# Satellite ACS Design during Orbit Injection using the SDRE Method

## Palavras-chave:

satellite control, nonlinear sdre method## Resumo

The performance of the Satellite Attitude Control System (ACS) during the orbit injection phase is of fundamental importance for the success of the mission. In this phase the satellite leaves the launcher with high angular velocity and then the ACS needs to manoeuvre the satellite to its normal mode of operation, which is characterized by an attitude of small angles. One way to achieve this transition between these two phases is using gas jets followed by reaction wheels. In this paper one investigates and develops by simulation the ACS algorithm to minimize space mission costs by reducing the number of errors transmitted to laboratory prototypes project. The high angular velocities of the satellite in the injection phase makes its dynamics highly nonlinear introducing some level of perturbation into the system. As a result, application of linear control technique cannot be able to design the ACS with adequate performance to reach the required level of appointment. To mitigate this problem, one will use the State-Dependent Riccati Equation (SDRE) method which can deal with nonlinear system. The SDRE controller design algorithm is based on gas jets and reaction wheel torques to perform large angle manoeuvre to reduce the high angular velocities to attitude with small angles. The criterion for the transition between the two operating modes is based on the decrease of the system energy. This investigation serves to validate the numerical simulator model and to verify the functionality of the control algorithm designed by the SDRE method. It is intended to use in the next phase of this research the Federal University of ABC (UFABC) 3D simulator which supplies the conditions for implementing and testing the SDRE algorithm in terms of hardware and software.