基于视线运动模型的椭圆轨道交会最优控制

针对航天器自主交会对接实际存在的接近方位角约束, 在视线坐标系内讨论了椭圆轨道最优交会控制设计问题. 根据椭圆轨道视线动力学模型具有时变非线性的特点, 分别采用状态相关Riccati方程(state-dependent riccati equation, SDRE)方法和\theta-D方法进行了最优交会控制器设计. 考虑到实际施加的控制力沿原轨道坐标系各轴向更易于实现, 结合SDRE方法中系统输入矩阵可与系统状态量相关, 进而设计了控制力沿轨道坐标系轴向的最优交会控制器. 数值仿真表明: 两种方法均实现了带有方位角约束的交会; \theta-D控制算法计算效率更高, 而SDRE控制算法精度较高, 且可以实现控制力沿轨道坐标系各轴定向施加. 

OPTIMAL CONTROL FOR ELLIPTIC ORBITAL RENDEZVOUS BASED ON LINE-OF-SIGHT DYNAMIC MODEL

Optimal control methods for autonomous rendezvous on the elliptical orbit were discussed in line-of-sight(LOS) coordinate frame. For the rendezvous courses with constrained proximity aspects, an LOS dynamic model with respect to LOS measurement information was adopted so that LOS angle could be controlled directly. Then the rendezvous problem was formulated as a nonlinear optimal control problem. The State-Dependent Riccati Equation(SDRE) controller and \theta-D controller were derived respectively. Also an SDRE approach with the control thrust along the axis of Local Vertical / Local Horizontal(LVLH) frame was discussed for the availability of control thrust. Numerical simulations demonstrated the feasibility of the control strategies in constrained-aspect rendezvous missions. The \theta-D controller got a higher computational efficiency and lower control accuracy comparing with the SDRE controller. Moreover, the SDRE controller also could be achieved while the control thrust fixed with the LVLH axis.