Development of Robust Controller for One Degree of Freedom Quasi-Zero Power Magnetically Suspended Thrust Bearing System

Thrust bearings are often used in different industrial applications with varying axial loads. Despite such use, these conventional thrust bearings are incorporated with unclean operating environments and undergo wear and tear due to physical contact, making it challenging to use in controlled industrial environments where environmental cleanliness is a pivotal factor.  This study presents the development of one degree of freedom magnetic suspension system equivalent to a vertical thrust bearing using a robust controller with a hybrid electromagnet which can perform disturbance rejection and handle model uncertainties. A finite element analysis has been performed to identify the properties of the hybrid electromagnet under varying parameters. The electrical system has been modelled as a RL circuit while a computer aided design of the mechanical system has been developed to analyse and validate the performance prior to the implementation in real system. The H∞ robust controller has been developed using the mathematical model of the system, which was developed along with system analysis. The developed controller was validated under known external disturbances and model variations and the system behaviour was analysed. The results demonstrate that the developed H∞ based system exhibits superior disturbance rejection compared to PID based control.