Rotor Vibration Reduction and Control via Flexibly-Mounted Internal-Stator Magnetic Bearings

  • Christopher Lusty

Student thesis: Doctoral ThesisPhD


Consideration has been given to the question of reducing and controlling vibration occurring in active rotor systems. The subject is of importance due to the widespread use of rotors within many engineering applications, coupled with the fact that one of the most problematic issues faced by designers of rotor systems is that of vibration. Furthermore, it is identified that improvements in the ability to handle vibration in high speed rotor systems will open up newopportunities for novel machine design and associated new capabilities.An overview of the history of rotor dynamics as a field is provided, highlighting both fundamental early work on the topic, as well as a range of research done with specific application to rotor vibration control. A novel design of an active rotor-vibration-reduction system is then proposed, consisting of a hollow rotor coupled to a exible internal secondary shaft via magnetic bearings. The uniquefeatures and benefits of this design are outlined, together with some numerical modelling of the vibration behaviour of such a system. The project required the design and fabrication of a bespoke test rig, and details of this process and the resulting rig are discussed. Special attention is given to the design of the magnetic bearings of the system, which employ a soft magnetic composite material and a novel, internalstator, homopolar geometry. The test rig was run, and two different control strategies for the magnetic bearings were explored for the purposes of achieving vibration reduction - one a traditional PID method, and the other a model-based H-infinity technique. A range of results describing the behaviour of the system under each of these control systems - as well as in the uncontrolled state - is presented. It is seen that the H-infinity controller can deliver substantial vibration reduction performance, and thereby the capability of the novel system topology for its designed purpose is proved.
Date of Award10 Nov 2016
Original languageEnglish
Awarding Institution
  • University of Bath
SupervisorPatrick Keogh (Supervisor)

Cite this