Monitoring the Health of Structural Systems from the Geometry of Sensor Traces

随着时间的推移和暴露于大载荷事件而发生的劣化会降低结构系统的安全性。干预措施的有效性和效率，以保持足够的可靠性取决于现有的信息，结构监测的目标是提供它。试图通过跟踪谐振频率表征恶化已经取得了有限的成功，由于小的灵敏度的功能相对于其不可约的变异性。该奖项支持一种完全不同的模式的研究：其中监测不是通过检查谐振频率进行的，而是通过检查由闭环操作中获得的测量结果构建的几何对象。在迄今为止所追求的道路上，收益来自于通过选择控制律来“调谐”被监视对象的能力。该研究成果将为结构健康监测系统的发展开辟一条新的途径。这条新的道路，以及由此带来的进步，将通过降低检查成本，推进基于状态的维护实践，并最终降低结构系统的生命周期成本，使美国经济受益。该项目的研究处于多个学科的交叉点，这方面被用于教育部分，旨在激励来自各个领域的学生和年轻研究人员。该奖项的研究将监控问题视为跟踪由轨迹生成的对象的几何形状，这些轨迹是在系统在非线性反馈下自主运行时遍历的。与线性反馈相反，线性反馈保留了经典的监控结构，从而推断出特征值的变化，非线性反馈试图将参考状态映射到吸引子的几何形状，并专注于系统变化如何影响所产生的流形。理论来指导如何指定的非线性控制，使系统有一个稳定的吸引子，具有可预测的吸引盆，目前缺乏。模拟指导的理论研究是这项工作的核心，旨在填补这一知识空白。该研究还处理的问题，如何选择的状态，从那里的系统是“推出”，所以必要的驱动的需求最小化;最小化的无穷大规范的驱动是重要的实用性的调查范式。虽然最佳的传感器和执行器的位置问题没有明确包括在该项目的范围内，在这两个问题的探索性工作计划。

Deterioration from the passage of time and from exposure to large loading events can reduce the safety of structural systems. The effectiveness and efficiency of interventions to maintain adequate reliability depend on the available information, and the objective of structural monitoring is to provide it. Attempts to characterize deterioration by tracking resonant frequencies has had limited success due to small sensitivity of the features relative to their irreducible variability. This award supports research on an entirely different paradigm: one where monitoring is carried out not by inspection of resonant frequencies, but by examination of a geometric object built from measurements obtained in closed-loop operation. Gains, over the path so far pursued, come from the ability to "tune" the monitored object by selection of the control laws. The results from this research will open a new path for developing structural health monitoring systems. This new path, and the progress that will come from it, will benefit the US economy by reducing the cost of inspections, by advancing the practice of condition based maintenance, and, ultimately, by reducing the life cycle cost of structural systems. The research in this project sits at the intersection of several disciplines and this aspect is exploited in an educational component designed to inspire students and young researchers from various fields. The research in this award casts the monitoring problem as that of tracking the geometry of an object generated by trajectories that are traversed as the system operates autonomously under nonlinear feedback. In contrast with linear feedback, which retains the classical monitoring structure, and thus infers about changes from eigenvalues, nonlinear feedback attempts to map the reference state to the geometry of an attractor and focuses on how system changes affect the resulting manifold. Theory to guide how to specify the nonlinear control so the system has a stable attractor, with a predictable basin of attraction, is currently lacking. The simulation-guided, theoretical research that is central to this work is intended to contribute in filling this knowledge gap. The research tackles also the question of how to select the state from where the system is "launched" so the demands on the necessary actuation is minimized; minimization of the infinity norm of the actuation being important to the practicality of the investigated paradigm. Albeit the optimal sensor and actuator placement problems are not explicitly included in the scope of the project, exploratory work in both of these issues is planned.