Conditions of stability and robustness of a single-channel invariant system of any order (Q1111994)

The conditions of stability and robustness (i.e., the error tends to zero) of a single-channel invariant system of stabilization are studied for a linear plant of any order with parameter deviations (including the case of short dead times and small lag). These conditions are quite rigorous, i.e., it is necessary to insert differentiating loops at the controller input that have an order equal to or by unity smaller than the order of lag of the plant. The result obtained makes it possible to ascertain the feasibility of controller designs in the form of a ``circuit with infinite gain'' and the difficulties involved in this.