Imbalance compensation for an AMB system with adaptive immersion & invariance control

Abstract

This study is concerned with the compensation of imbalance force existing in a three-pole active magnetic bearing (AMB) system. An adaptive compensation scheme is proposed using the method of immersion and invariance (I&I) control. The main idea of I&I control is to immerse a higher-order system into a lower-order target system. In this study, the target system will be the three-pole AMB system with known imbalance that is stabilized by an integral sliding mode controller (ISMC). In practical applications, the imbalance force may be unknown and may be changing during operation. The information of imbalance needs to be estimated online in order to realize the ISMC levitation control. To this aim, the adaptive compensation scheme is incorporated into the ISMC controller so that the closed-loop system forms the higher-order system for the design of I&I control. Numerical simulations verify the effectiveness of the proposed adaptive compensator for mass imbalance.

Performance evaluation of a three-pole magnetic rotor-bearing system

“…It is larger at high frequency band (larger than 100 Hz) and smaller at low frequency band (less than 60 Hz). For most of the frequency band, it is around 10 N/m to 4 10 N/m. 3.…”

“…2. The system has been extensively studied in [2][3][4][5][6]15]. For detailed specifications of the system, please refer to the above references.…”

“…The results clearly indicate that at the low frequency band (less than 60 Hz), the 3-pole AMB system possesses a relatively low dynamic stiffness (less than 100 N/m). At the high frequency band (greater than 100 Hz), the dynamic stiffness is relatively large (larger than 4 10 N/m). Due to the resonance, one can also see from Fig.…”

“…An integral sliding mode controller (ISMC) has been successfully applied to this system [3]. As shown in [3][4][5], the ISMC controller can stabilize the rotor with high accuracy under the no-load condition and zero rotation. In [6], however, one observed that there exists a steady state limit cycle where the rotor speed is nonzero.…”