In optimal control theory, a **control** is a variable chosen by the controller or agent to manipulate state variables, similar to an actual control valve. Unlike the state variable, it does not have a predetermined equation of motion.^{[1]} The goal of optimal control theory is to find some sequence of controls (within an admissible set) to achieve an optimal path for the state variables (with respect to a loss function).

A control given as a function of time only is referred to as an *open-loop control*. In contrast, a control that gives optimal solution during some remainder period as a function of the state variable at the beginning of the period is called a *closed-loop control*.^{[2]}

## See also

## References

**^**Ferguson, Brian S.; Lim, G. C. (1998).*Introduction to Dynamic Economic Problems*. Manchester: Manchester University Press. p. 162. ISBN 0-7190-4996-2.**^**Léonard, Daniel; Long, Ngo Van (1992).*Optimal Control Theory and Static Optimization in Economics*. New York: Cambridge University Press. p. 181. ISBN 0-521-33158-7.