An unstable steering task with a sonic-boom disturbance

•

September, 1972.

~ UNSTABLE STEERING TASK ITH A SONIC-BOOM DISTURBANCE

by

K. W. Lips

AN

UNSTABLE STEERING TASK

WITH A SONDe-BOOM DISTURBANCE

by

K. W.

Lips

Submitted August, 1972.

•

ACKNOWLEDGEMENT

Personal gratitude is extended to Dr. I. I. Glass and Dr. L. D. Reid for making this study possible. Of special value was the understanding and patience prpvided.

The time and cooperation volunteered by the staff and students to become subjects is sincerely appreciated.

The fin~ncial assistance received from the Ministry of Transport, the National Research Council and Air Canada is acknowledged with thanks •

..

SUMMARY

An initial study was made concerning the effect of sonic boom

distur-bances on an individual's compensatory tracking performance for an unstable systemo

In certain respects the tracking task simulated automobile driving.

It was found th at most individuals were disturbed and recovered in

varying degrees. These preliminary results,although somewhat qualitative, show

1. 2.

3.

4.

5.

TABLE (JJ! CONTENTS Notatiop Introduction Sonic~Boom Simulátion

Simulation of an Unstable Automobile Driving Task Experimental Det~i1s

4.1 Apparatus

4.2 Randon Input anà Scoring Technique 4.3 Subjects and Training

4.4 Testing Procedure with Sonic~Boom Disturbances 4.5 Interrogation Test Procedure

4 •. 6 Data Reduction Results and Discussion Conc1usions PAGE 1

3

3

4-

.

4

6 7 7

8

9 10 12 References 14

Appendix A: First Order Linear Unstab1e Systems Tables

A(s) ~

De

eet) Hz i(t) in in/sec Kn m(t) msec o(t) psf R

RMS

s sec SST T,g T p T r V V/in yes) ( 0) Note: NOTATION

transfer function for the vehicle dynamics vehicle dynamics feedback parameter

implies a-;zero value for frequency error signal

=

i(t) + met)

Hertz or cycles per second random input signal

inches

inches per second 10

3

ohms resistance vehicle dynamics output mil-liseconds

driver's wheel output pounds per square foot electrical resistance root mean square

the Laplace transform variable second(s)

flupersonic transport

time interval af ter the boom to loss of control

time interval af ter the boom to peak amplitude response time interval af ter the boom to complete recovery

volt

volts per inch

compensatory driver describing function

d( )/dt - total derivative with respect to time

1. INTRODUCTION

The day of commercial service for the supersonic transport (SST) appears to be rapidly approaching. Many answers, however, are needed concerning what effect the associated sonic-boom will have on humans, animal life, structures, and the world' s ecology in general. The present report deals with human

psycho-motor response to a sonic boom disturbance.

The somic boom is an aooustic signal and as such can be identified or assigned a signature based on its characteristic rise time, dur at i on , and peak overpressure (see Fig.

1).

The particular waveform generated (termed an N-wave) varies with aircraft characteristics such as Mach number, altitude, weight, shape, and type of manoeuvre being performed. It is also influenced by atmos-pheric conditions and loc al terrain. The SST overpressures at cruise are rated at 2 to 3 psf (Ref. 1). Actual Concorde rise time can be as low as 0.1 msec (ReL 2).

Eggleton (Ref. 1) presents a clear discussion of the elements of the boom to which people are sensitive. Essentially, rise time and peak overpressure determine subj:ective response. It is pointed out that the prime human response

is startle. Also noted is that precisely this reaction results in the boom being classed as annoying. The degree of startle is an inverse function of rise time but also depends on individual factors such as age, physical and mental health, degree of fatigue, and the type of activity being carried out. Feared

are the potential involuntary reactions accompanying startie. Could they be

so disastrous as to induce heart attacks for inst.ance? Would tThle abili ty of an

automobile driver be affected adversely in an emergency, such as duri~g a rapid

stop at a cross walk, to the point of producing fatal consequences?

In order to evaluate response to som~c booms, one has to be able to

carry out tests under controlled co~ditions with disturbances representative of those experienced or expected to be experienced from an SST. A travelling-wave horn facility at UTIAS is capable of closely simulating a wave form as produced by the Concorde (see Figs.l,2, and 3). Most important is that the

subjective loudness can be made equivalent within 10% (Ref. 2).

Some work has already been done to examinesuhe sonic boom startie phenomenon. Thackray et al (Ref. 3), for example, had individuals perform a two-dimensional compensatory task,where a small dot was to be kept centered on a display. Conprol was by means of a small control stick. Subjects were unaware of the precise nature of the disturbance to whiçh they were to be exposed.

Following a series of two-minute training runs the half hour test was done during which four booms were released - one, 2 minutes af ter the start, and the others

6

minutes apart. Heart rate and skin conductance were monitored.

For the ~urpose of arriving at a score, the one-minute intervals preceding and following the booms were divided into 5-second intervals. The larger the error signal the larger would be the number of times the integrating amplifier would be required to reset over a given time. Hence, the number of integrator resets during each 5~second period comprised the subject's score.

Sonic-boom generation was by means of a two-foot diameter fast-acting piston. Overpressure levels reaching the subjects were said to represent indoor situations and this were about an order of magnitude less than the outdoor booms. That is, for a 2 psf out door wave the subject experienced a 0.23 psf peak

over-pressure with an 18.0 msec rise time

(295

msec duration). As pointed out by Lin (Ref.

4),

however, the indoor amplitude can exceed the amplitude of the outdoor

wave. Rence, unless the room is completely isolated from the outside environment,

it is not valid te assume indoor overpressure levels will, in fact, be lower than the incident wave from outside.

The apparatus of Ref. 3 did not permit rise time control.

Results of this series of tests by Thackray et al (Ref.

3)

implied an

alerting effect due to the boom disturbances. As indicated, thoug~, such low overpressures may not truly simulate outdoor or indoor conditions. The major

problem relating to sonic boom simulation here is the large rise time since, as previously stated, any startle reflex is intimately connected with th is

particu-lar wave parameter. The spectral energy characteristics of a sonic boom are such

that much of the energy is contained in the sub-audible range. Reducing rise time results in additional energy being added to the audible range - hence a

louder effect (see Ref. 2). Thackrayet al point out that: " r ise times of

acoustic stimuli are significant determinants of the resulting behavioural

response, with startle responses occurring only if the rise times are sufficiently short". It is likely, then, that a classic startle was not initiated.

If a startle reflex did occur, the method of scoring could tend to

by-pass critical performance information existing in intervals less than

5

seconds.

A plausible explanation for the observed overall alerting effect

found in Ref.

3

is that the boom served as an acoustic stimulus rather than a

startle trigger.

For the study dealt with in this report, subjects performed a

one-dimensional compensatory tracking function. Physically, the equipment consisted of a steering wheel used in keeping centered asolid vertical line on an

oscilloscope display. This was situated in the interior horn test section. To

provide achallenging suitation, suitable control dynamies were instituted. As

well, a low-frequency random Gaussian input was applied. The situation ean be visua~ized as driving an unstable vehicle along a winding road (or an unpaved

rough road). Subjects were aware that a sonic boom disturbance might occur,

but did not know when or if they would actually occur at all during three

2-1(2

minute separate consecutive runs.

The score at the end of each run represented the integral of the

abso-lute value of the error signal. This provided an overall performance indicator. It was also decided to observe real-time behaviour and recoverynno

the boom disturbances by means of a continuous graphic readout of the error, wheel output, and score signal. A record of sonic-boom occurrence served to synchronize events directlyon the Otltput graph. Random input was also

re-corded in order to compare response to it with response to the boom stimulus. Being a preliminary investigation, a graphical record only was made. Rowever,

data could be stored on a magnetic tape and analyzed statistically on' a digital

computer.

A large number of variables (aircraft and flight characteristics, atmospheric conditions, local terrain, location, human physical, psychological

and social condition) determine the type of boom and its effect. Each variable,

interrelating the numerous factors would be very useful.

An

example would be

the evaluation of any correlation between human startle and boom rise time.

The ultimate goal of the approach indicated here would be to obtain sufficiently good data so.as to permit a statistical identification of reponse corresponding

to a given boom signature. That is, first find the distribution of sonic boom signatures, then determine the pattern of human response for such disturbances.

A brief study was carried out asking subjects a variety of questions during a run and comparing control response in this casewith response elicited

by the boom stimulus. 2. SONIC-BOOM SIMULATION

A large ~ravelling-wave pyramidal horn (Fig.

4),

in conjunction with

a fast acting, mass flow, control valve, simulated sonic-boom disturbances.

Additional details coneerning the operation of the faeility ean be found in

Ref.

5.

It is important to realize that the jet flow through the valve induces

jet noise whieh is superimposed on the simulated N-wave (Ref.

5).

Normally this is undesirable resulting in increased subjective loudness for the boom (Ref. 2).

An

effort was made to mimimize this eontribution by use of a rela -tively large throat area together with an aeoustie filter.

Referenee 2 evaluates the subjeetive loudness values of the wave forms generated by the horn. The following comparison applies to ~-wave signatures

of interest in this study.

Overpressure Duration Rise Time Subjective

(psf) (msec) (msec) Loudness

(sones,' )

Aetual Sonie 2 350 0.1 220

Boom 4 350 0.1 310

8 350 ,.() • 1 480

urIAS Horn Sonic 2 80 3.0 220

Boom (with aeoustic 4 80 3.0 330

Filter) 8 80 3.0 510

The 2 psf wave indieated here was the main wave form used during test -ing. Note, to prevent eehoes, a reflection eliminator was installed at the

end of the horn (Fig.

4).

Additional work is requiredlfb~it eompletely

effeetive.

3.

SIMULATION OF AN UNSTABLE AUTOMOBILE DRIVING TASK

The use of a'steering' eontrol mode, together with a standard size (15 i~. diameter) auto steering wheel provided the subjeets with the essential physieal components neeessary to perform a driving missio~. The experimental setup is given in Fig.

5.

A one-dimensional eompensatory tracking assignment was ehosen for its simplieity (henee minimum training). Visual display consisted of the horizontal displacement of a moving vertieal line (error signal) from

Basically, it was the task of the driver to follow a random function which forced the error bar off centre. However, rather than displaying the random function itself, an error signal equal to the sum of the vehicle dynamics output and the random input was displayed (Fig.

7).

In ot her words, the error could be nulled only if the driver responds instantaneously with a signalof equal magnitude and opposite sign - an impossible situation, hence there was always some error. This type of display characterizes 'compensatory' tracking.

Rather than providing direct position control, the task was made more challengi;qg by having the wheè1 output (driver control) signaUfiltereà through the dynamics of a first order linear unstable system. The analog solutions were taken to be accurate to within

5.0%

(Ref.

6).

For the convenience of the reader some properties of the system are presented in Appendix A. It should be kept in mind that it was not intended to precisely simulate the control dynamics of any specific vehicle or situatio~.

The control-disp~ay relationship was analogous to a driver trying to keep a lateral1y* unstab1e vehicle on a road which tends to excite the unstable mode. These road perturbations could be a result of changes in road direction or surface condition, say.

As well as simulating vehicle dynamics, the analog computer also generated the error signal (Fig.

7).

Behaviour of the overall system in the form of closed loop control is demonstrated in Fig.

8.

A clear distinction should be kept in minà regarding the two control systems involved. One deals with the vehicle dynamics alone, A(s), itself a closed loop system. The second

~oop is closed by the driver responding to an error signal made up of a random

input together with feedback from the vehicle dynamics output (Fig.

8).

4.

EXPERIMENTAL PROCEDURE

4.1 Apparatus

One of the major components, the horn sonic-boom simulator, has al-ready been described. Figures

5

and

9

illustrate the type and arrangement of equipment used at the test end of the harn.

Arl

overall functional perspective is shown in Fig. 10.

The driver was located in the interior test section of the horn, 70 feet from the apex (Fig. 4). Aside from controlled sonic booms, the location produced an environment free from distractions. Monitoring and test control were done outside the actual horn in the adjacent psychoacoustic test room

(Fig.4). Equipment set up in this area can be seen in Fig.

9.

Figure 10 illustrates the equipment interrelationship. An FM tape recorder supplied a random input to the ana10g computer which summed it to-gether with _. the vehicle dynamics output to generate the displayed error signal. ₎ Vehicle dynamics on the analog computer is the transfer function of a linear unstab~e first order system (Appendix A). Input to this sytem comes from the wheel output.

*

'Lateral' refbrs to that direction contained in the horiz9ntal plane of motiofrbut normal to the direction of the road.

Driver display was achieved via a Tektronix 535A single channel oscil-loscope set up on a custom-made table (Fig.5). The linear range of the oscil-loscope was ~ 1.25 inches. Sensitivities of 0.536 and 1.31 V/in were used. A sweep rate was chosen that would produce a steady solid line for zero input.

The scope was then placed on i ts side yieldi ng asolid vertical line horizontal:ly sensitive to input. Seating was provided in the form of a standard wooden

chair.

Display control was accomplished with a basic light-weight steering wheel mechanically c0upled to a conventional one-turn potentiometer and mounted at a convenient angle (Fig.5). The required steering force was negligible

(analogous to power steering). Absent from such an unloaded system was damping or b,ack-lash., The 1 Iffi (hot-molded composition) potentiometer supplied smooth linear adjustment with almast infinite resolution. The potentiometer was supplied with

_-

+ 15V. Wheel displacement was restricted to + 1250 or + 10.5

'

volts using mechanical wheel stops.

At the start of each run, zero wheel displacement was desirable. A straight line was drawn across the centre hub of the wheel. Orienting this line vertically produced an approximate neutral position. Wheel output, how-ever, was monitored on.the digital voltmeter so that a true null starting point was feasible.

Analog computation was carried out with a Philbrick RP manifold -a 15V system which also served as a power supply. The EP 85 AU amplifiers were used for all functions except the scoring integrator in which case a P25 AU amplifier was preferred because of its high ilinput impedance and lower

(X 1/1000) current, offset providing much more precise operation over longer time periods than the EP 85 AU. Accurate 10 turn 10 KQ potentiometers were used to complement the Philbrick unit.

Computing control modes of OPERATE, HOLD, RESET, and POT SET were handled using a series of 4 rotary switches specifically designed for the Philbrick unit and capa~le of handling the system of Fig. 7. Note that the functioning of the above circuit was verified by patching up the relevant circuitry on an Electronic Associates TR-48 analog computer. This computer was not sufficiently portable to be used during this initial study. Analog computation was an integral unit of the experiment, being used to set up the control dynamics as wetl as to perform signal summation and integration.

Driver display control was such that turning clockwise moved the vertical indicator to the right. The DC rate control gain, expressed in inches per second on the display per degree of wheel displacement was as follows:

Scope Sensitivity DC Gain

(V/in) {in/sec (displaYJjde~ree)

0.536 0.447

1.31 0.184

An

Ampex SP700 FM tape recorder furnished the low frequency (less than 3 Hz) ~andom input. This unit had a 0-2500 Hz response character-istic at speeds of 7.5 in/sec.

Accurate continuous graphic output was achieved with a multi-channel Honeywell 1508 Visicorder. The excellent frequency response characteristics permitted precise sensitive monitoring of the data. The device was fed by a H9neywell Galvamometer-Amplifier, Model T66A-500. Independent gain control

existed forr.each channel. Readout censisted of the input, error, wheel out-put, sonic boom and scoring. signals (Fig. 10) 0

Pressure level for the interior horn test section was monitored with the following Bruel and Kjaer equipment: microphone pickup No.4147, microphone holder No. UA 0271, and carrier system type 2631. Auxillary equipment included an independent power supply (Sorensen ~ Nobatron ~ 15-2) for calibration of the graphic readout, a stop watch to time the length of each run, a dig~tal voltmeter for monitoring wheel output and score, and an intercommunication system.

4.2 Random Input and Scoring Technique

Source for the input signal was a Gaussian noise generator (Medium frequency, Ref.7). A random signal 150 sec in duration constituted one run. Four such unique signals were recorded on the FM tape recorder. The use of different random signals was intended to counteract any conditioning that might result af ter repeated testing.

The De level over the 150 sec was kept less than 0.020 in of display. Because_of limited analog computing capacity this could not be monitored for each test run. However, a daily check was made using only the integrator seg-ment of Fig. 7(b). Input RMS levels of 0.052 in and 0.021 in were used with

scope sensitivities of 0.536 V/in and 1.31 V/in, respectively.

The above run sequences were chosen since all had (within 0.020 in of d'isplay) a constant value for a fixed input RMS level for

Io

150 i 2(t) dt

(checked on TR-48)

J

o

150

li(t)1 dt

Hence it was meaningful Since

J

1

5

0 li(t)ldi was

o

t o use

_J

150 le(t),[dt as a per ormance measurement. f o

constant (0.269 i~sec) it was not necessary to use it to non-dimensionalize the score. This approach was taken due to the lack of a computer squaring ability.

J

1-50

Score = le(t) Idt [in(of display)-sec]

o

If the individual were to react precisely and instantaneously in follqwing the input, a score of zero would result. However, the tracking is carried out by a human driver; hence a non-zer9 error and score. If the driver were not to respond at all, the score would equal:

J

150 li(t) Idt

=

0.269 in-sec(0.536 V/i~ and 1.31 V/in Display

(Note: this value was checked periodically, for each of the random runs, using the absolute value integrator - Fig.

7).

However, amplifier drift is sufficient to excite the unstable system to overload in a short time (10 seconds or less depending on the degree of instability) so that to arrive at this value the control dynamics must be disconnected prior to starting the

integration check.

4

·

.3

Subj ect and Training

Six volunteers, five male and one female, from staff and students at the Institute were involved in the_actual testing. All were experienced car drivers. Ages ranged between

25

and

54.

Table I gives additional rele

-vant inforroation.

Subjects I, 11 and 111 were given a brief training; the others'

were untrained. Training took place over a five-day period. The first three days involved introduction to equipment and actual runs with differing system parameters.

An

instability level demanding concentrated effort was chosen.

Final training involved a series of 20 runs taken over a tWb-day period.

Figure 11 shows the performance level achieved.

The .150 sec duration time per run was qpite adequate for test purposes. At the same time it was short enough to prevent the 0ccurrence of boredom or fatigue. Personal interest in the project and a competitive

spirit provided for performance motivation.

4.4

Testing Procedure with Sonic-Boom Disturbances

The basic technique was to carry out three consecutive 150 sec runs with a two-minute rest period af ter each one. The subject was told that he mayor may not be exposed to a sonic-boom disturbance during the test. In starting, the wheel input was nulled by means bf the test operator relaying the voltmeter readings to the driver verbally, and in this way guiding him to a true zero start. For a case of high instability such an approach is

important since any sroall initial input to the system, when starting, could prevent the driver from every gaining control, resulting in an aborted run.

To start each run the test operator would start the tape recorder and watch the output meter (and footage indicator) to pick up the beginning of a run. The computing system was put in the OPERATE mode by simply turning the rotary switch. Simultaneously, a stop watch was activated. The visi-corder was turned on about 10 seconds prior to the start of each run even if a boom was not to be released. Otherwise, the subject could have guessed during which run a disturbance was to be expected. In preparing the visi

-corder, a pre-test run was carried out to set the galvanometer gains to reasonable levels for each channel. Before every run a one-volt input was applied to each cha~el for five seconds thus calibrating it.

Each run ended wh en 150 sec had elapsed, according to the stop watch. By means of a simple rotary switch the computer was set in the HOLD mode to

enable the operator to record the subject's score by reading the voltmete~. Amplifier drift or capacitor leakage was not of sufficient magnitude to interfere with this mode of operation. Once the score was recorded, the switches were returned to the RESET mode and the system was ready for another run.

To release the sonic-boom a separate control box was provided which reqMired the pressing of a 'reset' and 'releaseJ _button.

_An

_{attempt was made}

to achieve a number of different responses by altering the distribution of disturbances applied during any given run artd by variation in system para-meters. The two major response classes sought were totalloss of control and partial control loss fO+10wed by recovery. A surprise element was kept in effect by releasing the booms randomly. A driver could experience a s0nic boom within 5 sec of starting, 5 sec prior to ending, anywhere between be-ginning and ending,. or af ter almost two complete runs. A series of up to fi ve consecutive booms were applied in some cases.

An

entire run might i~volve no booms or up to seven - some consecutive and some spaced 20 sec or more apart. Totalloss of control showed up but cases of partial control loss, especially with respect to amplitude, were not very ~ell defined at first. For this reason the instability was increased as to to 'tune'in' to a driver's critical performance region where hopefully his ability would be taxed to the limit and, as aresult, any distraction would be easily detected. In order to effectively provide a wider field of view for the driver, so that he would have time to respond rather than lose control by losing sight of the display, the display sensitivity was decreased by a factor of 2.5. As aresult the RMS level for the random input was also decreased. This method proved

succes sful~.

The unstable dynamics behaviour was such that even without an input signal the subject could be given a difficult task just controlling the un-stable signal growth. A larger instability level with zero input was feasible, thus providing another control zone in which to measure subject response. A stable system was simulated briefly but showed no definite results, even though a much higher RMS input level was used, hence it was not utilized.

In testing the naive subjects, they were allowed a 15-minute familia-rization period for examining equipment and actual tracking. This was the extent of training prior to being tested in the manner outlined above.

Since a 2 psf, 8~ msec duration boom had a subjective loudness

equal to a more or less typical Concorde boom, it was used almost exclusively during testing. In some instances 4 and 8 psf, 80 msec waveforms were tried. In a more detailed study, of course, a wider variety of waveforms could be tried.

4.5 Interrogation Test Proced~e

For the purpose of comparison with sonic-boom response, an alternative stimulus was presented to the driver in the form of a question asked by the operator over the intercom. Except for the nature of the disturbance, the

entire run procedur~ was identical with that used during sonic-boofus. Generally the question had a start and end followed by the driver's answer. These three events were recorded by applying a short one-volt input to the channel pre-viously reserved to record the boom. For very short questions only the start was recorded. Basically, the questions were either of a sim~le logic nature or required a simple direct answe~. They cou~d be classed as: arithmetic operation, alpha.betic<J d>rdering, factual, moral is sue. For example;

- 5 x 7 - 5 is ?

- rq (answer gr)

- Name the largest river in the world.

4.6

Data Reduction

Driver scores provided a 'gross' performance indicator for the 150 sec run interval, but if one was interested in determining exactly where

and in wh at manner a change in response occurred, real-time records (Figs. 12-25) had to be examined. ~able 11 presents scores achieved using different subjectsj stability levels, inputs, overpressures, and stimuli. To allow simple meaningful interpretation of input RMS level ani score, these values

were reduced to equivalent inches on the display-sec.

A wide spectrum of response, from virtually no reaction to a

well-defined control impairment followed by recovery, was indicated in the time

records. A certain degree of difficulty was experienced in trying to accurately

specify reaction time characteristics. The following discussion provides the

rationale used in dealing with records having measureable response characteri-stics. Figures

13

to 25, which represent only particul~ run segments, are

examples of time records which provide immediate visual evidence that the indi-vidual has definitely responded to the stimulus. The basic pattern of response

was considered as made up of a number of distinct elements. A predominant

response was an initial jerk or holding action occurring in less than. half a

J

second following the boom. Because of its abrupt appearance and short duration (that is, the actual length of the sp~ke or plateau), it was termed an 'initial' startle. The delay timedrom the boom to the start of an initial startle and startle duration were measured with a finely calibrated rule and magmifying glass. Despite this technique the recording time scale used still made if

difficult to obtain accurate measurements, The results (Table 111) would, however, certainly be realistic.

Following the initial startle, what might be termed a 'normal' or

'classic' startle, of ten appeared. This response was characterized by both

amplitude change and apparent frequency change with respect to pre=boom conditions. The time from the occurrence of the boom disturbance to the

peak amplitude of the startle (T

p) was measured. A visual estimate was used to determine when the signals had returned to their pre-boom status. The criteria used was that the amplitude envelope be returned to reasonable levels as well as the apparent frequency. The time involved in this case was

labelled T for 'total recovery'. ~his parameter was not precisely measurable for situatlons in which booms were spaced too closely or too near the end of a run. In many cases a partial recovery was indicated soon af ter the peak

amplitude response. It was felt, however, that this region was not sufficiently well-defined to examine on the basis of these results. The time to loss of

control

(Tt)

was quite explicit~y defined as the interval from the occurrence of the boom to the point when the error signal went out of view of the display

for the last time. Figures

13

to 25 illustrate the precise measuring

tech-niques emillpyed. Some of the results are listed in Table IV.

An attempt was made to follow a conservative philosophy in all

measurements. That is, recovery times were underestimated and initial startle

parameters overestimated, if there was any doubt during measurement.

An

effort

was not made to apply the above procedure to the interrogation response,since the precise location of the start of the stim~lus was too ambiguous.

Concerning the figures presented: they represent the results

provi-ding a relatively well-defined response (except Fjg .21, which is an example of negligible reaction).

5. RESULTS AND DISCUSSION

Exposure to somic-boom disturbances resulted in a variety of responses. The more significant results appear in Figs. 13-22. Figure 12 provides a

reference in that it depicts the response of subject I when no booms are present. oth€r figures show response to boom stimulus for identical random input. For example, looking at region 'A'-'A' of Figs. 12 and 14, one can see directly what effect the boom had on driver behaviour. Note that the boom consists of the main wave plus a number of smaller amplitude reflec-tions (Fig.l) which are also shown on the time records.

The most general pattern of response that can be put together from this series of tests consists of an 'initial' startle followed by a more classic startle and recovery (Fig.14). Contrary to results found in Ref. 3, this constitutes a negative infÈuence on performance since partial loss of control was experienced and score increased with respect to the trained levels (Fig.ll). The time takefrto reach peak amplitude response averaged 4.4~ secs and had a range of 2.55 to 8.40 sec (Table IV). Average recovery time was 14.8 sec ranging from 7.5 to 22.2 sec. A partial recovery af ter 8-3/4 sec occurred in Fig. 14.

~he control pattern of some drivers involved many jerks or holding motions, ~ut both for these drivers and for those for which this was not the case, a form of initial startle appeared to exist. As seen in Table IV the mean delay time and duration were approximately the same - just less than a quarter of a seconde The phenomenon occurs in almost all cases and is

indicated wherever possible. Figures 21 and 22 demonstrate the two categories present.

In instances where a complete loss of control was experienced, the time for this to occur following the final boom was an average 2.36 sec rang-ing from 0.625 to 6.56 sec (Tab~e IV).

The one response characteristic not quantitatively ineasured was the ratio of peak response magnitude to pre-boom magnitude. The problem lay in accurately identifying the amplitude levels prior to the boom. For well de-fined cases such as Fig.14, however,

it

couId safely be stated that peak response was at least a factor of two greater than the pre-boom amplitude envelope.

For many runs no random input was used. The main reason was to remove one of the measurement variables. By doing this one could more definitely determine if the subject was responding to the boom stimulus alone, since there was only driver-injected noise to react to. The use of high instability levels, however, complicated the interpretation of the re-sults since the individual could be providing very erratic response just in

coping with thes~ystem. Even with random input, stability level is signifi-cant in determining the driver's score (Table 11).

Either by makigg the task more difficult or by employing a psycho-.. logical 'trick' the subject could be made to lose control (Fig. 17). In two cases the individuals completed almost two full runs prior to a boom disturbance - both lost control even though they were trained at that

stability level. One subject mentioned that he began thinking of ot her things and was not prepared for the boom. Perhaps this is very significant since

people will normally not be anticipating a boom but will be thinking of other things. Interestingly enough this particular subject (lIl) was not very

sensitive to boom distractions throughout most of the experiment. On the

third consecutive run, a boom was released 10 sec from the start but subject

III did not have any trouble maintaining control. A similar procedure caused

the other subject (I) to once again lose control. The same method did not

result in subject II losing control at any time*. With no input but a higher

instability level subject II also lost control when exposed to a boom. Of

interest is the observation that additional difficulty arose if the

distur-bance coincided with a large wheel displacement. This is explainable as a

temporary increase in task difficulty which normally quickly disappeared or

control was recovered.

To stimulate a 'classic' startle the effective field of view had

to be expanded by decreasing the display sensitivity by a factor, 0f 2-1/2.

Thus the driver was given a better opportunity of correcting the error

instead of goigg off scale. Subject I provided ~he clearly defined response

of Figs. 14 and 18.

Subject I, the most consistently sensitive subject, did not show

any real significant reaction difference wh en exposed to higher overpressure

(Fig.19), but more quantitative analysis would be necessary to bear tbis out.

Figure 20 is a lucid illustration of a multiple-boom effect in which

driver performance deteriorates af ter each successive boom until, finally,

compl.ete 108s of Gontrol results.

In one instanee (subject VI), the amplitude envelope showed a definite

dip for about ten seconds following the boom, thus indicating an improved

performance. Subject II also had the least heart rate increase and heart rate

recovery time (Table I) when exposed to the boom. In general, insufficient

data exists to make any conclusions linking heart rate response to performance

response to sonic booms. The results collected do have a mean heart rate

recovery time comparable to performance recovery time (Tables I and IV).

In order to achieve as wide a variety of reactions as possible, bath

trained and naive subjj-ects were chosen for the tests. The trained driver

hopefully provided a more consistent, steady type of control so that even a

small change in performance would be revealed. Naive subjects, on the other

hard, are more erratic yet are more susceptible to produeing a large amplitude

reaction to any distraction. Also with the intent of solieiting a range of

reactions, a stable, as well as unstable, control was used. Figure 21 shows

the result for a trained subject (I) and stable system - only an 'initial'

startle is clearly defined. Subject V, however, provided a definite startle

and recovery whep using a stable system. She was untrained and exhibited

a marked physical response to booms (Table I).

Although in same situations a negligible response appeared, subjects

all agreed (independent1.y) that it was the first boom of the run that S,tartled

them most. It could!be because they develop a certain amount of anxiety in

anticipating a disturbance. ~hi~ emphasis on the first boom effect could not

be fully confirmed solely on the basis of results presented here.

* Note; ~owever, that subject II was the technician for the horn faeiLity,

A word is in order concerning the presence of the wide range of res-ponse from almost no reaction to a very definite reaction. Part of the answer lies in the uni~ueness of each individual's psychology and driving ability. However, even under identical conditions a subj ect does not yield an identical response - why? Partly this canbe explained by conditioning and training. Also, as with many systems depending on a large number of circumstances the response itself likely follows a statistical distribution.

For interrogation it is much more difficult to determine the exact starting poi~t of the stimulus. The general reaction appeared to be minor compared to the boom response (Fig. 22). Even subject I showed little dis-tinct or visually obvious results for most questions. Evidence was present of an 'initial' startle effect which eventually disappeared as the subjects gained experience. Subject 11 was the subje~t with the most training ánd exposure to the boom. It w'~uld appear that it is because of these factors that he showed the least reaction to the sonic disturbances. This belief is strengthened when it is seen that fuis reaction to interrogation is, in general, much more defini te than that of subject 1. Because of the lack of astrong interrogation effect no resutts were presented for subject I.

Fig}ll'e 23 shows reaction tG a simple and more difficult arithmetic question. In Fig. 22 the first question was factual; the second involved more involved arithmetic. Response to

ä

moral question and the effects of a misunderstood question are given in Fig. 24. The misunderstood question almost resulted in loss of contrGl (off the display). Reactions, then, did exist for more complex issues. But instead of a prolonged apparent change in frequency and amplitude, as for booms, the reactions in this case con-stitute a peak amplitude response taking less than five seconds for complete recovery.

As an initial study the experiment has served to provide insight

into the general nature of real-time human repponse to sonic-boom disturbances. It also serves as a guide in carpying out further studies such as the

statistical significance of response (hoth amplitude and frequency) under a variety of closely controlled conditions. During the tests parameters should be systematically varied in order to determine which are of most in-fluence. Subject-dependent parameters include age, training~ motivation, a~d number involved. The task simulated could be varied to include more precise models of actual steering-oriented functions thus relating directly to useful real-life situations. N-wave signatures could be altered - notably rise time and over-pressure. In order to vary rise time the loudspeaker -driven booth (Ref.

5)

located in the driver end of the hor~ facility (Fig.

4)wo~ld be used. Further study should be done toattach a probability to

'initial' startle effects for a variety of conditions. This would also be desirable for the rclassic' startle effect and control loss events. In carrying out further investigations the use of a large number of subjects unaware of the true nature of the disturbance can be highly recommended.

6.

CONCLUSIONS

On the basis of the findings obtained during this study, it can be said that sonic-boom disturbances of the type generated by the Concorde SST res»lt in a measura~le startle effect (performance deterioration during a tracking task) manifestingitself in somewhat different wayp for different individvals at different times.

Total performance loss as well as almost negligible change in per-formance were observed. Between these extremes was found a pattern involving an initial startle followed by peak amplitude response, sometimes partial recovery, and total recovery. This pattern, in general, is not similar to that obtained from startle following asimple question. The sensiti~ity

of the unstable vehicle dynamicsr,provided a flexible tool for extracting measureable results from whatcould, at times, prove to be an elusive res-ponse.

The problem of specifying a given response for a given sonic-boom signature and task would appear to be statistical in nature.

I

It should be kept in mind that the results apply only to that par-ticular task sifuulated during this study. Because of the small numbef of subjects and somewhat qualitative approach used in measuring reaction characteristics no 'final' conclusions are justified. Rather, the results provide a guide toward a poteptially fruitful area of research into the effect of sonic-boom disturbance on human response.

1. Eggleton, P. L. 2. Carothers, R. 3. '~hackray, R. I. Touchstone, R. M. Jones, K. N.

4.

Lin, Sui 5. Glass, 1. I. Ribner, H. S. GQttlieb, J. J. 6. Carlson, A. Hannauer, G. Carey, T. Hol~berg, P.J. 7. Reicl., L. D. 8. Kaplan, W. REFERENCES

The Senic Beom - Weighing lts Implications for Policy Consideration. CASI Journal, Vol. 18, No.5,1972.

Initial Calibration and Physiological Response Datafor the Travelling-Wave Sonic-Boom Simula-tor. M.A.Sc. Thesis, University of'l'Toranto

. (te be published)

The Effects of Simulated Sonic Booms on Tracking Performance and Autonomic Response. Federal Aviation Administr.ation Report No. FAA-AM-71-29, 1971.

Sonic Boom Analogues for Investigating Indoor Waves and Structural Response. UTIAS Tech. Note No.158, 1970.

Canadian Sonic-Boom Simulation Facilities. A paper to be presented at the 8th Congress of the International Council of the Aeronautical Sciences, Amsterdam, 28 Aug.- 2 Sept., 1912. Handbook of Ànalog Computation. Electronic Associates Inc., 2nd Ed., 1965.

The Measurement of Human Pilot Dynamics in a Pursuit-Plus-Disturbance Tracking Task. UTIAS Report No. 138, 1969.

Ordinary Differential Equations. Addison-Wes ley, 1958.

APPENDIX A: FIRST ORDER LINEAR UNSTABLE SYSTEMS

~he purpose of this Appendix is to provide a quick reference to relevant

details of the weil known first order system.

The differential, constant coefficient equation describing an unstaIDle

first order linear system is:

where

x - t3x

=

dx _dt - t3x

t

=

independent time variabie

f(t)

x = dependent variabie such as displacement

t3 system tmnstability) parameter

(A.l)

f(t) = the non homogeneous forcing term - in this case wheel output.

Looking at the situation from a control system point of view can IDe

helpful. x(t) then would represent the output resulting from the response of the system dynamies (left hand side of equation (A.l) to the input f(t).

Pictorially equation (A.l) can bevviewed as:

Error Output

Integration Inversion 1 - - -_ _ . . . - - -___ - x( t)

f + t3x '

-MUL:rIPLICATION

Simple Control System

'0' Input Response

When ~(t)

=

0 and x(O)

x(t)

x o

x the solution to {A.l) is: o

- an exponential divergence from the initial condition. Constant Inlut Response

In this case f(t) f

=

constant and x(O)

=

x . The ~olution ~0W is:

o 0

t3t x(t) =-fo/t3 + (x_o + fo/t3) e

diverging exponentially from the input value.

x(t) ···x .. ,0 fo X r---_~ o

The response is seen to be characterized as an exponential divergence (hence unstable), the rate of which is directly determined by the feedback

parameter t3. Any change in initial conditions servesto introdue new transients of exponential growth. Drift of amplifier output for the analog computer then, would alter system response.

Equation (A.S) gives insight into the nature of response to a very

low fre~ue,ncy- (23 cps) input. As an approximation one might regard the input

as a series of constant inputs each covering a finite time interval. Initial conditions also vary from input to inp~t. The term (x + f /t3) then is quite

o o ·

like+y to vary between positive and negative values - thus changing direction of divergence. This phenomenon provides the driver with control over the instability. This control can be made into a task itself. By use of a large enough t3 the system can be made extremely sensitive to any initial condition changes which themselves demonstrate a certain amoun of randomness because of amplifier imperfection.

System Transfer Function

With aids, such as Laplace Trans~orms, ane can arrive at a transfer function for the simple control system governed by equation (A.l). That is, _!

where

x(s)

=

s

=

complex variable suçh as jW

W = frequency

j

=

.,[..1

(A.@)

(

~

=

symbol indicating the Laplace transform of the indicated function. The DC (zero frequency) gain of (A.!) depends on x and t3. However, x can be qui te random and t3 is varied during experimentati8n to find tasks

o~ suitable challenge. In order to keep the overall vehicle dynamics De gain constant'while using different instability parameters, the system of equation (A.l) is simulated as indicated below and in Fig. 7(a).

f(t) x(t)

R integrator gain

(l/RC)

).. _{= pot setting}

~ = kÀ, and :t:or convenience set y = f(t) x Q

0 The ... abQve system can be expressed as

o x

=

Mx k)..y or x - = -y

for which a convenient DC gain of one exists.

A further elaboration on first order linear systems is to be found

in ReL

8.

As a point of interest, it should be noted that the unstable

situa-tion described here is representative of such phenomena as populasitua-tion growth,

TABLE I

SUBJEÇT DATA ~esults _~xposure of Refó 2 Due te

to 2 psf,80 msec N-vave SUBJECT AGE SEX GLASSES OCCU- IDRIVI~G , INCREASE IN TIME TO RECOVER

(YEARS) PAT I ON ~XPERIENÇE HEART RATE, TO INITIAL HEART

(YEARS)

(%)

RATE (sec.)

I 25 M Yes '. Student 8 11 11

Ir 31 M Ne Technical 10 12 13

IrI 33 M Yes Technical 15

IV 54 M No Profes'sor 32 3 13 V 27 F No Secretary 7 30 39

VI

38 M Yes Technical 20 2 3 Mean 11.6 15.tJ F - Female, M - Male VEHICLE ~ _-1

~UBJECT STABILITY sec

I Unstable 2.25 I

"

2.25 I

"

3.12 I

"

3.12 I Stable .025 I Unstable 2.50 1 " 3.65 I " 4.00 I Unstable 3.65 I

"

3.65 I " 3.65 I

_"

3.65 I 11 3.65 11 Unstable 2.25 II 11 2.25 II

_"

2.25 II

"

3.12 II 11 2.50 II

"

3.65 II

"

3.65 11 11 3.65 II 11 3.65 II 11 3.65 III

"

2.25 III

"

2.25 III " 2.25 III Stable .025 III Unstable 4.20 III 11 3.86 IV 11 1.54 IV 11 1.79 TABLE 11 SUBJECT PERFORMANCE RANDOM INPur INPill RMS LEVEL RUN (in. of display) 1 .052 1 .052 1 .052 1 .052 1 .180 1 .021 1 .021 1 .021 1 .021 2 .021 4 .021 0 0 0 0 1 .052 1 .052 1 .052 1 .052 1 .021 1 .021 0 0 0 0 0 0 0 0 1 .052 1 .052 1 .052 1 .18 0 0 0 0 1 .052 1 .052 TaDAL SCORE

NUMBER (in-sec) REMARKS

OF BOOMS 0 1.37 4 1.54 0 2.30 4 3.28 3 1.62 2 .755 4 1.44 4 psf 6 1.42 0 1.55 Interrogation 0 1.85 11 0 1.55 11 0 1.35 11 0 1.27 11 0 1.35 11 2 1.43 4 psf 3 1.36 8 psf 5 2.00 3 .763 4 1.88 4 psf 0 1.45 -Interrogation 0 1.08 11 0 1.22 11 0 .88 11 0 1.21 5 1.21 3 1.18 4 psf 4 1.54 3 1.55 2 1.11 0 2.47 4 3.82 continued .••.•.

Table II - continued ••••••• V Stable • 025 1 .021 0 2.57 V

"

.025 1 .021 1 2.42 V " .025 1 .021 3 2.31 VI Unstable 1.92 0 0 3

.53

"

2.40 ~ VI 0 0 3 1.90

Note:- All sonic-boom disturbances have an

eo

msec duration. - Unless otherwise noted the overpressure used was 2 psf.

- Wheel output gain for stahle system was

=

0.356 [in/sec(display/degree] TABLE III

, INITIAL ' STARTLE VALUES

f3 INPUT N-WAVE INITIAL

SUBJECT sec- 1 RMS OVER- STARTLE

LEVEL(in. PRESSURE DELAY DURATION REMARKS

of display) (psf) (msec) (msec)

I 2.25 .052 2 156 156 lst Boom I 2.50 .021 2 117 156

"

I 4.00 .021 2 117 156

"

IL 2.25 .052 4 312 234 Double Boom II 2.25 .0512 8 156 156 2nd Boom II 2.25 .052 8 156 78 3rd

"

II 3.12 .052 2 78 156 lst

"

II 3.65 .052 2 78 78 2nd

"

II 3.65 .021 4 390 312 lst " II 3.65 .()21 4 430 625 çnd

"

II 3.65 .021 4 390 312 lrd

"

II 4.37 .021 4 195 312 lst

"

III 3.62 .021 2 156 156 2nd

"

III 3.62 .021 2 156 234 lst

"

III 3.87 .021 2 156 195 2nd

"

IrI 3.87 .021 2 78 156 lst

"

IrI 4.21 .021 2 234 156 2nd " III 4.21 .021 2 78 117 lst

"

IV 1.79 .052 2 156 234 lst

_"

IV 1.79 .052 2 156 195 2nd

"

VI 1.92 .021 2 156 234 lst

"

VI 1.92 .021 2 156 274 2nd

"

VI 1.92 .021 2 117 234 3rd " VI 2950 .021 g 156 117 lst

"

V-I 2.50 .021 2 350 274 3rd

"

lMean 186 212

TABLE IV

REACTION ~IMES FOR CONTROL LOSS AND RECOVERY

STABILITY INPtJr TIME TO TIME TO TIME TO

SUBJECT LEVEL RMS PEAK AMPLI- TOTAL CONTROL

t3

LEVEL(in. TUI;lE RESPONSE RECOVERY LOSS REMARKS

sec- l of display T (sec.) Tr(sec.) Tt(sec.)

p I 2.25 .052 1.25 I 2.25 .052 3.12 4 psf. I 3.12 .052 .625 I 2.25 .052 2.55 7.15 first boom of the run I 2.25 .052 2.65 7.15 two consecu -tive booms I 2.50 .021 3.12 ;;0.3 I 2.50 .021 5.00 last boom 10 sec. befare end of run. I 3.65 .021 3.75 10.1 4 psf. I 4.00 0 4.05 7.5 11 3.26 0 1.~8 8 psf. I l 4.21 0 6.56 4 psf. 11 4.50 0 1.56 I l 4.37 0 8.40 22.2 4 psf. III 2.25 .052 1.55 111 3.87 0 6.20 13.8 Mean 4.46 14.8 2.36

Note:- In all cases response is for a boom having 80 msec duration)unless otherwise

.

oP ~ Q)

>

Rise Time

Duration

~I

IDEAL N-WAVE SONIC-BOOM PRESSURE PROFILE

Hor. Scale

50

msec/div.

ACTUAL SONIC-BOOM PRODUCED BY THE CONCORDE SST AIRCRAFT FIGURE 1

IDEAL AND REAL SONIC-BOOMS

Horizontal Time Scale (20 msecjdivision) (a) 2 psf Peak Overpressure

Horizontal Time Scale (20 msecjdivision)

(b)

4

psf Peak Overpressure

FIGURE 2

.§

ö Q) (f.l

....

UI Q) E-4 2 _.~ t: C UI ... 0. Q)

--> Q) ...J Reflections Q) s.. ;:l UI UI Q) s.. p... 0

Horizontal Time Scale: 1"

=

0.05 sec

-2

FIGURE 3(a)

c: 0 • .-<

...,

() Q) r.n.

...,

4 en Q) ~ c: ...

....

• .-< _en ... 0.. Q)

--IV

_\

. / Reflection > Q) ...:l Q) M ;:l en en Q) M p... 0

Horizontal Time Scale: 1"

=

0.05 sec

~

Reflection

-4

FIGURE 3(b)

~

PSYCHOACOUSTIC

TEST ROOf

'

.

l

MAIN

BUILDING

PSYCHOACOUSTIC BOOTH

j

-

lI

'

.

\

,

r

~

'----;

,

-

II

\

I

l

~

)~

PYRAMIDAL HORN

l

CONTROL ROOM

r"-

,I -

~~;~ij

-'-

I

- ___

~/

J -

=~

'i

-

--- - - -- -___ _ _

rh---

-

-

-

-+-- ---

-- - - -

---±-~_-=-~l---.:-.:--==.o;

I

_{, , - - - -}

'!-

'\ -,

---

t

_{--7 H •} (1--- \ El _

n

REFLECTION ELIMINATOR

JET-NOISE ABSORBER

o

5m

-===========

SCALE

\

INTERlOR TEST SECTION

PLAN VIEW

FIGURE

4

HORN FACILITY

SONIC-BOOM GENERATOR

FIGURE 5

YELLOW REFERENCE LlNES

GREEN MOVING ERROR LINE

FIGURE

6

WHEEL

INPUT

O(t)

VEHICLE DYNAMICS RANDOM

INPUT l(t)

(a) ERROR SIGNAL GENERATOR

PRECISION FULL-WAVE RECTIFIER

1 R

~

R

(b) ABSOLUTE VALUE INTEGRATOR FIGURE 7

SCHEMATIC OF ANALOG COMPurING SYSTEM

RMS

SET

.(t)

DC BIAS

DISPLAY DRIVER

. ( t)

l

e(t)

+

Y(s) 1 NPUT

&

WHEEL WHEEL

o(t)

OUTPUT

FIGURE 8

COMPENSATORY TRACKING

VEHICLE

m(t)

A( s) DYNAMICS S "U YSTEM UTPUT

FIGURE 9

INPUT TAPE RECORDER BOOM TRIGGER ANALOG COMPUTER CON'l'INUOUS GRAPHI C RECORDER

i(t), e(t), o(t),

score,

&

boom signal

FIGURE 10

WHEEL

DISPLAY

2.1

""

~ 1.9 lil I

]

~ ~ 1.7 .

~

.

t

_l\

_\, .c

<i\.\

11.5

I

~

.

j

1.3

~

,

y \\

,

'"

~

' v / \

V

\

l----~

\ __

r~

,

\ /

/1>---

'i\

~

'

,'

"--...\

,,"

'

'v'X

-

,'

-

';

-

--./

A----A.,

' "

' - , . J ! f

' , w " , _ ", __ -'< 0 ) ; , - '

'~

__

~--A

/

\

/

'

\

/

Subject I (':) G) Subject II A- - - ---8 Subject III - -' -Unatable ayate. (3 - 2.25

Rando. input signa! #1

0.052" input RMS ~----A I I I I I ,/~ ----z1{ "-~ 1.1tl---~---.----~---.---~---,---~---.---~--1 3 5 7 9 11

Conaecutive Run Nwaber

FIGURE 11 LEARNING CURVES

13

15

17 19

'I-Time (seconds) i i , i i i . .

o

10 20 30 40_~ 0 -1/1 Cl

i

1/1

1!

~

o

+10

+.5

i

_s

-.25 Score Booa Signal , A' I I

'A'

FIGURE 12 FuU Scale

Subject I - Uutable 8yatea ~ - 2.25

- .0,52" RMS input

Score 0 0

T.:

t1O o(t)

I

!

-lU

-.5

•

.!

T+ • .25 i(t) ~ H r'\ T

_{I I}

Tp P

--i

.2 pet 80 uec I .

~h~ ~f'1A~

.

\

A

AI

~A.lf\

A

~

.

'~ ~

V4

~,

\,J

'V '

~.

•

~ " Full Scal. >-. \

~

v \

J" \' \

I \ I I

V

~

_{: 1\'}

I \ ".

_1,l'\iïI\I~ 0 I \ I \I \ _{- 7 1 1} I \

I \ }

V -\

_{\.N\ /\/} f\ I

V\

IV

\,l

\,.I

V \

\

r

if I "" J V 1\& j

S

-.25

T1ae (seconde)

, - - - , I T 1 - r

o

10 20 )0 40 SO

FIGURE 13 Subject I - Unstable _{- .052" RMS} system _input ~ = 2.25

REPEATED SONIC-BOOM DISTURBANCES WITHOUT FULL RECOVERY - Score = 1.53" display

Tiae (seconds) T-- - -T I

o

10 • A • 20 T JO 40 50 r

I

'

2 psf

o

Score - Tn"'ol

~

80 ....

o

~j

A

~

Boo. Signa! +10 o(t) , A' FIGURE 14

Subject I - Unstable system ~

=

2.50

- .021" EMS input

o

o

Ti.e (BecondB) . - - - , , - - - I I I'"

o

10 20 JO 40 50 T r Score Boo. Signal T p 2 par 80 .Bec +10

:

fll~rAtf/~'~(----~'~I~\~~~IÎ'~·~\"--li----litr----t---~f_~~~~--~~~--~--ïf---4-i~-;----~~~---Art~~~~r-~~:L~

_{g, Ter v " ~ I "}

_I

_ft

_\'

_{/ ,}

I , 1\ ti , \ 1 ' t: i l

1 \ "

J ) 1\ , \ A M I \ I Q 1 \ 1 1 l i f l J \ l : V i l 11 ti + • .5 eet) .c 1\ I \ A.

/\I...L-8

1\ I \ I \ I V \ A \ J \ 1\

x

_ r

\

A.

J~

H _A7<F

_I"""

_{~ \ , \ I} i J 1 / \

~

P-Il

B

iet) O~I---FIGURE 15 INITIAL 'JERK'

Subject 111 - Unstable system ~

=

3.87

iet)

_o

i i i i , - - - I Ti ••

(a.conda)

o

5 10 15 20 25

FIGURE 16

Subject 111 - Unstable system ~

=

3.87

Score 0 Boom Signal 0 • +10

•

o(t)

i

0 -10 +.5 eet) 0

I

-.5

11

+.2.5

a

i

_•

0 iet)

s

-.25

d

.

5

io

15

~o

~.5-2 per 80.sec __ , I Tiae (seconds) v

(\\I~~~ 1~~

- Unstable system ~ = 2.25 - Score = 1. 97" display - .052" RMS input FIGURE 17

Score 0 Booa Signa! 0 +10 111 o(t) 11

_~

0

&

-10 +.s 111

.!

₍₎ eCt)

.s

i

0 111

8

-.s iet)

o

I 1 Ti ••

o

S ;0 11S

~o

is

IF(seeonds) T r T_p

fl

I

l

2 80 psf msec FIGURE 18

WELL-DEFINED RESPONSE WITH HIGH INSTABILITY AND ZERO RANDOM INPtJr SUBJECT I

Full Scale

- Unstable system ~

=

4.00 - Score = 1.42" display

Score 0 Booll Slgnal 0 o{t) eet) iet)

•

•

i

•

•

iS

+10

o

-10 +.5 0 ~

-.5

l+

e12

₅

~ co

S

0 -.125

o

I Tiae 5 10 15 T 20 25 (seeonda) Inlt1al Starlle (slope change) T_p FIGURE 19 r

RESPONSE USING A HIGHER OVERPRESSURE

4 per 80 asee Ml Scale - Subject I - Unstable system - t3

=

3.65 - .021" RMS input - Score = 1.44" display

Score 0 Booa S1gnal 0 11 +10 el o(t)

~

0 eet) iet)

!

-10 +.5

o

Cl -.5

.,

'5

+.25 ~

.s-f;

s

0 -.25

b

Si 110 liS

ia

y'

Tt

2 psf 80 uee Tiae (seconds) hU Saale

1\1.. I:

r-

In1 Ua! Startles

- Subject I '

- Unstable system

-

~

=

3.12

- .052" RMS input

Tbe (seconds) I I I -- - 1 I

o

10 20 )0 40 Score 4 psf

o-l

~

Boo. Signa! 80 asec 0 + Io

l

o

<t:

111 ~ ₀

ä

~ -10 eet) +.5 : 0 ~ J \ J \

I \ A

J

V I .

J

I

A

1\ l \

A

l\! \

J \

AA I I I I

l I

f\

tAl "

J

\A

Ii

A

A

n-L .c u ~

3

-.5

PI lil

a

+1 iet) ,

o

t

fI

A

MA

~ ~

---

AA

_r-I\. ""

.

J

vv~v V~V·V* "~

_I

\J7

Subject I - .tablo ... FIGURE 21 STABLE SYSTEM RESPONSE

10 ti

~

r:!

10

1!

~

~

_lil

a

-t Time (seconde) I T-- , , ,

o

1.0 20 JO 40

o __

~Sc~o~r~e~---Interrogation Signal

,..

~

,..

'Ij IQ ~ tl &; ~

.3

'Ij .~

----=

Cfl

A

A

~ -~'-

.

-o

---~

Full Scale i(t)

o

I

Subject II _ Unstable system

~

=

3.65

- Score

=

1.22" display FIGURE 22

I I Tille

o

5

10

15

20 25 (seconde)

Score

o

j

t

!nma1 Startl.

:!ij

J.nterroat on Signal j

A

o

+10 GIl ti ti ~ 0 I I \ I I ~I \ 1\ 'j ~I lil " 1=1 u i l GIl ti .c

~

-10

+.5

~ 0 I ' ~ Po r*'! , , .. I , '

::

_a

,_L'

•

_,~

-.5

o

iet) FIGURE 23

A TYPICAL INTERROGATION REACTION

Full Scale

Subject II

- Unstable system ~

=

3.65