Chapter 5 Robust Performance Tailoring with Tuning - SSL - MIT

are tailored such that the mass is concentrated towards the center of the array by
setting the batten height and width at the ends smaller than at the center. However,
the severity of the tailoring is different for each design. The PT design is closet to
the nominal design in that the widths are nearly equal along the truss and the bay
heights only differ by 0.7 m from the end to the center. The RPT and RPTT designs
are tailored more drastically in both bay width and height. The RPTT design has the
largest difference between the end and center bay heights (2 m). The mount radius
and isolator frequency are both decreased from nominal in the PT and RPT designs.
These values are kept at nominal in the RPTT design since tuning is only considered
on hardware in this optimization. The finite element models of the three designs are
shown in Figures 6-11 through 6-13.
Table 6.13: Design parameters for nominal and optimal TPF SCI designs.
Tailoring, �x Total Mass
h1 [m] h2 [m] w1 [m] w2 [m] rPM [m] fiso [Hz] [kg]
Nominal 1.0 1.0 2.0 2.0 0.05 8.0 2679.0
PT 1.824 2.522 1.760 1.780 0.03 6.56 2506.6
RPT 0.754 2.52 1.34 2.25 0.02 6.77 2264.2
RPTT 0.50 2.56 1.48 2.34 0.05 8.0 2801.2
The RMS OPDs between collectors 1 and 4 of each of the three designs are eval-
uated for the cases of nominal and worst-case uncertainty. The results are listed in
Table 6.14 and shown graphically in Figure 6-14. The nominal performance is in-
dicated by circles and the worst-case performance with solid error bars. As in the
development model, the PT design exhibits the best nominal performance (2.90 nm),
but is sensitive to uncertainty as evidenced by the large performance range between
the error bars. The nominal performance of the RPT design is worse than that of the
PT design (3.79 nm), but it suffers the least performance degradation at the worst-
case uncertainty vertex. The nominal and worst-case performances of the RPTT are
worse than those of either the PT or RPT designs. This result is due, in part, to the
fact that the tuning parameters are not part of the nominal RPTT design since they
are considered explicitly during hardware tuning.
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