Robustness of Adaptive Unbalance Control of Rotors with Magnetic Bearings

Abstract

Rotor unbalance in the primary cause of unacceptable vibration in rotating machinery. Over the last decade, researchers have explored different methods of taking advantage of the active nature of magnetic bearings to attenuate unbalance response including both feedback and adaptive open loop methods. An important issue in the application of this technology to industrial machines is the robustness of the unbalance control algorithm. The stability and performance robustness of a promising adaptive open loop control algorithm is examined. Expressions are derived for a number of unstructured uncertainties. Experimental results are then presented, which evaluate the algorithm's robustness with respect to three variations: gain schedule errors, random additive errors, and feedback loop gain. The robustness exhibited in these tests was quite good and, along with the excellent vibration attenuation obtained, recommend the algorithm for further testing and industrial application. The experimental results indicate that the theoretical robustness expressions do provide an upper bound on actual performance, however this bound is not tight. Although the conservatism in the results is partly due to the variations considered and the worst-case nature of the performance robustness guarantees, the results also indicate that further research is needed on unstructured performance robustness for this method of rotor vibration control.

Active Control for Multinode Unbalanced Vibration of Flexible Spindle Rotor System with Active Magnetic Bearing

“…The rotor has two vibration peaks at critical speed According to (8), the correcting electromagnetic force required for double nodes vibration controlled with double excitation nodes can be calculated in real time. When the active magnetic bearing nodes 1 and 3 are used as the excitation nodes, the vibration amplitudes of the rotor nodes 2 and 8 are shown in Figure 6.…”

“…Yu et al [7] used the active magnetic bearing as the actuator, which detected the transfer function model to obtain the influence coefficient matrix to achieve the vibration suppression of the flexible spindle rotor. Knospe [8] proposed a flexible rotor unbalance control method based on the influence coefficient method. Lee et al [9] proposed an active balancing method for rotating machinery using the influence coefficient method.…”

The Foundation of Electromagnets Based Active Vibration Control

“…AMB can be used to apply a synchronous force to the shaft to control the imbalance response, either to cancel the force transmitted to the base or to compensate for the vibration displacement of the shaft. In (Knospe et al, 1996;Knospe et al, 1995;Knospe, Tamer, & Fittro, 1997;Knospe, Tamer, & Fedigan, 1997) presented an adaptive open-loop control method for the imbalance displacement vibration control using AMBs. A synchronous force that consists of sinusoids that are tied to the shaft angular position via a key phasor signal was generated and applied to the rotor through the magnetic supporting bearings.…”

Active Balancing and Vibration Control of Rotating Machinery: A Survey

“…Knospe et al (1996Knospe et al ( , 1995Knospe et al ( , 1997aKnospe et al ( , 1997b Some other researchers working in DAVC for rotating machinery adopted a state space representation of a rotor system. The control inputs are lateral forces.…”