空间绳系拖拽系统摆动特性与平稳控制

考虑了任务星与废星的姿态运动以及系统组合体的面内外姿态运动,建立了绳系拖拽离轨系统动力学与控制模型,以切向常值推力下绳系拖拽轨道转移为任务过程,分析了任务星在喷气和零动量轮的限制姿态反馈控制条件下飞行时,废星姿态摆动、系统组合体面内外摆动和任务星姿态运动的规律及相互影响关系。采用留位和阻尼控制相结合的系绳张力复合控制方法,并结合任务星姿态控制,确保绳系拖拽转移安全平稳进行。仿真结果表明:常值推力下绳系拖拽轨道转移时,牵挂点偏置诱发的废星姿态周期性摆动会激发绳系组合体的面内外同频率高阶摆动,星体姿态运动是任务星姿态扰动力矩产生的主要因素;采用张力复合控制可有效消除废星姿态摆动并保持星间相对距离,结合任务星姿态控制,可实现离轨过程的平稳与安全,大幅减少任务星的姿控能耗。

Properties of pendulum motion of tether tugging system and its stable control

Taking account of the attitude motion of tethered system, mission satellite and abandoned satellite, dynamics and control models of tethered system are established. According to the flight process under a constant thrust in the tangential direction, an attitude control of mission satellite is adopted on the basis of thrusters and momentum wheels; then, the characteristics of the oscillation of abandoned satellite, the pendulum motion of tethered system and the attitude motion of mission satellite are studied and effects among each other are analyzed. In order to ensure the flight safety of tethered system, the tether tension control which includes damp control law and position-keeping control law, and mission satellite attitude control are adopted. Numerical simulation results indicate that the regular oscillation of abandoned satellite at a specific angular frequency which caused by the offset of hanging position may arouse high order pendulum motion of tethered system during deorbiting under a constant thrust. Furthermore, the attitude motions of satellites are the main factors which bring disturbance torque to mission satellite. In addition, the oscillation of abandoned satellite is damped out and the distance between satellites is maintained by the adopted tension controller, which guarantees the flight safety and stability of tethered system combining with mission satellite attitude control and also reduces energy consuming of mission satellite.