LMI approach to gain scheduled H/sub /spl infin// control beyond PID control for gyroscopic rotor-magnetic bearing system

Ultra high speed rotation in active magnetic bearing (AMB) systems with their complex structure requires powerful control system design approaches for robust stability and robust performance. Previous studies in robust control theory have offered comprehensive gain-scheduled control design approaches such as linear matrix inequality (LMI) based gain-scheduled control for linear parameter varying systems (LPVS) which are a certain class of linear time-varying systems such that state-space matrices of their plants are a fixed function of time-varying physical parameters. Rotor systems modelled with inclusion of gyroscopic effect can be considered as LPV systems because of the affine dependence of system natural frequencies on rotational speed which is taken as a time-varying parameter. These varying parameter values can be measured online during control operation. In this study, a commercially available and vertically designed rotor bearing system is modelled and controlled using LMI based gain-scheduled controller and compared with a PID controller. The results are reasonable and encouraging for future studies of AMB systems.