Tracking Performance Limitations under Disturbance or Uncertainty

This paper investigates tracking performance limitations of alinear time invariant (LTI) multivariable plant subject toexternal disturbance or model uncertainty. It attempts to extendsome recent results on tracking performance limitation in whichneither the disturbance nor the uncertainty is considered. Thereference signal to be tracked is a step signal. The trackingperformance is measured by the energy of the tracking error. Theexternal disturbance is assumed to be energy bounded and to beinjected into the input channels of the plant. The modeluncertainty is assumed to have some special structure and to havecertain induced norm bound. The performance limitation studied isthe minimal attainable value, under any controller structure andparameters, of the maximum tracking error energy for all possibledisturbance or uncertainty.