Research On Orbital Maneuver Dynamic And Control Of The Electrodynamic Tether

Orbital maneuver dynamic and control of the electrodynamic tether is the keytechnology in removing space debris using electrodynamic tether. This thesisexplores the orbital maneuver dynamic and control algorithm of the electrodynamictether, including active orbit boost and inactive deorbit process. The researchmainly covers the following points:Firstly, the non-tilted dipole model for the earth magnetic field and orbitalmotion function were addressed. Some useful theorems about Gauss pseudospectralwere presented. The reasonableness on the hypothesis of the rigid rod was analyzed.Then, the maximum active control current through the tether was calculatedaccounting for onboard power and the induced potential in the tether.Secondly, based on the motion function of libration in inclined circular orbits,the libration law of the tether accounting for the aerodynamic drag was studied andthe current control algorithm for suppressing the libration caused by biased torqueand initial disturbance was designed. The numeric simulation showed that smallercurrent was needed to suppress the libration of the tether if the designedmulti-segment structure of the electrodynamic tether was used.Thirdly, the current with five Fourier coefficients was designed for orbitalmaneuver control of the electrodynamic tether based on the long-term motionfunction of orbital elements. Considering the error caused by the hypothesis that theorbital elements ware constant, two methods were presented to improve the controlaccuracy. The numeric simulation verified the efficiency of the control algorithm.At last, gauss pseudospectral algorithm was used to perform the optimal control oforbital maneuver with three desired objectives: maximum orbital altitude change inthe limited time, maximum orbital inclination change in the limited time andminimum time for finishing desired orbital elements change. And the optimality ofthe results was verified.At last, the relation between the required time of deorbiting the satellite andthe arguments of the tether and the initial orbital elements was considered. Then,three resistance modulating methods under the hypothesis that the orbit of the mainsatellite changed slowly were explored to achieve the tether’s maneuvers from theinitial equilibrium to the required equilibrium. The numeric simulation testified thatthe three control methods could finish the transform, smoothly. The method withcritical damping cost the least transient period and power, and the method with overdamping cost the most transient period and power.