  Aiming at an obstacle avoidance problem with dynamic constraints for Unmanned
Surface Vehicle (USV), a method based on Circle Grid Trajectory Cell (CGTC) is
proposed. Firstly, the ship model and standardization rules are constructed to
develop and constrain the trajectory, respectively. Secondly, by analyzing the
properties of the circle grid, the circle grid tree is produced to guide the
motion of the USV. Then, the kinematics and dynamics of the USV are considered
through the on-line trajectory generator by designing a relational function
that links the rudder angle, heading angle, and the central angle of the circle
grid. Finally, obstacle avoidance is achieved by leveraging the on-line
trajectory generator to choose a safe, smooth, and efficient path for the USV.
The experimental results indicate that the proposed method can avoid both
static and dynamic obstacles, have better performance in terms of distance cost
and steering cost comparing with the related methods, and our method only takes
50% steering cost of the grid-based method; the collision avoidance path not
only conforms to the USV dynamic characteristic but also provides a reference
of steering command.
