Feedback synthesis with plant ignorance, nonminimum-phase, and time-domain tolerances

Abstract

This paper presents a design procedure for single-loop feedback systems in which the plant is nonminimum-phase, with ignorance in its parameters. The feedback system is to be designed such that the time response to a deterministic input lies within specified boundaries. Subject to the above, the design should be such as to minimize the effect of sensor noise at the input to the plant. The time domain tolerances are translated into equivalent frequency response tolerances. The latter lead to bounds on the loop-transmission L( jw), in the form of continuous curves on the Nichols chart. However due to the nonminimum-phase nature of the plant, it may happen that no L( jw) can be found so that the design specifications of the problem are achieved, unless they are changed accordingly.