A Fault-Tolerant Embedded System for Solar Sails

Abstract

Mankind has always dreamt of exploring the unknown universe To fulfil such a dream requires an appropriate transportation method To date hope for this dream to come true is still in the darkness because of limitations on technology manpower and costs Fortunately a light comes through when the unmanned solar sail vehicles powered by solar wind appear in recent years This invention not only lowers costs but also requires no fuel for the vehicles to move which easily solves the long distance cruising problem and draws hugely attentions from astronautic scientists However any accidents can lead to malfunction or course deviation of a solar sail due to the capricious nature in the outer space For example a monitoring camera in the solar sail might be hit by foreign material and because of angle offset becomes useless for the control system Or insufficient supply of solar energy causes the control system hardware out of function or even broken To monitor and control a solar sail thus requires a robust self-contained system that is energy efficient and fault-tolerant because a solar sail is nearly impossible to come down for repairs This study designs and implements a solar sail fault-tolerant monitoring system that comprises redundant hardware and software using hot standby and N-version programming technology The control hardware contains two identical embedded systems one called the master and the other slave By monitoring each other when the master is experiencing any problem the slave machine can take over all the tasks in a short time In the system simulations two cameras are responsible for monitoring a solar sail’s swings and the control software uses image processing results to calculate and if necessarily activate a self-healing process to restore these cameras’ correct positions To certain the correctness of the calculations the control software uses N-version programming fault-tolerant methodology using results from three different perspective of image processings The experiment results show that when a camera is hit by foreign matters the self-healing function can effectively restore its position for supervising the solar sail Experiments also confirm that the hand over between the master and the slave control hardware can be seamlessly done in a short time without compromising the functions of monitoring The control system is proved to be robust self-contained and fault-tolerant

Date of Award	2014 Sept 9
Original language	English
Supervisor	Tzone-I Wang (Supervisor)