Research On Key Technologies Of Orbit Design And Control For All Electric Satellite

It is well known that satellite propelled by electric propulsion(EP)system can potentially extend the lifetime of the satellite,improve the on-orbit performance and increase the payload fraction.Currently,EP system can achieve a high level of performance and it has been a mature and widely used technology on satellite.The EP system developed in our country has been in operation for more than 6000 hours,switches up to 3000 times in the experiment,and it has the ability of on-orbit reliable operation for more than 15 years.However,designing orbit transfers,precise acquisitions and orbit control for satellites propelled by EP system are challenging problem.This is because the analytical solutions for long powered arcs are not available,and hundreds or even thousands of orbital revolutions are involved in transfer process.The EP system space test program began as early as in1960 s.After that,the EP engines were mostly used to implement north south station keeping for geostationary satellites.Because of the significant advantages of the EP system,it is gradually used to implement orbit transfer for geostationary satellites.If a satellite reaches the geostationary orbit that foresee the use of EP system,the EP system is also used to implement station keeping and deorbiting,then this satellite is said to be a all electric satellite.One of the key issues for all electric mission is how to design transfer trajectory and orbit control strategy for all electric satellite.This paper focus on the concept,principle and design methods for orbit design and control.The main content of this paper includes the following several aspects.(1)Firstly,the basic theoretical knowledges include the time system and reference frame that required to describe the movement of all electric satellite are introduced in this paper.Then,the physical quantities required to describe the satellite state and the corresponding equations of motion are given.After a detailed description of the characteristics of each equation of motion,the dynamic model of all electric satellite orbit design and control is established using modified equinoctial elements.Finally,the effect of perturbations on orbital elements is analyzed,and numerical simulation results indicate the effect of perturbation is not negligible in transfer process.The perturbations should be considered in the transfer are selected according to the scale and scope of each perturbation.Besides,this analysis arranges perturbations by their effect on orbital elements.(2)Orbital averaging technique,Lyapunov stability theory,linear interpolation criterion and evolutionary algorithm are applied to design guidance law for minimum-time low-thrust orbit transfers and time-fixed minimum-propellant low-thrust orbit transfers.This involves constructing asuitable Lyapunov function that is always monotonic and minimum at the given target orbit.Then,the thrust-steering program presented here is given based on the Lyapunov stability theory.After that,the control gains are parameterized by the linear interpolation criterion and the subsequent constrained parameter optimization problem is solved using an improved cooperative evolutionary algorithm(ICEA).For time-fixed minimum-propellant transfer,the relative thrust effectively is analyzed and three burn structures are proposed.Numerical simulation results indicate the periapis and apoapsis centered burn structure is a minimum-fuel burn structure.(3)Orbital averaging technique,Lyapunov stability theory,artificial neural network(ANN)and evolutionary algorithm are applied to design guidance lawa for minimum-time low-thrust orbit transfers and time-fixed minimum-propellant low-thrust orbit transfers.This involves constructing a suitable Lyapunov function that is always monotonic and minimum at the given target orbit.Then,the thrust-steering program presented here is given based on the Lyapunov stability theory.After that,the ANN is adopted to implement control gains steering and the evolutionary algorithm is used as the learning algorithm for ANN.Numerical simulation results indicate the Lyapunov-based evolutionary neural guidance can achieve a higher on-orbit autonomous flight performance than Lyapunov-based parameters optimization guidance.(4)This paper presents a simple,real-time closed loop control scheme for geostationary satellite autonomous station keeping using EP system.The north-south and the east-west motion are decoupled,and station keeping maneuvers are planned on the thrust efficiency of the electric propulsion.The distribution of thrust arc is determined by parameters optimization method.The required knowledge of satellite position and velocity is given by orbital determine module,and the on/off time of the station keeping maneuver is determined by whether the distance to desired position beyond the maximum allowed value.Finally,numerical simulation results demonstrate the effectiveness of the proposed algorithm.