###### Abstract  
Rotors are often coupled with a stationary part by rolling element bearings. To suppress their excessive vibration, the bearings are inserted in squeeze film dampers. The control of damping in the support elements offers the possibility to minimize the oscillation amplitude of accelerating or decelerating rotors, passing the regions of critical speeds. The controllable damping effect can be achieved if the squeeze film dampers are lubricated with magnetorheological oil. The change in the applied current feeding the electric coil changes magnetic induction in the damper gap, which changes the oil damping properties. The minimum vibration amplitude of the rotor running up or down through the resonance area is accomplished if the current increase or decrease is not sudden, but if it is distributed in some time interval. This article concentrates on determination of the optimum parameters of this manipulation. The developed procedure leads to solving an unconstrained optimization problem with the implicit objective function. The evolution method was used for its solving. In the investigated case, the proposed procedure made it possible to reduce maximum vibration amplitude by about 40% compared with the uncontrolled current decrease. The main contribution of the conducted research work is presentation of a new and original procedure for controlling the damping effect in the rotor supports. It provides a new idea to the designers and engineers regarding how to minimize amplitude of the rotor vibration when passing the critical speed. In addition, the article points to a new area of utilization of controllable magnetorheological squeeze film dampers. accelerating rotors; rotors oscillation; magnetorheological squeeze film dampers; the damping control; optimization of the control parameters; evolution optimization method +
Footnote †: journal: Applied Mechanics and Physics Letters  
**Acticle**  
**Optimization of Control Parameters of Magnetorheological Squeeze Film Dampers to Minimize the Vibration Amplitude of Rotors Passing the Critical Speed**  
**[PERSON]. [PERSON]; [PERSON], [PERSON]; [PERSON], [PERSON] Optimization of Control Parameters of Magnetorheological Squeeze Film Dampers to Minimize the Vibration Amplitude of Rotors Passing the Critical Speed**  
**Citation:** [PERSON], [PERSON]; [PERSON], [PERSON]; [PERSON], [PERSON] Optimization of Control Parameters of Magnetorheological Squeeze Film Dampers to Minimize the Vibration Amplitude of Rotors Passing the Critical Speed**  
**J. [PERSON], [PERSON]; [PERSON], [PERSON]; [PERSON], [PERSON] Optimization of Control Parameters of Magnetorheological Squeeze Film Dampers to Minimize the Vibration Amplitude of Rotors  
which induces their vibrations, which are of large amplitude. The controlled change in the damping effect in the rotor supports and represents a significant tool for its attenuation. The rotors' starting-up and running-down are important phases of their operation and realization of technological processes. Therefore, the behavior of rotors when changing their angular velocity in the vicinity of the critical speed is still the subject of intensive investigations. The first and second impulse theorems and the Lagrange equations of the second kind were used by [PERSON] and [PERSON] [1; 2] to derive the equations of motion of a flexible accelerating rotor. The authors discussed the influence of additional inertia terms on rotor oscillation. The equations of motions of an accelerating rotor can also be obtained by extending procedures presented by [PERSON] et al. in [3]. The methodology of vibration-based crack diagnostics of rotors speeding up through the resonance area is reported by [PERSON] et al. [4]. [PERSON] and [PERSON] [5] used computational simulations to perform the study on the vibration of a starting-up Jeffcott rotor. The authors concluded that the overshoot of the start-up speed significantly increases the value of the maximum rotor lateral displacement. [PERSON] et al.