Modeling and Control of Soft Robots Actuated by Dielectric Elastomer

介电弹性体驱动的软体机器人的建模与控制

• 批准号: RGPIN-2018-06722
• 负责人: Su, ChunYi
• 金额: $ 2.33万
• 依托单位: Concordia University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=714402
• 关键词: Modeling; Control; Soft; Robots; Actuated

Over the last decade, soft robots have received tremendous interests for their potential applications. Soft robots mostly refer to robotic systems with soft or compliant structures and muscle-like actuation using soft or highly deformable materials. Unlike conventional robots, they can show high deformation under actuation and change their shapes continuously along their body length, similar to octopus arms, earthworms, and elephant trunks. Recent advances in soft actuation technologies have been favorable to development of soft robotics. Among soft actuation materials, dielectric elastomers (DEs), also known as dielectric electroactive polymers, represent an emerging/innovative class of soft actuation materials which exhibit relatively large deformations when solicited by an electric field. DEs consist of a film of elastic polymeric material covered on both sides by compliant electrodes. When a voltage is applied to the electrodes, the resulting electric field generates a compressive stress that produces a controllable deformation of the film. This deformation can be in some cases one or two orders of magnitude larger than the one obtained by other soft materials. This peculiarity, together with the lightweight, the high energy density, the fast response, and the low costs, makes DEs highly attractive for development of soft robots. On the other hand, robots made wholly or in part from materials that change the shape are more difficult to control than rigid robots. DEs are viscoelastic materials meaning that their stiffness changes with strain rate and frequency. Viscoelasticity complicates the modeling and control of the material response which is often characterized by creep, hysteresis, and stress relaxation phenomena. Owing to these intrinsic nonlinear and time variant characteristics, the precise control of DEs to determine the amount of voltage needed to obtain the deformation for soft robots becomes a non-trivial problem. In particular, hysteresis nonlinearity can significantly degrade actuator performance. However, compensating the hysteresis is a very difficult problem because the vast majority of existing control methods are only applicable to systems that are smooth and differentiable. Stress relaxation is also a significant shortcoming of DEs and can significantly degrade actuator performance over time owing to changes in elastomer thickness. Such time-variant performance characteristics are difficult to model and present challenging control issues. The objective of this research is the development of control theories, engineering design methods and technology for DE actuated soft robots to conform to their surroundings, navigate through unstructured environments, and grasp objects using whole arm manipulation in the presence of model uncertainties.

在过去的十年里，软机器人因其潜在的应用而受到了极大的关注。软机器人主要是指使用柔软或高度变形的材料，具有柔软或柔顺的结构和肌肉样驱动的机器人系统。与传统机器人不同，它们可以在驱动下表现出高变形，并沿着身体长度连续改变形状，类似于章鱼手臂、蚯蚓和大象的鼻子。近年来，软驱动技术的发展为软机器人技术的发展提供了有利条件。在软驱动材料中，介电弹性体(DES)，也被称为介电电活性聚合物，是一类新兴的/创新的软驱动材料，在电场的作用下表现出相对较大的变形。DES由一层弹性聚合物薄膜组成，其两侧覆盖有顺应性电极。当电压施加到电极上时，产生的电场产生压应力，从而产生可控的薄膜变形。在某些情况下，这种变形可能比其他软材料获得的变形大一个或两个数量级。这一特点，再加上其轻量化、高能量密度、快速响应和低成本等特点，使得DES对软机器人的发展具有极大的吸引力。 另一方面，完全或部分由改变形状的材料制成的机器人比刚性机器人更难控制。DES是粘弹性材料，这意味着它们的刚度随应变率和频率而变化。粘弹性使材料响应的建模和控制变得复杂，通常以蠕变、滞后和应力松弛现象为特征。由于这些固有的非线性和时变特性，DES的精确控制以确定软机器人获得变形所需的电压量成为一个不平凡的问题。特别是，迟滞非线性会显著降低执行器的性能。然而，补偿迟滞是一个非常困难的问题，因为现有的绝大多数控制方法只适用于光滑和可微的系统。应力松弛也是DES的一个重要缺点，随着时间的推移，由于弹性体厚度的变化，会显著降低执行器的性能。这种时变的性能特征很难建模，也很难提出具有挑战性的控制问题。本研究的目的是发展DE驱动软机器人的控制理论、工程设计方法和技术，以适应其周围环境，在非结构化环境中导航，并在存在模型不确定性的情况下使用全臂操作来抓取对象。