Moving sensors in structural dynamics

In the monitoring of structural systems, the use of multiple high end sensors may prove to be economically prohibitive. The alternative approach would be to use fewer devices that move across the span of the structural system. In the proposed approach, the dynamic of a one-dimensional system is evaluated using a velocity sensor that is able to move across the domain and obtains pointwise velocity measurements at the desired locations. Based on the measured velocities, a state estimator is developed. The gain of the filter depends on the motion of the sensor. The motion of the sensor is defined using Lyapunov redesign methods and depends only on the estimation error at the current sensor position. The guidance policy is performance-based and steers the sensor to spatial regions of the structure with larger estimation errors. The proposed approach is validated with a one dimensional flexible structure, described by an Euler-Bernoulli partial differential equation. The moving sensor is simulated with the use of a laser scanning vibrometer, that provides both the moving measurements and additional measurements against which the proposed approach will be validated. Once a large number of locations is measured, the experimental results are fed to the algorithm that selects the instantaneous sensor location. Experimental results for a linear cantilever are presented that show the benefit of using a state estimator with a moving sensor. Analysis on how the state observer gains are optimally chosen will also be presented. The approach is demonstrated to be feasible and robust.