Disturbance Rejection in the Control of a Maglev Artificial Heart

This paper is devoted to the development of an advanced controller for a maglev artificial heart: in particular, a magnetically levitated left ventricular assist device is studied and the disturbances from the natural heart are taken into account. The main goal is to define a control action able to reject dc as well as periodical disturbances from the control input in steady state. This is accomplished by exploiting the intrinsic instability of the system. The paper presents a couple of approaches for solving the problem: an internal model based approach and a solution based on adaptive observers. The internal model based solution relies on the knowledge of the frequencies of the sinusoidal disturbances affecting the system: this hypothesis is not far from the reality of the maglev apparatus as the shape and frequency of the quasiperiodic disturbance can be known with the addition of sensors. The design methodology based on the use of adaptive observers does not require the perfect knowledge of the frequencies of sinusoidal disturbances as an adaptive mechanism is presented to estimate them.