical system model based on uniaxial elongation is established. The right model has promoting effect on mechanistic study. By using the traditional mechanical strain energy function model, the model o f soft sensor is derived. And the model parameters is got by fitting test. By comparing the Yeoh model is be selected as design model of soft sensor. Then through the combination of theories and experiments, the electric model of soft sensor is established. The last step is finding the relationship of the electric model and the mechanical model, and constitute the electromechanical system model.On the basis, the sensing circuit of soft sensor is designed with nonlinearity error of less than 0.3%. A novel capacitance detection circuit based on current integration has been developed to eliminate ill effects of electrode resistance. Because most common capacitance meters were not designed to handle any significant electrode resistance and unable to measure the DES's capacitance correctly. By modularized design the analyzing principle, designing project, debugging circuit, and performance test have been done in detail.Finally, the related experiment of soft sensor has been performed. The selection criteria of technological parameter were given based on the analysis of how different parameters impact the cured film's performance. The linearity, hysteresis repeatability, sensitivity, stability and static error of soft sensor have been measured based on experiment. A experiment system of uniaxial stretching was established to measure performance of soft sensor. Five models of soft sensors are discussed, ranging in material and size.