可重复使用飞行器进场着陆拉平纵向控制

针对可重复使用飞行器（RLV）进场着陆拉平段的纵向控制问题，提出了反馈控制与前馈控制相结合的复合控制策略。设计反馈控制律参数，在此基础上基于时间加权高度跟踪误差/误差变化率平方积分指标优化设计前馈控制律参数。按输入补偿的前馈控制在不影响系统稳定性的前提下，提高了RLV对拉平着陆轨迹的跟踪精度，减小了RLV的接地散布。提出了基于积分器初值的控制律平滑切换方法，实现了RLV起落架释放前后不同控制律之间的平滑切换。仿真验证了拉平纵向复合控制和拉平过程中不同控制律之间平滑切换方法的有效性。 

Flare longitudinal control for approach and landing of reusable launch vehicle

To solve the flare longitudinal control problem for approach and landing of reusable launch vehicle (RLV), a compound control strategy based on combined feedback control and feedforward control is proposed. The feedback control law parameters were designed. The feedforward control law parameters were designed and optimized based on the index of time-weighted height tracking error and the integral for square of error change rate. Under the premise of not affecting the stability of the system, according to feedforward control with the input compensation, the tracking precision of RLV for the flare trajectory was improved and the ground distribution of RLV was reduced. The method of control law smooth switching was proposed by initial value of integrator, which realizes the smooth switching between the different control laws of the RLV landing gear before rand after release. Simulation verifies that flare longitudinal compound control law and the method of control law smooth switching are effective.