An Experiment for the Validation of Force Reconstruction Techniques on Flexible Structures

Dynamic force measurements are often corrupted by the structural dynamics of the surrounding support structure. Force reconstruction techniques aim to correct for these structural effects by using additional information such as a modal characterization of the structure, a finite element model of the assembly, or additional instrumentation. In practice, accurately measuring input forces to validate the techniques is often difficult or impossible. This work proposes a novel experiment that allows for measurement of the true input spatial force distribution acting on a structure for the purposes of experimentally validating force reconstruction techniques. In the proposed experiment, independently-controlled electromagnets are supported by force gages and used to excite a flexible structure. The reaction force from the electromagnet gives a measure of the applied forces over a given bandwidth, which can be used to validate force reconstruction techniques. This paper focuses on the design of such an experimental arrangement, and presents a numerical model which can also be used to validate force reconstruction techniques. Key components of this experiment are characterized to validate the measurements and methodology. The independently-controlled electromagnets can mimic different types of physical excitation forces, which allow for validation of various force reconstruction techniques aimed at niche applications. For example, the main application of the proposed experiment is to reconstruct unsteady fluid-borne forces generated on a flexible test structure. As such, a sample measurement mimicking forces generated by turbulent flow across a beam using electromagnets is provided.