Robust integral variable structure controller and pulse-width pulse-frequency modulated input shaper design for...

Area of Science:

• Aerospace Engineering
• Control Systems Theory

Background:

• Flexible spacecraft require sophisticated control for precise attitude maneuvers.
• On-off thrusters and rapid maneuvers can induce undesirable vibrations.
• Existing control methods may struggle with uncertainties and disturbances.

Purpose of the Study:

• To develop a robust dual-stage control system for flexible spacecraft attitude control.
• To integrate on-off thruster control with active vibration suppression.
• To enhance pointing accuracy and minimize vibration during maneuvers.

Main Methods:

• Design of an integral variable structure controller (IVSC) for attitude stabilization.
• Implementation of an asymptotic variable structure observer for state estimation.
• Modulation of thruster output using pulse-width pulse-frequency (PWPF) control.
• Application of input shaping to mitigate vibration induced by control commands.

Main Results:

• The IVSC ensures exponential convergence of attitude angle and angular velocity despite bounded uncertainties.
• PWPF modulation mimics continuous control profiles for thruster output.
• Input shaping effectively reduces vibration by modifying control commands based on system dynamics.
• Simulations demonstrate precise attitude control and significant vibration suppression.

Conclusions:

• The proposed hybrid control scheme effectively combines precise attitude control with active vibration suppression.
• The dual-stage approach offers robustness against uncertainties and disturbances.
• This method is suitable for flexible spacecraft requiring agile maneuvering with minimal vibration.