CubeSat Control using SDRE Method during the Orbital Injection Phase based on Thrusters

Accurately managing a CubeSat's orientation during the orbital injection phase is crucial for mission success. Concurrently, signal processing is vital for the CubeSat payload and its subsystems, particularly for the Attitude Control Subsystem (ACS). Typically, a CubeSat begins this phase with excessive angular velocity so that the controller needs to slew the CubeSat into small angle attitudes for normal operation mode. Cold gas thrusters are one method to perform this transition. This work applies an ACS algorithm during the orbital injection phase, of nonlinear dynamics behavior as angular velocities are high and perturbed in nature. Consequently, linear control methods may fail to meet performance and robustness requirements. To address this, we employ the State-Dependent Riccati Equation (SDRE) method, which is applicable to these types of nonlinear systems. The SDRE controller uses cold gas thruster torques to execute large-angle maneuvers, reducing high angular velocities. This study verifies the numerical simulator model, the control algorithm's functionality, and the signal between the controller and actuators, applying a full Monte Carlo perturbation model. Although the ACS algorithm is designed as a continuous-time system, it is now prepared for the next study phase, which involves analyzing discretization techniques and evaluating the sampling rate for the digital version of the SDRE controller.