| Space debris is mainly caused by the explosion of spacecraft in the launch mission,the upper stage of the rocket and the abandoned satellite.Due to the high relative speed,any collision would lead to catastrophic consequences,posing a serious threat to the normal operation of the aircraft and the safety of the astronauts.According to the collision cascade effect,when the space debris level rises to the explosion point,it is possible to make the near-space debris environment deteriorate sharply.Studies have shown that active debris removal is the only viable way to reduce the density of space debris.The tethered space-tug system captures the target from a distance and ensures the safety of the platform to a large extent.This paper investigates the tethered space-tug system to remove an abandoned satellite,and carries out the stability control and deorbiting research.The main contents are as follows:For the dynamic modeling of the tethered satellite system,the chaser and the target are considered as rigid bodies,and the attitude dynamics equation considering the torque generated by the tether tension is given.The tether is modeled by the bead method,the mass of the tether is concentrated on the bead point,and the damping spring model is between the bead points,and the formula for calculating the tension of each tether is given.The centroid dynamics equations of the chaser and the target are given according to the two-body dynamics.The environmental perturbation is considered in the model,including atmospheric resistance and earth oblateness perturbation.In view of the control of the tethered space-tug system,considering the flexibility of the tether,this paper studies the wave-based control(WBC)method,which can change the motion of the system and avoid collision.WBC does not require precise modeling and is highly robust.Firstly,the one-dimensional WBC controller design is analyzed and the controller parameters are determined.Finally,the WBC is extended to three dimensions to control the translation speed and motion direction of the system.Similarly,the WBC control scheme is also established for the roll,yaw and pitch channels of the chaser.The simulation results verifies the effectiveness of the WBC control algorithm.For the target deorbiting,this paper deals with three deorbit modes,namely single-burn deorbit,double-burn,and aerodynamic drag attenuation deorbit after a single burn.The single-burn deorbit takes moderate time as well as fuel consumption,and the landing site is predictable,which is the most suitable method among the three methods mentioned in this paper;double-burn method,although the landing site is controllable,but the fuel consumption is too high,almost twice the single-burn deorbit;The single-burn method consumes the least amount of fuel,but it can take a long time and the landing site cannot be determined. |
