NRI: Decentralized Feedback Control Design for Cooperative Robotic Walking with Application to Powered Prosthetic Legs

该项目致力于创建用于腿式运动的创新分散式控制器。分散控制器只需要本地信息即可完成其功能。在腿式运动的情况下，出于多种原因，分散化是可取的。对于假肢来说，其目的是替换失去的自然肢体，为用户连接大量传感器是不切实际的。因此，假肢装置必须主要依赖其自身的内置测量。去中心化的另一个优点是复杂性的管理。随着机器人变得越来越复杂，为了完整描述系统状态而必须监视的变量数量变得如此之大，以至于自上而下的控制器实施起来成本高昂或不可行。分散控制的挑战变得更加困难，因为步行和跑步是混合动态行为，也就是说，与脚在空中摆动时相比，例如，当脚踩在地上时，动态遵循一组完全不同的规则。该项目将解决由这些特征引起的大量分析困难。该项目将推动先进下肢假肢以及下一代腿式机器人运动技术的发展。该项目将研究分散式反馈控制器的系统设计，该控制器协调低维子系统以实现稳健的腿式运动，克服腿式机器人的维数诅咒，并利用动力假腿实现人机协作行走。该项目利用机器人技术、优化和反馈控制理论来推进两项关键创新：（1）创建算法来系统地设计用于协作子系统的鲁棒稳定分散控制器； （2）通过实验性四足动物和动力假肢将分散控制框架付诸实践。创建分散式非线性控制器以实现具有互连子系统的鲁棒动态行走的问题，仅通过公共步态周期定相变量进行协调，将在线性和双线性矩阵不等式的背景下制定。这些算法的理论意义包括：（1）它们是设计通用非线性分散反馈控制方案的有力工具； (2) 他们明确地解释了驱动不足，以解释非措手不及的行走运动； （3）它们提供高维、强交互的复杂步行模型子系统之间的协作； （4）它们可证明稳定步行机器人的全维混合动力学模型，而不是简化模型。这种分散控制框架在技术上具有重要意义，因为它可以很容易地转移到实用的高自由度腿式机器人以及用于身体康复的可穿戴机器人中。

This project addresses the creation of innovative decentralized controllers for legged locomotion. Decentralized controllers require only local information to accomplish their function. In the case of legged locomotion, decentralization is desirable for several reasons. For prosthetics, where the purpose is to replace a lost natural limb, it is impractical to wire the user with a profusion of sensors. Therefore the prosthetic device must primarily rely on its own built-in measurements. Another advantage of decentralization is the management of complexity. As robots become more sophisticated, the number of variables that must be monitored for a complete description of the system status becomes so large that top-down controllers are costly or infeasible to implement. The challenge of decentralized control is made substantially more difficult because walking and running are hybrid dynamic behaviors, that is, the dynamics follow a completely different set of rules when, for example, a foot is planted on the ground, compared to when it is swinging in the air. This project will address the substantial analytical difficulties caused by these features. This project will advance the state of the art in advanced lower limb prosthetics, as well as in locomotion for the next generation of legged robots. This project will investigate the systematic design of decentralized feedback controllers that coordinate low-dimensional subsystems to achieve robust legged locomotion, overcoming the curse of dimensionality in legged robots and enabling cooperative human-machine walking with powered prosthetic legs. The project draws upon robotics, optimization, and feedback control theory to advance two key innovations: (1) creating algorithms to systematically design robust stabilizing decentralized controllers for cooperative subsystems; and (2) transferring the decentralized control framework into practice with an experimental quadruped and a powered prosthetic leg. The problem of creating decentralized nonlinear controllers for robust dynamic walking with interconnected subsystems, coordinated only by a common gait cycle phasing variable, will be formulated in the context linear and bilinear matrix inequalities. The theoretical significance of these algorithms include: (1) they are powerful tools for the design of general nonlinear decentralized feedback control schemes; (2) they explicitly account for underactuation to account for walking motions that are not flat-footed; (3) they provide cooperation between subsystems of complex walking models with high dimensionality and strong interactions; and (4) they provably stabilize full-dimensional hybrid dynamical models of walking robots rather than simplified models. This decentralized control framework is technologically significant because it can be readily transferred into practical high-DOF legged robots, as well as wearable robots for physical rehabilitation.