Wat is the definition of a nicoles chart...wat is its usefulness in control system?

wat advantage do it provide?Wat is the definition of a nicoles chart...wat is its usefulness in control system?
The Nichols Plot is another way of studying the stability of control closed-lop systems. We have: Bode plot, Nyquist diagram, Nichols plot, Root Locus Plots; all these are used for the above purpose and one may have an advantage in some instance depending on your expertise.We generally study the open-loop transfer function before we close it and look for the natural frequency and damping of the closed-loop.The Nichols does not differ markedly from the other methods.