ABSTRACT
Stable response is a requirement for any control system. It ensures that the natural response to an initial condition excitation does not grow without bounds (or, more preferably, decays back to the initial condition) and the response to an input excitation (which itself is bounded) does not lead to an unlimited response. Asymptotic stability and boundedinput-bounded-output (BIBO) stability are pertinent in this context. In designing a control system, the required level of stability can be specified in several ways, both in the time domain and the frequency domain. Some ways of performance specification, with regard to stability in the time domain, were introduced in Chapter 7. The present chapter revisits the subject of stability, in time and frequency domains. Routh-Hurwitz method, root locus method, Nyquist criterion, and Bode diagram method incorporating gain margin (GM) and phase margin (PM) are presented for stability analysis of linear time-invariant (LTI) systems.
