Control Method For Approaching And Tracking The Non-cooperative Floating And Tumbling Target In Space

The failed spacecraft cannot provide cooperative and controlled attitude and orbit state for the On-Orbit Service satellite,and mantains floating in space with their orbit only affected by perturbative forces.Meanwhile,the space perturation moments will finally cause slowly rotating or tumbling.In this dissertation,the failed spacecraft with these three characteristics is named the floating and tumbling target in space.The On-Orbit Service(OOS)mission is faced with serious challenges,such as the high-dynamic and time-varying mission scenarios,measurement uncertainty and time-relay,multi-constraints,and so on.As one of the enabling technologies for the OOS mission,the control method for approaching and tracking the floating and tumbling non-cooperative target in space becomes the worldwide research hotspot and one of the most pressing problems.For this problem,after the dynamic characteristic modelling and analysis,this thesis focuses on two detailed problems,which are the planning of the safe approaching trajectory to the complex shaped tumbling target with multiple constraints,and the relative attitude and orbit coupled control for approaching and tracking the tumbling target.To solve the dynamic problems of approaching and tracking the typical tumbling satellite,the spiral nutation motion of the target is firstly analyzed,according to which,the mission procedure is designed containing two main phases,those are the attitude and orbit tracking state establishing phase,as well as the final approaching phase.The relative attitude and orbit coupled dynamic models are separately established for the motions between the centroids and surfaces of the chaser and target,then the coupled relationships between the relative attitude and orbit are analyzed.The propagation of measurement and navigation errors in the control system is also modelled,with their influences to control input errors analyzed by numerical simulation.Aiming at the safe approaching trajectory planning problem in the phase of the attitude and orbit tracking state establishing,two attitude and orbit trajectory planning methods are proposed respectively based on the Gaussian pseudo-spectral and the inverse dynamics in virtual domain.The multi-constraint models are established,comprehensively considering the constraints of collision avoiding,sight line tracking,thrust plume interference,limited control input,and so on.By solving the non-linear optimized control problem by using the Gaussian pseudo-spectral method(GPOPs),the planning method of safe approaching trajectory to the tumbling target is designed.Then,in order to increasing the trajectory planning and calculation efficiency,a rapid planning method is designed,which is based on the inverse dynamics in virtual domain(IDVD).Numerical simulations are implemented to demonstrate their capacities to obtain the time or energy optimized trajectory synchronously satisfying multiple constraints.The IDVD method shows significant advantage in computational efficiency,while it can only obtain the suboptimal trajectory.For the relative attitude and orbit coupled control problem in the phase of the attitude and orbit tracking state establishing,a dual sliding-mode surface control(DSMSC)method is proposed,with its efficiency verified by numerical simulations and ground micro-gravity tests.To improve the control performance impacted by bounded disturbance and parameter uncertainty,a dual sliding-mode surface control method is designed,with the closed-loop system stability is also proved.An attitude and orbit coupled DSMSC control method is then designed for approaching and tracking the floating and tumbling target.Comprehensively considering impacts from bounded disturbance,measurement errors,limited control input,parameter uncertainty,numerical simulations are carried out to compare the performances of the single sliding-mode surface control(SSMSC)law and the DSMSC.The second sliding-mode surface of the DSMSC is indicated to remarkably lower the steady statue control bias and noise,which is mainly because of introducing the statue bias integration into the control quantity and its ability to auto-compensate influences from negative factors.Furthermore,a set of ground micro-gravity semi-physical verification system is established,and a mission scenario is designed with the motion constrained in the orbit plane.Then,the efficiency of the DSMSC is verified in the real-time GNC close-loop system with micro-gravity dynamics.In order to solve the approaching and tracking control problem in the situation of direct relative measurement losing efficacy caused by the ultra-short distance during the final approaching mission phase,an indirect estimation assisted IBVS(IEA-IBVS)control scheme is proposed based on DSMSC method.Through the mission scenario analysis and numerical simulations,the control scheme using indirect estimation of the relative attitude and orbit is proved to be deficient,even may cause crash to the target.According to the image based vision servo(IBVS)method,the imaging and motion model is established.By introducing the IBVS expected generalized velocity and image coordinates' information into the DSMSC control close-loop,an indirect estimation assisted IBVS(IEA-IBVS)control scheme is proposed.The numerical simulation results indicate that,the IEA-IBVS can remarkably promote the relative attitude and position control accuracies,provide more safe,accurate,and stable relative attitude and orbit condition for final approaching and tracking the tumbling target in space.