Chapter 5 Robust Performance Tailoring with Tuning - SSL - MIT

Table 1.1: Effect of simulation results on mission.
# Simulation Action On-Orbit Result
Prediction Performance
1 good launch good success
2 good launch bad failure
3 bad no launch good delay
4 bad no launch bad delay
in the fourth scenario, the simulation correctly predicts poor performance and the
resulting launch delay and redesign is the appropriate action.
It is interesting to note that only the first scenario results in a successful mis-
sion. All other scenarios lead to failure or a delay in launch. The fourth scenario is
appropriate given the conditions and may eventually lead to success as long as the
simulation predictions continue to be correct after adjustments and redesign. In the
second and third scenarios the simulations predict the system operation incorrectly.
As a result, scenario two is a complete failure, while scenario three calls for unnec-
essary redesign that may lead to scenario two upon eventual launch. The simulation
prediction is therefore a single-point failure in this approach.
One way to increase the chances of mission success is to ensure that the simulation
predictions are always correct. Accomplishing this goal requires a large investment
in modeling and analysis. Uncertainty modeling, structural optimization and robust
design are all known techniques that are frequently employed to increase the accuracy
of performance predictions. Uncertainty modeling involves identifying the sources of
model uncertainty, quantifying them and producing bounds on performance predic-
tions. Uncertainty models are combined with structural optimization in the field of
robust design to find a design that meets the desired performance requirements and
is insensitive to model uncertainties. However, it is well known in the field of robust
control that robustness is achieved at the expense of nominal performance, and so, as
a result, these tools alone may not be adequate for a system that must meet aggres-
sive performance requirements under a high level of uncertainty. In this thesis, the
problem of how to extend robust design techniques to ensure that stringent perfor-
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