Session: 29-01 Active Controls of Rotordynamic Systems

Paper Number: 82528

82528 - Active Rotor Controller Design for Vibration and Bend Mitigation Utilizing Active Magnetic Bearings and Internal Shaft Actuation 

Active Magnetic Bearings (AMBs) offer several advantages over conventional rolling elements bearings that make them particularly suited to applications where the rotor operates without lubricant, under high temperature amplitude and when long operational life is required. In addition, the variable stiffness and damping facilitate the design when it comes to placing the resonance frequencies away from the operating range.

However, AMBs have limitations when it comes to their force capabilities. The magnetic material of the electro magnets will saturate when an increase in current does not increase the force, or when control bandwidth will limit when the coil amplifiers reach their maximum switching frequency. These limits can be reached when the rotor is initially balanced, when a temperature gradient induces a growing rotor thermal bend, or during operation when the mass unbalance distribution evolves due to erosion or deposition of material.

An active rotor has been designed with the aim to apply a bending strain on the rotor and improve the control capabilities, giving an increase in performance. The main advantage of on board control is that high speed synchronous forces can be generated by the shaft rotation without the need for a high frequency AMB actuator. Successful attempts include the use of piezo-electric sheets for square section shafts, or functionally graded material where a voltage can be applied to alter the dynamic behaviour of the rotor. However, these examples have limited force capabilities, and piezo-electric material require a voltage to be applied continuously to hold the force. An active rotor with an internal mechanism including actuators and a network of sensors has been designed to apply a counter bend and reduce the necessary control effort of the AMB system.

Focus has been set on very low onboard power consumption when the control position is set and high force capabilities.

This paper examines the options available to make the most out of this bending strain and work in tandem with the AMBs. Effectively, all control is at very low bandwidth. The goal is to minimise the vibration profile by defining a rotor model with no a-priori knowledge of the geometry and mass unbalance distribution. This will ultimately be highly valuable for applications where the load condition is evolving, or to retro-fit the algorithm and actuator on existing machines.

Presenting Author: Gauthier Fieux University of Bath

Presenting Author Biography: Gauthier Fieux graduated in Mechanical Engineering in 2018 at INSA Lyon in France and started his PhD the same year at the University of Bath in the UK. He worked as a trainee in industrial waste water management in Germany in 2015 and at the European Space Research and Technology Centre (ESTEC) in the Netherlands in 2017. He started with the fields of rotor dynamics during his master thesis with the re-levitation of rotor on active magnetic bearings, followed by modelling and experiments on spacecraft reaction wheels during his stay at ESTEC. His PhD focuses on the design, simulation and realisation of a novel active rotor topology supported by active magnetic bearings for vibration mitigation.

Authors:

Gauthier Fieux University of Bath
Nicola Bailey University of Bath
Patrick Keogh University of Bath