Research On Finite Time Attitude Maneuver Control Of Spacecraft

With the development of science and technology, much more demand for thespacecraft which can be rapidly mobilized. As a result of the complexity of spacemissions, the spacecraft should motorize rapidly to improve the convergenceperformance of the system, at the same time, because of the flexible appendagevibration and fuel consumption, the moment of inertia of spacecraft istime-varying and uncertainty, the orbiting spacecraft also subject to variousdisturbances coming from the external environment inevitably. Moreover, due toitself physical limitation, the actuator outputs are constrained, and the installationof the actuator always have installation errors. Due to the problems mentionedabove, it is necessary to take them into consideration while designing the systemcontrollers. The thesis aims to study the flexible spacecraft attitude maneuverdeeply and focuses on finite time convergence of the spacecraft. The maincontents of the thesis are presented as follows:At the first, the attitude kinematics and dynamics of the flexible spacecraftare established according to Euler Theorem and Lagrange’s principle separately.Then, a brief introduction about the relevant concepts and theorems of the finitetime stability, which is the foundation for the following controllers design andanalysis.Secondly, considering the attitude maneuver finite time control problem ofthe flexible spacecraft, in order to design the controllers conveniently, thecoupling item and external disturbance are treated as the totally disturbance.Then, a finite time control approach is developed based on the terminal slidingmode control law. This controller is considered the uncertainty of the moment ofinertia and the totally disturbance. However, the installation error caused by theactuator installation is inevitably, so a modified controller with an adaptivecontrol law is proposed to real-timely adjust the error is designed. Moreover, inorder to reduce the chattering phenomenon caused by the sign functio n, thesaturation function is used to replace it. At last, according to the finite timeLyapunov stability thermo and simulation results, the effectiveness of thecontrollers is verified.Finally, the boundary of the uncertainty of the moment of the inerti a and thedisturbance is hardly obtained exactly in the spacecraft system, in order to solvethis problem, an approximately treated is first to do with the spacecraft, then anadaptive control law is proposed to deal with the unknown parameter and anadaptive finite time controller is designed. Due to the saturated nonlinear characteristics of the actuator, the input torque is limited. Considering both of theactuator installation error and saturated nonlinear characteristics, a modifiedadaptive controller is designed. The proposed controller can ensure the systemsatisfy the requirement of the saturated. Both of the two controllers can let thesystem converge to a region which involve the sliding surface in finite time, theregion can be much smaller according to adjust the relevant parameters.Simulation results show the effectiveness of the controllers under the abovesituations.