Stability of Rotating Machinery Supported on Active Magnetic Bearings Subjected to Base Excitation

Abstract

The stability of rotating machinery is a major challenge for the floating production storage and offloading (FPSO) units such as steam turbines or centrifugal compressors. The use of active magnetic bearings (AMBs) in turbomachines enables high operating speeds, active mechatronic system for the diagnostics, and the control and enables downsizing of the whole installation footprint. In case of strong base motions, the rotor can contact its touchdown bearings (TDBs) which are used as emergency and landing bearings. The aim of this study is to assess the stability of a rotating machine supported on AMBs during severe foundation excitation. The combined effect of unbalance forces, base motion excitation, and contact non-linearity on a rotor–AMB system response is analyzed focusing on the capacity of an augmented proportional-integral-derivative controller to maintain the system stable. An academic scale test rig was used for the experimental investigations. The controller was efficient and able to maintain the system stable during and after the application of the excitation, but the dynamic capacity of the AMBs was largely oversized with respect to the studied system. In order to check the capacity of the AMBs, when they are designed as a function of the rotor weight and expected excitation, numerical simulations were carried out (downsized). A finite element (FE) model was developed to model the on-board rotor–AMB system. Predicted and measured responses due to impulse excitation applied on the foundations were compared. The capacity of the controller to maintain the system stability is then discussed.

Shock-induced persistent contact and synchronous re-levitation control in an AMB-rotor system

“…The amplitude of the rotor's synchronous frequency response is generally designed to be within the gap between the rotor and TDB; hence, rotor-TDB contact conditions do not exist. However, shock loads that rotating machines (especially onboard machines) may encounter during normal operation can lead to contact between the rotor and the TDBs, resulting in complex nonlinear vibrations and machine damage [17], [20], [22]. Therefore, it is necessary to investigate shock-induced contact response.…”

“…To date, there is a lack of published work relating to shock response and corresponding automatic re-levitation control of AMB-rotor systems. Jarroux et al [17], [18] observed the dynamic behaviour of an AMB-rotor system with strong base motion. The 6000 rpm rotor, which was placed on a shock platform and experienced sinusoidal disturbance (0.1-1.1 G amplitude at 20 Hz), returned to a stable state after rubbing with the TDBs for a short time.…”

Dynamic analysis and vibration control of a rotor-Active magnetic bearings system with base motion

“…They found that the vibration brought by the base motion was higher than that caused by the rotor mass unbalance. Jarroux et al (2020) studied the stability of the rotor-AMBs system under severe base motion and established the finite element model of the system. Chen et al (2019) studied the response characteristics of the base for an AMB under random excitation in a horizontal direction and then deduced the model of the rotor system.…”

Levitation Stability of the Passive Magnetic Bearing in a Nutation Blood Pump

“…The stability analysis was carried out on the basis of the Floquet-Liapunov theory for the stability of a periodic system. Jarroux et al (9) assessed the stability of a rotating machine supported on AMBs during severe foundation excitation. The combined effects of unbalanced forces, base motion excitation, and contact nonlinearity on a rotor-AMB system response were analyzed, focusing on the capacity of an augmented proportional-integral-derivative controller to maintain the stability of the system.…”