  To enhance the evacuation efficiency in partially observable asymmetric-exit
evacuation under guidance, a general framework of the dynamic guiding assistant
system is presented to investigate the effect of density control. In this
framework, several evacuation assistants are established to observe the partial
information of pedestrians' location and adjust the guiding signals of the
dynamic guiding assistant systems. A simple on-off-based density control
algorithm is proposed for the evacuation assistants according to the delayed
data of the observed information (i.e., pedestrian densities in the observed
regions near the corresponding exits). This paper provides strategic
suggestions on how to set the observed region and the target density by
involving a force-driven cellular automaton model. It is observed that the
proposed density control algorithm can control (positively affect) the global
distribution of the pedestrians' locations and suppress arching phenomena in
the evacuation process even using the observed partial information under time
delays. By imposing a moderate target density, the dynamic guiding assistant
system also suppresses the triggers of collisions around the exits and avoids
inefficiently separating the pedestrians. To enhance evacuation efficiency, we
reveal an interesting fact without loss of generality that we only need to
observe the pedestrians' location from a small region near the exit instead of
a large region when the time delay of the observed information is slight
enough. Our numerical findings are expected to provide new insights into
designing computer-aided guiding strategies in real evacuations.
