Experimental study on the whip elimination of rotor-bearing systems with electromagnetic exciters

The elimination of whip using electromagnetic exciters (EEs) is investigated in this paper. First, mathematical models of a rotor-bearing system are derived. The threshold of instability determining if the rotor-bearing system experiences fluid-induced instability is obtained. Then, an experimental rotor-bearing system is designed and constructed to justify the elimination of whip, and orbit, spectrum, and spectrum cascade plots are obtained from the experimental data. The proposed procedure applies root locus plots to simulate the threshold of instability, and the spring model is used to compute the stiffness that the system needs to address the whip problem. Moreover, design examples are illustrated to explain the calculation process that tackles the proportional (simulating stiffness) and derivative (simulating damping) parameters of the EE to improve the stiffnesses of the rotor-bearing system. The main contribution of the present experimental work is that by using the EE it is possible to increase the stiffness of the rotor-bearing system and lead to the rotor-bearing system with a higher threshold of stability and eliminate the whip instability.