Small-Scale Helicopter Blade Flap-Lag Equations of Motion for a Flybarless Pitch-Lag-Flap Main Rotor

Abstract

We derive the coupled flap-lag equations of motion, for a small-scale helicopter flybarless rotor, in the case of a rigid articulated Pitch-Lag-Flap (P-L-F) hinge arrangement. The (P-L-F) sequence is indeed much more useful for modeling the rotor dynamics of R/C helicopters. The derivation, obtained by the Lagrangian method, allows for hinge springs and viscous dampers, for both ClockWise (CW) and CounterClockWise (CCW) rotating main rotors, while keeping all hinges physically separated. Although the equations are valid for small flap, lag, and pitch angles, the exact tangential and perpendicular blade velocity expressions have been retained, hence full coupling between vehicle and blade dynamics is modeled. Additionally the paper reviews all assumptions made in deriving the model, i.e. structural, aerodynamics, and dynamical simplifications. The model has been compared with an equivalent FLIGHTLAB R rotor model, and simulation results show that the model validity is good to very good in hover and low speed, and fair to good at high speed.

Flatness Based Trajectory Generation For A Helicopter UAV

“…To train the NN model, we have used a high-order, nonlinear, helicopter flight dynamics model, based upon the work done in Ref. 45,46, although a Flightlab R 74 model applies equally well. We simulate an instantaneous engine failure starting from hover d , and then apply several sine-sweeps from 0.1 to 3 Hz, with varying amplitudes, for a duration of 3 seconds, on each control input channel separately.…”

“…Here, we have only retained the rigid-body equations of motions and the main rotor RPM (to allow for the computation of autorotative flight conditions). Indeed, the higher-order main rotor phenomena (dynamic inflow and blade flap/lag 45,46 ) may be taken into account through either (i) their corresponding steady-state expressions, and/or (ii) the addition of empirical coefficients resulting in a grey-box modeling paradigm. 47,48 By so doing we have reduced the model order, with the obvious advantage of great computational savings, see also our discussion in Ref.…”

Attitude and Flapping Angles Estimation for a Small-Scale Flybarless Helicopter Using a Kalman Filter

“…Three diverse flapping-lag-pitch hinge arrangements (F-P-L, F-L-P, and L-F-P) were investigated. In [19], the coupled flap lag equations of motion for a new hinge sequence (P-L-F) were introduced. The modelling of the main rotor dynamics for a small-scale helicopter flybarless rotor is better represented using this new arrangement.…”