Finding simple models for robust feedback control

The paper re-examines the problem of finding suitable simple models for robust feedback control after high order model fitting and model reduction. Norm-based approximate models are well known and this paper looks at whether more can be done without closed loop testing. A constrained optimization setup is introduced that searches for open loop models that are most suitable for robust control given the set of open loop frequency response measurements. The analysis of the problem relies on elementary robust control techniques that have been known for a long time. The findings are that norm-based frequency weighted open-loop model reduction may not be the best for robust control but can be used as an initial estimate. The paper proves that more optimization can be done without any further closed-loop experiments to be undertaken on the plant. Possible applications are to vibration attenuation and servo control where the plant can undergo thorough frequency response testing.