Integrated navigation and online trajectory convex optimization algorithm with single-star observation for UAVs

This research focuses on guidance and navigation methodologies for Unmanned Aerial Vehicles (UAVs), in the condition of no dependence on external devices and all-day working environment. To facilitate daytime navigation, a navigation system consisting of a single-star sensor and Inertial Navigation Systems (INS) is applied using the output data of single-star tracking process so that navigation accuracy can be improved. First, to track the navigation star, the sensor is controlled according to the position and attitude data provided by the INS. Then, the measurement equation and state equation are given according to the system model and starlight measurement. The navigation information is corrected through Kalman filtering. Considering the flight deviation caused by the attitude holding during the navigation star searching procedure, an online trajectory replan method via convex optimization is applied to reduce the computational burden. For efficient onboard computation of optimal UAV trajectories, the initial optimization formulation is recast as a finite-dimensional convex problem via discretization, increment of variable, and successive convexification. By innovatively incorporating the above technique routines, an integrated navigation and online trajectory optimization algorithm are developed so that not only the losing of navigation star tracking can be avoided but also the navigation accuracy can be enhanced. It differs from the mainstream methods in that a novel integration of the star navigation and online trajectory replan mechanism is constructed without any external devices to achieve high precision and autonomous navigation/guidance. Extensive simulations confirm the effectiveness (efficiency and precision) of the proposed approach, demonstrating its utility for enabling fully autonomous, all-weather UAV navigation and real-time trajectory planning, with potential extensions to other aerospace systems.