Reaction flywheel is a significant actuator for satellites' attitude control. To improve output torque and rotational speed accuracy for reaction flywheel, this paper reviews the modeling and control approaches of DC-DC converters and presents an application of the variable structure system theory with associated sliding regimes. Firstly, the topology of reaction flywheel is constructed. The small signal linearization process for a buck converter is illustrated. Then, based on the state averaging models and reaching qualification expressed by the Lee derivative, the general results of the sliding mode control (SMC) are analyzed. The analytical equivalent control laws for reaction flywheel are deduced detailedly by selecting various sliding surfaces at electromotion, energy consumption braking, reverse connection braking stages. Finally, numerical and experimental examples are presented for illustrative purposes. The results demonstrate that favorable agreement is established between the simulations and experiments. The proposed control strategy achieves preferable rotational speed regulation, strong rejection of modest disturbances, and high-precision output torque and rotational speed tracking abilities.
研究了采用双框架控制力矩陀螺(Double Gimbaled Control Momentum Gyroscope,DGCMG)的敏捷卫星姿态/角动量联合控制问题,针对DGCMG的饱和奇异问题,提出了基于Lyapunov的姿态/角动量联合控制方法。首先,建立了采用两个平行构型DGCMG的卫星姿态动力学模型,然后根据陀螺的力矩方程,通过可视化分析得出该构型只有内部隐奇异和饱和奇异两类奇异。隐奇异可以通过操纵律进行避免,而饱和奇异只能通过卸载方式来解决。为了避免采用推力器或磁力矩器等卸载方式带来的问题,设计了连续管理角动量的姿态/角动量联合控制器。此外,为了缩短系统的稳定时间,采用Sigmoid函数对控制器的参数选取进行了改进。该控制器完成敏捷卫星快速机动快速稳定任务的同时,还能连续调节角动量,达到姿态控制和角动量管理的折中。数值仿真结果验证了控制器的有效性。
A decoupling trajectory tracking method for gliding reentry vehicles is presented to improve the reliability of the guidance system. Function relations between state variables and control variables are analyzed. To reduce the coupling between control channels, the multiple-input multiple-output(MIMO)tracking system is separated into a series of two single-input single-output(SISO) subsystems. Tracking laws for both velocity and altitude are designed based on the sliding mode control(SMC). The decoupling approach is verified by the Monte Carlo simulations, and compared with the linear quadratic regulator(LQR) approach in some specific conditions. Simulation results indicate that the decoupling approach owns a fast convergence speed and a strong anti-interference ability in the trajectory tracking.
The problem of fault detection for linear discrete timevarying systems with multiplicative noise is dealt with.By using an observer-based robust fault detection filter(FDF) as a residual generator,the design of the FDF is formulated in the framework of H ∞ filtering for a class of stochastic time-varying systems.A sufficient condition for the existence of the FDF is derived in terms of a Riccati equation.The determination of the parameter matrices of the filter is converted into a quadratic optimization problem,and an analytical solution of the parameter matrices is obtained by solving the Riccati equation.Numerical examples are given to illustrate the effectiveness of the proposed method.
