Dynamic Stability of a Helicopter with an External Suspended Load

Abstract

A simplified but comprehensive model for helicopter and external suspended load, based on the linear superposition of effects, is defined. The coherence of the external load modal response and of the helicopter response to control input is verified through available reference data. Finally, the impact of the slung load on the overall system dynamic stability, on the helicopter response to control input, and on flight qualities is assessed. Nomenclatureforces vector, N DOF degrees of freedom F force vector, N f residual g gravity acceleration, m/s 2 i, j, k unit vectors along x, y, z axis J x , J y , J z , J xz moments of inertia, kg · m 2 K suspension line elastic constant, N/m K G gravity forces vector, N L suspension line length, m [L BE ] rotation matrix from body to inertial axes M, N moments w.r.t. y and z axes, Nm m mass, kg p, q, r angular speed w.r.t. x, y, and z axes, rad/s R position vector, m S reference area, m 2 u, v, w velocity components along x, y, and z axes, m/s V velocity vector, m/s X, Y, Z forces along x, y, and z axes, N [X] states vector L elongation vector (cable)

Quadrotor Robust Fractional-Order Sliding Mode Control in Unmanned Aerial Vehicles for Eliminating External Disturbances

“…where m L is the mass of the load. Furthermore, the aerodynamic drag of this is expressed [28][29][30][31].…”