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

该项目致力于为腿部运动创造创新的分散式控制器。分散控制器只需要本地信息就可以完成它们的功能。在腿部运动的情况下，分散是可取的，原因有几个。对于假肢，其目的是替换失去的自然肢体，为使用者连接大量传感器是不切实际的。因此，假肢装置必须主要依靠它自己的内置测量。去中心化的另一个好处是管理复杂性。随着机器人变得更加复杂，为了完整描述系统状态而必须监控的变量数量变得如此之大，以至于自顶向下的控制器成本高昂或无法实施。分散控制的挑战变得更加困难，因为行走和跑步是混合的动态行为，也就是说，例如，当一只脚放在地上时，与它在空中摆动时，动力学遵循一套完全不同的规则。该项目将解决由这些特征造成的大量分析困难。该项目将推动先进的腿部假肢技术的发展，以及下一代步行机器人的运动能力。本项目将研究分散反馈控制器的系统设计，这些控制器协调低维的子系统以实现健壮的腿部运动，克服腿部机器人的维度诅咒，并使具有动力假肢的人机协同行走成为可能。该项目利用机器人学、最优化和反馈控制理论来推进两个关键创新：(1)创建算法来系统地设计协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电动假肢。在线性和双线性矩阵不等式的背景下，构造仅由一个公共步态周期相位变量协调的具有互联子系统的分散非线性控制器用于鲁棒动态步行的问题。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)它们明确地考虑了欠驱动以解释非平足步行运动；(3)它们提供了高维和强交互的复杂步行模型的子系统之间的协作；(4)它们证明了步行机器人的全维混合动力学模型是稳定的，而不是简化的模型。这种分散的控制框架具有重要的技术意义，因为它可以很容易地转移到实用的高自由度腿部机器人，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.