Configuration Optimization Of Distributed SAR And Configuration Control Based On Event-triggering Mechannism

Spacecraft formation flying has characteristics of “clustering” and “spatial distribution”.Compared with single satellite,this two characteristics bring huge technical advantages for formation flying.Therefore,the pattern of satellite formation flying has attracted much attention since its emergence in the 1990 s.In recent years,space experts have also made unremitting efforts to apply the theoretical achievements of formation flying to practical engineering projects.The Distributed Synthetic Aperture Radar System is the product of combining satellite formation technology with spaceborne radar technology.Satellite systems under certain formation configuration can provide a long variable baseline for Synthetic Aperture Radars,greatly improving radar performance and providing a good platform for radar measurement systems.In the space interferometry mission,the formation configuration is generally large and the distance between the satellite is long.In this case,the communication bandwidth might be insufficient.Event-triggering is a kind of control strategy proposed for the case of lacking communication resources.Based on the In SAR task,the configuration optimization is carried out in this paper and the maintenance control is studied with event driven strategy.The main research contents of this paper are as followsThe multi-baseline configuration optimization problem of formation satellites is studied under the background of In SAR tasks.Design steps are divided into three steps.In the first step,the relationship between the height error and the baseline is established,and the relationship between the baseline vector and the formation configuration parameters is also established.The optimization design of the long baseline is carried out with the general formation configuration parameters be the design variables,and with the time ratio of a certain height measurement error be the objective function.The second step,combining different phase estimation methods,optimizes the proportion of long and short baselines.The purpose is to reduce the difficulty of phase unwrapping.The third step is to use the optimization results of long and short baselines,complete the design of a multi-baseline configuration.Considering the case that the number of formation satellites is small and the leader and the follower formation control structure is adopted,the configuration maintain controller is designed.First,the LQR optimal controller and the inverse optimal controller are designed for a disturbance-free nominal system.Second,an integral sliding mode robust controller is designed to eliminate disturbances and model uncertainties terms.Finally,combining the optimal control and sliding mode control,to maintain the optimal sliding mode controller.Through simulation,it is proved that the optimal sliding mode controller can make the formation configuration stable near the desired configuration in the presence of disturbance,which makes up for the poor robustness of the optimal controller.In the case of a distributed formation,a position synergetic controller based on an Event-triggering mechanism is designed.First of all,on the assumption of undirected communication topology,the formation position synergetic control problem is described.Secondly,use the system current state to design the Eventtrigger mechanism threshold.Then,in the presence of external disturbances and considering the uncertainty of quality parameters,an adaptive position synergetic control based on Event-trigger mechanism is designed.Then,taking into account the actual situation,the effectiveness of the above controller under the condition of limited control force was deduced.Finally,in order to overcome the Zeno phenomenon in the steady state of the system,a static threshold is introduced in the Event-trigger threshold.The simulation verified the effectiveness of the controller.