Embedded Development of the Attitude Stabilisation System for the FENRIR platform

This document is a master's thesis report about the embedded software development of the attitude stabilisation system (ATSS) for the free falling unit (FFU), made by the REXUS project FENRIR. The report covers a description of the entire development process, from design to implementation and testing. FENRIR's FFU is designed to be ejected from a sounding rocket during flight, and the ATSS is a three-axis reaction wheel system to control the angular velocity of the FFU after ejection. The control system for the ATSS was designed as a cascaded PID control system. It was implemented using C and FreeRTOS on an STM32U575ZIT6 microcontroller. Most of the testing was performed using a simulation model created in Simulink with the Simscape add-on. The test results from the simulation indicate that the ATSS is able to successfully reduce the angular velocity of the FFU, but it has not yet been verified to work during an actual flight.