Sliding mode control techniques for combined energy and attitude control system

Combined Energy and Attitude Control System (CEACS) is an optimization approach that combines the energy storage system and the attitude control system. With a double counter rotating flywheel simultaneously serving as energy storage device and as attitude control actuator, CEACS requires an accurate control strategy to obtain the mission requirements. In addition, it is important to design the control law to be invariant to uncertainties and disturbances, and guarantee robustness as CEACS inherits these in-orbit uncertainties. This paper presents a nonlinear control employing sliding mode to enhance the CEACS attitude control capability. The mathematical model for the conventional and boundary layer sliding mode controls are developed herein for CEACS. The controller provides enhancement in pointing accuracies, reasonable transient responses and a robustness against uncertainties and in-orbit disturbances

Singularity-free integral-augmented sliding mode control for combined energy and attitude control system

A combined energy and attitude control system (CEACS) is a synergized system in which flywheels are used as attitude control actuators and simultaneously as a power storage system. This paper, a subsequent to previous research on CEACS, addresses the attitude-tracking problem. Integral Augmented Sliding Mode Control with Boundary-Layer (IASMC-BL), a locally asymptotically stable controller, is developed to provide a robust and accurate solution for the CEACS’s attitude-tracking problem. The controller alleviates the chattering phenomenon associated with the sliding mode using a boundary-layer technique. Simultaneously, it reduces the steady-state error using an integral action. This paper highlights the uncertainty of inertia matrix as a contributing factor to singularity problem. The inversion of the uncertain inertia matrix in simulation of a spacecraft dynamics is also identified as a leading factor to a singular situation. Therefore, an avoidance strategy is proposed in this paper to guarantee a singular-free dynamics behavior in faces of the uncertainties. This maiden work attempts to employ the singularity-free Integral Augmented Sliding Mode Control with Boundary-Layer (IASMC-BL) to provide a robust, accurate and nonsingular attitude-tracking solution for CEACS

Aircraft pitch control tracking with sliding mode control

Sliding mode control (SMC) is one of the robust and nonlinear control methods. An aircraft flying at high angles of attack is considered nonlinear due to flow separations, which cause aerodynamic characteristics in the region to be nonlinear. This paper presents the comparative assessment for the flight control based on linear SMC and integral SMC implemented on the nonlinear longitudinal model of a fighter aircraft. The controller objective is to track the pitch angle and the pitch rate throughout the high angles of attack envelope. Numerical treatments are carried out on selected conditions and the controller performances are studied based on their transient responses. Obtained results show that both SMCs are applicable for high angles of attack

Sliding mode control techniques for combined energy and attitude control system

Attitude control and power storage subsystems are two of the essential utilities provided on a satellite. As they compromise a significant fraction of a satellite’s weight, a synergism concept that integrates these two into one subsystem can reduce the mass and volume of a satellite. The reduction will decrease the total cost of development and deployment of a satellite. A combined energy and attitude control system (CEACS) is an optimization concept that utilizes flywheels as a means of power storage and simultaneously as attitude actuators. A series of work on CEACS have proposed solutions for the satellite’s attitude control problems. However, the analysis disregarded the high non-linearity involved in the satellite’s attitude control itself. In addition, the proposed controllers’ feasibility in presence of unknown disturbances and uncertainties were not examined. This thesis addresses a more complex attitude-tracking problem. This work proposes the use of the sliding mode control technique for the attitude-tracking problem of CEACS. Furthermore, an enhanced sliding mode control (SMC) technique is introduced to achieve robustness against uncertainties and external disturbances. Integral Augmented Sliding Mode Control with Boundary Layer (ISMC-BL), a locally asymptotically stable controller, is developed to provide a robust and accurate solution for the CEACS’s attitude-tracking problem. The controller alleviates the chattering phenomenon influence on the attitude tracking performance that is associated with the conventional sliding mode using a boundary layer technique. Simultaneously, it reduces the steady-state error using an integral action. The numerical evaluation of the proposed controller demonstrates an enhanced attitude control accuracy in the presence of the system’s uncertainties and external disturbances. However, ISMC-BL suffers from overshoots in its transient response. In addition, the model focuses only on mission with small attitude orientations involved. Therefore, this thesis proposes a Nonsingular Terminal Sliding Mode (NTSM) control scheme for a global attitude-tracking mission of a CEACS. The nonlinear system herein is subjected to unknown but bounded disturbances and uncertainties. The Lyapunov stability theorem is used to prove the finite-time convergence in both reaching and sliding phase. The proposed method avoids the inherited singularity of conventional terminal sliding mode. The numerical analysis provides proofs of the controller’s robustness in rejecting the unknown disturbances and keeping the attitude errors as small as possible under the influence of uncertainties. The results provided by NTSM control method demonstrate the superiority of this sliding mode scheme compared to the previous proposed techniques for the CEACS’s attitude control