Precise Attitude Control Techniques: Performance Analysis From Classical to Variable Structure Control

Abstract

Small satellites have begun to play an important role in space research, especially about new technology development and attitude control. The main objective of this research is the design of a robust flight software, in which the key feature is suitably designed control laws to guarantee the robustness to uncertainties and external disturbances. To accomplish the desired mission task and to design the robust software, a classical Proportional Integrative Derivative (PID) method and two robust control system technologies are provided, focusing on applications related to small satellites and on the real-time implementability. Starting from PID approach, simulations are performed to prove the effectiveness of the proposed control systems in different scenarios and in terms of pointing stability and accuracy, including uncertainties, measurement errors, and hardware constraints. Different control techniques are analyzed: (i) a tube-based robust model predictive control (MPC) and (ii) a variable gain continuous twisting (CT) sliding mode controller. Both controllers are compared with loop shaping PID controller.

Failure Identification Method and LMI-Based Control System for Small Spacecraft

“…where A ∈ R 6,6 , B u ∈ R 3,6 , and B w ∈ R 3,6 are the Jacobian matrices of ẋ computed with respect to x, u, and w, respectively.…”

“…For what concerns C z , D u , and D w , it is possible to follow the same approach of the equation that is used to describe the measurements, but for the purposes of this study, we chose to assume C z ∈ R 6,6 as the identity matrix I 6 and D u , D w ∈ R 3,6 as the null matrices.…”

“…where the matrix is identified as M, and Q ∈ R 6,6 , Y ∈ R 3,6 and γ > 0 are the problem variables. The solution of these LMIs is processed using a mathematical solver.…”

“…The attitude accuracy is usually a function of the mission scenario and spacecraft characteristics; some mathematics related to the accuracy evaluation for different missions can be found in [1] and in [2] for a real-time implementation. A pointing stability index, for example, can be evaluated during the most critical maneuver phases, as detailed in [3]. Moreover, the reduced mass causes the spacecraft to be more sensitive to external perturbations, and momentum exchange devices (MEDs) have more limitations due to their smaller dimensions.…”