The present paper proposes an algorithm for finding the stability margins and cross over frequencies for an uncertain fractional-order system using the interval constraint propagation technique. It is first shown that the problem of finding the stability margins and crossover frequencies can be formulated as an interval constraint satisfaction problem and then solved using the branch and prune algorithm. The algorithm guarantees that the stability margins and the crossover frequencies are computed to the prescribed accuracy. The proposed algorithm is demonstrated on a noninductive cable system and also on a practical application of a gas turbine plant.

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