Stability is the property of a dynamical or control system whereby its state remains bounded and returns toward an equilibrium following a disturbance, rather than diverging. Formalised through notions such as Lyapunov stability and bounded-input bounded-output stability, it is a primary design objective for any feedback controller. Ensuring stability is prerequisite to performance, since an unstable system cannot be made to track references reliably.
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- It is the foundational requirement of controller design, since performance objectives such as tracking and disturbance rejection are meaningless for a divergent system. A correctly tuned Feedback Loop is the principal means of achieving stability, adjusting actuation in response to measured error, and stability analysis sits at the centre of the Control Systems Domain alongside controllability and robustness.