Close-range Orbit And Attitude Tracking Control For Non-cooperative Targets

While people are exploring and utilizing the space field,space science and technology are also developing rapidly,so more and more satellites are launched into space.After years of service,some of these satellites are unable to work properly due to fuel exhaustion or parts damage.Outside,There are some abandoned spacecraft left in space due to the failure of the launch mission,as well as some waste generated during the launch and space debris generated during the collision.These space wastes have lost their ability to control themselves.The inability to take the initiative to leave the original track not only occupies valuable orbital resources,but also has a certain impact on the work and safety of other satellites in orbit.Under this circumstance,space-orbiting services aiming at repairing faulty spacecraft and cleaning up space debris have emerged as the times require,and become a research hotspot in the field of aerospace technology.In general,the objectives of on-orbit services(such as dead satellites,hostile satellites,and space debris)are non-cooperative,so how to achieve high-precision attitude-coupling control of service spacecraft without obtaining accurate relative motion information.It has become the focus of the field of rail services.Therefore,this paper takes the capture of space non-cooperative targets as the background and the space non-cooperative satellites as the goal,and studies the approximation and tracking of non-cooperative targets in close range and super close range.Firstly,several reference coordinate systems are defined,and the absolute orbital dynamic equations and absolute attitude dynamics equations of the tracking satellite and the target satellite are respectively established.Based on the established absolute dynamic model,the relative orbital dynamic equations and relative attitude dynamics equations between the tracking satellite and the target satellite are derived.Based on the established absolute dynamic model,the relative orbit dynamics equation and relative attitude dynamics equation between the tracking satellite and the target satellite are derived.Then,considering the robustness of sliding mode control to unknown bounded disturbances and system uncertainties,the sliding mode control theory is used to design the relative orbit and attitude coupling control algorithm for tracking satellites to noncooperative target satellites in close range.Firstly,a control law based on traditional sliding mode is designed,and the condition of reaching the sliding surface in a limited time under the condition that there is bounded deviation of the control quantity is analyzed.The simulation verifies that the traditional sliding mode has a general control effect on systems with unknown bounded interference and system uncertainty.Then,in order to achieve better control effect,the unknown external disturbance and system uncertainty are compensated.An adaptive sliding mode control law with preset adjustment time is designed.The simulation verifies that adaptive sliding mode control do better than traditional sliding mode control for systems with unknown bounded interference and system uncertainty.Finally,for the approach and tracking of non-cooperative targets in the case of super close distance,at this time,the visual measurement equipment such as the camera on the tracking satellite cannot capture the complete target satellite information due to the angle of view,and thus the accurate relative posture cannot be obtained.So it's unable to achieve stable attitude-coupling control.In order to solve this problem,the son-mother satellite scheme is adopted,and the parent satellite stays at a safe distance to provide the target satellite with the attitude and orbit measurement information of the target satellite,and the satellite carries the catching device to achieve the final tracking and capture.Based on this scheme,a hybrid visual servo control method is proposed.The indirect estimated image visual servo method is used to control the relative position,and the relative attitude is tracked by the image features of the windsurfing board or the satellite main part.The simulation proves that the control method can ensure that the son-satellite can safely approach the target satellite,and the control error can reach the capture requirement.