Internal Sensing and Actuation Topologies for Active Rotors

Abstract

Active control constitutes the state of the art in vibration management in rotating machines. However, existing designs are impractical and costly, and hence not yet widely applied. The goal of the research reported here was to develop a design which would allow the implementation of active technology in a wider range of rotating machine applications. Thus, this study focuses on a novel active rotor topology, consisting of a hollow rotor with internally mounted sensors and actuators. This layout provides greater freedom to select the sensorand actuator positions along the rotor, and naturally protects the devices fromharsh working environments.The research was structured according to four themes. Firstly, the conceptfeasibility was explored by constructing a fully functioning prototype. MEMSaccelerometers and mass balancer actuators were mounted in an assembledrotor, together with a microcontroller and radio unit to enable wireless transmission of data. Secondly, the behaviour of MEMS accelerometers in a rotating frame of reference was studied. An output model was derived and applied to the study of whirl orbits and transient vibration. Further, techniques were developed to extract mean displacement and angular velocity information from the sensor signals. An analysis of potential sources of measurement error was conducted, and methods for their mitigation devised. The third theme focused on developing active vibration control techniques suitable for use with active rotors. The core of this work is the development and successful implementation of a non a priori method, Algorithmic Direct Search Control. This technique enables vibration to be minimised without knowledge of the system characteristics, by applying a direct search optimisation technique as a control law. Finally, the combination of active rotors and Active Magnetic Bearings was considered to tackle the problem of sensor/actuator non-collocation. The challenge of levitating a rotor on AMBs using only internal accelerometers was approached via integration-based displacement information extraction, to exploit existing PID controllers. This method proved unfeasible in practice, but valuable lessons were derived from the study.The key finding of this work is that active rotor technology is versatile, cost-effective, powerful and feasible. As such, it offers great potential as a routeto achieving a more practical and generalised implementation of active controltechnology in rotating machinery.

Date of Award	1 Mar 2017
Original language	English
Awarding Institution	University of Bath
Supervisor	Patrick Keogh (Supervisor)