NRI: FND: COLLAB: Optimal Design of Robust Compliant Actuators for Ubiquitous Co-Robots

机器人装置的运动是通过称为致动器的装置使其关节运动来实现的。这个国家机器人计划（NRI）项目旨在了解如何为人机交互机器人设计兼容的执行器，在各种任务和情况下都是节能和安全的。与刚性致动器不同，柔性致动器可以存储和释放机械能以提高效率，并吸收冲击以提高安全性，这使得它们在可穿戴机器人（即假肢和外骨骼）中特别受欢迎。然而，必须仔细选择执行器的柔性元件（例如，电机和机器人关节之间的弹簧）才能实现这些优势，这限制了以前的实现仅限于特定的用例。该项目中的数学框架将使柔性执行器的设计能够改变其物理特性，以确保在相互作用从温和到强烈变化时的安全性和效率。兼容的执行器在各种条件下都很强大，可用于许多应用，允许以较低的成本进行大规模生产。这些执行器的能源效率将增加移动协作机器人的电池范围，并允许在可穿戴机器人中使用更小、更轻的电池。这项工作对于在实验室以外的不确定的现实世界中，机器人和人类之间安全、节能的交互的柔性执行器技术的普及具有重要意义。该项目将建立一个鲁棒的凸优化框架，用于设计系列弹性执行器（SEAs），在满足执行器/安全约束的同时，在全球范围内最小化电能消耗。在设计SEA时，弹性元件的参数表示（例如，线性弹簧的刚度）通常针对单个任务（轨迹和负载）进行优化。然而，这种模式有两个关键的局限性：1)解决方案仅在给定的参数空间内是最优的；2)弹性的好处（即效率和顺应性）在特定的操作条件之外可能完全丧失。非线性串联弹性元件可以通过在不同工作点提供不同的刚度特性来潜在地解决这些问题，但弹簧的理想参数化是未知的。因此，需要一个非参数的、健壮的优化框架来开发SEA技术，该技术可以在各种情况下实现各种任务（可定制性），以便与人类进行无处不在的交互（可伸缩性）。已有工具可以解决参数不确定的凸优化问题，但目前尚不知道SEAs的设计是一个凸问题。该项目的总体目标是：1)理解SEA能耗的凹凸性作为刚度特性的函数；2)理解如何设计非线性串联弹性元件以在满足约束的情况下实现最大效率；3)理解如何设计对不确定性具有鲁棒性的SEA。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Motion of robotic devices is achieved by enabling the movement of its joints by devices called actuators. This National Robotics Initiative (NRI) project seeks to understand how to design compliant actuators for human-interactive robots that are energy-efficient and safe across a wide variety of tasks and situations. Unlike rigid actuators, compliant actuators can store and release mechanical energy for greater efficiency and absorb shocks for greater safety, which has made them especially popular in wearable robots (i.e., prostheses and exoskeletons). However, the compliant element of the actuator (e.g., a spring between the motor and the robot joint) must be carefully chosen to achieve these benefits, which has restricted previous implementations to specific use cases. The mathematical framework in this project will enable design of compliant actuators that change their physical properties to guarantee safety and efficiency as interactions vary from gentle to forceful. Compliant actuators that are robust to a wide range of conditions can be used for many applications, allowing mass production at lower cost. The energy efficiency of these actuators will increase the battery range of mobile co-robots and allow the use of smaller, lighter batteries in wearable robots. This work is significant to the ubiquity of compliant actuator technology for safe, energy-efficient interactions between robots and humans in uncertain real-world situations outside the laboratory.This project will establish a robust convex optimization framework for designing series elastic actuators (SEAs) that globally minimize electrical energy consumption while satisfying actuator/safety constraints. When designing an SEA, a parametric representation of the elastic element (e.g., the stiffness of a linear spring) is typically optimized for a single task (trajectory and load). However, this paradigm has two key limitations: 1) solutions are only optimal within the given space of parameters, and 2) the benefits of the elasticity (i.e., efficiency and compliance) can be entirely lost outside of specific operating conditions. A nonlinear series elastic element can potentially solve these problems by providing different stiffness characteristics at different operating points, but the ideal parameterization of the spring is unknown. A non-parametric, robust optimization framework is therefore needed to develop SEA technology that can achieve a variety of tasks in a variety of situations (customizability) for ubiquitous interaction with humans (scalability). Tools exist to solve convex optimization problems with uncertainty in their parameters, but the design of SEAs is not currently known to be a convex problem. The overall goals of this project are then to 1) understand the convexity of SEA energy consumption as a function of stiffness characteristics, 2) understand how to design nonlinear series elastic elements to achieve maximal efficiency while satisfying constraints, and 3) understand how to design SEAs that are robust to uncertainties.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.