BIO-01 RADIAL HYDRAULIC FORCE ESTIMATION IN A MAGNETICALLY LEVITATED CENTRIFUGAL BLOOD PUMP(Bio-medical Equipments I,Technical Program of Oral Presentations)

Abstract

In order to solve the problem of lack of heart donors, ventricular assist devices have been developed and used as a bridge to transplant, a bridge to recovery or as destination therapy. Among these devices, maglev rotary pumps have been shown to deliver good clinical results with low blood damage, low risk for blood clot formation and high durability. In order to improve the magnetic bearing design, hydraulic forces acting on the maglev impeller should be precisely evaluated, however direct measurement is impossible due to absence of a rotor shaft. In this study, we propose using disturbance force observer in a two degrees-of-freedom radial controlled maglev centrifugal blood pump to estimate the radial hydraulic force acting on the maglev impeller. The radial dynamic characteristics of the maglev impeller change with flow conditions, so they were evaluated under different rotational speeds and flow resistances, and the radial disturbance force observers were designed based on the linear models obtained for a given rotational speed. Applying these observers at different rotational speeds and flow resistances, under continuous flow, we observed little variation of force direction with respect to rotational speed and proportionality between the force magnitude and the flow rate, being the maximum force 1.3 N for a flow rate of 6.8 L/min at 1700 min^<-1>. Under pulsatile flow, as in ventricular assistance, the estimated hydraulic forces followed the pulsatile flow oscillation at 60, 70 and 80 bpm, and the backflow could also be observed.