空间飞行器大角度姿态机动控制能量优化

Fuel optimization for large angle attitude maneuver control of spacecraft

摘要:

空间飞行器姿态控制系统以开关式小推力器为执行机构, 为实现该飞行器在执行Rest-to-Rest大角度姿态机动任务的过程中消耗燃料最小化,从姿态控制律设计和姿态机动指令设计两方面出发进行能量优化.首先, 给出了空间飞行器6个脉冲式姿控发动机布局, 建立了用四元数描述的空间飞行器大角度姿态机动非线性控制系统的数学模型.在此数学模型的基础上,设计了一种空间飞行器三轴大角度姿态机动非线性PD控制律,并用Lyapunov方法证明了非线性姿态控制系统的稳定性.设计了三轴姿态控制中6个脉冲式姿控发动机的分配逻辑.为了配合开关式小推力器以脉冲宽度调制方式近似输出连续型控制量并减少燃料消耗,在非线性PD控制律中引入了3个开关门限,并应用粒子群与遗传算法优化选取这些开关门限.在Rest-To-Rest的大角度姿态机动指令设计中,提出了一种令欧拉角匀速变化的角速度和四元数指令规划方法,提高了姿态控制系统的瞬态响应品质,并相对于阶跃型指令明显减少燃料消耗.结果表明,数值仿真验证了非线性控制律的开关门限设计,以及Rest-To-Rest的大角度姿态机动指令设计在减少燃料消耗方面的有效性.

Abstract:

The optimal design for the attitude control system of a spacecraft with on-off impulse thrusters as actuators was studied. For the spacecraft actuating a large angle rest-to-rest attitude maneuver, proper attitude control law and proper attitude commands were designed to reduce the fuel consumption of the thrusters. First, the configuration of six impulse attitude thrusters on the spacecraft was given, and a nonlinear system model to describe the large angle attitude motion of the spacecraft was established using the quaternion tool. With this model, a nonlinear PD control law was designed to steer the spacecraft in actuating large angle maneuvers, and the stability of the nonlinear attitude control system was proved by the second method of Lyapunov. Then, the allocation logic of the six impulse thrusters in the three axis attitude control system was proposed. Since the nonlinear PD control law has to be implemented with the pulse width modulation technique, three switching thresholds were introduced into the nonlinear PD control law to reduce the consumption of fuel. The switching thresholds were selected using the particle swarm optimization technique. A scheme of scheduling the quaternion command for the rest-to-rest large angle attitude maneuver was proposed by steering the Euler angles to reach their aims with uniform angular rates. The scheme was helpful for improving the transient property and reducing the fuel consumption of the control system compared with the conventional step commands. Simulation results verified the effectiveness of the control law and the scheme of scheduling the commands.