Variable structure control (VSC) is a form of discontinuous nonlinear control. The method alters the dynamics of a nonlinear system by application of a highfrequency switching control. The statefeedback 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:
 Low sensitivity to plant parameter uncertainty
 Greatly reducedorder modeling of plant dynamics
 Finitetime convergence (due to discontinuous control law)
The weaknesses of SMC include:
 Chattering due to implementation imperfections
 Overfocus on matched uncertainties (i.e., uncertainties that enter into the control channel)
However, the evolution of VSC is an active area of research.^{[2]}
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09b Using the GSV instruction, Get System Variable in the conveyor logic.

Introduction to System Dynamics: Overview

Soft Starter VS Variable Frequency Drive│
Transcription
See also
 Variable structure system
 Sliding mode control
 Hybrid system
 Nonlinear control
 Robust control
 Optimal control
 Hbridge – 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 slidingmode controlled systems.
 Switching amplifier – Uses switchingmode control to drive continuous outputs
 Deltasigma 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 slidingmode control)
 Pulse density modulation – A generalized form of deltasigma modulation.
 Pulsewidth 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: SpringerVerlag. ISBN 9783540328001.
Further reading
 Hasan K. Khalil (2002). Nonlinear Systems (3rd ed.). Upper Saddle River, NJ: Prentice Hall. ISBN 0130673897.
 Utkin, V.I. (1992). Sliding Modes in Control and Optimization. SpringerVerlag. ISBN 9780387535166.
 Zinober, A.S.I., ed. (1990). Deterministic control of uncertain systems. London: Peter Peregrinus Press. ISBN 9780863411700.
 Zinober, Alan S.I., ed. (1994). Variable Structure and Lyapunov Control. London: SpringerVerlag. doi:10.1007/BFb0033675. ISBN 9783540198697.