Electr Eng (2008) 90:407–421 DOI 10.1007/s00202-007-0091-1 ORIGINAL PAPER A model-based flexural rotor vibration control in cage induction electrical machines by a built-in force actuator Antti Laiho · Kari Tammi · Kai Zenger · Antero Arkkio Received: 24 August 2007 / Accepted: 2 November 2007 / Published online: 5 December 2007 © Springer-Verlag 2007 Abstract In this paper active control of flexural rotor vibration in electrical machines is examined. We consider attenuation of discrete low-frequency range forced vibration components by means of an adaptive harmonic control stra- tegy. A built-in force actuator for actively generating force on the machine rotor is investigated. Previously, such an actuator has mainly been used in bearingless machine design for rotor levitation. The action of the actuator is based on electrome- chanical interaction between the rotor and the stator of the machine. A low-order linear parametric state-space model is derived for the actuator–rotor system. Parameter estima- tion is carried out using simulation data obtained from a detailed two-dimensional time-stepping finite element field- circuit model of the machine. Hence, model-based control design is performed using the identified model. The control- ler is verified by embedding it into the finite element analy- sis. As a result we present a virtual plant of the machine with vibration control. The virtual plant is introduced as a means of vibration control design prior to implementing the control algorithms in a real machine. Simulation results using real A. Laiho (B ) · K. Tammi VTT Technical Research Centre of Finland, P.O Box 1000, 02044 VTT, Finland e-mail: Antti.Laiho@vtt.fi K. Tammi e-mail: Kari.Tammi@vtt.fi K. Zenger Control Engineering Laboratory, Helsinki University of Technology, 02015 TKK, Finland e-mail: Kai.Zenger@tkk.fi A. Arkkio Laboratory of Electromechanics, Helsinki University of Technology, 02015 TKK, Finland e-mail: Antero.Arkkio@tkk.fi machine data and finite element time-stepping method are presented. Keywords Vibration control · Rotordynamics · Electrical machines · Bearingless drives · Self-bearing machines · Electromechanics · Adaptive harmonic control · Force actuation · Unbalanced magnetic pull · System identification · Evolution algorithms 1 Introduction In rotating machinery, the harmonic disturbance forces may excite harmful rotor vibrations. Indeed, the low-frequency range vibratory effects are the most important sources of rotor vibration in rotating machinery [1]. Typically, the har- monic disturbances consist of rotation speed harmonics, i.e., sub-multiples and multiples of rotation speed. In electrical machines, in addition to these harmonics, various other har- monic vibration sources are present. These include stator and rotor slotting harmonics, static and dynamic rotor eccentri- city and possible faults such as broken rotor bars [2–4]. In electrical machinery, vibratory effects may increase load or vibration level in bearings with intensified bearing wear and fatigue leading to reduction in life-time. In fact, in induction machines with conventional bearings, 42–50% of the faults are bearing related [5]. Furthermore, unwan- ted effects such as noise may appear. In its extreme, rotor vibration may couple with electromechanical system and destabilize it leading to system break-down [6]. In any case, the rotor vibration brings out limitations in machine design. The machine critical speed, most cases set by the first flexu- ral rotor bending mode, is a limiting factor which reduces operation speed range. Traditionally, electrical machines are 123