Linear and nonlinear control of a three pole combined radial and axial active magnetic bearing - a comparison

Abstract

This paper analyses two control strategies, linear and nonlinear, for a 5-axis magnetic suspension system built with two three pole combined radial and axial bearings. Therein soft magnetic composites (SMC) are used as iron core material to carry the required three-dimensional flux distribution. While the linear approach has been designed around the CLARKE-Transformation to stabilize the bearing, the nonlinear one is based on feedback linearization to achieve a stable system even in the case of minimal bias flux. The paper outlines the control strategies and the controller design. Both schemes are compared regarding command response, decoupling performance and stability margin based on experimental results in the time and the frequency domain.

A novel twin-shaft rotor layout with active magnetic couplings for vibration control

“…At present, the use of SMC material in magnetic bearings is very limited, for example, external stator magnetic bearings incorporating SMC cores have been considered by Fleischer and Hofmann. 25,26 In this paper, SMC is considered for the core for the internal stator homopolar magnetic bearing design. SMC offers some clear advantages over laminated steel.…”

Decoupling control based on linear/non‐linear active disturbance rejection switching for three‐degree‐of‐freedom six‐pole active magnetic bearing

“…Without efficient decoupling measures, it is difficult to realise high speed and high precision stable operation of magnetic bearing system. At present, scholars at home and abroad have done a lot of research on decoupling control, and have achieved fruitful research results, in which inverse system decoupling control [17, 18], sliding‐mode control [19], feedback linearisation control [20], redundant coordinates control [21] and neural network decoupling control [22] have become the focus of research. In [17], a control strategy that combines inverse system method and internal model control is proposed to improve the stability of magnetically suspended rotor system.…”

“…The overall robust stabilising controller is verified both numerically and experimentally. In [20], three‐pole radial‐axial hybrid magnetic bearings are controlled by feedback linearisation control, and the radial and axial suspensions are controlled at the same time, and compared with the PID controller. The experimental results show that the feedback linearisation is smaller than that of the PID controller in steady state, and the power consumption is reduced by 30%.…”