Comparative study of rotor active vibration control performance utilizing H-infinity and mu-synthesis
Matheus Freire Wu1; Ricardo Ugliara Mendes1; Katia Lucchesi Cavalca1
1 UNICAMP
doi:10.20906/CPS/COB-2015-0171
Resumo
Currently rotating machinery are largely used in many industrial sectors due to their broad range of applications, such as motors, turbines, compressors, and others. The growing demand for more efficiency requires faster, powerful and reliable rotors. Among the main obstacles that oppose the operation characteristics mentioned before are the vibrations associated to unbalance, that compromise the useful life of the mechanical system components. Hydrodynamic bearings are an interesting option for shaft support since they offer a good relation involving supported load and operational speed, low friction coefficient, high damping capacity and theoretically infinity useful life. However they present a downside, the so called fluid-induced instability, that induces the system auto-excitation and creates a operational speed threshold due to high vibration levels. In order to reduce the undesirable vibration effects caused by unbalance and fluid-induced instability, there are different approaches, being one of them the active vibration control. There are distinct techniques and kinds of controllers available for this application, such as the well known PID (proportional differential integrative controller) which presents simplified mathematical model and good performance, but usually limited to simpler systems. For more complex applications, finding an acceptable PID tuning requires filters and different adaptations that demands a high experienced control designer. On the other hand, rotating machinery, in comparison to static structures, presents parameters that depend on the rotational speed, mainly the dynamic variation due to the gyroscopic effect and the stiffness and damping characteristics related to the oil film at the bearings. Therefore, the mathematical model is a function of the rotational speed, and consequently, a controller designed for one rotation may not present the same performance for others, even causing damages like instability. An alternative is to apply robust model based controllers, s
Palavras-chave: Rotor dynamics; Robust control; Vibration control