Attitude Control Law Design of Experimental Winged Rocket Using Engine Gimbal Control

Abstract

Kyushu Institute of Technology has been developing fully reusable space transportation system since 2005. WIRES#015, the subscale flight model of suborbital vehicle will be launched from Mojave Desert, California in 2020. The engine employs thrust vector control (TVC) system to improve the control performance during the ascent phase where dynamic pressure is low for instance at the launcher exit. However, natural frequency of the vehicle attitude motion may become higher than the cut-off frequency of the actuator, when the vehicle experiences maximum dynamic pressure, and the actuator performance becomes saturated. In this research, the attitude control law on the longitudinal and lateral motion using thrust vector control and aerodynamic control surfaces in powered flight was designed based on eigenvalue analysis, and the response of pitch angle and TVC actuator performance was evaluated based on non-linear flight simulation. In conclusion, two findings are obtained. At first, the designed control system has appropriate damping ratio on short period mode and enough stability margin of open loop transfer function, which meet the control design requirement. Second, flight simulation shows that the control law stabilizes vehicle attitude with the influence of gimbaling reaction torque, while TVC actuator is not saturated. In future, possible disturbances such as steady wind and combined use TVC and aerodynamic control surfaces for fault tolerance and high angle of attack maneuverer in abort flight will be installed into this flight simulation.