Iterative Guidance Scheme for a Satellite Launch Vehicle along a Three-Dimensional Trajectory

This paper discusses one of the state-of-the-art guidance laws developed for Satellite Launch Vehicles known as the Iterative Guidance Mode (IGM). The purpose of this paper is to compare the results of IGM with a benchmark optimal solution to check its optimality and to check whether it is implementable in real-time. SLVs are used to carry and inject payloads into their designated orbits. Since there can be many unpredictable disturbances during the flight such as variations in performance of the propulsion system, vehicle mass and atmospheric uncertainties, a guidance law is therefore necessary to ensure the successful injection of the payload into its orbit. In this paper, the IGM algorithm is implemented in its original form in an exo-atmospheric phase along a three-dimensional trajectory. The benchmark solution is developed using an indirect method from optimal control theory which uses Pontryagin’s minimum principle. Various assumptions are made in order to simplify the problem. The closed-loop guidance simulations are carried out in MATLAB/SIMULINK environment. The results and the comparison with benchmark solution show that IGM gives near-optimal results. A Monte-Carlo analysis is also performed to evaluate its performance in the presence of various perturbations and it is shown that IGM retains its optimality under nominal and off-nominal flight conditions and the execution time for a single guidance loop shows that IGM can be implemented in real-time.