GNC robustness stability verification for an autonomous lander

Abstract

In the context of Solar System exploration, autonomous planetary surface missions represent, nowadays, an important step in scientific research. Nevertheless, the design of landing Guidance, Navigation and Control sub-systems is one of the most challenging and complex tasks. Indeed, during the propelled landing phase, the system must be controlled in closed-loop, ensuring the stability of the lander motion with a certain level of robustness. This paper proposes a novel procedure for the verification of the lander nominal and robust stability. The first step is to perform a model simplification, in order to reduce the involved degrees of freedom and allow a decoupled analysis of the rotational and translational dynamics. Then, the classical stability theorems are applied, taking also into account the uncertainties due to actuators and sensors. Next, a robustness stability verification is performed by means of μ-Analysis. Finally, a Monte Carlo campaign is carried out, using an End-to-End simulator in order to verify, in the time domain, the reliability of the analytical stability analysis. The procedure is applied to a case study representing a descent module during the controlled landing phase on the Mars surface.