介电型电活性聚合物传感单元设计

Design of Dielectric Electroactive Polymer Sensing Cell

基于介电型电活性聚合物(DEAP)变形时的电容变化原理,设计并实现一种传感单元,其内框可在平面内移动,用于检测平面位移。建立该传感单元的几何模型,得出其电容变化和内框位移的关系。采用差动测量法测量敏感单元电容变化,建立了面对面敏感单元的电容差值和内框平移量的关系。利用该传感单元设计了一个二自由度角度传感器用来测量关节转角,同样采用差动测量法建立了电容差值和转角的关系。实验测得其沿X轴和Y轴平移灵敏度为-57.2 pF/mm和-58.0 pF/mm,绕X轴和Y轴旋转灵敏度为-139.4 pF/(°)和141.6 pF/(°)。测试结果与分析结果较为吻合,验证了DEAP应用于位移传感器和角度传感器的可行性。

As a new smart material, dielectric electroactive polymers （DEAP） have shown great promise in the fields of sensing and actuation owning to their excellent overall performance, including large deformation, high efficiency and energy density. Based on the capacitance change principle of the polymer when deformed, a sensing cell composed of an outer frame, an inner frame and a sheet of DEAP film that was divided into four partitions coated with flexible electrode was designed and implemented. When the DEAP film was stretched or shrunk by the mobile inner frame, the flexible electrodes on both sides of the film come closer together or away each other, respectively, leading to changes in capacitance. A geometrical model of the proposed sensing ceil was developed and the relationship between the capacitance of the sensing cell and the displacement of the inner frame was deduced. A differential approach was used to measure the variation of the capacitance of the parts face to face, and the capacitance difference of two opposite parts in function of the inner frame in-plane displacement was developed. Moreover, 2-DOF angular sensor by the sensing cell was designed and applied to angle measurement, and similarly, a differential approach was used to obtain the curve of the capacitance difference with the joint＇ s rotational angle. The experimental sensitivities of X-translation, Y-translation, X-rotation and Y-rotation were respectively - 57.2 pF/mm, - 58.0 pF/mm, - 139.4 pF/（°） and 141.6 pF/（°）, which were agreed well with the theoretical results. The research result verifies the feasibility of the application of DEAP in displacement sensor and angle sensor.