Rotorcraft Real Time Damage Alleviation through Load Limiting Control

Abstract

This paper presents an in-flight damage alleviation system for rotorcraft based upon an in-the-loop structural model which provides component damage estimates as feedback to the control system for control gain adjustment. Using a dynamic inversion control system architecture coupled with an artificial neural network based damage model, a substantial increase in the lifespan of specific rotor head structural components has been found with minimal impact to the handling qualities of the rotorcraft. NomenclatureD = component damage D r = normalized component damage D f = final component damage ̇ = component damage rate n = number of cycles to failure N Z = vertical load factor q = pitch rate ̇ = pitch acceleration V z = vertical speed = vertical speed command W i = weighting factor ζ = damping ratio σ = stress θ = pitch attitude θ cmd = commanded pitch attitude ̇ = pitch rate ̈ = pitch acceleration τ = time constant ω n = natural frequency 1

Helicopter Load Factor Limit Protection Method Based on A Predictive Control Algorithm for Vertical Maneuvering

“…The basic flight control law is adopted as the command model tracking control structure, which includes the command model, inverse model, and stability loop, and its schematic diagram is shown in Figure 1. The direct restriction method of the command model given in the literature [7] is only applicable to the command model tracking control structure or dynamic inverse control structure and only to the vertical RC response type in it. In contrast, the control power restriction method based on the load factor predictive algorithm can be adapted to any control structure because the essence of the method is to restrict the control power of the collective stick, and therefore it is applicable to both the vertical RC response type and the vertical DC response type.…”

“…The neural network model and its inverse are used to predict the control margin, and the pilot's control is prompted and restricted by the joystick force sensing system, so as to realize the protection of the boundary parameters of the flight envelope. Thaiss [7] et al realized load factor protection by limiting the output of the command by the command model in the command model tracking control structure. Kimball [8] et al realized the protection of rotor shaft torque and rotation speed by designing feedback control law based on sensor data on V-22 Osprey.…”