A simple sun-pointing magnetic controller for satellites in equatorial orbits

Abstract

This paper describes a simple satellite attitude controller designed to run on a fairly low capability processor. The controller is intended to be used in a contingency mode when the spacecraft flight computer and full sensor and actuator suite are not available, making use of only analog-output sensors (three-axis magnetometer and sun sensors) and analog-input actuators (magnetic torque rods or coils). The controller is designed to keep an axis near the principal axis of maximum inertia pointed at the sun. Because control torques may only be applied in a plane perpendicular to the local geomagnetic field the control scheme uses a very low control bandwidth in conjunction with gyroscopic spin stabilization.While originally designed for a satellite in a high-inclination orbit, the spacecraft was adapted for a new mission in a nearly equatorial orbit, where purely magnetic attitude control is not typically used because the direction of the local geomagnetic field is nearly constant during an orbit. This paper reviews the design of the original controller as well as the modifications which were made to improve performance in the nearly equatorial orbit. Statistical performance results based on Monte Carlo simulations are included. 1,2

Attitude control system of the Delfi-n3Xt satellite

“…The modi¦ed Bdot mode implements a Bdot control law in addition to magnetic torques that spin up the satellite longitudinal axis to a desired spin rate. The control law is described in [3]. Only the MGM and the MTQ will be used in this mode.…”

“…Gyro biases can, however, be estimated using standard techniques. This paragraph describes a method that estimates the angular velocity vector from LoS measurements [3]. Let b and s denote the unit Earth magnetic ¦eld and unit Sun vector measurements along the frame B.…”

“…The gyro-based and estimation-based angular rates are implemented in this work. This control law was proposed in [1,3,4]. To maintain the desired spin rate around the B z axis, the following torque is needed:…”

Microsatellite Attitude Determination and Control Subsystem Design and Implementation: Software-in-the-Loop Approach

“…The dominant source of the residual magnetic field is the spacecraft magnetic moments. This instantaneous magnetic disturbance torque due to the spacecraft effective magnetic moment and the geocentric magnetic field can be described as follows [9][10][11][12][13]:…”

Sun-Pointing Attitude Control Scheme for Magnetic-based Satellite

“…As to Ref. [18][19][20], the proposed sun-pointing control schemes combined PD control technique and spin motion, which could achieve sun-pointing effect. However, these schemes are designed according to engineering experience, and no literature has proposed the controllability and stability proofs of the attitude control schemes.…”