一种可检测三维力的新型柔性电容式触觉传感器研究

In recent years, capacitive sensors have become one of the main directions in present domestic and international research on robot tactile sensors, due to their excellent characteristics such as high sensitivity, reliable precision, fast response and so on. In order to improve their flexibility, design proposals with electrodes embedded in a flexible substrate are often adopted, in which the overall range of curvature and deformation are limited, and therefore the applications will be restricted greatly. In this proposal, we intend to use the flexible parallel micro-capacitors as the sensitive units, which are prepared by conductive adhesives and insulating silicone polymers. Moreover, a new design of sensor structure will be proposed, in which the upper and lower plates are "oblique-crossed" and then the capacitor of several output units are obtained, by which three-dimensional force can be detected. The main research contents are listed as follows: ① irregular deformation of the flexible units expecially the edges will be explored, and the law of deformation of the units under the normal/shear force will be studied and validated; ② theoretical model of the capacitance with the irregular deformation, and the influence of the "edge effect" will be studied, by which the variation mechanism of the deformation-capacitance will be clarified; ③ with combination of the force-deformation linear superposition theory and the constraint of sensor structure, the problem of nonlinear coupling between variables of the sensitive units will be studied, and therefore the prediction model of three-dimensional force will be established, by which the optimized structure of the sensor can be explored. The anticipated results will provide theoretical and technical supports for the exploitation of large-scale array capacitive tactile sensors with the detection of three-dimensional force.

电容式传感器具有灵敏度高、精度可靠和响应速度快等优点，已成为机器人触觉传感器研究的热点。为改善电容式传感器的柔性，目前国内外学者多采用柔性衬底嵌入电极的方案，但其整体弯曲和变形幅度较小，适用范围有限。本项目基于导电胶和绝缘硅胶等聚合物，研制一种新型柔性微型平板电容敏感单元，并基于此敏感单元构建了一种新型上下极板"斜交叉"组合式传感器结构，可同时获得多个单元电容输出，实现三维力检测。研究内容包括：①探讨柔性单元特别是其边缘的不规则形变问题，分析、验证其在法/切向力加载时的形变规律；②探索不规则形变下电容计算的理论模型，分析电容的"边缘效应"干扰，完善敏感单元的形变-电容变化机理；③在此基础上，结合力-形变的线性叠加原理和传感器的结构约束，解决传感器各敏感单元变量的非线性耦合问题，建立三维力预测模型，探寻其优化结构。预期研究成果将为大规模阵列式柔性三维力触觉传感器的研制提供理论基础和技术支持。

智能化是未来机器人发展的方向，而感知是实现智能化的基础。触觉是机器人实现与外界环境直接作用的重要媒介，它仅次于视觉，具有很强的敏感能力。因此触觉传感器的发展是机器人传感器技术领域中一个必不可少的部分。电容式传感器具有灵敏度高、精度可靠和响应速度快等优点，已成为机器人触觉传感器研究的热点。本项目拟设计一种新型全柔性电容式传感器结构，在对其形变规律和电容敏感机理理论分析和仿真的基础上不断优化传感器结构，从而有效提高了传感器的力敏感特性。基于位势理论的推导结果和COMSOL的电容仿真结果，总结得到：同等量级的单维法向力和切向力加载时，法向力加载时的形变及相应电容变化比切向力加载时大很多，即法向力比切向力更敏感；敏感度与材料的泊松比有关；更者，法向力加载比切向力加载的电容变化线性度更好；对介电层的微结构化可有效提高新型电容触觉传感器的灵敏度。据此优化并制备了一种新型电容性超灵敏柔性触觉传感器，实验结果表明：介电层经过微结构化处理的电容单元的电容输出即力响应特性有极大的提高，增加传感器尺寸在一定范围内能提高S2阶段（受力后期相对平缓变化阶段）的响应特性。在本项目执行的同时，受电容式传感器微结构化和阵列化的启发，我们还制备了一种新型电阻式柔性三维力传感器；基于材料力学理论分析了三维力加载时微结构各段柱体电阻的变化规律；分别对其加载法向力、切向力和三维力进行多物理场仿真，并针对多维力加载时的维间耦合，提出了一种基于BP神经网络的解耦算法从而使传感器能精准检测出三维力信息。本项目研究成果将为大规模阵列式柔性三维力触觉传感器的研制提供理论基础和技术支持。