Modeling and robust control of self-sensing magnetic bearings with unbalance compensation

This paper presents a complete model of four radial DOF self-sensing magnetic bearing systems which includes all interactions between the different degrees of freedom. A method for controlling self-sensing magnetic bearings with unbalance compensation is also presented. The method uses the Q-parameterisation theory. The Q-parameterization controller is an observer-based stabilizing controller with a free parameter Q, which makes it suitable for robust control of self-sensing magnetic bearings. The free parameter and can be chosen through optimization to achieve robustness, noise minimization and to compensate for the unbalance forces. We give a complete four radial DOF mathematical model of the self-sensing magnetic bearing in state space form. We explain the Q-parameterisation controller design of the self-sensing magnetic bearing. Unbalance compensation is achieved by airgap regulation, current regulation and force regulation (automatic balancing), by a suitable choice of Q. The control problem is formulated as an optimization problem in the free parameter and whose constraints are sensor noise, actuator noise and unbalance sinusoidal disturbance rejection. The obtained controllers have 24 states for the current and airgap regulation designs and 20 states for the force regulation design. Finally, several simulations were obtained to evaluate the proposed controller. The results obtained showed that both robust stability and unbalance compensation are achieved.