Editing Sliding mode control (section)

{{short description|Method in nonlinear control theory}}
{{Use dmy dates|date=August 2021}}
In [[control system]]s, '''sliding mode control''' ('''SMC''') is a [[nonlinear control]] method that alters the [[dynamic system|dynamics]] of a [[nonlinear system]] by applying a [[discontinuous]] control signal (or more rigorously, a set-valued control signal) that forces the system to "slide" along a cross-section of the system's normal behavior. The [[state space (controls)|state]]-[[feedback]] control law is not a [[continuous function]] of time. Instead, it can switch from one continuous structure to another based on the current position in the state space. Hence, sliding mode control is a [[variable structure control]] method. The multiple control structures are designed so that trajectories always move toward an adjacent region with a different control structure, and so the ultimate trajectory will not exist entirely within one control structure. Instead, it will ''slide'' along the boundaries of the control structures.  The motion of the system as it slides along these boundaries is called a ''sliding mode''<ref name="Zinober1990">{{Cite book
 | editor-last  = Zinober
 | editor-first = A.S.I.
 | title        = Deterministic control of uncertain systems
 | publisher    = Peter Peregrinus Press
 | place        = London
 | year         = 1990
 | isbn         = 978-0-86341-170-0
 | editor-link   = Alan S.I.&nbsp;Zinober
}}</ref> and the geometrical [[locus (mathematics)|locus]] consisting of the boundaries is called the ''sliding (hyper)surface''. In the context of modern control theory, any [[variable structure system]], like a system under SMC, may be viewed as a special case of a [[hybrid system|hybrid dynamical system]] as the system both flows through a continuous state space but also moves through different discrete control modes.