Analysis of attitude synchronization control for spacecraft formation flying via hardware-in-the-loop simulation

다국어 초록 (Multilingual Abstract)

Formation flying of multiple artificial satellites is one of the key technologies in future space missions. One of the most challenging problems in formation flying missions is spacecraft attitude synchronization for constructing an interferometer. Since various attitude control techniques have been recently developed for spacecraft formation flying, implementation of a control test is an important task. This current study performs three main tasks. First, nonlinear control techniques, relating to attitude synchronization problems for formation flying spacecraft, are formulated using Reaction Wheel Assemblies (RWAs). This includes which includes well-known modern control theories such as Lyapunov-based adaptive control technique and the optimal control via State-Dependent Riccati Equation (SDRE) technique. The Lyapunov-based adaptive control scheme is designed to evaluate state feedback and output feedback. It takes into consideration both of regulator and tracking problems for optimal control, based on the SDRE technique. The stability region of the optimal tracking controlled system using SDRE is also estimated numerically. Second, the attitude controller, consisting of relative control as well as absolute control, is designed to reduce attitude error in formation flying spacecraft. The aim of relative control is to synchronize the attitude motions of spacecrafts in formation. In local coupling systems, state-dependent connectivity reduces the computational complexity of relative control. Third, an air-bearing-based Hardware-In-the-Loop Simulator (HILS) validates the proposed control laws in a real-time environment. The HILS air bearing system provides a low-torque circumstance, which mimics the space environment. It also effectively verified control law on the ground. The HILS utilizes three RWAs and eight thrusters as actuators. The PC104-type embedded computer (on-board PC), in the HILS, communicates with a host PC and attitude sensors; The least squares method with batch processing and the recursive least squares method are used to estimate mass properties, such as the mass distribution and moment of inertia of the HILS. The proposed control laws, including the Lyapunov-based adaptive control and the SDRE discrete optimal tracking control for spacecraft formation flying, are implemented in the HILS. The stability of the proposed control laws is validated using the HILS, and also simulated numerically. In the experiments, the HILS is treated as a physical spacecraft and additional virtual spacecrafts perform an attitude synchronization mission. The results of both the numerical and experimental simulations confirm the effectiveness of the control algorithms for attitude synchronization in a spacecraft formation flying mission. Consequently, experiments using the HILS in a real-time environment can appropriately validate the numerous spacecraft attitude synchronization algorithms for the formation flying spacecraft with RWAs.