Trajectory Planning And Control For Safly Approaching Space Rolling Target

Spacecraft will gradually lose communication ability so it cannot provide their own attitude and orbit inf ormation when they are in disrepair for a long time.Under the influence of space perturbation,it may even become a space rolling target,occupying orbit resources and endangering the working spacecraft.Therefore,it is very important to provide on-orbit services for these satellites in space.The task of approaching the space rolling target safely at close range is an extremely important part for the on-orbit service.This paper takes the space rolling satellite as the target,and studies the safety approach to the space rolling target in the close range.First of all,the kinematic models for approaching to the rolling target is established.The common coordinate system of space rendezvous and docking mission is given,and the orbit and attitude kinematics a nd dynamics equations of chaser and targeter are established respectively.Thus,the relative dynamic equation between the chaser and the targeter is derived.Based on the deviation between the actual trajectory and the expected trajectory,a con trol-oriented second-order nonlinear motion model of trajectory and attitude is established.The establishment of the model provides a basis for the subsequent research work.Secondly,based on the convex optimization method,a real-time trajectory planning algorithm for safely approaching the rolling target is designed.Taking into account the high dynamics of the rolling satellite,combined with the idea of sequence iteration,a trajectory optimization algorithm that can update the starting point and the ending point in real time and actively avoid obstacles is designed,and a trajectory optimization model for approaching the rolling target is constructed.Then,the above model is transformed into convex and discrete sub models,which can be used by convex optimization algorithm.Simulation shows that the trajectory optimization algorithm is safe and efficient.Finally,an adaptive sliding mode controller is designed for the second-order nonlinear system.The model contains a large number of measurement errors and bounded disturbances.The advantage of sliding mode control is that it has strong robustness to disturbances and unmodeled dynamics,so it is very suitable for the control algorithm of the rolling satel lite approximation task.In this paper,an improved adaptive sliding mode control method is designed to solve the control problems under the influence of factors such as system parameter uncertainty,measurement error,bounded interference,and limited input.It can increase the control gai n when necessary,and reduce the design cost.It takes into account the fact that the accurate initial value cannot be obtained when generating the reference trajectory.The stability of the designed control law is analyzed and the mathematical simulation is carr ied out.The results show that the tracking error can converge to a small neighborhood near zero in a preassigned time.The simulation shows the effectiveness of the control algorithm.