A novel MIMO random control strategy for efficient response replication at the component level

This study focuses on Multiple-Input Multiple-Output (MIMO) vibration control tests, designed to accurately mimic a structure’s operational vibration environment. Usually, in MIMO random tests, the control target is based on a reference Spectral Density Matrix (SDM) in the frequency domain, comprising Power Spectral Densities (PSDs) and Cross Spectral Densities (CSDs). The reference SDM is initially defined with predefined PSD profiles and later completed using various methodologies. However, introducing different CSD terms can significantly impact the structure’s response intensity, potentially deviating from real operating conditions. This paper introduces a novel methodology, named Minimum PSD Method (MPM), that aims to replicate a random vibration environment at the component level with minimal excitation. The approach pre-defines the phase and correlation of the reference SDM that maximize the response of the Unit Under Test (UUT). Then, the reference SDM is completed with the minimum PSD values ensuring that the structure’s response in the laboratory aligns with the target vibration environment. This manuscript provides the mathematical implementation of the MPM. In addition, the MPM is studied in an experimental campaign comprising two test cases: one conducted on an aluminium cantilevered beam, the other on an Exhaust Gas Recirculation (EGR) assembly. The experimental campaign allows assess the capabilities of MPM by means of drives reduction, replication of the UUT response and fatigue damage inflicted to the UUT. This method enhances the consistency of laboratory tests with actual operational environments while minimizing the required energy and preserving the excitation system’s integrity.