Abstract:
The VentrAssist implantable rotary
blood pump, intended for long term ventricular assist,
is under development and is currently being tested
for its rotor-dynamic stability. A shaftless impeller,
which also acts as the rotor of the brushless DC
motor, is passively suspended in the pump cavity by
hydrodynamic forces.
The paper presents experimental investigation
of the displacement of the impeller within the cavity,
which will play an integral role in obtaining approval
for clinical trials.
Displacement of the impeller is measured using
Hall effect sensors located at different positions on
the pump under different pump-operating conditions.
Voltage output from the sensors are converted into
impeller movement in five degrees of freedom (x, y,
z, Ox and Oy). The sixth degree of freedom (Oz), the
rotation about the impeller axis, is determined by the
commutation performed by the motor controller.
To determine experimentally the undamped
dynamic characteristic of the hydrodynamic bearing,
future measurements of bearing forces combined
with the results of impeller displacement presented
in this paper will allow for the calculation of
stiffness coefficients for the hydrodynamic bearing.
