  We introduce the notion of online reactive planning with sensing actions for
systems with temporal logic constraints in partially observable and dynamic
environments. With incomplete information on the dynamic environment, reactive
controller synthesis amounts to solving a two-player game with partial
observations, which has impractically computational complexity. To alleviate
the high computational burden, online replanning via sensing actions avoids
solving the strategy in the reactive system under partial observations.
Instead, we only solve for a strategy that ensures a given temporal logic
specification can be satisfied had the system have complete observations of its
environment. Such a strategy is then transformed into one which makes control
decisions based on the observed sequence of states (of the interacting system
and its environment). When the system encounters a belief---a set including all
possible hypotheses the system has for the current state---for which the
observation-based strategy is undefined, a sequence of sensing actions are
triggered, chosen by an active sensing strategy, to reduce the uncertainty in
the system's belief. We show that by alternating between the observation-based
strategy and the active sensing strategy, under a mild technical assumption of
the set of sensors in the system, the given temporal logic specification can be
satisfied with probability 1.
