Robust control for high-performance materials testing

The use of root-locus-based robust design techniques in the design of a digital controller for a high-performance variable-amplitude fatigue test is described. Evaluation of the resulting controller on a prototype laboratory materials testing system, designed to simulate the mechanical stress loads experienced by certain aircraft components, shows that it meets design performance goals of 0.25% specimen load accuracy while providing robustness to specimen compliance over a 10 to 1 range. This performance significantly exceeds that obtained with traditional hand-tuned controllers.<
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