NRI: A Variable Stiffness Artificial Muscle Material for Dexterous Manipulation

该项目的目标是创造一种结合了创新驱动和集成传感的材料。驱动原理是基于双稳态电活性聚合物。这包括夹在两个柔性导电层之间的电绝缘聚合物薄片。聚合物片材表现出相变，当温度超过相变值时，柔量有较大的增加。为了驱动材料，首先将其加热到相变上方，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，可能增加了几百%。这些高应变与边界约束相结合，会导致执行器的大位移。然后，材料被允许冷却并转变回僵硬的形式，锁定新的致动器位置，并允许移除电势。测量压力或触摸的薄膜传感器与执行机构片集成在一起。由此产生的高应变、可变顺应性、自我感知的设备非常适合具有肌肉般的灵活性的机器人操作手。这种机械手将应用于各种各样的机器人系统，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类人机器人。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、沟通和人际交往技能。该项目研究一种结合了可变刚度、大应变驱动和传感的人造肌肉材料，并探索这种材料在广泛的机器人应用中至关重要的灵巧操作的应用。它与传统机器人的不同之处在于，操作是以对象为中心的。对象可以具有各种不同的形状、刚度、表面纹理和重量。人工肌肉结合了感知、驱动和可变刚度，以产生从温和的触摸到牢固的抓取的灵活操作，并具有局部可控性。电活性聚合物在复制人类肌肉的活性和结构特性方面表现出了希望。在这些“人造肌肉”材料中，介电弹性体表现出低硬度、高驱动应变和力输出。双稳态电活性聚合物具有高达1000倍的刚性可变。在软化状态下，双稳聚合物的行为像弹性体，可以像介电弹性体那样被驱动。可变刚度和大应变驱动的结合将使新一代人造肌肉能够用于生物启发的机器人应用。将展示一种6指机械手，可以握住和举起包括鸡蛋、高尔夫球、智能手机在内的各种物体，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.