  This paper investigates the planning and control problems for multi-robot
systems under linear temporal logic (LTL) specifications. In contrast to most
of existing literature, which presumes a static and known environment, our
study focuses on dynamic environments that can have unknown moving obstacles
like humans walking through. Depending on whether local communication is
allowed between robots, we consider two different online re-planning
approaches. When local communication is allowed, we propose a local trajectory
generation algorithm for each robot to resolve conflicts that are detected
on-line. In the other case, i.e., no communication is allowed, we develop a
model predictive controller to reactively avoid potential collisions. In both
cases, task satisfaction is guaranteed whenever it is feasible. In addition, we
consider the human-in-the-loop scenario where humans may additionally take
control of one or multiple robots. We design a mixed initiative controller for
each robot to prevent unsafe human behaviors while guarantee the LTL
satisfaction. Using our previous developed ROS software package, several
experiments are conducted to demonstrate the effectiveness and the
applicability of the proposed strategies.
