Investigation of rotorcraft-pilot couplings under flight-path constraint below the minimum-power speed
Investigation of rotorcraft-pilot couplings under flight-path constraint below the minimum-power speed
复制标题
低于最小功率速度的飞行路径约束下旋翼机-飞行员耦合的研究
作者：
L. Lu;G. Padfield;M. Jump
在某些情况下，飞行员的闭环控制会导致人机组合系统变得微稳定甚至不稳定。无论飞行员是控制姿态还是控制飞行路径，这种情况都可能发生。本文研究了航迹约束下直升机在最低速下的稳定性问题。该工作为航迹处理质量标准提供了理论依据，特别是在所谓的动力曲线后侧的飞行。利用弱耦合系统理论，通过对直升机纵向动力学进行划分，研究了直升机纵向动力学中三个相互作用的子系统——激波模式、飞天模式和升沉模式。在一定条件下，对航迹或垂直速度的强控制会导致机-机系统不稳定，为保证喘振运动和航迹运动的稳定，反馈增益值之间存在冲突。这种冲突构成了旋翼机-飞行员耦合不良的潜在来源。如果集体控制的使用受到限制，问题就会加剧。在地面模拟和飞行试验中对这一现象进行了探讨，为理论提供了验证。
Abstract In some situations, closed loop control by the pilot can result in the combined pilot-aircraft system becoming marginally stable or even unstable. This can happen whether the pilot is controlling attitude or flight path. In this paper, an investigation into helicopter stability under flight-path constraint below the minimum-power speed is reported. The work provides a theoretical basis for flight path handling qualities criteria particularly for flight on the, so-called, back-side of the power curve. The research uses the theory of weakly coupled systems by partitioning the helicopter longitudinal dynamics to investigate three interacting subsystems – classically the surge mode, the phugoid mode and the heave mode. Under certain conditions, strong control of flight path or vertical speed is shown to drive the aircraft-pilot system unstable and a conflict is shown to exist between feedback gain values to guarantee stability of both the surge and the flight path motions. This conflict constitutes a potential source of adverse rotorcraft-pilot couplings. The problems are exacerbated in cases when the use of collective control is restricted. The phenomenon is explored in both ground based simulation and flight test to provide a verification of the theory.