Design of an Attitude Control System for the Multi-Mission Platform and its Migration to a Real Time Operating System

This paper presents the first of four parts of the academic design of an Attitude Control System (ACS) for the Multi-Mission Platform (MMP) and its migration to a Real Time Operating System. The MMP is a three axis stabilized artificial satellite now under development at the National Institute for Space Research (INPE). Such design applied some software engineering concepts as: 1)visual modeling; 2)automatic code generation; 3)automatic code migration; 4)soft real time simulation; and 5)hard real time simulation. A block diagram based modeling and a virtual time simulation of the MMP ACS in its nominal operational mode were built in the MatrixX 7.1 environment satisfying the three axis pointing and stabilization requirements. After that, its AutoCode module was used to generate C ANSI code representing the block diagram model. Time characteristics were added to the ACS generated code to make it the real time control software of MMP nominal operational mode. Four operating systems were used for code migration: 1)Windows 2000 (first part); 2)Mandrake Linux 10.1 (second part); 3)RedHawk Linux 2.1 (third part); and 4)RTEMS 4.6.2 (fourth part). Software migration characteristics were described for each of these four computational environments. The results shown the advantages of using those software engineering concepts in the MMP ACS development. They also show excellent agreement between the virtual time simulation results and those obtained with Windows 2000 simulation.