Trajectory Optimization Method for a UUV Based on Minimum Snap

To solve the problem of polynomial trajectory deviation from the original straight path and to allow an unmanned undersea vehicle(UUV) to pass an obstacle area smoothly and safely, a polynomial trajectory optimization method for a UUV based on the seventh-order minimum Snap method is proposed. First, based on the initial path generated by the A* algorithm, reference points for trajectory optimization are selected according to the principle of the preview line. Next, the minimum Snap trajectory is fitted under the constraints of two different equations, and the intermediate balance point is added to the trajectory according to the continuity constraint for offset optimization. Indicators are set to evaluate the degree of offset before and after the optimization. Finally, a simulation experiment is performed in a constructed obstacle environment to obtain three different trajectories under the constraint of time consistency. The simulation results show that obstacles are avoided by the vehicle when it follows a trajectory under the zero constraint; however, this trajectory is a polyline. Furthermore, the trajectory in which the continuity constraint is considered is smoother; however, its offset is larger. The optimization method can generate a smoother trajectory with a smaller offset.