Usv Trajectory Planning for Time Varying Motion Goals in an Environment with Obstacles

Safe and efficient following of a time varying motion goal by an autonomous unmanned surface vehicle (USV) in a sea environment with obstacles is a challenge. The vehicle’s tracking capability is inherently influenced by its dynamics, the motion characteristics of the motion goal, as well as by the configuration of obstacles in the marine environment. We have developed an approach that utilizes a lattice-based trajectory planning to generate a dynamically feasible, resolution optimal, collision-free trajectory to allow the vehicle to reliably reach the motion goal. We utilized a trajectory following controller to achieve high tracking efficiency while still preserving motion safety. The entire approach is based on the developed USV system architecture that encapsulates the necessary trajectory planning components. We demonstrated the effectiveness of the developed planner in a simulated environment with static obstacles. In addition, we have developed a physical evaluation setup. INTRODUCTION Autonomous unmanned surface vehicles (USVs) [1] have been emerging as an attractive alternative to human-driven boats in a wide variety of missions that require reliable sea navigation. Examples of such missions include harbor patrolling and protecting important assets in vulnerable areas [2, 3], surveillance [4], environmental monitoring [5], etc. These applications usually require the vehicles to carefully navigate through locations with many obstacles with variable dimensions and shapes such as boats, shorelines, or docks. Many of the applications require frequent computation of a motion goal by the USV to successfully fulfill its task. The motion goal may be rapidly changing and express different motion patterns depending on the task. Examples of the tasks include interception, follow target boats, rules of the road (COLREGS) [6], intruder blocking [7], etc. In this paper, our focus is on the development of a trajectory planning approach for safe and efficient following of a moving target in a marine environment with obstacles (see Figure 1). Safe and efficient target following requires the autonomous USV to keep the target within a user-specified distance range. The vehicle needs to maintain sufficient velocity as well as have the ability to negotiate sharp turns that could lead to deviations from its intended trajectory ∗Address all correspondence to this author.