Investigation of the Effectiveness of Dynamic Seat in a ...

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AIAA Modeling and SimulationTechnologies Conference and Exhibit6-9 August 2001 Montreal, Canada

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AIAA 2001-Investigation of Effectivenessof the Dynamic Seatin a Black Hawk Flight SimulationWilliam W.Y. ChungCharles H. Perry, Jr.Norman J. BengfordLogicon Operations & ServicesMoffett Field, CA

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INVESTIGATION OF EFFECTIVENESS OF THE DYNAMIC SEATIN A BLACK HAWK FLIGHT SIMULATION

William W.Y. Chung*Chuck Perry

Norm BengfordLogicon Operations & Services

Moffett Field, California

AbstractLow cost motion devices have been sought to providemotion cues in ground-based flight simulators to meetmission objectives. The ability to provide high frequencyvibrations makes the dynamic seat attractive to helicoptertraining applications. Previous studies have found thatdynamic seats enhance the realism of the cockpit and affectpilot workload. This investigation used a three degree-of-freedom dynamic seat, i.e., heave, surge, and sway, withlimited travels in a research simulator configured as a UH-60Black Hawk. The seat's effectiveness was studied usingacceleration/deceleration, bob-up/bob-down, hover, pirouette,sidestep, and vertical landing maneuvers. Results from fourdifferent motion cueing levels, i.e., the dynamic seat,hexapod-like system, hexapod-like plus seat shaker, andlarge travel plus high frequency vibrations, found thedynamic seat has positive subjective effects in some of themaneuvers. However, no significant objective performanceeffects were found due to the dynamic seat.

IntroductionLow cost alternatives to traditional motion platforms havebeen sought to provide motion cues in ground-based flightsimulators to meet mission objectives. One method thathas been shown to be effective is the dynamic seat, whichprovides high-frequency/low-amplitude motions at the pilotstation. Subjectively, high frequency vibration cues providefamiliar cockpit oscillations due to structure, rotordynamics, and airspeed for a helicopter flight simulation.Objectively, the limited onset cues may aid the pilot todevelop similar control strategies in meeting missionrequirements.

Previous studies1'2 have shown that there are benefits inusing limited-travel vibration devices in helicoptersimulations, especially as a training device. White1 foundthere was a significant difference in collective activity in abob-up task using an idealized helicopter simulation withand without a g-seat. The g-seat had two independentactuators in heave degree-of-freedom (DOF) and was mountedon a three DOF motion platform, i.e., heave, pitch, and roll.

* Senior member.

Copyright ©2001 by the American Institute of Aeronautics andAstronautics, Inc. No copyright is asserted in the United States underTitle 17, U.S. Code. The U.S. Government has a royalty-free license toexercise all rights under the copyright claimed herein for GovernmentalPurposes. All other rights by the copyright owner.

The cockpit had a field-of-view (FOV) of 48 degrees inazimuth and 36 degrees in elevation. White also reports thatpilots were more consistent in maintaining a linearrelationship between collective activity and time to impactin a hurdle task with the g-seat. Pilot comments in thisstudy gave preference to the use of the g-seat.

Greig2 investigated the effectiveness of a multi-axis dynamicseat in the simulation of a Lynx helicopter on the LargeMotion System (LMS) at UK's Defence Research AgencyAdvanced Flight Simulator (AFS). The dynamic seat had 5independent hydraulic actuators to produce three DOFmotion in heave, surge, and sway. The LMS has five DOF,i.e., heave, sway, roll, pitch, and yaw, and a FOV of +/- 63degrees in azimuth and 24 degrees in elevation. The studyfound that subjective pilot ratings and comments favor theuse of a dynamic seat in the five tasks evaluated, i.e.,sidestep, quick hop, lateral jinking, spot turn, and NoEcourse.

The Joint Shipboard Helicopter Integration Process (JSHEP),a Navy program sponsored by the Office of the Secretary ofDefense, was initiated to investigate the minimum ground-based simulation requirements to develop the launch andrecovery operational envelope. Among many JSHIPinvestigation objectives, a multi-axis dynamic seat, Figure1, that was similar to Greig's investigation was one of thesimulation cueing devices evaluated. For this purpose, aUH-60 Black Hawk motion-based flight simulationexperiment was developed at NASA Ames Research Center'sVertical Motion Simulator (VMS), Figure 2, using sixADS-33D3 maneuvers. The JSHIP simulator cockpit has aFOV of 220 degrees in azimuth and 70 degrees in elevation.

Four different motion cueing levels were chosen toinvestigate the effects of the dynamic seat. The effectivenessof the dynamic seat was then determined by comparingpilots' workload, the perceived vehicle performance, and taskperformance in six selected maneuvers.

Experiment DescriptionMath ModelA high fidelity mathematical model of the UH-60A BlackHawk known as Gen Hel4 was used in the investigation.The real-time simulation had a frame rate of 100 Hz. Inhover and low speed, the Black Hawk was configured to havean augmented angular rate command system, and the

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collective controlled vertical acceleration. The angular ratefrequency responses at hover generated by a handlingqualities analysis program, CIFER35, are shown in Figure3, and the heave control response is shown in Figure 4.

Motion CueingFour levels of motion cueing were developed to investigatethe effects of the dynamic seat. They are:

I. The 3-DOF dynamic seat: Uses all three DOF of thedynamic seat, i.e., heave, sway, and surge. The dynamicseat provided high frequency heave and lateralvibrations, onset cues for heave, sway, and surge, andsustained sway and surge motion cues.

II. Hexapod-like travel: The VMS was driven by adaptivemotion drive algorithms developed for a hexapodmotion system6'7 with six 60-inch stroke actuators.

III. Hexapod-like travel plus dynamic seat with only heavemode: The VMS was driven the same way as Level II.The dynamic seat was activated in heave DOF only as aseat shaker to provide the vertical vibration cues.

IV. Large motion travel plus 2-DOF dynamic seat: FullVMS travel was utilized to achieve the best possiblemotion fidelity. VMS was driven by the standardclassical motion drive algorithms. The dynamic seatwas activated in two DOF, i.e., heave and sway, tosupplement the large motion travel with high frequencyvibration cues. The dynamic seat commands, whichprovided sustained surge and sway components, weredisabled.

Level I motion represents a low-cost option in providingmotion cues. Level II represents a motion cueing fidelitythat is common to the training community. With theaddition of a seat shaker feature, any difference betweenLevel II and IE could be attributed directly to the effect ofhigh frequency heave vibration. Level IV represents the bestpossible ground-based motion cueing fidelity by using thefull translational travel envelope of the VMS.

Displacement, rate, and acceleration limits of the VMS and ahexapod-like system are shown in Table 1. The small-amplitude frequency responses of the VMS are plottedagainst the FAA Advisory Circular 120-638 motionspecifications as shown in Figure 5. The motion fidelityaccording to Ref. 9 for all six DOF is shown in Figure 6.Another important motion fidelity factor, the lateraltranslational motion relative to simulator roll motion, tomaintain the proper specific force direction, is low for thehexapod-like case (Level n and III), and is high for the largemotion case (Level IV), according to Ref. 10.

Motion Cueing - Dynamic SeatA multi-axis dynamic seat11 provided by the Army ApacheTraining Command was integrated in one of the VMS'sinter-changeable cabs. The dynamic seat has fourindependent actuators to provide three DOF of motion, i.e.,

heave, sway surge, and. The performance of each actuator isshown in Table 2. The small-amplitude frequency responsesof the four actuators are shown in Figure 7.

The high frequency heave vibration cues were generated bythe seat pan and driven directly according to four per rev ofthe UH-60 rotor rpm, i.e., at 17 Hz. According to pilotcomments, one per rev high frequency lateral vibration cueswere added to the back pad to mimic the UH-60 cockpitvibration characteristics during flight. The magnitude ofheave vibrations was adjusted based on the Bob-Up/Bob-Down flight test data. The dynamic seat's gains andfrequency content were adjusted to match the power-spectraldensity of the vertical acceleration sensor response takenfrom the flight test as shown in Figure 8. The onset cuesin heave due to pilot control inputs and/or flight conditionshave four components, which are translational lift,collective, normal acceleration, and airspeed. Thetranslational lift provides the vibrations due to the change ininflow orientation between the forward and aft portions ofthe rotor disk in the speed range between 20 and 30 knots.

Sustained sway acceleration cues were developed by movingthe back pad laterally as a function of pilot-station lateralaccelerations. Onset lateral acceleration cues were generatedby feeding roll angular acceleration and the high frequencycomponent of lateral acceleration to drive the back pad inlateral motion.

Sustained deceleration was generated by moving the back padforward and the seat pan downward synchronously.Sustained acceleration was developed by moving the backpad aft and the seat pan upward together. Onset longitudinalacceleration cues were generated by feeding pitch angularacceleration and the high frequency component oflongitudinal acceleration to drive the back pad fore and aft.

Visual CueingThe cockpit, as shown in Figure 9, with a wide field-of-view(FOV) display system, producing 220 degrees in azimuthand 70 degrees in elevation, was specially designed anddeveloped for the JSHIP experiment. The primary imagegeneration system is a five-channel E&S ESIG 4530 systemoperating at 60 Hz with a transport delay measured at 60msec. The projection system used a projector-mirror designwith five BARCO projectors.

A high resolution LHA visual model, LHA-5 USS Peleliu,was used for all test maneuvers. The model consists of3000 textured polygons and employs 4 levels-of-detail. AnE&S 3-Dimensional (3D) sea wave model providedadditional wave dynamics relative to wave heights andperiod.

Aural CueingThe simulator cab had a stereo sound system with sixspeakers and one sub-woofer around the pilot to provide highquality aural cues that included main rotor, tail rotor, engine,

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transmission, air, and landing gear as functions of collectivecontrol and flight conditions. Sound cues were evaluated byUH-60 pilots and were found to be representative of the UH-60 in test tasks evaluated.

Task Description

Six maneuvers modified from ADS-33D for shipboardoperations were evaluated in the investigation. They wereAcceleration/Deceleration, Bob-up/Bob-down, Hover,Pirouette, Sidestep, and Vertical Landing. Descriptions ofmaneuvers and performance criteria are presented in Ref. 12.Four experienced Army test pilots participated in thisevaluation.

An additional test was done fixed-base with the dynamic seaton and off using a modified Bob-Up/Bob-Down maneuver toevaluate the effectiveness of the dynamic seat independent ofplatform motion. Instead making a Bob-Down maneuverimmediately after a brief stabilization at the top, pilots wereinstructed to maintain stabilization for at least 10 secondsbefore initiating a Bob-Down. Three UH-60 pilots (twoNASA and one Army) participated in this test.

ResultsSubjective EvaluationsHandling Qualities Rating (HQR)13 results for the six ADS-33D maneuvers are shown in Figure 10. Results from the3-DOF dynamic seat, Level I, compare well with the largemotion plus 2-DOF dynamic seat, Level IV, exceptAcceleration/Deceleration and Sidestep, where maneuvers insurge and sway DOF are more dominant. Heave vibrationcues do improve the HQR for most of the maneuvers whencomparing Level III motion with Level II motion.

HQR results for the fixed-base Bob-Up/Bob-Down task withthe dynamic seat on and off are shown in Figure 11. AMotion Fidelity Scale9 (MFS), as shown in Table 3, wasused to subjectively determine consistency between perceivedvisual cues and motion cues. MFS results with the seat onand off are also shown in Figure 11.

Objective Performance DataObjective performance data were analyzed for two testmaneuvers, i.e., Bob-Up/Bob-Down, and Vertical Landing.Both maneuvers emphasized the vertical DOF, which wasrelevant to VMS large motion and the dynamic seat'sprimary motion cueing characteristic, i.e., heave.

In the Bob-Up/Bob-Down task, the simulated Black Hawk'saltitude offset at the lower hover position was analyzed toinvestigate the pilot's altitude stabilization performance afterthe bob-down. Maximum descent speed was also analyzedto investigate the pilot's vertical speed control relative to thebob-down task. Both results are shown in Table 4.

In the Vertical Landing task, the pilot's landing spot offsetin longitudinal and lateral directions were analyzed as well asthe maximum descent speed. Results are shown in Table 5.

In the fixed-base Bob-Up/Bob-Down test, the simulatedBlack Hawk's altitude offset at the lower hover position andthe maximum descent speed with and without the use of thedynamic seat are shown in Table 6.

Power spectral density (PSD) of the collective and pilot'scut-off frequency were analyzed to characterize the pilot'sinner-loop response that was related to work load and thetask. The PSD directly reflects pilot control magnitude inthe frequency domain. The cut-off frequency is defined as ameasure of the pilot's control activity bandwidth. When theaircraft's bandwidth exceeds the task bandwidth, the pilotcut-off frequency approaches the pilot crossover frequencyand gives a good approximation of the task bandwidth.14

The purpose of using these measurements was to investigatethe motion cueing effects in pilot control strategy andaggressiveness. Studies have shown that improved motionfidelity has led to increases in pilot's gain and crossoverfrequency.15'16 Consequently, higher pilot gain leads tolower control PSD.

Average Root-Mean-Square (RMS) of the collective PSDand average pilot cut-off frequencies for four different levelsof motion cueing conditions are shown in Table 4 for theBob-Up/Bob-Down maneuver and in Table 5 for the VerticalLanding. Average RMS of the collective PSD, and pilot'scut-off frequency of the fixed-base Bob-Up/Bob-Down testare shown in Table 6.

DiscussionSubjective Data - HQRAs shown in Figure 10, according to the average HQRs,Level IV motion shows the best match with the flight testdata among all six ADS-33 maneuvers. Level ffl alsoshows good results when compared with the flight test data.The differences between Level EH and IV are minimal.Overall, pilots gave good marks to Level IV on motioncueing fidelity, citing that there was no negative cueing andthat the realism was good.

Level I motion shows a good match in mean HQR with theflight test data in Hover and Vertical Landing tasks. Inanother vertical DOF task, Bob-Up/Bob-Down, the dynamicseat also fares well relative to the flight data with a meanHQR difference of 0.25 (AL_I/Flight=0.25). Level I has theworst mean HQR in Acceleration/Deceleration (AL.IAnight=0.85) and Sidestep (A^^g^ =0.5) tasks, which may beattributed to the lack of motion travel in those two DOF.Level I also has the largest standard deviation in Pirouette(aL.!=1.29), Sidestep (0^=1.0), and Vertical Landing (a^r=0.63). The widespread ratings suggest there is aninconsistency in pilots' determination in their workload andvehicle performance relative to the task. Some pilots



commented that using the back pad to provide sustainedsway cues was unnatural because only the upper bodymoved.

Level II motion shows a poor match in mean HQR relativeto the flight test data (AL.II/FHght >0.5) forAcceleration/Deceleration (AL_H/FIight =0.65), Hover (AL.,I/Fliglu=0.75), and Sidestep (AL_Il/FUglu =0.8). Level II has thelargest standard deviation in Acceleration/Deceleration (aL_n=0.96), and Bob-Up/Bob-Down (aL.n=1.15).

Level III improves the mean HQR relative to flight test datain Acceleration/Deceleration (AL_III/LII=0.25), Hover (AL.III/LII=0.75), Sidestep (AL.III/L.n =0.68), and Vertical Landing (AL_m/L-ii =0.25) tasks. Level HI matches very well with theflight test's mean HQR in Bob-Up/Bob-Down (AL.III/Flight=0.17), Hover (AL.IiyFlight =0), Sidestep (AL_III/Flight =0.12), andVertical Landing (AL_in/FUght =0.25). The results suggest thatthere is a benefit of having the high frequency heavevibration in a motion platform.

Level IV, the large motion travel and the 2 DOF dynamicseat, matches well with the mean HQR from the flight testin Acceleration/Deceleration (AL_IV/Flight =0.2), Bob-Up/Bob-Down (AL.IV/Flight =0), hover (AL_IV/Flight =0.29), and VerticalLanding (AL.rv/Flight =0.14).

Subjective Data - Fixed-BaseFrom Figure 11, with the dynamic seat on, the mean HQRof the Bob-Up/Bob-Down task improves by 0.5 relative tothe seat-off condition. The standard deviation of the meanHQR with the seat on (o>seat-on=0-71) is also smaller thanwith the seat off (aSeat_on= 1.325). Both results indicate animprovement in pilots' workload and their determination ofthe vehicle performance when the dynamic seat was on.

Motion Fidelity Scale results in Figure 11 show that pilotswere less objectionable to the cueing differences between theflight response perceived from visual and the motion cueswhen the dynamic seat was on. All three pilots found theonset cues were helpful and recommended the use of the seatfor the Bob-Up/Bob-Down task. Two of the pilotsrecommended the use of the vibration cues.

Objective Data - Bob-Up/Bob-DownFrom Table 4, the average altitude stabilization error at thelower hover position after a bob-down for all four motioncueing levels are very similar and are well within thesatisfactory performance criterion, i.e., +/- 3 ft, for the task.Level IV motion has the smallest standard deviation (aL_IV=0.33 ft), but differences are relatively small.

There is little difference in average maximum descent speedamong the four motion cueing levels. Level I motion andLevel II motion, however, have larger standard deviations,i.e., 2.82 ft/sec and 3.17 ft/sec respectively, which indicatespilots were not as consistent in their vertical speed control.The mean standard deviations for the other two motion

cueing conditions are 0.86 ft/sec for Level III andl.08 ft/secfor Level IV.

There is very little difference in average collective RMS andpilot cut-off frequency in this task. With platform motionon, i.e., Level II, III, and IV, the data show a trend withlower collective RMS and higher pilot cut-off frequency asthe motion cueing fidelity increases from Level II to IV.This trend is consistent with the concept that pilot's gainand crossover frequency increases as the motion cueingfidelity improves. The increased pilot gain subsequentlyleads to lower control RMS. The 3-DOF dynamic seat,Level I, however, has the lowest collective RMS and a pilotcut-off frequency higher than the two hexapod motion cueingconditions which contradicts the trend. One possibleexplanation could be found in the pilot comments where allpilots explicitly indicated that they relied more on visualcues such as the superstructure to judge the translational ratewhen platform motion was absent.

Objective Data - Vertical LandingFrom Table 5, landing spot offsets in longitudinal andlateral directions for all four motion-cueing levels aresimilar. No obvious trends could be found. Only Level IVmotion had an average longitudinal offset that was withinthe satisfactory performance criterion, i.e., +/- 1 ft.

There is an obvious trend in the average maximum descentspeed, where the maximum descent speed decreases as themotion fidelity increases from Level I through Level IV.This result is consistent with the finding from a PIO study17

and shows pilots are more conscious of the descent speed asthe motion fidelity improves.

The difference in average collective RMS and pilot cut-offfrequency was relatively small among the four motioncueing levels. The large motion travel plus 2-DOF dynamicseat, Level IV, had the least average collective RMS and thepilot cut-off frequency suggests pilots might be easing offthe collective due to pronounced vertical speed cues. Thesmall standard deviations under the Level IV motion, i.e.,0.02 inch for collective RMS, 0.01 rad/sec in pilot cut-offfrequency, and 0.77 ft/sec in the maximum descent speed,suggest pilots were more consistent in controlling thevertical speed in Level IV than in the other three levels.

Objective Data - Fixed-BaseFrom Table 6, the altitude error when stabilizing after thebob-down for the Bob-Up/Bob-Down task is improved whenthe dynamic seat is on, 1.12 ft vs. 1.52 ft when the dynamicseat is off. There is little difference in the other threeobjective measurements, which suggests the dynamic seathelps in improving realism of the Bob-Up/Bob-Down taskand the task performance, but not pilots' perception of thevertical speed and their control activities.



ConclusionsThere are benefits to use the dynamic seat in ground-basedflight simulations. However, dynamic seat alone may notbe adequate to meet certain mission requirements.

Addition of high frequency heave vibrations to the hexapod-like system has positive effects both subjectively andobjectively.

Large motion travel with the 2-DOF dynamic seat has theclosest representation of the flight.

References

1. White, A.D.: "G-Seat Heave Motion Cueing forImproved Handling in Helicopter Simulators," AIAA-89-3337-CP, 1989.

2. Greig, I.: "Evaluation of a Multi-Axis Dynamic CueingSeat for Use in Helicopter Training Devices," DefenceResearch Agency, United Kingdom, I/ITSEC 1996, Orlando,FL, November, 1996.

3. Aeronautical Design Standard, Handling QualitiesRequirements for Military Rotorcraft, ADS-33D, July 1994.

4. Hewlett, J.J.: UH-60A Black Hawk EngineeringSimulation Program: Vol. I - Mathematical Model, NASACR-166309, December 1981.

5. Tischler, M. B., Cauffman, M.G.: "Frequency-ResponseMethod for Rotorcraft System Identification: FlightApplications to BO-105 Coupled Rotor/FuselageDynamics," Journal of the American Helicopter Society,Vol 37, No 3, pgs 3-17, July 1992.

6. Parrish, R.V., Dieudonne, J.E., Bowles, R.L., andMartin, Jr., D.J., "Coordinated Adaptive Washout forMotion Simulators," Journal of Aircraft, Vol. 12, No. 1,Jan., 1975, pp. 44-50.

7. Dieudonne, J.E.; Parrish, R.V.; and Bardusch, R.E.: "AnActuator Extension Transformation for a Motion Simulatorand an Inverse Transformation Applying Newton-Raphson'sMethod", NASA TN D-7067, 1972.

8. AC-120-63, Helicopter Simulator Qualification, U.S.Department of Transportation, Federal AviationAdministration, October 1994.

9. Schroeder, J.A.: "Helicopter Flight Simulation MotionPlatform Requirements," NASA/TP-1999-208766, July1999.

10. Mikula, J.; Chung, W.W.; and Tran, D.: "MotionFidelity Criteria for Roll-Lateral Translational Tasks,"

AIAA Modeling and Simulation Technologies Conference,Portland, Oregon, AIAA 99-4329, August, 1999.

11. Corlyon, P. and Humphrey, T.: "Force and VibrationCueing with a Multi-Axis Dynamic Seat," I/ITSEC 1999,Oriando, FL, November, 1999.

12. Roscoe, M.F.; Wilkinson, C.H.; and VanderVliet,G.M.: "The Use of ADS-33D Useabie Cue EnvironmentTechniques for Defining Minimum Visual FidelityRequirements," AIAA Modeling and SimulationTechnologies Conference, Montreal, Quebec, Canada, AIAA2001-4063, August 2001.

13. Cooper, G. E., and Harper, R. P., Jr.: "The Use ofPilot Rating in the Evaluation of Aircraft HandlingQualities," NASA TN D-5153, April 1969.

14. Blanken, C.L. and Pausder H.-J.: "Investigation of theEffects of Bandwidth and Time Delay on Helicopter Roll-Axis Handling Qualities," Journal of the AmericanHelicopter Society, July 1994, Vol. 39 No. 3, p24-33.

15. Stapleford, R.L.; Peters, R.A.; and Alex, F.R.:"Experiments and a Model for Pilot Dynamics with Visualand Motion Inputs, " NASA CR-1325, 1969.

16. Jex, H.R.; Magdaleno, R.E.; and Junker, A.M.: "RollTracking Effects of G-Vector Tilt and Various Types ofMotion Washout," NASA CP-2060, November 1978, pp.463-502.

17. Schroeder, J.A.; and Chung, W.: "Simulator PlatformMotion Effects on Pilot-Induced Oscillation Prediction,"Journal of Guidance, Control, and dynamics, May-June2000, Vol. 23, No. 3, p438-444.



Table 1. VMS and Hexapod-Like operational limits

Axis

RollPitchYaw

LongitudinalLateralVertical

DisplacementVMS

±18±18±24±4

±20±30

Hexapod-Like±18±18±24±4±4

3.3 up/ 2.5 down

Velocity

±40±40±40±4±8

±16

Acceleration

±115±115±115±10±16±24

All numbers, units ft, deg, sec

Table 2. System limits of the Dynamic Seat

DisplacementVelocityAcceleration

Seat-Pan (heave)± 0.59 inch± 2.4 in/sec± 39.4 in/sec2

Back- Pad (sway)± 0.59 inch± 2.4 in/sec± 39.4 in/sec2

Back-Pad (Surge)± 0.59 inch±0.8 in/sec± 39.4 in/sec2

Bucket (heave)± 0.59 inch± 2.4 in/sec± 39.4 in/sec2

Table 3. Motion fidelity scale

High Fidelity

Medium Fidelity

Low Fidelity

DescriptionMotion sensations are not noticeably differentfrom those of visual flightMotion sensations are noticeably different fromthose of visual flight, but not objectionableMotion sensations are noticeably different from thoseof visual flight and objectionable

Score1

2

3

Table 4. Objective data for Bob-Up/Bob-Down task

Bob-Up/Bob-Down

Altitude error(lower hoverposition),., ftMaximumdescent speed,ft/secRoot-Mean-Square,Collective,inchesPilot cut-offfrequency,rad/sec

Average1 standarddeviationAverage1 standarddeviationAverage1 standarddeviation

Average1 standarddeviation

3-DOF dynamicseat (Level I)

1.450.57

-10.832.82

0.3720.10

1.340.29

Hexapod likeonly (Level II)

1.360.46

-11.473.17

0.4450.12

1.280.26

Hexapod like +seat shaker(Level III)

1.10.64

-11.870.86

0.4350.08

1.260.17

Large motion +2-DOF dynamicseat (Level IV)

1.410.33

-11.681.08

0.4150.12

1.370.31



Table 5. Objective data for the Vertical Landing task

Vertical Landing

Landing spotoffset,longitudinal, ftLanding spotoffset, lateral, ft

Maximumdescent speed,ft/secRoot-Mean-Square,Collective,inchesPilot cut-offfrequency,rad/sec

Average1 standarddeviationAverage1 standarddeviationAverage1 standarddeviationAverage1 standarddeviation


3-DOF dynamicseat (Level I)

1.271.19

1.050.74

-4.772.43

0.70.2

0.930.16

Hexapod likeonly (Level II)

1.11.04

1.180.8

-4.552.33

0.750.11

0.9250.15

Hexapod like +seat shaker(Level III)

1.350.54

1.190.73

-3.721.58

0.620.22

0.910.08

Large motion +2-DOF dynamicseat (Level IV)

0.540.34

1.291.33

-2.870.77

0.630.02

0.830.01

Table 6. Objective data for a Bob-Up/Bob-Down task in fixed-base

Bob-Up/Bob-Down(Fixed-Base)

Altitude error(lower hoverposition), ftMaximumdescent speed,ft/secRoot-Mean-Square,Collective,inchesPilot cut-offfrequency,rad/sec

Average1 standarddeviationAverage1 standarddeviationAverage1 standarddeviation


Dynamic SeatOn1.120.47

-13.303.32

0.620.2

1.220.18

Dynamic SeatOff1.520.32

-13.693.19

0.580.23

1.200.19



Figure 1. 3 degree-of-freedom (heave,surge, and sway) dynamic seat

Figure 2. Vertical Motion Simulator (VMS)

1.0 10 20Frequency (rad/sec)

Roll rate/Lateral stick (rad/sec/in)———— Pitch rate/Longitudinal stick (rad/sec/in)------ Yaw rate/Pedal (rad/sec/in)

Figure 3. Angular rate response of thesimulated UH-60 Black Hawk

MIs

1.0 10Frequency (rad/sec)

Normal acceleration/Collective (ft/sec2/in)

Figure 4. Simulated UH-60 Black Hawkcollective response



CDE 0

l-io

10 10U 10

101

Frequency (Hz)Logitudinal acceleration responseVertical acceleration responsePitch acceleration response

10Frequency (Hz)

Roll acceleration responseLateral acceleration responseYaw acceleration response

Figure 5. VMS frequency response vs. FAA AC 120-63 motion system specification

100 h

§

6fc

•8

O"fi 02 <&*1u 2C3 1~H

£ ®

§£

Angular Rate Specific force

Lowfidelity

Mediumfidelity

Highfidelity

oA.

•Lowfidelity

Medium2^ fidelity

High "fidelity

100

S

S

§

§Ph

ase

dist

ortio

n in

deg

rees

@ 1

rad/

sec

0.2 0.4 0.6 0.8 1.0

Angular Gain@ 1 rad/sec

Roll Pitch YawLarge motion O A DHexapod-iike • A, •

0 0.2 0.4 0.6 0.8 1.0

Translational Gain@ 1 rad/sec

Surge Sway HeaveLarge motion O A DHexapod-like • A •

Figure 6. Motion cueing fidelity of the experiment



-400

1.0

Frequency (rad/sec)Seat pan (heave) displacement response

——————— Fore-and-aft (surge) displacement response— - - - - - - - - - Lateral (sway) displacement response— - - — - - Bucket (not used) displacement response

Figure 7. Dynamic seat actuator frequencyresponse

FREQUENCY (RAD/SBC)

——— UH-60 pilot station vertical acceleration PSD, flight test data———- UH-60 pilot station vertical acceleration PSD, JSHIP Level IV............. UH-60 pilot station vertical acceleration PSD, JSHIP Level I

Figure 8. Auto-Spectrum of normal accelerationof flight test, large motion, and the dynamic seat(ft/sec2)2

Figure 9. Field-of-view inside the cockpit



HandlingQualitiesRating

Inadequate

no(4) (5) (6) | (4)

(4)

Satisfactory

Level (L) IV III II IAccel/Decel

LIV III II I LIV III II I LIV III II I LIV III II IBob-Up/ Hover Pirouette Sidestep

Bob-Down u S.DOF Dynamic SeatFlight Test - Day LII Hexapod only

LHI Hexapod + Seat ShakerLIV VMS + 2-DOF Dysnamic Seat <#>number of runs

LIV III II IVerticalLanding

Qmean• standard deviation

Figure 10. Handling Qualities Ratings of six ADS-33D maneuvers

7

HandlingQualities 6Rating

5

4

3

2

1

Low

Inadequate"~ " Motion

FidelityAdequate Scale

Medium

h-J. +-TFHigh

Satisfactory

C)-f1

On Off On OffDynamic Seat Dynamic Seat(Fixed-Base) (Fixed-Base)

Figure 11. Handling Qualities Ratings and Motion Fidelity Scales of thefixed-base Bob-Up/Bob-Down task


Investigation of the Effectiveness of Dynamic Seat in a ...

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