直升机尾桨完全失效后自转着陆轨迹优化

为了研究直升机尾桨完全失效后自转着陆的最优轨迹和操纵过程，建立相应的飞行动力学模型并采用最优控制方法进行计算分析。建立直升机6自由度刚体飞行动力学模型，在模型中加入可以描述尾桨完全失效和自转着陆阶段发动机出轴功率以及旋翼转速变化的相关方程，并将直升机尾桨完全失效后的自转着陆问题转换为非线性最优控制问题进行求解。以某型号单旋翼带尾桨直升机为样机，计算空中停车自转着陆过程，并与飞行试验数据进行对比，验证了所建模型和最优控制方法的准确性。计算分析该型号直升机在以巡航速度下前飞时，尾桨完全失效后自转着陆的最优轨迹和操纵过程。从结果可以看出：尾桨完全失效时，直升机在旋翼反扭矩的作用下会产生较大的偏航角速度和侧滑角变化，进而产生复杂的耦合运动，驾驶员在关闭发动机进行自转着陆操作的同时，还需要通过操纵横向周期变距稳定滚转角，并以侧滑的方式来稳定横航向的姿态角，最后安全着陆。计算得到的最优轨迹和操纵过程，与工程试飞得出的定性的结论和建议相符。

Helicopter autorotation landing trajectory optimization after tail-rotor total failure

The optimal landing trajectory and control process of helicopter autorotation after tail-rotor total failure is studied using optimal control method.A six-degree-of-freedom rigid-body flight dynamic model was developed with equations describing the tail-rotor total failure and the available shaft power as well as the rotor speed variation in the autorotation landing procedure.The autorotation landing procedure after tail-rotor total failure was transcribed into an optimal control problem and solved by numerical method.A single-rotor heli-copter with tail rotor was taken as the sample,and the calculated optimal autorotation landing procedure in en-gine failure was in good agreement with the flight test data,which shows that the flight dynamic model and the optimal control method are feasible.Finally,the helicopter optimal autorotation landing procedure after tail-ro-tor total failure in cruising speed was investigated,and the results show that:when the tail-rotor fails,the air-frame will experience large variations of yaw rate and sideslip angle under the effect of rotor anti-torque,which leads to a complex coupled flight.Therefore,the pilot who turned off the engine and is operating the autorota-tion landing needs an extra series of controls to stabilize the roll and yaw attitude through lateral cyclic pitch and sideslip.The optimal trajectory and the control process are in line with the qualitative conclusions and rec-ommendations obtained from the engineering flight tests.