On controllability for stochastic control systems when the coefficient is time-variant

This paper investigates the controllability problem of time-variant linear stochastic control systems. A sufficient and necessary condition is established for stochastic exact controllability, which provides a useful algebraic criterion for stochastic control systems. Furthermore, when the stochastic systems degenerate to deterministic systems, the algebraic criterion becomes the counterpart for the complete controllability of deterministic control systems.