Research On Control Technologies Of Microsatellite Proximity Operations

Servicing spacecraft's proximity operation technologies can improve working efficiency and real-time performance of space services.As the proximity operations require precise position and attitude control,and the effectiveness of the control methods will directly affect the performance of the servicing spacecraft and the final servicing quality,the control technologies needed in proximity operations are studied deeply in this paper.Take into account the microsatellite approach to a non-cooperative target spacecraft which orbits near the geosynchronous orbit to perform in-orbit surveillance missions,the control methods in this process are studied in detail.For the high accuracy of the flight process,the entire process is divided into two phases: the first stage with relative distance from 400 m to 100 m and the second stage with relative distance from 100 m to 10 m.Firstly,the problem of model establishment in proximity operations is studied,the relative motion orbital dynamics model and attitude motion model of microsatellite are built.The control problems in the first phase of the microsatellite operations are studied.Through the analysis of the thruster layout,a thrust distribution scheme is designed based on the look-up table method for the impulse thrust mode.A guidance logic and a control logic based on turn-burn-turn method are designed to complete the switching between orbit control and attitude control.At the same time,a non-singular fast terminal sliding mode torque controller is also designed.Finally,the final relative position error and the final relative velocity error obtained through simulation are 0.273 1m and 0.002m/s respectively and the relative attitude and angular velocity can converge in a very short time.Thus,the validity of the guidance and control logic as well as the performance of the torque controller are verified through simulation results.The control problems of the second phase of the microsatellite operations are studied.For the continuous thrust mode,a thrust distribution scheme is designed based on the linear programming method.A new guidance and control scheme is designed and the various constraints needed to be considered are given.The original problem is transformed into a convex problem through convexification.Then the idea of iterative solution is introduced and the optimal trajectory and the desired control command are obtained by using the model predictive control algorithm based on sequential convex programming method.Then the actual control force and control torque command output through the thrust distribution scheme and act on the microsatellite.Finally,the simulation results show that each planning time is less than the update time of the guidance system.The sensor field-of-view constraint,the final state constraint and the control force and the control force and control torque amplitude constraint are all satisfied in the simulation process.Thus,the effectiveness of the control scheme is verified through simulation results.