Chapter 5 Robust Performance Tailoring with Tuning - SSL - MIT

mance requirements are met on-orbit when high-uncertainty models and simulations
are depended upon for launch decisions is addressed.
1.2.2 Approach
The approach taken in this thesis is a formal synthesis of robust structural design
and hardware tuning. The burden of uncertainty management is shared by both
simulation and hardware. Instead of mitigating uncertainty through robust design
or excessive modeling and component prototyping, it is managed by optimizing for
a mix of performance, robustness and tunability. Such a scheme addresses the prob-
lem of performance prediction accuracy vs. design flexibility by choosing parameters
that can be tuned during component testing, system integration, or on-orbit, to af-
fect the system performance thereby increasing hardware design flexibility. If the
system is designed such that these parameters have enough authority to guarantee
that performance requirements can be met regardless of where the actual system lies
in the uncertainty space, then the resulting system is significantly more likely to be
successful.
Consider the effect of such a design methodology on the scenarios in Table 1.1.
The simulations are augmented with a formal pre-launch and on-orbit tuning pro-
cess so that the predictions only need to meet performance within specified error
bounds. If the system is guaranteed to be “tunable” within these bounds then the
scenarios are as shown in Table 1.2. The simulation prediction metric has changed
from “good” or “bad” to “meet requirement” or “within bound.” This distinction is
made because if the prediction does not meet requirements, but is within the tunable
range then launch is still the correct action. Note that all four situations lead to
launch and mission success. The dependence on simulation is reduced by allowing for
on-orbit adjustments and the requirements for launch are relaxed to allow for model
uncertainty resulting in a greater probability of mission success.
When discussing the design methodology throughout the thesis the following ter-
minology is used. The term Performance Tailoring (PT) describes the process of
structural design for performance only, i.e. structural optimization without consid-
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