Spacecraft Relative Position And Attitude Integrated Control Based On Fractional Order Slide Mode Control Strategy In The Final Approach Phrase

Mature spacecraft rendezvous and docking technology is the basis for the establishment of the space station.With the increasing number of space missions,the complexity of the space mission is increasing,which brings forward higher requirements for the rapidity,accuracy and energy consumption of spacecraft control.This thesis based on the background of space rendezvous and docking,which studies the position and attitude coupled control with the method of fractional order sliding mode and the parameters of fractional order sliding mode control law are optimized.Firstly,the kinematics and dynamics modeling of spacecraft rendezvous and docking is investigated.This paper introduces the concepts of quaternion and dual number and their operation rules.According to the concept of spiral motion,the relative kinematics equation of rendezvous and docking is established under the description of dual quaternion.Based on the knowledge of momentum theorem,the dynamic equation of a single spacecraft is derived.Furthermore,the relative motion dynamics and kinematics equations are derived.The attitude motion and orbital motion of spacecraft are described in an integrated way.The coupling characteristics of relative motion between spacecrafts are analyzed.Secondly,the fractional sliding mode control strategy for spacecraft rendezvous and docking is studied.This paper introduces the concept of fractional order and numerical calculation method.In this paper,the fractional sliding surface and the sliding mode reaching law are designed by adding the fractional calculus term into the traditional sliding surface and the sliding mode reaching law.The feasibility of the theory is proved,and the simulation experiment is carried out.A simulation experiment is carried out in the presence of external disturbances and model uncertainties.The results show that fractional sliding mode control strategy for the rendezvous and docking in the final approach has strong robustness and anti-interference,can meet the high precision,rendezvous and docking approach phase control anti-interference and robustness requirements.Finally,the parameter optimization problem of fractional order sliding mode control law is studied.Considering the response time,energy and error,the fitness function is selected.The optimization process of particle swarm optimization algorithm isintroduced.In the optimization process,it is found that the optimal fitness value and the optimal parameters are different when the parameters are selected.Analysis of the particle swarm optimization algorithm in the initialization mode and the lack of particle update method makes it easy to premature convergence and stagnation in local optima.The chaos theory is introduced,and the initialization and update of particle swarm algorithm are improved.The simulation results are given to verify the feasibility of the chaos particle swarm optimization algorithm for solving the parameter optimization problem of fractional order sliding mode control law.