Single axis random vibration control testing: experimental assessment of SISO and MIMO control strategies

In random vibration control testing, the nowadays common practice to replicate in the laboratory the operational vibration environment is the sequential Single-Input Single-Output (SISO) vibration control testing: the test specimen is sequentially rotated and three orthogonal axes are individually excited exploiting a single axis shaker. With SISO control strategy, just the drive axis of vibration is feedback controlled. In order to verify the validity of the single axis control test, the vibration levels on the two axes orthogonal to the main axis of vibration should not exceed acceptable thresholds. Significant advances in test hardware and control software, in addition to test facility designed for multi-axial excitation, have made possible to perform vibration testing using Multi-Input Multi-Output (MIMO) control strategy. Besides the feedback control of the main axis, the MIMO control configuration allows the simultaneous control along the two cross axes, thus improving the quality of the single axis test. This work presents a test campaign carried out on an exhaust gas recirculation valve, an automotive component used to reduce the emissions in internal combustion engines. A single axis shaker and a 3-DoF shaker table have been used for performing sequential single axis vibration tests by adopting SISO and MIMO control strategies. The objective of the research is to critically compare the test results and to provide a detailed analysis on how to better exploit the potential of the MIMO control strategy for definitely avoiding cross axis vibration problems.