Variable structure control (VSC) is a form of discontinuousnonlinear control. The method alters the dynamics of a nonlinear system by application of a high-frequency switching control. The state-feedback control law is not a continuous function of time; it switches from one smooth condition to another. So the structure of the control law varies based on the position of the state trajectory; the method switches from one smooth control law to another and possibly very fast speeds (e.g., for a countably infinite number of times in a finite time interval). VSC and associated sliding mode behaviour was first investigated in early 1950s in the Soviet Union by Emelyanov and several coresearchers.[1]
The main mode of VSC operation is sliding mode control (SMC). The strengths of SMC include:
H-bridge – A topology that combines four switches forming the four legs of an "H". Can be used to drive a motor (or other electrical device) forward or backward when only a single supply is available. Often used in actuator in sliding-mode controlled systems.
Switching amplifier – Uses switching-mode control to drive continuous outputs
Delta-sigma modulation – Another (feedback) method of encoding a continuous range of values in a signal that rapidly switches between two states (i.e., a kind of specialized sliding-mode control)
Pulse-width modulation – Another modulation scheme that produces continuous motion through discontinuous switching.
References
^Emelyanov, S.V., ed. (1967). Variable Structure Control Systems. Moscow: Nauka.
^Edwards, Cristopher; Fossas Colet, Enric; Fridman, Leonid, eds. (2006). Advances in Variable Structure and Sliding Mode Control. Lecture Notes in Control and Information Sciences. Vol. 334. Berlin: Springer-Verlag. ISBN978-3-540-32800-1.
Zinober, Alan S.I., ed. (1994). Variable Structure and Lyapunov Control. Lecture Notes in Control and Information Sciences. Vol. 193. London: Springer-Verlag. doi:10.1007/BFb0033675. ISBN978-3-540-19869-7.
Steinberger, M.; Horn, M.; Fridman, L., eds. (2020). Variable-Structure Systems and Sliding-Mode Control. Studies in Systems, Decision and Control. Vol. 271. London: Springer-Verlag. doi:10.1007/BFb0033675. ISBN978-3-030-36620-9.
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