Development of a steepest-descent control solution for Multi-Input Multi-Output swept sine testing in a virtual shaker environment

Abstract Multiple-Input Multiple-Output (MIMO) sine sweep is nowadays acknowledged to be one of the best excitation techniques for the modal testing of large aerospace structures, being an optimal solution in the tradeoff between high-quality FRFs testing time. Due to the test levels that can be reached during the sine sweeps and the increasing complexity and cost of the test articles, monitoring the recordings of multiple transducers translates in the actual need of guaranteeing that the responses are controlled on-line to a (safe) reference level. The development of a dedicated MIMO control strategy is very challenging, especially as a consequence of the transient behavior of the sweeps. This work proposes to investigate a solution for the on-line control of a MIMO continuous swept sine test combining the harmonic estimator with a steepest descent feedback control, typically adopted for the cancellation of tonal disturbances. The controller is developed in a virtual shaker testing environment, in order to tackle, already in the development stage, the effects that can be encountered during an actual test and that cannot be modeled with a linear system identification.