Stability criteria in non-polar diagrams

Control engineering education textbooks usually restrict the verification o f the systems stability with the Nichols' cartesian and Bode's logarithmic representations to the single case when the number of poles with positive r eal part is zero and when the curve presents a single phase margin or a sin gle gain margin. This paper presents a general procedure to analyse absolut e stability in non-polar diagrams and solves an interesting example, both f or educational purposes.