Comparison of single-input single-output and multi-input multi-output control strategies for performing sequential single-axis random vibration control test

This study investigates the use of single-input single-output and multi-input multi-output control strategies for performing single-axis vibration control tests. In particular, the work addresses the problem of high-level cross-axis responses during those tests. To compare the two control strategies, the study presents a test campaign carried out on an automotive component by exploiting two different test facilities: a single-axis shaker and a three-degree-of-freedom shaker table. The analysis points out the limitations of the single-input single-output control strategy. The coupling between the excitation system and the test specimen causes cross-axis excitations that compromise the test validity. In some cases, the cross-axis vibration level even exceeds the acceptable threshold of 14 dB. The multi-input multi-output control strategy instead, besides the feedback control of the main axis, allows the simultaneous vibration control along the two cross axes, thus, improving the quality of the single-axis test. Moreover, the work provides a detailed study followed by practical examples on how to better exploit the evident potential of the multi-input multi-output control strategy for definitely avoiding cross-axis vibration control problems.