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

机器人设备的运动是通过被称为致动器的设备使其关节能够运动来实现的。 这个国家机器人计划（NRI）项目旨在了解如何为人类交互式机器人设计符合要求的执行器，这些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获得更高的效率，并吸收冲击以获得更高的安全性，这使得它们在可穿戴机器人中特别受欢迎（即，假体和外骨骼）。然而，致动器的柔性元件（例如，电动机和机器人关节之间的弹簧）必须被仔细地选择以实现这些益处，这限制了先前的实施方式到特定的使用情况。该项目中的数学框架将使柔顺致动器的设计能够改变其物理特性，以保证安全和效率，因为相互作用从温和到有力。适应各种条件的柔性致动器可用于许多应用，从而能够以较低的成本进行大规模生产。这些执行器的能效将增加移动的协作机器人的电池续航里程，并允许在可穿戴机器人中使用更小、更轻的电池。这项工作是非常重要的顺应致动器技术的普及，安全，节能的机器人和人类之间的互动在不确定的现实世界的情况下out-laborator.This项目将建立一个强大的凸优化框架设计的系列弹性致动器（SEAs），在全球范围内最大限度地减少电能消耗，同时满足致动器/安全约束。当设计SEA时，弹性元件的参数表示（例如，线性弹簧的刚度）通常针对单一任务（轨迹和负载）进行优化。然而，该范例具有两个关键限制：1）解决方案仅在给定的参数空间内是最优的，以及2）弹性的益处（即，效率和顺应性）在特定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，但是弹簧的理想参数化是未知的。因此，需要一个非参数的，强大的优化框架来开发SEA技术，可以在各种情况下实现各种任务（可定制性），与人类的无处不在的互动（可扩展性）。工具存在，以解决凸优化问题的不确定性，在其参数，但设计的SEA目前还不知道是一个凸问题。本项目的总体目标是：1）了解SEA能量消耗的凸性作为刚度特性的函数，2）了解如何设计非线性串联弹性元件以在满足约束的同时实现最大效率，和3）了解如何设计对不确定性具有鲁棒性的SEA。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的学术价值和更广泛的影响评审标准。

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.