Abstract
Development of nanosatellites with CubeSat stan-dard allow students and professionals to get involved into the aerospace technology. In nanosatellites, attitude plays an im-portant role since they can be affected by various disturbances such as gravity gradient and solar radiation. These disturbances generate a torque in the system that must be corrected in order to maintain the CubeSat behavior. In this article, the kinematic and dynamic equations applied to a CubeSat with three reaction wheels are presented. In order to provide a solution to the atti-tude maneuvering problem, three robust control laws developed by Boskovic, Dando, and Chen are presented and evaluated. Furthermore, these laws are compared with a feedback control law developed by Schaub and modified to use Quaternions. The simulated system was subjected to disturbances caused by a Gravity Gradient Torque and misalignments in the reaction wheels. The effectiveness of each law is determined using the Average of Square of the Commanded Control Torque (ASCCT), the Error Euler Angle Integration (EULERINT), the settlement time, the estimated computational cost (O), and the steady-state error (ess).
Highlights
The CubeSat standard, developed in 1999, is intended to reduce development time and costs, as well as increase accessibility to space for students and teachers [1]
Control algorithms have been developed for non-linear systems. These include a feedback control developed by Schaub in [5] where Modified Rodrigues Parameters (MRP) are used to describe the attitude of a satellite, and a Variable Speed Control Moment Gyro (VSCMG) is used as an actuator
Scarritt in [8] estimated a gain applied to the modeled inertia tensor and a rotation associated with the misalignment of the reaction wheel obtaining a robust control algorithm with a high computational cost (O)
Summary
The CubeSat standard, developed in 1999, is intended to reduce development time and costs, as well as increase accessibility to space for students and teachers [1]. This controller was not effective under external disturbances. Chen [10] developed a robust controller that considered input constraints based on the fast non-singular terminal sliding mode surface (FNTSMS). This controller needed an inertia a priori information but was capable to reject nonlinear disturbances and to keep the tracking error around zero.
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