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

该项目解决了为腿部运动创造创新的分散控制器的问题。分散控制器只需要本地信息来完成其功能。在有腿运动的情况下，分散化是可取的，有几个原因。对于假肢来说，其目的是替换失去的自然肢体，用大量的传感器连接用户是不切实际的。因此，假肢装置必须主要依靠其自身的内置测量。去中心化的另一个优点是管理复杂性。随着机器人变得越来越复杂，为了完整地描述系统状态而必须监控的变量数量变得如此之多，以至于自上而下的控制器变得昂贵或不可实现。分散控制的挑战变得更加困难，因为走路和跑步是混合动力行为，也就是说，当一只脚放在地上时，与它在空中摇摆时相比，动力学遵循的是一套完全不同的规则。本项目将解决由这些特性引起的实质性分析困难。该项目将推动先进下肢假肢的发展，以及下一代有腿机器人的运动。本项目将研究分散反馈控制器的系统设计，该控制器协调低维子系统以实现鲁棒的腿式运动，克服腿式机器人的维数诅咒，实现人机协作行走与动力假肢。该项目利用机器人、优化和反馈控制理论来推进两个关键创新：(1)创建算法，系统地设计用于合作子系统的鲁棒稳定分散控制器；(2)将分散控制框架应用于实验四足动物和动力义肢。为具有互联子系统的鲁棒动态步行创建分散非线性控制器的问题，仅通过一个共同的步态周期相位变量进行协调，将在线性和双线性矩阵不等式的背景下进行阐述。这些算法的理论意义包括：(1)它们是设计一般非线性分散反馈控制方案的有力工具；(2)它们明确地解释了驱动不足，以解释非平足行走的运动；(3)具有高维、强交互的复杂行走模型子系统之间的协同作用；(4)证明了它们能稳定行走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。

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.