| With the development of aerospace technology and the burgeoning demand for space exploration,agile maneuvering and earth observation satellites have attracted wide research,and have played important roles in various engineering applications.And the attitude maneuverability of satellites greatly determines the efficiency and accuracy of performing tasks.In the various actuators,Control Moment Gyroscope(CMG)as an angular momentum exchange device,with the principle of rotating the gimbal to output the control torque,has the advantages of continuous output torque,and high output accuracy so that it has been widely used in satellite attitude stabilization and attitude maneuver.However,when all output torques are coplanar or collinear,CMG clusters cannot output torque in the direction orthogonal to them,known as the geometric singularity of CMG.In addition,due to the increase in the mechanical and supporting electrical construction of the gimbal,it is prone to failure.Especially when one of more control torque gyros are completely faulty and only three worked,the non-redundant CMGs cannot provide additional degrees of freedom to avoid singularity.It will greatly reduce the control accuracy with the increase of induced error,so it is necessary to analysis and study the non-redundant CMGs.This dissertation comes from the satellite attitude maneuvering control project of a research institute,and focuses on the following aspects for non-redundant CMG:First of all,a systematic survey of the current research status of this subject was conducted,including CMG products,on-orbit applications and fault cases,typical maneuvering strategies,and satellite attitude maneuver control methods.Then,the satellite attitude motion and CMG clusters were modeled,and based on the singularity criteria,the singular characteristics of CMGs before and after the fault are analyzed.From a visual point of view,the angular momentum envelope surface and the elliptical and hyperbolic singularities are drawn by numerical method,and we also calculated typical configuration indices to analyze the performance changes of CMG numerically,which lays an empirical basis for the design of the subsequent steering strategy.Considering that most of the existing steering laws based on the pseudo-inverse form of the Jacobian matrix are prone to encounter matrix irreversible problems,based on the idea of inverse kinematics,the gimbal angles are directly calculated.Firstly,this paper derived the onedimensional multiple equation of gimbal angles.Then,in order to solve the problems including solving difficulty,configuration limitations,a numerical iteration method based on the Cyclic Coordinate Descent(CCD)is proposed.Using the gimbal angles of the previous step as the initial value to iterate quickly,by updating each momentum of CMG to the homologous surface perpendicular to the gimbal axis,this method improves the computational efficiency.Based on discrete control,the steering law is designed,and combined the hierarchical saturation PID controller to complete the simulation verification of the steering law.Aiming at the problem of the local steering laws inevitably using induced errors to escape the singularity,a path planning method based on adaptive pseudo-spectrum method is proposed.The global state trajectory including satellite attitude parameters,CMG gimbal angles and gimbal rates are planned.with the gimbal angular accelerations as the control variables and the design of the composite performance function,we tested various working conditions including gimbal angle re-orientation,singularity escape and others.Further considering the bounded disturbance,an on-line route re-planning is proposed.When the open loop maneuver error exceeds the allowable tolerance,re-planning is enabled to minimize the open loop errors.And then,a terminal sliding mode controller is designed to eliminate the errors.Finally,the simulation verifies the effectiveness of the open loop maneuvering combined with the closed loop error elimination. |
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