Page 326 - Control Theory in Biomedical Engineering

300 Control theory in biomedical engineering

Fig. 9 Example of Seek thermal application used during actuation.

to note is the stability in 90% and 80% PWM. As shown in the graphs, tem-
peratures in the 80% and 90% PWM rise steadily in a staircase manner while
cooling down almost instantaneously. However, the 100% PWM produced
results that are more haphazard and less predictable. Hence, these two
PWMs are favored for use in the NasoXplorer.

3.3 Dynamic force test with changes in temperature

The objective is to test out varying stiffness of each material (Figs. 10–14)
and assess suitability for our project.
Larger currents produce more significant amounts of heat. This translates
to more significant flexibility changes and can be seen in all the graphs where
values for 0.5A were consistently higher than that of 0.3A, except for RGD
8705 during the early parts of the actuation. For RGD 8730 (pure Vero-
Clear), the sample broke apart during testing. Hence, through this test,
we recommend a mixture of rigid and flexible polymers.

RGD8730
Power ON Power OFF
0.1
0.08
Force (N) 0.06
0.04
0.02
–0.02 0 1
516 1031 1546 2061 2576 3091 3606 4121 4636 5151 5666 6181 6696 7211 7726 8241 8756 9271
Data points taken at 100HZ
RGD8730 (0.3A) RGD8730 (0.5A) ON/OFF
Fig. 10 Force graph for material RGD-8730.