“Multibody Analysis of Rotorcraft-Pilot...
Transcript of “Multibody Analysis of Rotorcraft-Pilot...
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2nd IMSD, Stuttgart – Friday June 1, 2012 2nd IMSD, Stuttgart – Friday June 1, 2012
“Multibody Analysis of Rotorcraft-Pilot
Coupling”
V. Muscarello, P. Masarati, G. Quaranta
Dipartimento di Ingegneria Aerospaziale
2nd IMSD, Stuttgart – Friday June 1, 2012
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2nd IMSD, Stuttgart – Friday June 1, 2012
2 OUTLINE
Multibody Analysis of Rotorcraft-Pilot Coupling
1. INTRODUCTION
2. NUMERICAL APPROACHES
3. MODEL DESCRIPTION
4. PILOT BIOMECHANICS
5. RESULTS
6. CONCLUSIONS
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2nd IMSD, Stuttgart – Friday June 1, 2012
3 OUTLINE
Multibody Analysis of Rotorcraft-Pilot Coupling
1. INTRODUCTION
2. NUMERICAL APPROACHES
3. MODEL DESCRIPTION
4. PILOT BIOMECHANICS
5. RESULTS
6. CONCLUSIONS
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2nd IMSD, Stuttgart – Friday June 1, 2012
4 INTRODUCTION
Multibody Analysis of Rotorcraft-Pilot Coupling
Rotorcraft-Pilot Coupling Phenomena: PIO
Pilot Induced Oscillation;
Rotorcraft-Pilot Coupling Phenomena: PAO
Pilot Assisted Oscillation;
Intentional application of erroneous controls;
Consequence of insufficient or misleading cues;
Frequency range: below 1 [Hz];
Unintentional application of controls;
Caused by vibrations in the cockpit at frequencies above the bandwidth of
the pilot himself;
Frequency range: between 2 8 [Hz];
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2nd IMSD, Stuttgart – Friday June 1, 2012
5 INTRODUCTION
Multibody Analysis of Rotorcraft-Pilot Coupling
Rotorcraft Comprehensive Modeling:
Detailed aeromechanics of the rotors;
Structural dynamics of the airframe;
Flight mechanics of the vehicle;
Actuators and sensors dynamics;
Flight Control Systems;
The voluntary/involuntary behavior of the pilot;
Pilot
Rotorcraft
“The analysis of this class of problems
requires very versatile and, at the
same time, very efficient tools”
Drive Train dynamics;
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2nd IMSD, Stuttgart – Friday June 1, 2012
6 INTRODUCTION
Multibody Analysis of Rotorcraft-Pilot Coupling
Typical rotorcraft frequencies:
“Rotorcraft models need to cover all aspects of aeromechanics”
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2nd IMSD, Stuttgart – Friday June 1, 2012
7 OUTLINE
Multibody Analysis of Rotorcraft-Pilot Coupling
1. INTRODUCTION
2. NUMERICAL APPROACHES
3. MODEL DESCRIPTION
4. PILOT BIOMECHANICS
5. RESULTS
6. CONCLUSIONS
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2nd IMSD, Stuttgart – Friday June 1, 2012
8 NUMERICAL APPROACHES
Multibody Analysis of Rotorcraft-Pilot Coupling
Multibody Analysis: MBDyn
Free general purpose multibody software - http://www.mbdyn.org
Formulation: DAE
Newton-Euler equations of motion of rigid bodies;
Connections with elastic/viscoelastic internal forces
or kinematic constraints;
Possibilities to introduce deformable components:
Lumped linear/angular springs;
Non-Linear FE Beams and Shells;
Simple Aerodynamics using BE/MT approach.
Analysis:
Time marching analysis using A/L-stable linear multistep integration schemes;
Eigenvalues and eigenvectors obtained using system identification based on POD.
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2nd IMSD, Stuttgart – Friday June 1, 2012
9 NUMERICAL APPROACHES
Multibody Analysis of Rotorcraft Pilot Coupling
Linearized Analysis: MASST
Numerical code, for aeroservoelastic analysis of Rotary Wing Aircraft
Key elements:
State Space approach;
Connector of Reduced Order Models (ROM);
Availability for rotary wing technologies;
Easy integration with theory of control;
Developed in MatLab®, easily usable through a GUI;
Previous work about MASST:
P. Masarati, V. Muscarello, G. Quaranta. “Linearized aeroservoelastic analysis of rotary-wing aircraft”. In
36th European Rotorcraft Forum. Paris, France, September 7-9 2010;
P. Masarati, V. Muscarello, G. Quaranta. “Robust aeroservoelastic stability of helicopters: application to the
air/ground resonance”. In 67th AHS Annual Forum, Virginia Beach, VA, May 3-5 2011;
P. Masarati, V. Muscarello, G. Quaranta, A. Locatelli, D. Mangone, L. Riviello, L. Viganò. “An integrated
environment for helicopter aeroservoelastic analysis: the ground resonance case”. In 37th European Rotorcraft
Forum. Ticino Park, Italy, September 13-15 2011.
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2nd IMSD, Stuttgart – Friday June 1, 2012
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Modern Aeroservoelastic State Space Tools:
Sub – Structures / Dynamic Models Original
Domain
Example source
software
1. Airframe Structural Dynamics Time NASTRAN or GVT
2. Airframe Unsteady Aerodynamics Frequency NASTRAN (DLM)
3. Rotors Aeroelasticity Time CAMRAD JA
4. Drive Train Time MatLab / Simulink
5. Servo-Actuators Frequency MatLab / Simulink
6. Sensors and Filters Frequency MatLab / Simulink
7. Controllers (FCS) Time MatLab / Simulink
8. Pilot Biomechanics Time MatLab / Simulink
For each element type,
an arbitrary number of
blocks can be added
to the main model!
Items 1 4: Basic Aeroelastic Analysis;
Items 1 5: Aeroservoelastic Analysis;
Items 1 8: Closed Loop Aeroservoelastic Analysis;
NUMERICAL APPROACHES
Multibody Analysis of Rotorcraft Pilot Coupling
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2nd IMSD, Stuttgart – Friday June 1, 2012
11 OUTLINE
Multibody Analysis of Rotorcraft-Pilot Coupling
1. INTRODUCTION
2. NUMERICAL APPROACHES
3. MODEL DESCRIPTION
4. PILOT BIOMECHANICS
5. RESULTS
6. CONCLUSIONS
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2nd IMSD, Stuttgart – Friday June 1, 2012
12 MODEL DESCRIPTION
Multibody Analysis of Rotorcraft-Pilot Coupling
IAR-330 PUMA
General characteristics:
Parameter Value Units
Gross Weight 7400 [Kg]
Max speed 140 [Kts]
MR Radius 7.49 [m]
MR Solidity 0.0913 [-]
MR Lock Number 8.70 [-]
MR Speed 270 [rpm]
MR Flap frequency 1.03 [/rev]
MR Lag frequency 0.26 [/rev]
Aeroelastic data references:
W.G. Bousman, C. Young, F. Toulmay, N. E. Gilbert, R. C. Strawn, J. V. Miller, T. H. Maier, M. Costes and P.
Beaumier. “A comparison of lifting-line and CFD methods with flight test data from a research Puma helicopter.”
TM 110421, NASA, October 1996.
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2nd IMSD, Stuttgart – Friday June 1, 2012
13 MODEL DESCRIPTION
Multibody Analysis of Rotorcraft-Pilot Coupling
Airframe structural model
Generic Aerodynamic forces for
Fuselage aerodynamics;
Horizontal/Vertical tail aerodynamics.
Rigid Body element;
Main rotor aeroelastic model
Blade structure: 5 three-node non-linear beams;
Blade aero: Blade Element / Momentum Theory.
Exact kinematics of pitching mechanism;
Tail rotor model
Lateral follower force Y;
Servo-actuators
MR swashplate actuators;
TF Servo – valve;
Sensors
Accelerations on pilot seat;
Positions on pilot seat;
8 Normal modes (Modal Joint);
DPTRIM YYYY
MBDyn: IAR-330 dynamic model set-up
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14 MODEL DESCRIPTION
Multibody Analysis of Rotorcraft-Pilot Coupling
MASST: IAR-330 dynamic model set-up
Airframe structural model
6 Rigid body modes;
Stability derivatives;
Reduced order model;
Main rotor aeroelastic model
DOFs in multiblade coordinates;
3 bending & 2 torsion modes;
LTI models about trim condition;
6 hub modes for CMS connection;
Displacement set (MR hub, TR hub, pilot seats);
Tail rotor model
Lateral force Y;
Loop ;
Scheduled gain with V∞;
Servo-actuators
3 Main rotor, 1 Tail rotor ;
TF Servo - valve;
TF Dynamic compliance;
Sensors
Accelerations on pilot seat;
Positions on pilot seat;
8 Normal modes;
Pv PYvYY //
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2nd IMSD, Stuttgart – Friday June 1, 2012
15 MODEL DESCRIPTION
Multibody Analysis of Rotorcraft-Pilot Coupling
Model Validation: Isolated Main Rotor – Southwell diagram
Small discrepancies only on
the second lead-lag mode; MBDyn versus MASST
Blade collective frequencies in vacuum;
Frequencies at RPM 100 [%]
correlate very well also with
those reported by Bousman et
al.
The linear Lead/Lag damper
has been included in the
analyses, with a nominal value
of Cξ = 7000 [N*m*s/rad].
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2nd IMSD, Stuttgart – Friday June 1, 2012
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MBDyn versus MASST
Blade mode shapes in vacuum;
RPM = 100% - COLL = 0 [deg];
1st Lead-Lag 1st Flap
Good correlation of the mode
shapes, considering also the
pitch – bending couplings;
MODEL DESCRIPTION
Multibody Analysis of Rotorcraft-Pilot Coupling
Model Validation: Mode Shapes (1/3)
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2nd Flap 2st Lead-Lag
Good correlation of the mode
shapes, considering also the
pitch – bending couplings;
MODEL DESCRIPTION
Multibody Analysis of Rotorcraft-Pilot Coupling
Model Validation: Mode Shapes (2/3)
MBDyn versus MASST
Blade mode shapes in vacuum;
RPM = 100% - COLL = 0 [deg];
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3rd Flap + Torsion 1st Torsion
Good correlation of the mode
shapes, considering also the
pitch – bending couplings;
MODEL DESCRIPTION
Multibody Analysis of Rotorcraft-Pilot Coupling
Model Validation: Mode Shapes (3/3)
MBDyn versus MASST
Blade mode shapes in vacuum;
RPM = 100% - COLL = 0 [deg];
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2nd IMSD, Stuttgart – Friday June 1, 2012
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CT/ σ - Thrust Coefficient
Discrepancies at high
collective pitch values, related to
large non-linear displacements.
MODEL DESCRIPTION
Multibody Analysis of Rotorcraft-Pilot Coupling
Model Validation: Rotor performances in hover
MBDyn versus MASST
Performances in Axial Flow;
Collective pitch ranging from -2° to 15°;
CP/ σ - Power Coefficient
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2nd IMSD, Stuttgart – Friday June 1, 2012
20 OUTLINE
Multibody Analysis of Rotorcraft-Pilot Coupling
1. INTRODUCTION
2. NUMERICAL APPROACHES
3. MODEL DESCRIPTION
4. PILOT BIOMECHANICS
5. RESULTS
6. CONCLUSIONS
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2nd IMSD, Stuttgart – Friday June 1, 2012
21 PILOT BIOMECHANICS
Multibody Analysis of Rotorcraft-Pilot Coupling
Active Pilot (AP) Model:
Intentional/Voluntary action to control the vehicle;
Passive Pilot (PP) Model:
Origin: vibrations produced by the helicopter and filtered by the pilot body;
Pilot as “regulator” to maintain the steady condition;
Follow a desired pattern: “pursuit task” (predict the vehicle behavior);
Consequence: the pilot’s arm vibrates, introducing involuntary commands
into the control system;
Model: “Crossover” model proposed by McRuer & Jex.
Model: Mayo TFs pilot models introduced to investigate “Collective Bounce”
phenomena.
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2nd IMSD, Stuttgart – Friday June 1, 2012
22 PILOT BIOMECHANICS
Multibody Analysis of Rotorcraft-Pilot Coupling
Pilot Loop Closure for Collective Control:
Rotorcraft model
)(sHAP
)(sHPP
θ0 θ0AP
θ0PP
+
+
+
-
zref
zseat
zseat
zseat ..
seatPPseatrefAP
PPAP zsHzzsH )()()(000
Pilot Task: maintain the vertical position
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2nd IMSD, Stuttgart – Friday June 1, 2012
23 PILOT BIOMECHANICS
Multibody Analysis of Rotorcraft-Pilot Coupling
Active Pilot (AP) Model:
1) Crossover model:
2) Task: Maintain vertical position
3) Thrust: Blade Element Theory
4) Task TF:
ejcAPtask e
jjHjH
)()(
gMTzM
R
z
R
INT b
446
2
2
2
4
6)(
R
INMss
R
IN
sH
b
b
task
ACTIVE PILOT TF
Crossover ωc = 1.00 [rad/sec]
Time Delay τe = 0.38 [sec]
Cut-Off Frequency ωl = 3.10 [rad/sec]
LP
jctaskAP He
jHH e
1
Task + Integrator/Crossover;
Delay: Second order Padè;
2nd order Butterworth LP filter;
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2nd IMSD, Stuttgart – Friday June 1, 2012
24 PILOT BIOMECHANICS
Multibody Analysis of Rotorcraft-Pilot Coupling
1) Mayo Ectomorphic TF:
2) Passive Pilot TF:
3) High Pass filter:
3.45270.13
3.45219.5)(
2
ss
s
z
zsH
seat
collMayo
PASSIVE PILOT TF
Gear Ratio Gc = π/10 [rad/%]
Collective bar length L = 0.35 [m]
Collective bar angle θL = (35/180) π [rad]
Cut-Off Frequency ωh = 3.10 [rad/sec]
Passive Pilot (PP) Model:
1
1)(
2
0
seat
coll
L
c
seat
PPz
z
sL
G
zsH
1
1)(
2
0
seat
coll
hL
c
seat
PPz
z
sL
G
zsH
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2nd IMSD, Stuttgart – Friday June 1, 2012
25 OUTLINE
Multibody Analysis of Rotorcraft-Pilot Coupling
1. INTRODUCTION
2. NUMERICAL APPROACHES
3. MODEL DESCRIPTION
4. PILOT BIOMECHANICS
5. RESULTS
6. CONCLUSIONS
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2nd IMSD, Stuttgart – Friday June 1, 2012
26 RESULTS
Multibody Analysis of Rotorcraft-Pilot Coupling
MBDyn: Trim with Active Pilot ad Tail Rotor follower force
Trim performances in Hover and FF
Total pin joint at the CG;
Plunge motion and yaw rotations permitted;
Hover: Velocities – Modal Node Collective (AP) – TR Force (PD Controller)
The Active Pilot and the Tail
Rotor controller are able to
stabilize the motion, maintaining
the trim condition.
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2nd IMSD, Stuttgart – Friday June 1, 2012
27 RESULTS
Multibody Analysis of Rotorcraft-Pilot Coupling
Stability of the Active Pilot Model
Gain on AP model:
Gain factor on the crossover frequency;
Increasing GAP, the pilot becomes more
aggressive, destabilizing the motion;
The Passive Pilot is not
considered in this step.
Analyses have been performed
at different AP gains.
Rotorcraft model
)(sHAP
)(sHPP
θ0 θ0
AP
+ +
-
zref
zseat
zseat APG
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2nd IMSD, Stuttgart – Friday June 1, 2012
28 RESULTS
Multibody Analysis of Rotorcraft-Pilot Coupling
Stability of the Active Pilot Model
Gain on AP model: Hover
Aggressive AP is not able to reach the trim;
Increasing GAP, corrections on the collective
lever are introduce with high amplitude;
Frequency/Damping AP mode w.r.t. GAP Real/Imag part of AP mode w.r.t. GAP
LIMIT GAIN IN HOVER
MBDyn GAP = 2.00
MASST GAP = 2.15
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2nd IMSD, Stuttgart – Friday June 1, 2012
29 RESULTS
Multibody Analysis of Rotorcraft-Pilot Coupling
Stability of the Passive Pilot Model
Gain on PP model:
GPP is interpreted as a scaling of gearing ratio;
GPP can be also associated to amplifications of
the seat acceleration caused by deformations.
Small changes in the PP gearing
ratio, related to GPP, doesn’t affect
the active pilot.
A real active pilot would adapt
the gain changes of gearing ratio.
Rotorcraft model
)(sHAP
)(sHPP
θ0 θ0
AP
+ +
-
zref
zseat
zseat 1
PPG
zseat ..
θ0PP
+
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2nd IMSD, Stuttgart – Friday June 1, 2012
30 RESULTS
Multibody Analysis of Rotorcraft-Pilot Coupling
Stability of the Passive Pilot Model
Gain on PP model: Hover & FF at μ = 0.2
Perfect agreement between MBDyn/MASST;
Lower gains are required in forward flight;
Hover: Frequency/Damping w.r.t. GPP FF: Frequency/Damping w.r.t. GPP
Hover FF μ = 0.2
MBDyn GPP = 1.40 GPP = 1.30
MASST GPP = 1.40 GPP = 1.35
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Stability of the Passive Pilot Model
RESULTS
Multibody Analysis of Rotorcraft-Pilot Coupling
1 Pilot passive model; 2 Collective lever ; 3 Main rotor actuators (1,2,3);
4 Main rotor collective pitch; 5 Main rotor collective flap; 6 Airframe plunge motion;
Pilot pole eigenvector: RPC mechanism / Vertical Bounce
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2nd IMSD, Stuttgart – Friday June 1, 2012
32 RESULTS
Multibody Analysis of Rotorcraft-Pilot Coupling
Active Pilot performing maneuver:
ADS-33: Vertical maneuver
Good candidate to trigger collective bounce;
Anti wind-up on AP input: Limit integral action
of crossover model.
Saturation boundaries have
been set to +/- 5 meters;
Rotorcraft model
)(sHAP
)(sHPP
θ0 θ0
AP
+ +
-
zref
zseat
zseat
zseat ..
θ0PP
+
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2nd IMSD, Stuttgart – Friday June 1, 2012
33 RESULTS
Multibody Analysis of Rotorcraft-Pilot Coupling
Vertical displacements Collective control
Active Pilot performing maneuver:
ADS-33: Vertical maneuver
Active pilot able to follow the trajectory;
Pilot-vehicle response is very slow.
The Active Pilot model has been
designed to maintain the position
(position task). When performing
vertical maneuver the pilot model
is characterized by a velocity
task.
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2nd IMSD, Stuttgart – Friday June 1, 2012
34 RESULTS
Multibody Analysis of Rotorcraft-Pilot Coupling
Remarks: Active Pilot
The crossover model is able to stabilize the helicopter motion maintaining the
trim conditions (position task);
Pilot aggressiveness is analyzed considering a fictitious gain, GAP, in the
feedback loop, increasing the crossover frequency;
The “aggressive” active pilot is not able to reach the trim condition. The
corrections on the collective lever are introduced with high amplitude and the
strong thrust variations move the helicopter away from the reference
condition;
When performing vertical maneuver the crossover model is able to follow the
requested trajectory, even if the pilot-vehicle response is slow. In these
cases, the pilot is characterized by a velocity task, in order to reach the
requested trajectory as soon as possible;
Future research will be focused on the design of a most sophisticated active
pilot model, characterized by a task switching/scheduled approach.
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2nd IMSD, Stuttgart – Friday June 1, 2012
35 RESULTS
Multibody Analysis of Rotorcraft-Pilot Coupling
Remarks: Active Pilot
The passive pilot TF is introduced to analyze the helicopter proneness at the
collective/vertical bounce phenomena, considering different gains, GPP, in the
control loop;
Remarks: Passive Pilot
The gain GPP can be interpreted as a scaling of the gearing ratio between the
collective lever displacement and the main rotor collective pitch, or it can be
associated to amplifications of the seat acceleration caused by airframe
deformation;
The instability mechanism, in hover and forward flight, is predicted by MBDyn
and MASST. Both analyses show similar results. Thus the collective bounce
phenomena is essentially linear;
It should be noted that rotorcraft dynamics are characterized by coupled
symmetric and antisymmetric motions, whose coupling is magnified at high
flight speed. The coupling with cyclic controls and the possibility to analyze
unsteady maneuvers could represent an interesting extension of the present
research.
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2nd IMSD, Stuttgart – Friday June 1, 2012
36 OUTLINE
Multibody Analysis of Rotorcraft-Pilot Coupling
1. INTRODUCTION
2. NUMERICAL APPROACHES
3. MODEL DESCRIPTION
4. PILOT BIOMECHANICS
5. RESULTS
6. CONCLUSIONS
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2nd IMSD, Stuttgart – Friday June 1, 2012
37 CONCLUSIONS
Multibody Analysis of Rotorcraft-Pilot Coupling
Conclusions:
State of the art in the aeroservoelastic analysis of rotorcraft pilot coupling
phenomena;
Two approaches used:
1 Multibody: to investigate the detailed aeromechanics of the vehicle;
2 Linear, using comprehensive rotorcraft aeromechanics solvers;
The voluntary and involuntary interaction of the pilot with the vehicle has been
investigated with respect the collective control loop;
Both models are able to predict the instabilities generated by the voluntary
and involuntary control inputs;
Transient responses have been performed considering the vertical maneuver
prescribed by ADS-33;
Future developments: active pilot model with task switching/scheduled
approach and coupling with cyclic controls.
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2nd IMSD, Stuttgart – Friday June 1, 2012
38 CONCLUSIONS
Multibody Analysis of Rotorcraft-Pilot Coupling