Fuzzy Logic Controller for Small Satellites Navigation

Abstract : The development of a navigator for small satellites (SSN) is in progress with a joint effort of Space Engineering and ASI in the fram of a technological development program dedicated to SME. The navigator aims at operating satellites in orbit with a minimum ground support and very good performances, by the adoption of innovative technologies, such as attitude observation GPS, attitude state estimation by Kalman Filter and fuzzy logic for attitude control. The SSN is very attractive in space applications where analytical non-linear models prevent an easy synthesis of classical controllers, and where the volume of parameters affecting the plant behavior is very high. The navigator was verified through HW-in-the-loop simulations and the following feature emerged: - three axes control with control performances compatible with Earth observation missions with optical payloads - autonomous on-board management, and non-nominal pointing capacity without ground planning, permitting to acquire images without scheduling in advance - independence from ground commands in selecting operational modes - autonomous wheels desaturation - autonomous system reconfiguration in response to unexpected events, such as sensors or actuators failures -capability to perform both large re-pointing in low times and accurately maintain attitude - robustness against external and internal disturbances and large variations of platform parameters.