Proceedings of the International Seminar Comfort on Board and Operability Evaluation of High-Speed Marine Vehicles, Genova, Italy, November 25th, 1994

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COMFORT ON BOARD AND

OPERABILITY EVALUATION

OF HIGHT-SPEED MARINE

VEHICLES

conference proceedings

Genova, 25 th November 1994

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International Seminar on "COMFORT ON BOARD AND

OPERABILITY EVALUATION OF HIGH SPEED MARINE

VEHICLES"

Genoa, 25th November, 1994

Summary

P. Crossland (DRA, U.K.), J.L. Caldwell (DREA, Canada), A.E. Baitis (CDNSWC, USA), F.D.

Holcombe (NBDL, USA), R. Strong (INM, U.K.)

."Quantifying Human Performance Degradation in a Ship Motion Environment: Experiments at the

US Naval Hydrodynamic Laboratory" Abrahamsen (DNV, Norway)

"DNVC Comfort Class, a New Concept Ensuring Acceptable Noise and Vibration Levels on Board Fligh Speed Vessels"

Sebastiani (CETENA, Italy)

"Human Factors Consideration in Evaluating the HSMV Seakeeping Performance"

P. Crossland (DRA, U.K.), R. Strong (INM, U.K.), A.J. Thomas (DRA, U.K.)

"Assessing the Effects of LFE Stabilisation on Human Performance" L. Grossi (FINCANTIERI Naval Division, Italy)

Quantifying Human Performance Degradation in a Ship Motion Environment: Experiments at the US Naval Biodynamics Laboratory.

P. Crossland (Defence Research Agency, UK)

J.L. Colwell (Defence Research Establishment Atlantic, Canada) A.E. Baitis (Naval Surface Warfare Center, Carderock Division, USA) F.D. Holcombe (Naval Biodynamics Laboratory, USA)

R. Strong (Institute of Naval Medicine,'UK)

Abstract

This paper describes recent ship motion simulator experiments to examine the effects of ship motions on human performance. Volunteer navy personnel performed representative physical and cognitive tasks while being exposed to simulated ship motions, derived from

a frigate in sea state five. The experiments were conducted in two phases at the US

Naval Biodynamics Laboratory (NBDL). Phase I examined motion inducedinterruptions

(MII), which occur when ship motions cause a person to stumble or slide, and motion

induced fatigue (MIF). The goals for this phase were to provide empirical

data for a

mathematical model for predicting the occurrenc,e

of Mlls, and to determine if an

increase in energy expenditure due to ship motions could be reliably measured. PhaseII

examined a variety of existing computer and paper based tests for assessing human

cognitive and psychomotor performance. The goals for this phase were to identifyreliable

performance assessment tests for use at sea,

and to obtain preliminary data on

the

sensitivity of various human abilities to ship motions. Also, data from Phase II could be used for validation of a sea sicicness, fatigue and performance assessment questionnaire developed for use during naval operations.

Introduction

The value of any method for assessing crew performance at sea depends upon the chosen

criteria. Currently, most criteria for naval operations are empirical, based upon

experience with existing destroyers and frigates. A typical criterion for personnel

operations on deck is that the root mean square (RMS) roll should not exceed four

degrees. aearly, the operations are not limited by the deck being inclined to

four degrees; although occasional extreme inclinations to much greater angles canbe limiting.

In many cases, personnel operations are most limited by the lateral

and vertical

accelerations associated with these deck inclinations. Thus, it is inappropriate to use roll

angle as the sole lateral motion criterion for deck operations. Using angular limitsfor criteria is especially misleading when assessing the operability of unconventional craft

such as Small Waterplane Area Twin Hull (SWATH) ships or high speed marine vehicles. The frequencies associated with the angular motions of the SWATH are generally lower than those observed on a conventional frigate and therefore result in lower accelerations on the SWATH. Conversely, the frequencies associated with high speed craft are much higher than those observed on a typical frigate, resulting in higher accelerations.

The series of ship motion simulator (SMS) experiments described here addresses

particular aspects of human performance, with emphasis on motion induced interruptions and the effects of ship motions on cognitive performance. A motion induced interruption (MII) occurs when the ship motions cause a person to lose balance by tipping or sliding.

The general approach is to expose human subjects (volunteer US Naval personnel) to

representative ship motions in the SMS. The effects of these motions on human

performance are quantified by observing direct effects (e.g. the incidence of a stumble)

and by measuring a variety of physiological parameters which may or may not have a direct cause/effect relationship with the motions (e.g. EKG heart rate).

Background

In 1989, an international workshop on Warship Operability was held at the Defenc,e Research Establishment Atlantic (DREA) to discuss seakeeping in ship design. At this workshop, it was proposed that thc three participating nations (US, UK, and Canada) should join in a collaborative venture to sponsor a series of human factors experiments

at the US Naval Biodynamics Laboratory (NBDL). This facility was chosen because of its resident expertise in human perfcrmance experimentation, and because it was the only

ship motion simulator (SMS) with motion ranges sufficiently large (especially vertical motion) to be of practical use for this work. Subsequently, the Netherlands joined this

ad hoc working group, which adopted the title "ABCD working group on human

performance at sea" (ABCD = American, British, Canadian and Dutch). This working

forum for information exchange, collaborative planning, and joint sponsorship of research and development on human performance at sea. The imrnediate application for this work

is in the naval environment; however, most of this work will also be of use for civilian

government and commercial applications.

The first major activity for the ABCD worlcing group was to develop the programme of

work which led to the human performance experiments described here. These

experiments at NBDL were jointly funded by American, British, and Canadian naval

research and ship design agencies, while the Dutch contributed via ongoing exchange of

information from their research programme at the TNO Human Factors Research

Institute, sponsored by the Royal Netherlands Navy. Information exchange between

ABCD member agencies is accomplished under existing national memoranda of

understanding.

3. Theoretical Review

There are three critical ingredients for predicting the operational performance of any

ship: a description of the environment in which it will operate; a method for predicting the ship's motions in response to the environment; and seakeeping criteria which establish

the effects of these motions on the ship's operational performance.

Methods for describing the environment and calculating ship motions are well established.

Statistical data bases are available to describe the occurrence and severity of the waves in various locations [e.g. Juszko and Graham, 1992], and linear strip theory methods provide adequate ship motion predictions for operability assessment of conventional

frigates and destroyers [e.g. Crossland, 1991]. Only recently has effort been devoted to establishing platform independent seakeeping criteria; in other words, criteria which are not based solely on experience with existing ships and ship systems.

A number of representative naval tasks'have been defined [Graham and Colwell, 19901,

which describe in general terms how human performance can be quantified

for the

purpose of evaluating ship operability. This is a "top-down" approach, where it is hoped that generic measures of performance such as the MII model, can be used for shipdesign trade off studies and for operational guidance. Conversely, the more detailed 'bottom-up" approach must be used when analysing any specific real task, as is done for the cognitive performance experiment.

3.1 Motion Induced Interruptions (MI1)

Baitis, Woolaver and Beck [1983]introduced the concept of motion induced interruptions

(MII) and developed the lateral force

estimator (LFE) approach for estimating the

occurrence of MIIs from lateral forces acting on the person. Graham [1990] extended this

frequency domain, which is better suited for use with contemporary strip theory methods.

Non-zero vertical acxelerations introduce asymmetry, and so two "generalized LFE"

expressions are required, one for tipping to port, GL, , and the other for tipping to

starboard, GL2 ,& n-3 A.

1 A

GL2 = 2 + _71`" GL, = :62 + gw

where, is the roll angle and 13.2 and 153 are the lateral and vertical acc,eleration

respectively (in fixed earth axes). The ratio

1Ih is the "tipping coefficient", which

represents the person's body geometry with vertical centre of gravity at h and one half stance width i, see Figure 1. An analogous set of expressions is also developed for the

body tipping frontwards and backwards, using one half shoe length. d in place of 1.

7;

M. = TT

T

Facing Aft Facing AR Roll Stbd Down Pitch Bow Down

Figure 1: Asslmled MU model

The generalized lateral force estimators can be calculated in the frequency domain by

assuming they follow the Rayleigh distribution. From this, the number of Mils expected during any particular span of time can be calculated, as follows.

1(

h

2 _GLi

where, Aft is the number of MlIs (i = 1 or 2 for tipping to port or starboard), Tris the time span of interest (seconds), T. is the zero crossing period of the generalised lateral

force estimator.

for using the MII model in seakeeping assessment [Graham, 1990]; however, this does not account for the human's ability to compensate for ship motion. The main goal for

Phase I of these NBDL experiments is obtainempirical tipping coefficient values from

observing real human performance in the sirnulator. It is expected that the human ability to "move with the ship", as well as the tendency to anticipate future motionwill provide

a more stable platform than the simple rigid body geometry would indicate and so, in

effect, increase the tipping coefficient.

The MII model was further refined to include an additional terrn to take account of the moment induced on the body by the rotational rnotion of the ship [Graham, Baitis and

Meyers, 1992]. The moment of inertia of the person was estimated by treating the body as an ellipsoidal cylinder of height 2h.

This refinement gave an additional term of

114

to both and 153

3

Other refinements made in this reference were to

include the effects of steady and

unsteady winds; however, this extension is not explored in the current experiments. This work also proposed that seakeeping criteria should be presented in terms of limits onthe

occurrence of the degrading events which directly affect any particular operation, as

opposed to more generic measures of overall ship motions. For example, instead of using

criteria limits values for RMS pitch and roll angles, it is more useful to consider events such as the frequency of occurrence ofMIIs (either tipping or sliding).

Under most conditions, MIIs associated with tipping occur before sliding becomes a

problem; however, in some conditions (e.g wet deck), sliding problems may dominate.

Graham, Baitis and Meyers [1991] describe a frequency domain method for estimating the incidence and severity ofsliding, which includes the (linearized) forces due to roll,

pitch, lateral and vertical accelerations,and also the effects of non-zero heel angle.

3.2 Cognitive performance

The MII model describes a simple cause and effect relationship between the ship motions

and the human's physical response; unfortunately, such simple models do not exist for

"higher order" human cognitive and psychomotor functions. In the absence of a direct

model, the following two step, indirect approach is used:

from ship motions, estimate symptomatology; and, from symptomatology, estimate performance,

where, "symptomatology " describes the presence and severity of the various syrnptoms produced by the ship motions.

symptoms are reviewed in Colwell [1989]. O'Hanlon and McCauley [1974] and McCauley el al [1976] describe a model for predicting motion sickness incidence (MSI), from the amplitude, frequency, and duration of exposure to vertical accelerations caused by ship motions. MSI is simply the percent of people who vomit when exposed to two hours of ship motions. Lawther and Griffin [1987] describe a method of calculating the vomiting incidence (VI, analogous to MSI) using a 'dose' parameter which quantifies cumulative

exposure to vertical accelerations. In both cases, the link between MSI and vertical accelerations is empirical, in the same manner as traditional criteria based on ship roll and pitch motions. The effects of other ship motions on MSI are not modelled, but the

method should be adequate for most typical motions encountered in conventional frigates and destroyers. Efforts by various researchers to predict MSI in more complicated motion environments (e.g. high speed vessels) have not been successful.

Lloyd and Andrew [1977] applied the MSI model to ship operations in rough weather.

The accelerations were assumed to be distributed according to the Gaussian probability

density to obtain an expression for the average acceleration. These approximations allowed the MSI formula to be used to make an estimate of the proportion of people who will suffer from seasickness in a given set of conditions at sea. Colwell [1994]

introduced an empirical habituation function for use with the MSI model, which extends

its application from the original short term exposures of only a few hours to longer

exposures of many days, as encountered in the naval environment.

Methods for assessing motion sickness incidence, as described above, are a useful step towards predicting operability; however, as yet there are no means of relating motion sickness (or fatigue) to task performance. One method to obtain information on the

effects of sea sickness (and other problems) on task performance is a questionnaire. The NATO sea sickness, fatigue and performance assessment questionnaire (PAQ) [Colwell and Heslegrave, 1993] was developed fo'r use during normal naval operations. The main purpose for the PAQ is to develop a large database on the incidence and severity of sea sickness and fatigue symptoms, and their perceived effects on human performance. The PAQ will also identify the presence and severity of performance problems related to MIN

and whole body vibration, but these are not the central focus. Once a sufficiently large database has been collected, it should indicate (for the first time) the general extent to

which ship motion induced human performance problems exist during naval operations, and hopefully be a source for trend analysis to develop statistical estimators for relating sea sickness and fatigue symptomatology to performance degradation. The self assessment

of performance, which is a central theme of the PAQ, is not validated; however, one objective of the Phase II cognitive experiment described here is to provide preliminary

data for this purpose. The main goals for the cognitive experiment are to investigate the effects of ship motions on human cognitive performance per se , and to develop validated

human performance tests for use at sea.

Test Facility

The NBDL Ship Motion Simulator (SMS) is located at the NASA Michoud Assembly

Facility in New Orleans Louisiana, USA. TheSMS consists of a cabin of cubical shape

with sides of about 2.5 metres length, mounted on a roll and pitch motion actuator, which

is in turn mounted on a large vertical motion platform.

Table 1 summarizes the motion capabilities of

the SMS, and Figures 2 and 3 show

schematic views of the SMS exterior and interior floor plan.

Table 1: SMS System Capability

Visual and audio links between the interior of the cabin and the external control area

allow continuous observation and communication with the subjects. A second, identical floor mounted cabin was used for the static control experiments. The static anddynamic

runs were balanced for order effects.

Summary of Experiments

5.1 Mll and Energy Expenditure

The goals for this phase of the experiment wereto obtain empirical tipping coefficients

for the Mil model described earlier, and to determine if increased energy expenditure

caused by ship motions could be reliably measured. There are two types of MIIs for

which empirical tipping coefficients are required; body lateral (i.e. tipping sideways), and body longitudinal (i.e. tipping frontwards and bacicwards). Of these two cases, the lateral

MII is of greatest interest, as it models the natural stance taken when postural stability

becomes compromised (e.g. the person is oriented sideways with respect to

the

predominant motion, in this case ship roll). During the experiment, while subjects are

exposed to the simulated ship motions, the occurrence of each MII wasnoted both by an

independent observer (external to the SMS cabin), and verbally by the subject in the

cabin. Empirical tipping coefficients are calculated after the fact by examining forces

acting on the subjects at the time that each MII occurred.

Parameter Heave Pitch Roll

Displacement Velocity/rate Acceleration Usable bandwidth +-3.5 m +-5mls +-0.9g 0.03 - 10 Hz +-15 degrees +-25 degs/s +-150 deg/s2 0.06 -3.0 Hz +-15 degrees +-25 deg/s +-150 degs/s2 0.06-3.0 Hz

PORT

PORT SCHEMATIC LOOKING FWD CABIN TILT TABLE MOVING A-FRAME HEAVE GUIDE RAIL AFT HEAVE GUIDE RAIL ROLL AXIS PITCH AXIS

Figure 2: NBDL Ship motion simulator

VCR.

STBD

ISTICO

Figure 3: Schematic of SMS, internal view of floor arrangement

6r₂

_RFALM

r7-27-7-latAlirgi-§:1;0-ff;.',In I weLqnt .:rmummi ..2 Si 1. 4 ' 8 ' I camera s) Caarra 02 4 CA o x 1 1 1 Red X Sigifiiiiiiiii,der C-amra 01 (2) 4- Croon I (1) (1)

In addition to the observed and reported

Mlls, measurements taken during the

experiment include: cabin rnotions, both input (or demand) signals and subsequent cabin motions; vertical and lateral accelerations at floor level in the centre of the cabin; subject referenced body accelerations using a triaxial accelerometer in a backpack worn by the subject; forces produced by the subject'sfeet from three force plates mounted flush with

the centre of the cabin floor, and, EKG heart rates. Also, three video cameras mounted

inside the SMS cabin provided complete video records of the subject's stance throughout

each experiment run. Fach subject wore a tight fitting overall with video targets at the

body's nominal centre of gravity and at major body joints. Also, during the pre-test pilot

study performed to refine the simulated

ship motion profiles, subjects wore special equipment for measuring oxygen consumption. Comparison of each subject's oxygen

consumption between static and dynamic

conditions provided the data on energy

expenditure discussed later, but the equipment was considered too bulky for inclusion in

the main experiment runs.

Sufficient information for calculating tipping coefficients is provided by the recorded SMS

cabin motions and the MII incidents themselves. The remaining parameters measured

during the experiment will provide data for the possible future development of more

detailed postural stability models, for either standing or more complex dynamic tasks. The

video records were analysed to provide asingle "snap-shot" view of each subject's real stance during each experiment run.

A total of fifteen human research volunteers (HRVs), all male USN personnelbetween

the ages of 17 and 24, were used

in this experiment. Each subject performed the

following sequence of five physical tasks

while exposed to two separate one

hour

simulated ship motion profiles:

standing facing 'astern' (2 minutes) - to observe body lateral Mils caused

while standing sideways with respect to the relatively large amplitude roll motions;

weight positioning task (1 minute) - the subject lifts a weig-ht and slides it

through a horizontal slot (a simplified model of a weapons loading task);

raised weight, standing facing astern

(1 minute) - subject holds a weight

overhead, to observe the effect of a change in the centre of gravity position

on body lateral MM. Due to safety considerations, the weight was a light

weight styrofoam cylinder (0.6 kg, 15 cm diameter and 60 cm long) and so the change in CG was primarily due to the lifted arms.

walking (1 minute) - subject traverses the cabin (port/starboard),

approximately three steps between turns; and,

standing facing to 'port (1 minute) - to observe body longitudinal Mlls caused while standing facing towards the relatively large amplitude roll motions.

This six minute sequence of taslcs was repeated ten times during each experiment run.

Instructions for changing between tasks were issued by a recorded script, synchronized with the SMS motion control system. An independent physician was present at all times

who could (and on occasions did) terminate the experiment run due to concerns on the subject's well being, based either on visual observations or the EKG records, or at the

subject's re,quest.

Only the standing tasks (1, 3 and 5) are related to the static MI' model, and only these

taslcs were located over the force plates mounted in the cabin floor. The

weight positioning and wallcing tasks were introduced to provide insight on the effects of Mlls

on more complicated tasks (to determine if it may be possible to use equivalent static

tipping coefficients to represent these complicated tasks), and to reduce the inevitable

boredom associated with one hour of standing still in a moving simulator.

Two different simulated ship motion profiles were used, derived from predicted motions at the flight deck of a USN FFG7 class frigate in sea state five, with a ship speed of ten knots in short crested irregular seas with significant wave height of 3.25 metres and wave modal period of 10 seconds. One motion profile represented bow seas (i.e. waves coming from 45 degrees off the bow) and the other represented stern quartering seas (designated Hotel and Lima, respectively). The key difference between these motion conditions is the

relative frequencies of the pitch and vertical motions; Hotel for the relatively high

frequency bow seas, and Lima for the relatively low frequency following seas. Since roll

motion transfer functions are relatively narrow banded (i.e. the ship only responds to a narrow range of wave frequencies), the roll frequencies are not much different for the

two conditions.

Since the SMS cannot replicate lateral motion, the gain of the SMS roll control signal

was increased to promote the body lateral Mlls which were of highest interest. Pre-trial

predictions using static tipping coefficiénts (based on body geometries) indicated that

lateral MIIs would not be experienced until roll amplitudes approaching the SMS

mwdmum capability of +/- fifteen degrees were experienced. Also, the pilot study

indicated that motion sickness became a problem for the unhabituated subjects, and so

the vertical accelerations were reduced by about twenty percent for the main experiment runs.

5.2 Cognitive Experiment

The primary goal for this phase of the NBDL experiments was to assess the effects of

ship motions on human cognitive and psychomotor task performance (i.e. purely mental

and mental/physical tasks); however, before this could be accomplished, the first step must be to validate the performance assessment tests themselves. A wide variety of

performance (e.g. sleep deprivation, heat or cold, work load, etc.), but few have been

used in a motion environment. Before any

performance tests can be used in a new

environment, it is important to validate them, as the new environment may affect the test, as well as affecting the human performing the test.

Thus, the cognitive experiment serves hvo purposes: (i) to begin development of a suite of performance assessment tests for use in a ship motion environment (real or simulated),

and (ii) to provide insight into the effects of the ship motions on task performance, as measured by the tests. Additionally, the experiment will provide data for validating the

subjective performance assessment approach used in the NATO performance assessment questionnaire (PAQ), by allowing comparison ofself rated performance with measured performance.

The general approach used in this experiment was to expose subjects to ship motions

while performing a sequence of computer and paper based tests, including motion

sickness and fatigue questionnaires(described later). A total of 48 volunteer US Naval

personnel have each been exposed to four, 90 minute sessions in the SMS. The first

session was primarily concerned with cognitive performance tests, and the second was

primarily psychomotor tests (it was expected that a single, three hour session would

promote an unacceptably high incidence of motion sickness). For each subject, the testing was spread over two days with a static and dynamic run of each day. The motion profile used for this experiment was based on the Hotel profile used in the MII experiment, but not modified to increase roll and reduce vertical motion. Each subject also performed an analogous training session in a static condition. The SMS cabins (both static and dynamic)

were configured to hold two subjects, each seated at a computer workstation equipped

with a keyboard, track ball, monitor and audio system. The subjects were separated by

a partition and restrained by seat belts. Each subject wore a light weight, helmet mounted communication system. Theprelimilary experiment results presented later in this paper

are only for the first 36 subjects, the results for the

remaining subjects are not yet

available, as the tests were completed very recently.

One of the most difficult problemsassociated with this experiment wasselection of the

performance assessment tests. It would be desirable to combine a variety of relatively

pure, single ability tests with more complex tests which involve a variety of human

abilities; however, no suitable complex tests could be identified. The complex testswhich

were considered either did not provide meaningful measurement capabilities, or they

required too much training before the subjects reached a stable level ofperformance.

A set of suitable cognitive performance tests were developed

using the abilities

classification procedures, or taxonomy, due to Fleishman [Fleishman and Reilly,1992]. Fleishman's taxonomic approach is often used to develop human performance assessment

identifies the individual human ability e-mployed for each component. A total of 52

separate abilities are identified in the taxonomy, grouped into four categories; cognitive,

psychomotor, gross body, and sensory (see Table A.1 of Appendix A). One difficulty

associated with this approach is combining results from individual ability tests to

represent overall performance on a complex, real task; however, the insights provided by this approach are invaluable for identifying the relative importance of each ability.

This approach was seen as the most practical choice for this work; but it is not the only

approach. For example Wickens, [1984] multiple resource processing theory could have

been used as an alternative.

For this experiment, the taxonomy approach was used to identify the abilities required

for maintaining ship position while performing replenishment at sea (RAS), also called

undenvay replenishment (UNREP). This activity was chosen because it is a vital

shipboard function that involves a wide variety of ship's personnel who employ a broad spectrum of abilities to accomplish their respective tasks. Task analysis indicated that this activity involves ten separate job categories: officer of the watch, signalman, helmsman,

lee helmsman, after steersman, radar operator, electronics technician, rig operator(s),

throttleman, and oil king (or chief stoker). Each job was analysed and broken down into

the required human abilities, and a provisional test battery for assessing these abilities

was chosen for a pilot study. This paper summarizes the process used for test selection; future reports will document details of this work.

Initially, more than one test was selected for most abilities; however, in some instances only one test was deemed suitable, and in a few instances, no suitable test was identified. Test selection was based on the following criteria:

the test should be reliable;

a stable score should be achievable;

the test must demonstrate ainstruct validity (i.e. it should measure the ability for which it was designed) which should not be compromised by the motion

environment;

the test should not be too easy, nor too difficult (floor and ceiling effects);

it should not be susceptible to cheating or compromised by discussion

between subjects;

the test must have a history of previous use in stress research;

the test should be easy to administer and its results should be easy to score

objectively;

the test should be easy for the subjects to understand;

it should be amenable to translation in a number of different languages;

for future considerations, the test should be widely available and reasonably priced; and,

11) if computer based (which is desirable), the test should be easily portable and

not require expensive special equipment.

Some of these criteria were evaluated in pre selection screening and others were

evaluated during a pilot study (Le. in the SMS). The final list of tests and abilities

selected for the main SMS experiment includes 31 tests for 20 different abilities, as shown

in Table A2. This list represents those

abilities judged most irnportant for the RAS

activity, which also had suitable tests available. Due to time constraints, several abilities

had to be deleted which otherwise would be of interest, namely; problem sensitivity,

category flexibility, fluency of ideas, mathematical reasoning, number facility; originality, and written comprehension.

Most tests were computer based; the subjects were trained to an asymptotic level before

the experiments. Instructions for written tests were displayed on the performance

assessment computer and, where required, verbal instructions were issued by computer audio track.

6. Discussion of Preliminary Results

6.1 Motion Induced Interruptions

'There are two general approaches forcalculating empirical tipping coefficients from the

MII experiment: local analysis, where the forces acting on the subject at the time of each

MII are examined; and, global analysis, where the total number of Mils observed are

related to the overall motion environment. This summary of preliminary resultsconsiders

only MIls observed during static standing tasks

1 (body lateral Mils) and 5 (body

longitudinal Mils). Future publications will provide details on Mils and empirical tipping coefficients for all five tasks.

The total number of MIIs observed during the experiment varied with the motion profile

(Hotel or Lima), as shown in Table 2.

Table 2: Total Number of MIIs Observed

As expected, there were significantly more longitudinal Mils than lateral, as the normal

body posture provides least resistance against tipping frontwards and backwards. A

perhaps unexpected trend is the discrepancy between motion profiles; for lateral Mlls,

Hotel Lima

Body Lateral MIIs 88 30

the Hotel motion profile produced the most events, whereas for longitudinal MI's, the Lima motion profile produced the most events.

Inspection of the local forces acting at the time of MII events (i.e. local acceleration

vector expressed by the generalized lateral force estimator, GL) led to the realization that

different types of MIls had to be identified, as shown in Table 3. Also included in this table is the total number of MIIs (for both types of MIN in both motion conditions)

associated with each category.

Type Description No. MIIs

A MII at or near smooth peak in GL 229

MII in opposite direction 8

MII at obvious discontinuity in GL, 27

and not near peak

AC MII at or near peak, but GL not smooth 181

MII not explained by GL 31

E MII too near start or end of task 22

(+2/-1 sec)

MII already identified for current GL peak 27

X other 5

Table 3: Classification of MI1 types

The difference between these MII categories is in some cases qualitative, and in other

cases quantitative. The most important distinction is between types A and AC, since the

great majority of events fall into one of these categories (69% for lateral and 81% for longitudinal Mils). For both A and AC.types, the MII occurred at or very near a peak

in local forces acting on the subject-, however, for the A type, the forces (or variation of GL with time) were smooth, or almost sinusoidal (typical of frigate motions); whereas for

the AC type, the forces were not smooth. The question remains as-whether a tip

occurring at an AC peak (i.e not smooth) would have occurred if the peak had have been smooth. Two types of "unsmoothness" could be identified; one related to the ir-regularity of motions expected in a natural sep.way and the other related to physical characteristics of the SMS (i.e. at some times, it appeared that a high frequency oscillation of the SMS cabin occurred unexpectedly). Since the distinction between a smooth and unsmooth

peak is subjective, the MII events were independently classified by two analysts, withvery

similar results. All empirical tipping coefficients discussed later are for the A and AC

types combined. Other types of Mils were not included in the analysis; but it is important

that occur when there is no significant force acting on the subject in the direction of

interest, but there is in the opposite direction. For

example, during task 1 when the

subject is standing facing aft and generally experiencing large lateral motions from roll, then type B describes the MIIs which occur when there was no significant lateral force,

but there is'Pa peak in longitudinal force (i.e. the subject likely tipped frontwards or

backwards): This ambiguity could be resolved by examining video

records. Type C

describes Mils which occur at times when the local forces acting on the subject are not

large, but the forces change in an "unpredictable" way (e.g the subject anticipated one

type of motion but a different one occun-ed). This suggests that the mechanism producing

the MII is related to the subject's anticipation of future motion, which may be an

important and separate mechanism to consider for future work. The type D MII is one

that occurs during relatively quiescent periods, when the SMS cabin is barely moving. It

is possible that the subject's attention wandered, or that some other mechanism was

acting (e.g. motion sickness symptoms).Type E describes those Mils that occurred very

near to the start or end of a task (i.e. just after or before changing taslcs); these Mils are discarded as the subject was likely to be still changing tasks. The net effect of discarding these Mils is to ignore the first and last motion cycle in each task. The type F MII occurs

when more than one tip or stumble is caused by (or associated with) a single peak in

local forces. A typical situation is where the subject regains his balance for a brief period,

but then stumbles again during a single motion cycle. Since the MII model can only

predict the number of events per motion

cycle, type F MIIs should not be counted (although they may indicate that the MII was especially severe). Finally, the typeX MII

is used to clas.sify all events not described by the preceding types. A typical type X MII

is one which occurs after the SMS motions have stopped, but before the

entire experiment protocol has finished (as happened a few times in runs terminated due to

growing motion sickness symptomsin ihe subject). In this case, the MII was formally

reported by either the subject or observer, but it

is not interest for the current MII

model.

-Table 4 summarizes the results for tipping coefficients calculated using both the local and global analysis approaches; these represent the average of all the subjects.The differences between body lateral and body longitudinal tipping coefficients are asexpected. The lower

values for body longitudinal tipping coefficients indicate, as expected, that this type of

MII occurs at lower levels of force than the body lateral Mil (i.e a person is less stable when standing facing into the primary lateral force than when standing at right angles to

it). Differences between motion conditions for the same type ofMII are not great and

may lie within experimental error; however, in

three of the four cases, the

tipping

coefficient is greater in the Lima profile than its equivalent in the Hotel profile. This may

frequency profile. This further suggests a possible frequency dependence for the tipping coefficient, which is not incorporated in the MII model.

Table 4: Empirical Tipping Coefficients

Figure 4 shows both tipping coefficients for each subject plotted on an arbitrary scale of height of the subjects centre of gravity; the figure gives an indication of the spread of the

data. There appears to be very little spread in the longitudinal tipping coefficient in the

local analysis, which is rather encouraging. There is more spread in the calculation of the body lateral tipping coefficient (for both global and local analysis). A point to note is the number of subjects who did not experience any body lateral MIIs (without exc,eption all subjects experienced body longitudinal MIIs). Three subjects did not experience lateral

Mlls in the Hotel profile and 5 in the Lima profile. Therefore, the variability in the

lateral tipping coefficient is not fully defined by these experiments.

6.2 Energy Expenditure Preliminary Results

Energy expenditure was investigated during the Mil experiment pilot study by measuring subjects' oxygen consumption while perf.orming the sequence of MII tasks. This interest in energy expenditure is due to the likely association between the accumulation of effects

of work done by altering posture to compensate for ship motions and the development

of motion induc,ed fatigue, MIF. Other likely mechanisms for the development of fatigue in prolonged exposure to ship motions may be related to the quantity and quality of rest and sleep, as affected by motion sickness symptoms, and/or by the physical effects of the motions themselves. These long term effects cannot be examined in the relatively short experiment runs used in these experiments.

Figure 5 uses a bar chart format to summarize the energy expenditure results for the

eight subjects tested (the numbers correspond to subject identification codes). Two bars

are used for each subject; the unshaded bar represents energy consumption in the static

condition (i.e.

cab not moving), and the shaded bar shows the corresponding

measurement in the moving SMS.

Lateral Mlls Longitudinal MIIs

Local Anlysis HOtel Profile 0.235 0.185 Lima Profile 0.229 0.200 Global Analysis Hotel Profile 0.288 0.204 Lima Profile 0.294 0.221

0.1

Local Analysis: Lateral Mils (Standing Facing Stern)

* 1

bit * '

I

* 1

* I

*

1

II

_Il

_II

₀

g

mA

1

E

LA

.0

Global Analysis: Lateral Mils (Standing Facing Stern)

.

*1

* *

_' I

*i

* 1

*

' II

_Ai

II

-

_tk

_a

_gin

a

o

Hotel Lima No Miis .11

Local Analysis: Longitudinal Mils (StandingFacing Port)

AA

A

_a

SIN

0.95 1.00 1.05 1.10 1.15

Height to Centre of Gravity (m)

Figure 4: Sample Tipping Coefficients

0.1 O.2

a02

0.1 0.3 0.2

For comparative purposes, the right most bar shows the equivalent energy expenditure

for walking on level ground at a pace of about 2 milesihr (3.2 km/hr). It is clear that the subjects expended more energy in the motion environment; however, the amount of extra

energy expended is relatively small.These results are encouraging, as they suggest that

measuring oxygen consumption is a reliable (or at least consistent) method for examining the effects of ship motions on energy expenditure. It is reasonable to expect that greater

differences behveen static and moving conditions would be found for longer term

exposures, and for more severe motion profiles as commonly encountered in smaller

vessels. 1=1 Stet E223hlotlon 0.6 0.5 0.4 ." 0.3 -0.2 0.1 o 257 262 260 252 256 261 251 259 Su bject Number

Figure 5: Energy expenditure

6.3 Cognitive Experiment Preliminary Results

Table A.3 summarizes preliminary results for the first 36 subjects in the cognitive

experiments.

A significance test was carried out on the results of the test battery in the static and dynamic conditions. The details of the test are shown in Appendix A. The significance

test is based upon the null hypothesis that the means of the results from both conditions

are the same. The significance level is the size of the test for which the null hypothesis is just rejected; any smaller size and it would not. The value p, shown in some of the tables is often used to suggest how strong the evidence is in favour of the alternative hypothesis, i.e that the means are different.

A subjective conversion between the p-values and a verbal statement of the weight of

evidence is as follows :

E

I

o

p < 0.001

p <0.010

p <0.025

p <0.050

p <0.109.

p >

0.10Ó

So, for example, a value of p < 0.001 is very strong evidence to suggest a difference between in the static and motion conditions.

In general, the effects of motions on task performance (from a point of view of exercising an ability) can be summarised as follows

Motion

very strong evidence of difference between motion conditions

strong evidence fairly strong evidence some evidence slight evidence no real evidence. Energy expended Motion sickness Direct effects Arousal Fatigue Task Performance

Fatigue was not a problem during this nominal 90 minute test period performing

cognitive tasks while seated, as the associated energy expenditure should be low.

In general, the direct effects of motions on different categories of human abilities can be

ranked in order of sensitivity to motions asfollows:

Mechanical (MII) Most effect Psychomotor

Visual

Purely cognitive least/no effect

The main study indicates that for relatiVely short exposures to motions, purely cognitive

skills are not degraded. Test involving psychomotor skills revealed more significant

differences. Arousal effects appear significant; one observation made during the main

study of the cognitive experiments was that once volunteers were being recruited from sources external to NBDL the motion sickness incidence of allsubjects became zero. This

indicates the strong influence that attitude and expectation may have on behaviour. The

results of the motion sickness questionnaires must be interpreted with caution in the light

of such observations. Similarly, where there are significant differences observed in

cognitive or psychomotor performance, and MSI is also noticeably different, it will be

important to ascertain whether

task performance is similarly influenced by attitude

change i.e where attitudes are such as to suppress motion sickness symptomalogy, are

6.4 Questionna'ire Preliminary Results

Two questionnaires were administered during both the MII and cognitive experiments.

The NATO sea sicicness, fatigue and performance assessment questionnaire (PAQ)

[Colwell and Heslegrave, 1993] was administered near the end of each experirnent run, but while the SMS was still in motion. Results for the PAQ have not yet been analyzed. In

addition, a subset of the NBDL motion sicicness questionnaire (MSQ) was

administered during the runs, and preliminary results are discussed below.

The MSQ checklist, shown in Table B.1 of Appendix B, consists of 25 questions. Nine

responses to the questions are based on the four point Likertscale; 15 are simple yes/no items, the final question is not scored.

Table B.2 shows the results of administering the Checklist to subjects during the MII study. The table shows the difference behveen the pre-test and post-test results in the

dynamic condition.

The Student's t-test revealed no significant differences in post-test means of the overall

questionnaire in dynamic and static conditions; however, each motion condition there were significant differences between the pre-test and post-test means. For the purpose of evaluating subjective symptomatology, each item on the Checklist was compared individually. The most reliable indicators of motion sickness appear to be those most

commonly associated with nausea. There were significant differences between the post-test means of dynamic and static motion conditions for:

General discomfort Boredom Drowsiness Fullness of head Increased salivation Stomach awareness Nausea

And, as shown in Table B.3, within the dynamic group there was sh-ong-evidence (p <

0.01) to suggest differences in the means of the pre-test and post-test in the dynamic

condition for:

General discomfort Drowsiness

Headache Nausea

and fairly strong evidence (p < 0.025) to suggest differences in the means of the pre-test and post-test in the dynamic condition for:

Increased salivation Vomiting

Note that the subjects were withdrawn from the motion sirnulator when significant motion

symptoms became apparent, and so the incidence of vomiting observed is lower than

might be expected. One would expect a significantdifference (p < 0.001) between static and dynamic conditions for vomiting, if all experiment runs were extended to the full one

hour duration.

f;

The MSQ tesults indicate that the symptoms of motion sickness were more apparent in the MIL study (Table B.2) than the cognitive study (Table B.2). There were a higher number of p's < 0.001 in the MII study than the cognitive study. This is probably due to

the higher angular motions experienced

in the Mil study (despite the fact the MSI

calculations are based entirely on vertical

accelerations). It could also be due to the

differences in the level of activity experienced in both studies. In the cognitive study, the

seated subjects were occupied in performing demanding taslcs. In the MII study the

subjects had long periods of standing

around doing nothing. Perhaps the lack of a

comparable need to concentrate on the task in hand has led to an increase in symptoms

of motion sicicness?

7. Conclusions

This paper has described a set of unique

experiments to quantify the effects of ship

motions on the crew performance. Data from these experiments will be valuable for

validation of postural stability models. A

significant amount of data has yet to be

analysed and will be the subject of furtherwork.

The MII model proposed by Graham, [1990] has been validated to some extent. Both

global and local analysis have found empirical values for the tipping coefficients; values that are not significantly different from those proposed by Graham, [1990].

However, limitations in the maximum roll and pitch motion capability of the NBDL

simulator, and especially in the absenceCif lateral motion and yaw, have compromised the

realism of the motion histories used in Phase I of the experiments. It is likely that the

lack of pure linear lateral motion is the primary cause for the unexpectedly low incidence

(an in some cases the complete lack) of body lateral MIIs.

Further experimental work is planned at a motion simulator at the Defence Research

Agency (DRA) Bedford, UK This simulator can replicate ship motions in five degrees

of freedom (i.e all motions except surge). So, it can be used to obtain lateral tipping

coefficients for the MII model in

completely realistic conditions (in frigates, surge

accelerations are usually significantlylower than other motions

Phase II of the NBDL experiments have successfully identified a cognitive testbattery for use (or at least to be partly used) in further tests of this nature.The study has shown that

for relatively short exposures to motions purely cognitive skills are not degraded; tests

Further experimental work is also planned for the motion simulator at the TNO Human

Factors Research Institute, The Netherlands. This work will pay particular attention to to the effects of energy expenditure on motion induced fatigue in a higher frequency

motion environment (i.e small boat motions). The work will also examine cognitive and psychomotot task performance effects for significantly longer exposures to motions (from

4 to 6 houri).

Further work concerning Phase II of the work could be to validate the performance tests battery by comparison with real task performance at sea, and simultaneously to evaluate

the potential of the NATO Performance Assessment Questionnaire [Colwell and

Heslegrave, 19931 as an alternative and more sirnply administered means of assessing performance at sea.

It is possible to factor analyse the results of the questionnaires. Characteristically, two primary factors can be extracted, one associated with fatigue and boredom, and one

associated directly with sickness and other motion sickness symptoms. In view of the

significant pre- and post-test differences in the questionnaire responses, but non

significant motion comparison, a further analysis could be conducted to elucidate these experimental findings.

Acknowledgements

This project was supported by the Procurement Executive, Ministry of Defence, Canadian

Department of National Defence and the United States Department of the Navy.

0 Copyright 1994. United States Department of the Navy; Copyright 1994. Department of National Defence Canada for Her Majesty the Queen; British Crown Copyright 1994

/MOD. Published with the permission of the Controller of Her Britannic Majesty's

Stationery Office.

References

-A E Baitis, D -A Woolaver, T -A Beck. Rudder Roll Stabilisation for Coast Guard Cutters and Frigates. Naval Engineers Journal 1983.

A C Bittner, J C Guig-nard. Human Factors Engineering Principles for Minimising Adverse Ship Motion Effects: Theory and Practice. Naval Engineers Journal, Vol 97, No.4 1985.

J L Colwell. Human Factors in the Naval Environment: A Review of Motion Sickness and Biodynamic Problems. DREA Technic-al Memorandum 891220. September 1989. Unlimited Distribution.

J L Colwell, R J Heslegrave. Seasickness, Fatigue

and Performance Assessment

Questionnaire. DREA Report 93/105. September 1993. Unlimited Distribution

J L Colwell. Motion Sickness Habituation in the Naval Environment., DREA Technical Memorandutn 94211. May 1994. Unlimited Distribution.

P Crosslnd. User Guide for the PAT-91 Suite of Ship Motion Computer Programs. DRA/Mar/TR91316. September 1991.

E A Fleishman, M E Reilly. Handbook ofHuman Abilities: Definitions, Measurements and Job Task Requirements. Palo Alto, CA: Consulting Psychologists Press, Inc. 1992.

R Graham. Motion Induced Interruptions as Ship Operability Criteria. Naval Engineers

Journal, Vol 102, No. 2, March 1990.

R Graham, A E Baitis, W G Meyers. A frequency Domain Method for Estimating the

Incidence and Severity of Sliding. D'TRC Report SHD-1361-01. August 1991.

R Graham, A E Baitis, W G Meyers. On the Development of Seakeeping Criteria. Naval

Engineers Journal. May 1992.

R Graham, J L Colwell. Assessing the Effects of Ship Motions on Human Performance: Standard Tasks for the Naval Environment. NATO Working Paper AC/141(IEG/6)SG/5-WP/15, November 1990

J F O'Hanlon, M E McCauley. Moti.rn Sickness Incidence as a Function of Frequency and Acceleration of Vertical Sinusoidal Motion. Aerospace Medicine 1974.

B A Juszko, R Graham. Development of a Statistical Wave Climate Description Based on 10-Parameter Spectra. 3rd International Workshop on Wave Hindcasting and Forecasting. Montreal, May 1992.

A Lawther, M J Griffin. Prediction of the Incidence of Motion Sickness from the Magnitude, Frequency and Duration of Vertical. Oscillation. Journal of the Acoustical Society of America. 82(3). September 1987.

ARJM Lloyd, R N Andrew. Criteriafor Ship Speed in Rough Weather. 18th American

M.E. McCauley, J.W. Royal, J.E. Shaw, and L.G. Schmitt, Motion Sickness Incidence; Egiloratory Studies of Habituation, Pitch and Roll, and the Refinement of a Mathematical Model, Human factors Research inc., Technical Report 1733-2, April 1976.

C D Wickehs. The structure of attentional resources.. R Nickerson ed. Attention and

i;

APPENDIX k. PHASE H, COGNITIVE EXPERIMENTTABLES

- uogniuve P - Psychomotor B - Gross Body

S - Sensory

Table A.1. Fleishman's taxonomyof human abilities

Ability Type Ability Type*

1. Oral Comprehension

;

2. Writteti Comprehension ; 3. Oral E.xpression . . 4. Written Expression 5. Fluency of Ideas 6. Originality 7. Memorization 8. Problem Sensitivity 9. Mathematical Reasoning 10. Number Facility 11. Deductive Reasoning 12. Inductive Reasoning 13. Information Ordering 14. Category Flexibility 15. Speed of Closure 16. Flexibility of Closure 17. Spatial Orientation 18. Visualisation 19. Perceptual Speed C C C C C 27. Finger Dexterity 28. Wrist-Finger Speed

29. Speed of Limb Movement

30. Selective Attention 31. Time Sharing P P P P P C C C C C C C C C 32. Static Strength 33. Explosive Strength 34. Dynamic Strength 35. Trunk Strength 36. Extent Flexibility 37. Dynamic Flexibility 38. Gross Body Coordination

39. Gross Body Equilibrium 40. Stamina B B B B B B B B B C C C C C 41. Near Vision 42. Far Vision

43. Visual Colour Discrimination 44. Night Vision 45. Peripheral Vision S S S S S S S S S S S S 20. Control Precision 21. Multilimb Coordination 22. Response Orientation 23. Rate Control 24. Reaction Time 25. Arm-Hand Steadiness 26. Manual Dexterity P P P P P P P 46. Depth Perception 47. Glare Sensitivity 48. General Hearing 49. Auditory Attention _ 50. Sound Localisation 51. Speech Hearing 52. Speech Clarity

Table A.2. Final Test Battery

_

Human Ability Name of Test

Oral comprehension Watson-Barker Listening test

Written expression

-;

ETS Controlled Association ETS Figure of Spee,ch

I,

Membrization

'

WRPAB Pattern Comparisons I & II

WRPAB Digit Recall TNO Taskomat

Deductive reasoning CCAB Logical Relations WRPAB Logical Relations Inductive reasoning ETS Letters Sets

CCAB Missing Items Inforrnation ordering Following Directions

Speed of closure ETS Gestalt Completion

ETS Concealed Words Flexibility of closure ETS Hidden Figures

ETS Hidden Patterns

Spatial orientation ETS Card Rotation

OMPAT Match to Sample

Visualisation ETS Paper Folding Test

Surface Development

Perceptual speed ETS Number Comparison

ETS Finding A's

Control precision ANAM Pursuit Tracking

Response orientation WRPAB Four Choice Reaction Time

Rate control WRPAB Time Wall

Reaction time Simple Reaction Time

Manual dexterity Minnesota Rate Manipulation Test

Finger dexterity Purdue Pegboard

Arm hand steadiness Lafayette steadiness tester hole

-Multilimb coordination Lafayette 2 arm coordination

Table A.3: Phase II Cognitive Experiment Main study, preliminary results.

Ability Static Dynamic T-test

p

Test N Mean SD N Mean SD

Deductive reasoning

CCAB Logical relations 36 1285.7 167.6 32 1275.6 182.2 > 0.1 WRPAB,Logical relations 35 48.8 1.6 32 48.6 2.0 > 0.1

Flexibility offelosure

BIS Hidden figures 36 6.0 4.4 35 4.4 4.0 <0.1

ETS Hidden patterns 36 57.3 21.8 35 58.4 24.2 > 0.1

,

Inductive reasoning

CCAB Missing iterns 36 1354.9 151.9 32 1396.0 163.2 - > 0.1

EIS Letter sets 36 10.0 2.4 35 10.0 2.3 > 0.1

Information ordering

EIS Following direction 36 6.6 2.1 35 6.7 2.3 > 0.1

Memorization

WRPAB Digit recall 34 6.7 2.2 32 6.5 2.0 > 0.1

WRPAB Pattern comparison I 36 8.0 1.5 32 7.2 1.5 <0.025

WRPAB Pattem comparison II 36 7.6 1.4 32 7.7 1.5 > 0.1

Oral comprehension

Watson Barker listening test 36 19.2 4.8 32 19.0 4.9 > 0.1

Perceptual gpeed

E IN Finding As 36 31.1 10.2 32 29.6 10.1 > 0.1

EIS Number Comparison 36 14.5 4.3 33 12.9 4.3 <0.1

Spatial orientation

OMPAT match to sample 35 10.0 2.4 33 9.1 2.4 <0.1

EIS card rotations 36 61.1 14.6 32 58.8 16.7 > 0.1

Speed of closure

ETS concealed words 36 14.9 4.0 33 13.7 3.1 < 0.1

ETS Gestalt completion 36 7.4 1.4 32 6.9 1.5 < 0.1

Time Sharing

ETS paper folding 36 5.1 2.3 33 5.3 2.2 > 0.1

EIS Surface development 36 16.5 8.1 34 16.7 9.3 > 0.1

Written expression

EIS Controlled associations 36 15.7 8.2 34 15.6 8.5 > 0.1

ETS Figures of speech 36 10.0 3.2 33 10.1 3.0 > 0.1

Control precision

ANAM Pursuit tracking 36 10.1 8.4 33 11.1 11.7 > 0.1

Rate Control

WRPAB Time wall 36 6.1 2.7 32 6.4 3.3 > 0.1

Reaction time

STRES Simple reaction time 36 201.5 62.3 33 192.2 69.6 > 0.1

Response orientation

WRPAB Choice reaction time 35 6.3 1.1 32 6.1 1.0 > 0.1

WRPAB Choice reaction time accuracy 35 48.9 1.4 32 48.7 2.0 > 0.1

Arm hand steadiness

Lafayette steadiness tester 34 56.1 27.4 33 85.6 40.8 < 0.001

-Finger dexterity

Purdue pegboard fight hand 36 17.0 2.8 29 17.0 3.8 > 0.1

Purdue pegboard left hand 35 16.8 2.4 33 17.0 2.4 > 0.1

Purdue pegboard both hands 36 24.0 8.0 33 22.0 7.1 > 0.1

Purdue pegboard assembly 36 . 9.7 1.6 33 9.2 1.7 > 0.1

Manual dexterity

minnesota rate manipulation 36 32.1 6.5 34 33.4 7.6 > 0.1

Multilimb coordination

Lafayette 2-arm coordination clockwise 36 1.3 2.7 32 2.4 3.2 > 0.1

Lafayette 2-arm coordination 36 1.0 1.5 33 2.3 2.8 < 0.025

anticlockwise 36 30.8 15.3 32 36.5 18.4 < 0.1

Lafayette 2-arm coord. clockwise time 36 25.0 13.8 33 26.1 13.6 > 0.1

Lafayette 2-arm coord. anticlockwise time

Wrist finger speed

Tapper board right hand 36 81.1 13.2 28 80.9 20.4 > 0.1

APPENDIX B: MOTION SICKNESS QUESTIONNAIRE

ANSWER THIS WHETHER ON WATCH OR NOT

SYMPTOMATOLOGY CHECICLIST - HOW YOU FEEL NOW

General Discomfort none [] slight [I moderate severe []

Fatigue none [] slight [] moderate [] severe []

Boredom none [] slight [] moderate [] severe El

Mental depression no [] yes []

Drowsiness none [] slight [] moderate [] severe

Headache none [] slight [] moderate [] severe []

Fullness of head no [] yes []

Blurred Vision no [] yes []

Dizziness with eyes open no [] yes []

Dizziness with eyes closed no [] yes [] not tried []

Salivation INCREASED none [] slight [] moderate [] severe []

Salivation UNUSUAL no [] yes []

Salivation DECREASED none [] slight [] moderate [] severe []

Sweating none [] slight [] moderate [] severe []

Faintness no [] yes []

Aware of breathing no [] yes []

Stomach Awareness no [] yes []

Nausea none [] slight [] moderate [] severe []

Burping no [] yes [] No. of times

Confusion no [] yes []

LOSS of appetite no yes []

INCREASED appetite no [] yes []

Desire to move bowels no f] yes []

Vomiting no [] yes []

OTHER...(describe)

Table B.2 Phase I MII Experiment- Syrnptomatology Checklist, Summary of Results

Syrnptom Pre-test (dynamic) Post-test (dynamic) T-test

P N mean SD N mean SD 1. General discomfort 36 0.083 0.368 36 0.694 0.822 <0.001

2. Fatigui

36 0.083 0.280 36 0.833 0.811 <0.001 3. Boréciom 36 0.083 0.280 36 0.528 0.941

<0.01

4. Mental depression 36 0.056 0.232 36 0.083 0.280 > 0.1 5. Drowsiness 36 0.167 0.447 36 0.583 0.841

<0.01

6. Headache 36 0.194 0.525 36 0.694 0.786 < 0.01 7. Fullness of head 36 0.167 0.378 36 0.250 0.439 > 0.1 8. Blun-ed vision 36 0.000 0.000 36 0.056 0.232

<0.1

9. Dizziness with eyes open 36 0.028 0.167 36 0.139 0.351

<0.025

10. Dizziness with eyes closed 36 0.000 0.000 36 0.111 0.398 < 0.1

11. Salivation increased 36 0.000 0.000 36 0.417 0.732 < 0.001 12. Salivation unusual 36 0.333 0.478 36 0.472 0.506 > 0.1 13. Salivation decreased 36 0.000 0.000 36 0.000 0.000 -14. Sweating 36 0.083 0.368 36 0.833 0.941 < 0.001 15. Faintness 36 0.028 0.167 36 0.111 0.319

<0.1

16. Awareness of breathing 36 0.139 0.351 36 0.333 0.478 < 0.05 17. Stomach Awareness 36 0.111 0.319 36 0.444 0.504 < 0.001 18. Nausea 36 0.056 0.333 36 0.722 0.914 < 0.001 19. Burping 36 0.000 0.000 36 0.361 0.487 <0.001 20. C,onfusion 36 0.000 0.000 36 0.000 0.000 -21. Loss of appetite 36 0.028 0.167 36 0.222 0.422

<0.01

22. Increased appetite 36 0.056 0.232 36 0.056 0.232 > 0.1

23. Desire to move bowels 36 0.083 0.280 36 0.056 0.232 > 0.1

Table B3 Phase II Cognitive Experiment- Symptomatology Checklist, Summary of

Results

Syrnptom Pre-test (dynamic) Post-test (dynamic) T-test

P N mean SD N mean SD 1 1. General discomfort , 49 0.082 0.344 39 0.462 0.790 <0.01 2. Fati/fue 49 0.061 0.242 39 0.256 0.637

<0.05

3. Boredom 49 0.102 0.306 39 0.282 0.686

<0.1

4. Mental depression 49 0.000 0.000 39 0.000 0.000 -5. Drowsiness 49 0.061 0.243 39 0.462 0.756 < 0.01 6. Headache 49 0.082 0.277 39 0.410 0.677

<0.01

7. Fullness of head 49 0.122 0.331 39 0.282 0.456 < 0.05 8. Blurred vision 49 0.020 0.143 39 0.077 0.270 > 0.1

9. Dizziness with eyes open 49 0.000 0.000 39 0.051 0.223

<0.1

10. Dizziness with eyes closed 49 0.041 0.200 39 0.103 0.307 > 0.1

11. Salivation increased 49 0.020 0.143 39 0.256 0.637 <0.025 12. Salivation unusual 49 0.082 0.277 39 0.051 0.223 > 0.1 13. Salivation decreased 49 0.000 0.000 39 0.026 0.160 > 0.1 14. Sweating - - - -15. Faintness 49 0.020 0.143 39 0.051 0.223 > 0.1 16. Awareness of breathing 49 0.102 0.306 39 0.077 0270 > 0.1 17. Stomach Awareness 49 0.184 0.391 39 0.308 0.468 < 0.1 18. Nausea 49 ' 0.163 0.373 39 0.641 0.903 < 0.01 19. Burping 49 0.082 0_277 39 0.205 0.409 < 0.1 20. Confusion 49 0.000 0.000 39 0.000 0.000 -21. Loss of appetite 49 0.041 0.200 39 0.051 0.223 > 0.1 22. Increased appetite 49 0.061 0.242 39 0.026 0.160 > 0.1

23. Desire to move bowels 49 0.041 0.200 39 0.103 0.307 > 0.1

"DNVC CbMFORT CLASS", A New Concept Ensuring Acceptable

Noise and Vibration Levels on Board

High Speed Vessels

By Kai A Abrahamsen

DNVC A/S,

1322 112rvilc,

Norway

Abstract:

Noise, vibration and sea induced motion are probably the most important parameters

determining the comfort on board high speed ferries. Other parameters are climate, air pollution, lighting, seating comfort, space, availability of safety measures, crew and interior appearance.

Ilgh speed passenger vessels are inherently more noisy than conventional passenger

vessels, due to high power to weight ratios, short transmission paths and restricted space and weight allowance for noise reducing measures. The high speed and moderate size of such vessels make them potentially vulnerable to strong sea induced motions.

In order to assist owners and yards to improve the comfort on boardhigh speed passenger

vessels, the DNVC "ComfortEvaluation" may be of valuable assistance. The "Comfort Evaluation comprises the DNV "Comfort Class" and a service for calculation of the

"Sea Comfort Index".

"Comfort Class" is a voluntary class

notation specifying comfort criteria for noise, vibration and indoor climate. The

"Sea Comfort Index" is a

systematic approach to

evaluation of the probability of motion sickness among passengers and crew.

1.

INTRODUCTION

The future success of the high speed vessel industry depends on the ability of high

speed vessels to carry passengers safely and comfortably at high speed over exposed waters. The safety aspect is being taken care of by ordinary classification rules as well

as regulations specified by IMO and national authorities.

Comfort has traditionally been regarded as an important property of a design, but has frequently been dealt with in a rather random way. Owners, shipyards and designers have had difficulties in communicating due to lack of accepted criteria and inadequate knowledge in this field. Some projects have been able to specify certain criteria based on previous experience, others have had to rely on the ability of all parties involved to

deal with a rather rough and often imprecise specification. This unsatisfactory situation

is the reason for the development of the DNV Comfort Evaluation which comprises

the DNV "Comfort Class" and a service for calculation of the "Sea Comfort Index".

"Comfort Class" is a voluntary class notation specifying comfort criteria for noise, vibration and indoor climate. The class is issued when the fulfilment of the criteria has

been verified by measurements. Noise , vibration and climate are classified according

to a comfort rating from 1 to 3, which reflects "acceptable" to "high" levels of

comfort. In addition to state requirements to defined comfort related standards, the rule text describes measurement procedures, international standards to be followed and the instrumentation to be used for measurements. This information is important for the

true assessment of vessel comfort, but is often missed in the building specification.

"Sea Comfort Index" is a measure of the probability of motion sickness among

passengers and crew. For two different vessels operating in the same area, the "Sea Comfort Index" will give an objective evaluation of the seakeeping performance of

vessels in relation to human comfort. Sea comfort rating of this kind is particularly well

suited for relative comparison between different vessel designs and routes. The "Sea Comfort Index" is initially offered as an advisory service, but will at

a later stage be

2.

nit; CONCEPT OF COMFORT

Comfort is:4:1' efined as "A State of Physical Well Being". The overall perception of

comfort oñ board a passenger ship depends on a number of different factors associated

4

with the on board environment, safety, facilities, design and space, see table 1.

Investigations on the relative importance of environmentalfactors among seafarers, ref. / GOETHE et. al. (1978) & SAN (1978)1, haveshown that noise, -vibration and sea induced motions are rated as the clearly most troublesome factors. Other factors such as climate,

air pollution, lighting, etc., were rated as troublesome by substantially fewer of the

subjects.

Although the referenc,ed investigations dealt with able seamen on board large merchant ships, one may assume that the same situation roughly will apply to passengers on board

fast ferries. lEgh speed, compact design,

light weight

structures and high power

requirements are factors that make high speed ferries vulnerable to unfavourable motions

as well as high noise and vibration levels. Hence, it is important to take care of these

properties during the design of a vessel.

The ability of

a vessel to operate

cotnfortably under varying climatic conditions is

important. Many high speed vessels operate incountries with highly variable climate or

they are transferred between differentpart's of the world depending on season. For such

vessels it is important to have a documented ability to maintain a satisfactory interior climate under varying environmental conditions.

Safety Emergency equipment Alarms Escape routes Crew appearance Information Environment

Sea Induced Motion

Noise Vibration Indoor Climate Illumination Odour Restaurants/Cafeterias Shops Sanitary facilities Information/Assistance Service Entertainment Design Architectural design Window vision Outward appearance Cabin layout Furniture Spaciousness of interior Passenger density Loftiness Cabin size

Table 1,

Aspects influencing the overall perception of comfort on board a

ship.

3.

CRITERIA FOR NOISE, VIBRATION, CLIMATE AND SEA

INDUCED MOTIONS

3.1 General

International standards have been used as foundation for the "Comfort Class" rules,

but have not necessarily been adhered to. When determining criteria to comfort on board

high speed vessels, due consideration has to be given to technical and practical

limitations inherent in the design and construction of the vessels. Otherwise rather

unrealistic criteria would be derived. It is therefore important to see the criteria in

relation to the situation on board a high speed vessel and not be confused by what one could require in a different situation. The concept of comfort will be relative to what it is practical to achieve for a particular application. Hence, the comfort criteria for high

speed vessels may have to be adjusted if future design

developments improves the

attainable comfort levels significantly.

The criteria for noise and vibration discussed below apply to steady state normal transit

conditions. It is self evident that short and infrequent exposures should be considered

separately. The criteria for sea induced motions apply to time averaged exposures.

The noise, vibration and climate criteria are divided into three groups depending on

the level of comfort achieved, i.e. comfort rating

number (crn)

1, 2 and 3,

where cm n (3) represents the higstest comfort level

and cm (1) represents an

acceptable level of comfort.

The lowest cm-number achieved for noise or

vibration will determine the overall rating for noise and vibration. This means that a

vessel meeting crn (2) for vibration

and cm n (3) for noise will be denoted cm n (2). A separate cm-number will be given for