Attitude control for a nano-satellite

Abstract

Nano-satellites are classified as satellites weighing less than 20kg. This dissertation

presents the design and development of an Attitude Control System (ACS) for a nanosatellite.

The ACS onboard a satellite controls the actuators to orientate the satellite to its

desired orientation such as facing the solar panels towards the sun or orientating the

camera towards the place of interests to capture images. A Model Predictive Control

(MPC) algorithm has been formulated for the attitude control of VELOX-I. Results show

that the ACS is capable of handling the saturation of actuator. The performance has also

been verified experimentally using an air bearing platform.

In a typical satellite configuration, it is common to have a fourth reaction wheel mounted

on a tilted axis for fault redundancy. Due to the constraint of the weight and size for the

satellite, there is no redundancy of ACS. To address this issue, a distributed MPC has

been proposed for attitude control utilizing both the reaction wheels and magnetic

actuators. The simulation results show that the hybrid control system is able to maintain

3-axis control even if a single axis wheel fails. The distributed control scheme is also

shown to react faster than a centralized control scheme. Harvesting of solar power is

required for a satellite to continue operation. The proposed distributed MPC will be

critical for VELOX-I to maintain the sun pointing orientation for harvesting solar power

in the event of single axis reaction wheel failure.