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Research Papers

# Bioaeroservoelastic Analysis of Involuntary Rotorcraft-Pilot Interaction

[+] Author and Article Information
Pierangelo Masarati

Associate Professor
Dipartimento di Scienze e
Tecnologie Aerospaziali,
Politecnico di Milano,
Milano 20156, Italy
e-mail: pierangelo.masarati@polimi.it

Giuseppe Quaranta

Assistant Professor
Dipartimento di Scienze e
Tecnologie Aerospaziali,
Politecnico di Milano,
Milano 20156, Italy
e-mail: giuseppe.quaranta@polimi.it

See http://www.mbdyn.org/ for further information.

1Corresponding author.

Contributed by the Design Engineering Division of ASME for publication in the JOURNAL OF COMPUTATIONAL AND NONLINEAR DYNAMICS. Manuscript received July 15, 2013; final manuscript received August 26, 2013; published online February 13, 2014. Assoc. Editor: Parviz Nikravesh.

J. Comput. Nonlinear Dynam 9(3), 031009 (Feb 13, 2014) (9 pages) Paper No: CND-13-1182; doi: 10.1115/1.4025354 History: Received July 15, 2013; Revised August 26, 2013

## Abstract

This work presents the integration of a detailed biomechanical model of the arm of a helicopter pilot and an equivalently detailed aeroservoelastic model of a helicopter, resulting in what has been called a ‘bioaeroservoelastic’ analysis. The purpose of this analysis is to investigate potential adverse interactions, called rotorcraft-pilot couplings, between the aeroservoelastic system and the controls involuntarily introduced by the pilot into the control system in response to rotorcraft vibrations transmitted to the pilot through the cockpit: the so-called biodynamic feedthrough. The force exerted by the pilot on the controls results from the activation of the muscles of the arms according to specific patterns. The reference muscular activation value as a function of the prescribed action on the controls is computed using an inverse kinetostatics/inverse dynamics approach. A first-order quasi-steady correction is adopted to mimic the reflexive contribution to muscle activation. Muscular activation is further augmented by activation patterns that produce elementary actions on the control inceptors. These muscular activation patterns, inferred using perturbation analysis, are applied to control the aircraft through the pilot's limbs. The resulting biomechanical pilot model is applied to the aeroservoelastic analysis of a helicopter model expressly developed within the same multibody modeling environment to investigate adverse rotorcraft pilot couplings. The model consists of the detailed aeroelastic model of the main rotor, using nonlinear beams and blade element/momentum theory aerodynamics, a component mode synthesis model of the airframe structural dynamics, and servoactuator dynamics. Results in terms of the stability analysis of the coupled system are presented in comparison with analogous results obtained using biodynamic feedthrough transfer functions identified from experimental data.

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## Figures

Fig. 1

Block scheme of the vertical bounce feedback loop between pilot biomechanics and rotor aeromechanics

Fig. 2

Multibody model of the arm holding the collective control inceptor

Fig. 3

Nondimensional functions used in Eq. (1)

Fig. 4

Muscular activation levels for the 10%, 50%, and 90% collective control device reference position (muscle numbers from Table 2)

Fig. 5

Collective control BDFT (harmonic excitation)

Fig. 6

Collective control NMA (harmonic excitation)

Fig. 7

Comparison of the collective control BDFT between an unloaded inceptor and one loaded with a steady 100 Nm torque (position task, 50% reference collective rotation, harmonic excitation)

Fig. 8

Comparison of the collective control NMA between an unloaded inceptor and one loaded with a steady 100 Nm torque (position task, 50% reference collective rotation, harmonic excitation)

Fig. 9

Envelope of the collective control BDFT

Fig. 10

Envelope of the collective control NMA

Fig. 11

Vertical maneuver: vertical displacement (top), acceleration (mid), and collective control rotation (bottom)

Fig. 12

Vertical acceleration of the helicopter center of mass in hover

Fig. 13

Frames of the main rotor motion taken at azimuth increments of 72 deg during a cycle of collective bounce oscillation after the instability developed into a limit cycle oscillation

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