Oil whip instability control using μ-synthesis technique on a magnetic actuator

Rotating machines have a wide application range and since those machines have high trust levels, several rotor vibrations control methods are investigated in order to avoid sudden cracks, improve rotor performance or even to reach higher operation speeds by controlling some instabilities, critical speeds resonances or oil whip effect. Rotor instabilities are associated to the operation speed and can have structural or dynamic sources from the shaft, bearings and foundation or even from an actuator external force. This work focuses on a strategy that uses the μ-synthesis control technique to attenuate the oil whip instability effect of flexible hydrodynamically supported rotors and allows the rotor to operate in higher speeds. For the identified rotor model and the synthesized controller applied on a magnetic actuator, the control system stability and performance specifications are analyzed with regard to the model uncertainties and μ-synthesis controlled vibration levels are compared to PID controller in vertical and horizontal directions. The performance specifications within the μ-synthesis are optimized to suppress unbalance vibration and, in order to contribute to industrial acceptance, the controller design is presented as a strategy which focuses on a design at reduced effort.

► μ-synthesis is an uncertainty-based control technique.
► Dynamic characteristics of the rotating system change due to lubricated bearings.
► μ-synthesis control tackles the problem of fluid induced instability.
► Experimental μ-synthesis control implementation leads to strong reduction of vibration level.
► μ-synthesis technique used the experimental characterization of the rotating system.