Active Magnetic Bearings (AMB) have been proposed by many researchers and engineers as an alternative to replace traditional contact bearings in rotors and driveshafts. Such active, non-contact bearings do not have frictional wear and can be used to suppress vibration in sub- and supercritical rotor dynamic applications. One important issue that has not yet been addressed in previous AMB driveline control studies is the effect of non-constant velocity (NCV) flexible couplings, such as U-Joint or disk-type couplings. The NCV effects introduce periodic parametric and forcing actions that are functions of shaft speed, driveline misalignment and load-torque. Previous research has found that NCV couplings can greatly impact stability and cause significant harmonic excitation at integer multiples of the shaft speed. Thus, to ensure closed-loop stability and acceptable performance of any AMB-driveline with NCV couplings, these effects must be accounted for in the control law design. In this paper, a hybrid control law consisting of an analog PD feedback controller augmented with a slowly updating, multiple harmonic adaptive vibration control (MHAVC) is developed for a U-joint-driveline system supported by AMBs. The function of the PD controller is to ensure closed-loop stability and convergence of the MHAVC, while the MHAVC suppresses the steady-state vibration. Closed-loop stability, convergence, and performance are investigated over a range of shaft speeds for various misalignment and load-torque levels. It is found that there is an optimal range of P and D feedback gains that ensures both convergence of the MHAVC and maximizes the robust stability of the closed-loop system, with respect to NCV effects. Furthermore, it is demonstrated that the MHAVC can effectively suppress the multi-harmonic vibration induced by shaft imbalance and NCV coupling effects without knowledge of the disturbance input distribution.

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