Biomedical Engineering Reference
In-Depth Information
FIGURE 3-37
Sanyo Denki
103H8222-0941
stepper motor.
Specifications of the larger Sanyo Denki 103H8222-0941 stepper motor shown in
Figure 3-37, are as follows:
•
Holding torque: 4.13 Nm
Step angle: 1.8
◦
•
•
Voltage: 3.88 V
•
Current/phase: 4 amp
•
Ohm/phase: 0.97
•
Inductance/phase: 3.60 mH
Flange size: 86 mm
2
(3.39 in
2
•
)
•
Connection: 6 Lead
Rotor inertia: 2.9 kg.m
2
(
×
10
4
•
)
•
Mass: 2.5 Kg
3.2.4.6 Biomechatronic Applications
Peristaltic pumps provide medical facilities with accurate and repeatable pumping perfor-
mance by the using microprocessor-controlled stepping motors. They are used to pump
blood for heart-lung machines and kidney dialysis units. By varying the diameter of the
tubing or the step rate of the motor, the pump volume and rate can be easily changed and
controlled. Various fluids can be processed using the same pump by simply changing the
tubes and reprogramming the pump parameters. Nothing but the tube touches the fluid,
thus eliminating the risk of cross-contamination between the pump and the fluid.
3.2.5 Linear Actuators
There are many different methods of producing controlled linear motion, or linear posi-
tioning. Conventional means include air cylinders, ball screws, cables and pulleys, or even
stacks of piezoelectric elements, but probably the most common is a stepping motor in
which the shaft is replaced by a screw. The center part of the rotor is tapped to convert
it to a “nut” that is threaded onto a screw. By preventing the screw turning (antirotation),
it can move axially to give the linear motion required. The increment that is the linear
progression corresponding to each step of the motor is given by the screw pitch divided by
the number of motor steps. This is selected to suit the actuator characteristics required. The
longer the pitch, the quicker the advance but the lower the force of the device. Conversely,
a fine pitch limits the advance rate but increases the force available.
