Page 548 - Handbook of Biomechatronics

542 Graham Brooker

The mass is 770g which is significantly heavier than the roller-screw-based
device. The controller comprises a microprocessor that reads the Hall-effect
signals and drives a MOSFET-controlled H-bridge that powers the actuator
coil from a 9-V DC source. The control unit has two modes, a fixed rate
mode where a constant frequency signal is provided to the actuator, and
a full fill/full eject (FFFE) mode that uses the Frank-Starling control mech-
anism to govern the pump speed.
The measured pump performance is shown in Fig. 16. For a head of
100mmHg the maximum output was 6.1L/min at 155bpm with a power
consumption of 8W. The maximum efficiency was 16.3% at a pump rate of
135bpm. In the FPPP mode the pump output was 7.9 and 5.1L/min for
loads of 60 and 120mmHg, respectively with the pump rate decreasing
by 54bpm over that range. The stroke volume remained between 38 and
3
43cm .
An alternative to the pneumatic drive method is the one used by the
AbioMed TAH which is symmetrical dual-cavity hydraulically driven blood
pump replacing both the right and left hearts. Each pump is capable of deliv-
ering more than 8L/min. Blood is pumped from the superior and inferior
vena cava to the lungs through the pulmonary artery by the right pump and
from the pulmonary veins to the rest of the body via the aorta by the
left pump.
The heart pump consists of the following components as shown in
Fig. 17:
• Hydraulic pump—An efficient electric motor spins the impeller inside
the centrifugal pump at 10,000rpm to create the required hydraulic pres-
sure in a silicone hydraulic fluid.

Fig. 16 Measured characteristics of the linear actuator pump. (Based on Fukui, Y.,
Funakubo, A., Fukunaga, K., 2004. Development of the assisted artificial heart with linear
motor actuator. In: SICE 2004 Annual Conference.)