Research On Anti-disturbance Of Small Spacecraft Attitude Control System

Attitude control plays a central role in spacecraft control and determines the accuracy of the whole spacecraft control system.In the recent decades,the research on the attitude control of spacecraft has maintained high attention and kept high heat in the field of control theory.However,taking into account the changes of the working environment,the miniaturization of the spacecraft structure and the precision of the task requirements,the anti-disturbance performance of the spacecraft attitude control system are needed to be improved nowadays.The higher requirement of anti-disturbance performance not only promotes the combination of advanced control theory and attitude control problem,but also requires researchers to discuss the anti-disturbance mechanism in small spacecraft attitude control design theoretically.Therefore,combining the concepts and methods in advanced nonlinear control theory,it is of great theoretical significance to recharacterize and describe the anti-disturbance problem of small spacecraft attitude control system.Associated with the concept of(integral)input-to-state stability,regulation theory,small-gain theorem and other key technologies in nonlinear control,this paper aims at solving attitude tracking and regulation problem in small spacecraft attitude control with external disturbances,and giving the controller design manner.Besides,based on external stability analysis,the anti-disturbance performance of attitude control system is discussed.The main work of this paper is summarized as follows:(1)The problem of attitude tracking and modeled disturbance rejection with known frequencies is discussed and the method of regulation theory based dynamic controller design is studied.Firstly,we define a quaternion-based nonlinear coordinate transformation,leading to an attitude deviation system meeting the structure of output feedback normal form with unity relative degree.Secondly,an ISS-Lyapunov candidate function is designed and the inverse dynamics of the deviation system is proved to be input-to-state stable.Thirdly,based on canonical internal model approach,a dynamic compensator is designed to achieve disturbance rejection.Moreover,the output regulation problem is transformed to a stabilization one with respect to an augmented system.Finally,we design an errorbased high-gain stabilizer,rendering the resultant attitude deviation closed-loop system input-to-state stable.The proposed controller achieves not only modeled disturbance with known frequencies rejection,but also unmodeled disturbance attenuation.Simulation and experiments show the efficacy of the proposed method.(2)The problem of attitude tracking and unmodeled disturbance rejection with unknown frequencies is discussed and a nonlinear internal model based dynamic controller is designed.Firstly,regarding to the modeled disturbance with unknown frequencies in attitude deviation system,we construct an uncertain exosystem and make an attempt to give a nonlinear steady-state generator which can compensate the uncertain steady-state term.Secondly,based on the nonlinear steady-state generator,we design a nonlinear internal model.Thirdly,we achieve modeled disturbance compensation by the nonlinear internal model approach.Moreover,by nonlinear coordinate transformations,we construct an augmented system,leading to the problem conversion from output regulation to stabilization.Finally,we design an error-based high-gain stabilizer,rendering the resultant attitude deviation closed-loop system integral input-to-state stable.The proposed controller achieves not only modeled disturbance with unknown frequencies rejection,but also unmodeled disturbance attenuation.Simulation and experiment show the efficacy of the proposed method.(3)The problem of attitude maneuver of small flexible spacecraft with modeled disturbance is discussed and an internal model based nonlinear controller is designed.Firstly,several coordinate transformations are proposed,leading to a new attitude deviation system.Secondly,the attitude maneuver of small flexible spacecraft is converted to a specific problem of design of an input-to-state stable controller.Finally,we design an internal model based nonlinear dynamic controller which makes the closed loop attitude deviation system ISS.The proposed controller achieves not only attitude maneuver and flexible appendages vibration suppression,but also modeled disturbance rejection and unmodeled disturbance attenuation.Simulation shows the efficacy of the proposed method.(4)The problem of attitude regulation by event-based control with input disturbance attenuation is investigated.We propose an ISS-based high-gain stabilizer to achieve eventtriggered attitude controller design.Firstly,based on Rodriguez parameter based attitude dynamics and desired attitude trajectory,we establish an attitude error system and formulate the event-based attitude regulation problem.Secondly,we design an error based high-gain stabilizer and verifying ISS properties of error kinematics and error dynamics subsystems,giving the gain function of each subsystem.Thirdly,we discuss the external stability of the attitude error closed-loop system based on small-gain theorem.Finally,an event-based attitude controller is redesigned.The proposed controller achieves not only attitude regulation with any specified precision,but also input disturbance attenuation.Simulation and experiments show the efficacy of the proposed method.(5)The problem attitude regulation by measurement feedback and event-based control is investigated.We discuss the solvability of the problem and propose an ISS-based highgain stabilizer to achieve event-triggered attitude controller design.Firstly,regarding to the attitude error system,we verify the solvability of the problem of attitude regulation by measurement feedback.Besides,we also revisit the input-to-state stability of the inverse dynamics.Secondly,a high-gain measurement feedback controller is designed for attitude error dynamic system,characterizing the ISS property of that subsystem.Thirdly,based on ISS-Lyapunov method,the attitude error closed-loop system is proved to be input-tostate stable with respect to measurement disturbance.Finally,we implement an eventbased attitude controller redesign.The proposed controller achieves not only attitude regulation with any specified precision,but also measurement disturbance attenuation.Simulation and experiments show the efficacy of the proposed method.