Flexible attitude control design and on-orbit performance of the ZDPS-2 satellite

Abstract

ZDPS-2, the 2nd generation nano-satellites designed and manufactured by Microsat Research Center of Zhejiang University, were successfully launched by the new generation rocket CZ-6 on Sep 20th, 2015. They are two 20kg identical nano-satellites (ZDPS-2-A and ZDPS-2-B) with a large deployable mechanism with a truss structure. The main mission of these two satellites is on-orbit demonstration of several new technologies, including large lightweight and flexible deployable mechanisms, a custom-designed panoramic wide field of view micro camera Sun sensor and infrared Earth sensor, and a micro-propulsion system as well as dual-satellite formation flying technology. The satellite is a 25cm cube with a deployable mechanism, whose fundamental frequency is only approximately 0.13Hz. This brings several challenges to attitude control. Flexible structure dynamics and its influence on attitude stabilization must be taken into consideration. A robust control scheme is developed by fully utilizing environmental torques with limited control actuator capability. On-orbit performance verified this design. ZDPS-2 satellites have successfully achieved rate damping, sun-pointing control and 3-axis stabilized Earth-pointing control, with a control accuracy of 5° (3σ) and stability superior to 0.1°/s (3σ). This paper demonstrates the flexible attitude dynamics modeling, illustrates the attitude control system design of ZDPS-2 and presents the on-orbit performance as well.