Attitude Control Of The Spacecraft Based On A Quaternion Model

Since the founding of New China,we have made remarkable achievements in aerospace technology field and China's space dream has always inspired our Chinese descendants from generation to generation.From Dongfanghong-I,i.e.,the country's first artificial satellite,to Shenzhou V,which is the first manned spacecraft later,and current BeiDou Navigation Satellite System,which serves for "One Belt and One Road",we Chinese have witnessed the rapid development of China's space industry.However,there is no doubt that we are supposed to overcome plenty of technical difficulties and make sequential progress.Furthermore,it is the attitude stabilization of a rigid spacecraft that is one of the indispensable missions,because spacecrafts are expected to have a perfect attitude in many space tasks(such as solar energy absorption,earth observation,etc.).It is obvious that spacecraft can expand the scope of application and gain more valuable information if they finish the corresponding space tasks efficiently and rapidly.Nevertheless,attitude control is a strongly nonlinear and coupled control problem,and it is still a hot and difficult point in the control field.There are several kinematics description approaches of the spacecraft attitude system,for example,direction cosine,Euler angles,quaternion and Rodrigue parameters.Since the quaternion description method own the least number of parameters and the global non-singularity,spacecraft attitude control system based on the quaternion description method is investigated in this thesis.On the other hand,the majority of attitude controllers are designed in the sense of continuous time,and then implemented on the digital platform,in which the control algorithm is actually base on an extremely small and periodic sampling,which can be regarded as a continuous feedback control approximatively.Therefore,the above control method will naturally be confined by the hardware itself in some degree.Additionally,frequent updating of the control signals may also lead to some unacceptable closed-loop performance,which may reduce the operation life of the spacecraft.Based on the research status discussed above,the sampled-data control is mainly proposed for the attitude stabilization of a rigid spacecraft.The main research content and innovation of the thesis are presented as follows:1)A periodic sampled-data controller is proposed in the thesis,and the correspond-ing linear quadratic regulator,that is,a performance index function is taken into consideration as well.2)An event-triggered sliding mode controller designed,which makes the loop-closed system robust and corresponding event-triggering scheme with Zeno phenomenon is avoided.The first chapter gives the research purpose and significance of thesis design,and some research status at home and abroad.Then,the research object is proposed,namely,the related system models,that is,the attitude control system model and its corresponding first-order approximation model and Lagrange model.It is worth noting that the model uncertainties and external disturbances are not taken into consideration in above models,and we will consider both of them in Chapter 4.In the second chapter,we mainly study a periodic sampled-data controller.We use the Lyapunov stability theory and the discretization and time-delay methods of the sampled-data system to obtain the state feedback gain K by solving sets of linear matrix inequalities(LMIs).It is shown that the obtained state feedback controller can not only effectively stabilize the system,but also optimize the system performance locally,that is,it is an LQR controller.Finally,some numerical simulations illustrate the validity of the designed controller.In the third chapter,an event-triggered sliding mode control is proposed for the attitude stabilization in presence of model uncertainties and external disturbances.Moreover,it is demonstrated that the proposed controller makes the closed-loop sys-tem robust and Zeno phenomenon is avoided.Simulations are shown to verify the effectiveness of the designed controller.