Design of Attitude Determination and Control System for Hokkaido Satellite

Paper number

IAC-05-B5.6.A.01

Author

Mr. Koichiro Sugimoto, Hokkaido University, Japan

Coauthor

Mr. Daigaku Igarashi, Hokkaido University, Japan

Coauthor

Dr. Kosei Ishimura, Hokkaido University, Japan

Year

2005

Abstract

This paper describes design and performance verification of attitude determination and control system for Hokkaido Satellite. The satellite is a small satellite that is 50*50*50 cm3 and 50 kg. The satellite will be launched in 2007 into 566.9 km sun-synchronous sub-recurrent orbit with 97.66 deg inclination. At the altitude, major disturbance torque is magnetic one. The main missions of the satellite are earth observation at sunlit and laser communication at sunshade. The purpose of the attitude determination and control system is to stabilize the attitude around three-axis during these missions. The stabilization is established by three-axis attitude control with a bias-momentum wheel. The required attitude accuracy is 3 deg regardless of sunlit or sunshade. The required accuracy is somewhat worse as compared to that of traditional satellite for earth observation but the accuracy is sufficient because of the pointing control of mission equipment itself. The satellite with the bias-momentum wheel has passive stability and robustness. The components for the attitude control system are a momentum wheel along pitch axis, three magnetic torquers along three-axis, a sun sensor, an earth sensor along yaw axis, a magnetometer and an Inertia Reference Unit (IRU). As these components, commercial-off-the-shelf and self-produced products will be used. The main control modes of the satellite are an attitude acquisition mode, an earth acquisition mode, a normal mode (a mission mode) and a safe-hold mode. The attitude acquisition mode is the operation from separation of the satellite to sun acquisition for keeping power of the satellite. It consists of three sequences: de-spin, spin-up and sun acquisition. The earth acquisition mode consists of spin axis control to direct the axis toward a normal of the orbit plane, momentum transfer, and earth acquisition. The normal mode is the operation during the missions. In the mode, a new pointing control law is proposed for the wheel-stabilized earth pointing satellite. The proposed law achieves simultaneously nutation dumping and angular momentum direction control relative to orbital coordinate system. It consists of pitch axis control by the momentum wheel, roll/yaw axes control by magnetic torquers and angular momentum control by magnetic torquers.
The attitude determination method based on the Kalman filter is used in the normal mode. The attitude determination law is formulated to satisfy the required attitude determination accuracy (1 deg) regardless of sunlit or sunshade. The method consists of attitude update by the earth sensor and attitude propagation by the IRU. It can estimate three attitude angles and IRU bias rates without a yaw sensor. The purpose of the safe-hold mode is to keep only power and heat balance. In the mode, only a nadir angle and angular momentum are controlled. The control law in the safe-hold mode is identical with the last sequence in the attitude acquisition mode.
In this paper we formulate the attitude determination laws and control laws for the Hokkaido satellite. From the various simulations, it is confirmed that the determination laws and control laws can achieve the required attitude accuracy and the tolerable attitude control time.

Abstract document

IAC-05-B5.6.A.01.pdf

Manuscript document

IAC-05-B5.6.A.01.pdf (🔒 authorized access only).

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