中文摘要：

针对由飞轮控制的欠驱动航天器，研究了直接以飞轮转速为控制输入时航天器姿态的小时间局部可控性与可镇定性。首先，视飞轮转速为输入，将航天器与飞轮总角动量守恒的约束直接纳入系统动力学方程中。然后，利用非线性系统的可控性与可镇定性理论分析该系统方程在分别带有一个和两个飞轮时的控制特性。结果表明，仅在带有两个非共轴的飞轮时航天器的姿态才有可能满足局部可控；同时，系统已经不能被时不变光滑状态反馈渐近镇定，但至少可以被分段连续的状态反馈渐近镇定。据此，设计了基于四元数的非光滑控制器使得航天器的姿态迅速镇定，同时飞轮转速不超过最大转速，既验证了理论分析结果的正确性，又具有一定的实用意义。

英文摘要：

Small-time local controllability （STLC） and stabilizability of the spacecraft attitude underactuated by reaction wheels （RWs） were investigated with the wheel speeds as control inputs. Firstly, with the wheel speeds being treated as inputs, the conservation constraint of the total angular momentum of the spacecraft and RWs was directly brought into the dynamics of the system. Then nonlinear controllability and stabilizability theory were utilized to analyze the control property of this dynamics with one and two RWs respectively. The results show that the STLC of the spacecraft attitude is possible only when two non-coaxial RWs are available. Simultaneously, the system cannot be asymptotically stabilized by a time-invariant smooth feedback, but it still can be asymptotically stabilized at least by a piecewise continuous feedback. Accordingly~ a nonsmooth control law based on quaternion was constructed to stabilize the spacecraft attitude with wheel speeds under the saturation limits, which not only confirms the theoretical outcomes but also is practically useful.