火箭垂直返回双幂次固定时间收敛滑模控制方法

垂直起降可重复使用火箭返回飞行时受到复杂扰动和强不确定性影响,其姿态系统呈现出强非线性和高动态的特点.为克服扰动影响实现对姿态角指令的快速高精度跟踪,提出了一种基于双幂次固定时间收敛滑模面和固定时间收敛扰动观测器的快速高精度姿态跟踪控制器.对于返回飞行姿态控制系统中的有界匹配扰动,为避免观测器的调节过程影响控制系统的性能,在控制器的设计中引入了固定时间收敛扰动观测器,从而实现了对扰动的快速高精度估计；为实现姿态跟踪控制器的固定时间收敛,给出了基于双幂次修正项的一种双幂次固定时间收敛滑模面；基于观测器输出和双幂次固定时间收敛滑模面设计了快速姿态跟踪控制器,通过引入固定时间收敛扰动观测器的输出以补偿扰动影响,从而在允许的精度损失下去除不连续控制项以抑制滑模抖振. 最后通过返回飞行大气层内气动减速段的数值仿真验证了观测器和基于固定时间收敛扰动观测器的固定时间收敛滑模跟踪控制器的性能.

Double-order power fixed-time convergence sliding mode control method for launch vehicle vertical returning

Due to the complex disturbances and uncertainties in return process, the attitude system of vertical takeoff vertical landing (VTVL)-reusable launch vehicle (RLV) is nonlinear and high dynamic. To solve the nonlinear attitude tracking control problem with complex disturbances in the return process of VTVL-RLV, a composite fast attitude tracking control method consisting of double-order power fixed-time convergence sliding mode surface and fixed-time convergence disturbance observer (FxTDO) was proposed. The FxTDO was introduced to obtain high precision approximation of the bounded matched disturbance and avoid the influence of the observer on the performance of the control system. In order to achieve fixed-time convergence of attitude tracking controller, the double-order power fixed-time convergent sliding mode surface was given based on double-power correction terms. By introducing the disturbance approximation to directly compensate the matched lumped disturbance in double-order power fixed-time convergence sliding mode control law, the discontinuous control term was removed to reduce the chattering phenomenon at permissible loss of convergence accuracy. Simulation results of the aerodynamic deceleration flight phase revealed the effectiveness of the FxTDO and the proposed FxTDO-based fixed-time convergence sliding mode tracking control method.