Guidance, navigation, and control system simulations via integrated orbit and attitude hardware-in-the-loop simulator for satellite formation flying

다국어 초록 (Multilingual Abstract)

Satellite formation flying, which is considered an innovative technology for advanced space missions, refers to the concept of multiple small satellites undertaking a common mission as a group. Compared to conventional monolithic satellites, satellite formation flying offers improved reliability, flexibility, and cost effectiveness. A fundamental issue of satellite formation flying is the development of a guidance, navigation, and control system. Such a system is essential to the mission performance of the flight of a satellite. Many of the studies concerning satellite formation flying are practically related to the development of theories or algorithms for the guidance, navigation, and control system. However, these theories and algorithms need to be verified in real situations. A hardware-in-the-loop (HIL) simulation can provide such an environment where new theories, algorithms, and hardware technologies can be developed, demonstrated, and verified. The goal of this dissertation is therefore to establish a HIL simulation environment for satellite formation flying and to accomplish a formation reconfiguration mission in the same manner as an actual satellite using the guidance, navigation, and control algorithms.Previous studies regarding the development of a hardware-based simulation system have separately developed an orbit system and an attitude system. This dissertation is distinct because the developed integrated HIL simulator can simultaneously perform orbit simulation and attitude simulation. The integrated simulator consists of an orbit HIL simulator based on a GPS RF signal simulator and an attitude HIL simulator based on a 3-DOF tabletop air-bearing system; the system performs four processes (orbit determination, orbit control, attitude determination, and attitude control) that interact in the same manner as in actual flight. The orbit determination process is conducted using a relative navigation algorithm using double-difference GPS measurements and an extended Kalman filter (EKF). The orbit control process uses a sub-optimal state-dependent Riccati equation (SDRE) nonlinear control technique. The attitude determination process is supported by an attitude heading reference system (AHRS) sensor, and the attitude control process uses a proportional derivative (PD) feedback controller to control the attitude HIL simulator via three reaction wheel assemblies.To evaluate the developed integrated HIL simulator, integrated orbit and attitude simulations are performed for a formation reconfiguration scenario. By performing the four processes adequately, the desired formation reconfiguration from a baseline of 500 m to 1,000 m is achieved with meter-level position error based on the relative navigation with millimeter-level relative position error. This integrated simulation demonstrates the performance of the integrated HIL simulator and the feasibility of the applied algorithms in a real-time environment. In conclusion, the integrated HIL simulator developed in this dissertation can be used as a ground-based testing environment to reproduce possible formation flying operations of actual satellites.