Research On Formation Control Of Electric Solar Wind Sails Near Geosynchronous Heliocentric Displaced Orbit

With the development of science and technology, people have increased enthusiasm of exploration into deep space. Traditional spacecraft will carry too much fuel.during deep-space exploration since its small specific impulse. A new type of spacecraft- electric solar wind sail(E-sail) with unlimited specific impulse has great potential for deep space exploration. E-sail provide thrust by electrostatic Coulomb interaction with the plasma flow in solar wind and can apply to many non-Keplerian orbits, such as heliocentric displaced orbit. In recent years, ESA and NASA have been carrying out E-sail research and many relevant tests. In this paper, under the ground of heliocentric displaced orbit and relevant tasks, we study its feasibility, trajectory optimization and formation control methods using E-sail.First, we deduced entire E-sail thrust equation through thrust model for a single charged tether and simplified the equation. Moreover, we set up a set of corresponding orbital dynamics equations.Then, we derive kinetic equation for E-sail heliocentric displaced orbit. And we defined three different kinds of E-sail heliocentric displaced orbits and analyzed feasibility of the three orbits. Later we apply a Gaussian pseudospectral method for E-sail trajectory optimization from Earth orbit to geosynchronous heliocentric displaced orbit. The nonlinear programming problem obtained by Gaussian pseudospectral method is solved by genetic algorithm and sequential quadratic programming method.Finally, a relative dynamics equation of two E-sails in formation flying on a geosynchronous heliocentric displaced orbit under the consequece of the following E-sail flying nearby the main E-sail. After linearization of relative dynamics equation, we use Lyapunov to analysis the stability of the linearized relative dynamics equation. Also, the Linear-Quadratic Regulation is applied to the formation of the two E-sails. For a sequence while the velocity of the E-sails can not be measured, a control method based on Active Disturbance Rejection Control(ADRC) is designed and another sequence of inaccurate model is also discussed and simulated in this paper.