NRI: A Variable Stiffness Artificial Muscle Material for Dexterous Manipulation

该项目的目标是创造一种将创新驱动与集成传感相结合的材料。驱动原理是基于一种可伸缩的电活性聚合物。这包括夹在两个柔性导电层之间的电绝缘聚合物片。聚合物片材表现出相变，随着温度超过转变值，顺应性大幅增加。为了驱动材料，首先将其加热到转变以上，然后在聚合物上施加电势。静电力将导电层拉在一起，增加了薄片的面积，可能增加了百分之几百。这些高应变与边界约束相结合，导致致动器的大位移。然后，材料被允许冷却并转变回刚性形式，锁定在新的致动器位置并允许电势被移除。测量压力或触摸的薄膜传感器与致动器片集成在一起。由此产生的高应变，可变顺应性，自我感知，设备是非常适合于机器人操纵器与肌肉一样的灵巧。此类操纵器将应用于各种机器人系统，包括假手、患者康复设备、顺应性手术器械、人造器官和用于辅助生活的人形机器人。该项目将为少数民族高中生提供暑期研究实习机会。本科生和研究生也将参与该项目，以获得实践研究经验，以及分析，沟通和人际交往能力。该项目研究了一种结合可变刚度，大应变驱动和传感的人工肌肉材料，并探索了该材料在广泛的机器人应用中急需的灵巧操作中的应用。它与传统机器人的不同之处在于操作是以对象为中心的。物体可以具有各种不同的形状、硬度、表面纹理和重量。结合传感、致动和可变刚度的人造肌肉期望产生从轻柔触摸到牢固抓握的灵巧操纵，具有局部可控性。电活性聚合物已经显示出再现人类肌肉的活性和结构特性的前景。在这些“人造肌肉”材料中，介电弹性体表现出低刚度、高致动应变和力输出。双稳态电活性聚合物具有高达1000倍的刚度变化。在软化状态下，可固化聚合物表现得像弹性体，并且可以像介电弹性体一样被致动。可变刚度和大应变致动的组合将使新一代人造肌肉能够用于仿生机器人应用。一个6指机械手将被证明可以抓住和举起各种物体，包括鸡蛋、高尔夫球、智能手机，并从牙膏管中挤出指定长度的牙膏。

The goal of this project is creation of a material combining innovative actuation with integrated sensing. The actuation principle is based on a bistable electroactive polymer. This comprises an electrically insulating polymer sheet sandwiched between two flexible conductive layers. The polymer sheet exhibits a phase transition, with a large increase in compliance as temperature exceeds a transition value. In order to actuate the material, it is first heated above transition, then a potential is applied across the polymer. Electrostatic forces pull the conductive layers together, increasing the area of the sheet, possibly by several hundred percent. These high strains, combined with boundary constraints, cause large displacements of the actuator. Then the material is allowed to cool and transition back to the stiff form, locking in the new actuator position and allowing the electric potential to be removed. Thin film sensors measuring pressure or touch are integrated with the actuator sheets. The resulting high-strain, variable-compliance, self-sensing, device is well-suited for robotic manipulators with muscle-like dexterity. Such manipulators would have application to a wide variety of robotic systems, including prosthetic hands, patient rehabilitative equipment, compliant surgical instruments, artificial organs, and humanoid robots for assisted living. This project will provide summer research intern opportunities for minority high school students. Undergraduate and graduate students will also participate in the project, to gain hands-on research experience, and analytical, communication, and inter-personal skills.This project investigates an artificial muscle material combining variable stiffness, large-strain actuation and sensing, and explores the application of the material for dexterous manipulation that is critically needed in a wide range of robotic applications. It differs from traditional robotics in that the manipulation is object-centered. The objects can have various different shapes, stiffness, surface texture, and weight. Artificial muscles combining sensing, actuation, and variable stiffness are desired to produce dexterous manipulations from gentle touch to firm gripping, with local controllability. Electroactive polymers have shown promise for reproducing both the active and structural properties of human muscles. Among these "artificial muscle" materials, dielectric elastomers exhibit low stiffness, high actuation strain and force output. Bistable electroactive polymers have stiffness variable up to 1000 times. In the softened state, the bistable polymer behaves like an elastomer and can be actuated like a dielectric elastomer. The combination of variable stiffness and large strain actuation will enable a new generation of artificial muscles for bioinspired robotic applications. A 6-finger manipulator will be demonstrated to grip and lift a variety of objects including eggs, golf balls, smartphones, and to squeeze a specified length of toothpaste out of the tube.