ONBOARD TRAJECTORY OPTIMIZATION FOR RADIUS TO FIX TURNS

This paper presents an onboard optimization approach used to generate trajectories for Radius to Fix (RF) turns within an integrated flight guidance and control system. An Optimal Control Problem (OCP) is formulated such that it accounts for the geometric constraints of the RF leg as well as the dynamics and limitations of the closed-loop controlled aircraft. The optimization-based approach overcomes the drawbacks of a geometric trajectory generation method previously published by the authors, which used clothoids for the entry and exit segments of the RF trajectory. Here, the optimization algorithm is functionally decoupled from the safetycritical fight guidance and control modules by means of a Safety Gateway, which verifies the outcome of the optimization algorithm. Optimization as well as verification are performed onboard and online. Besides the OCP formulation, the paper presents details on how the optimization algorithm is embedded into the modelbased software design in MATLAB/Simulink™ to enable deployment on a mission computer. Furthermore, a simulation framework is described that represents the system concept for onboard optimization consisting of the Flight Control Computer (FCC) and the mission computer, which carries out the optimization tasks asynchronously and returns the optimal results via the Safety Gateway to the FCC. This simulation framework is used to illustrate the enhancement of the proposed approach using a flight dynamics model of a CS-23 aircraft.