SUGISAKAMASANORI

Journal of Robotics, Networking and Artificial Life
Vol. 9(4); March (2023), pp. 385–389
ISSN (Online):2352-6386; ISSN (Print):2405-9021
https://alife-robotics.org/jrnal.html

Jun Nakamura1*, Nozomi Komiya2
1

Chuo University, Faculty of Global Management, 742-1 Higashinakano, Hachioji-City, Tokyo, 192-0393, Japan
Institute of Policy and Cultural Studies, Chuo University, 742-1 Higashinakano, Hachioji-City, Tokyo, 192-0393, Japan

2

Received 13 December 2021
Accepted 08 April 2023

Skill transfer
Experienced worker

In quality inspection, which is the final stage of the manufacturing process, there is an operational
manual on how the object should be inspected. In this study, we followed the gaze of the workers
to search for the "way of looking" at the objects to be inspected, which is not described in themanual. As a result of experiment, we found a difference of the reciprocating eye movements
between skilled worker and the beginner. It is suggested that this indicates a way of looking at
inspection that has been unconscious until now.
© 2022 The Author. Published by Sugisaka Masanori at ALife Robotics Corporation Ltd.
This is an open access article distributed under the CC BY-NC 4.0 license(http://creativecommons.org/licenses/by-nc/4.0/).

Reciprocal motion
Quality inspection
Manufacturing

beginner in consideration of human resource
development. SMEs do not have an abundance ofsufficient human resources and their inspection team isobliged to be slim. Therefore, an experiment wasconducted with limited subject, i.e, one skilled worker asa benchmark and one young beginner as a comparison.
At this time, we believe "work procedures" areinsufficient for quality inspection, and how do theyactually inspect the precautions written in the work
instruction handbook? Hence, the authors have come into
consideration that gaze measurement would be effective
against visual inspection, and conducted an experimentusing eye tracking system in this paper.
The history of gaze measurement is very old. In thepast, the direct observation method was used to observe
the movement of the cornea and capillaries with thenaked eye, and the afterimage method was used to project
the generated afterimage on the retina onto a screen andquantitatively measure the movement [3]. When it comesto the current direct observation method, for example,

1. Introduction
With the widespread use of IoT and AI, robotization has
made remarkable progress in manufacturing processes,
but the gap in labor productivity at small and mediumsized firms, which are inferior to large firms, isunfortunately widening [1]. As a matter of fact, there arestill many handy manual operational processes in thesites of SMEs, and human resource development throughimprovement activities and creativity is required. For thisreason, the authors have been conducting research onorganizational learning in SMEs in terms of the skill
transfer and improvement of work efficiency [2].
While daily improvement activities are being carriedout at workplaces, the reality of efforts to improve work
efficiency is that they are often focused on work
procedures, which are merely defined in work instruction
handbook. Therefore, the authors decided to focus on
quality inspection, which is greatly influenced by humanresources, and to analyze both the skilled worker and theCorresponding author’s E-mail: jyulis.77f@g.chuo-u.ac.jp, nozokomisan@gmail.com, URL: https://www.chuo-u.ac.jp/english/, the first author’slaboratory URL: https://j-nakamuralab.com/385

eTobii Technology's Tobii Pro Glass 3, has 16 LEDs and4 eye cameras built into the lens to measure eye
movements [4], and we take this Glass as a tool toobserve eye tracking for quality inspection worker in a
manufacturing factory.
The type of gaze can be further divided into three,such as Tremor, Drift, and Micro-saccade [5]. Tremor, asa small back-and-forth motion, makes observationdifficult. Drift is the initial gaze that occurs
simultaneously with Tremor or during Micro-saccade,which is a short and fast viewpoint motion to correct Drift[6].

••2. Quality Inspection of Fuel Cell Piping

As a result of the eye-tracking of the experienced
operator, the quality inspection of 15 pipes in 377.56
seconds was recorded. The average speed of theinspection was 20 seconds per pipe, although there weresome inspections of five pipes side by side forcomparison and re-inspection of one of the 15 pipes.
In eye-tracking, fixation is often extracted and thelocation of the gaze is observed. However, since the timerequired for the quality inspection of piping is so shortthat the extraction of fixation is limited, we decided tocapture the movement of the eye and follow its trajectory.
Among the inspection processes, we focused on theinspection of both side edges, which requires changing
the angle of gaze, and found that the longest time was0.521s while the shortest was 0.181s, before polishing theedge. The results are shown in Figures 2 viewing the edge
from the front, and Figure 3 viewing the edge from theside. We can see that both eye movements look like areciprocating motion.
As for the pipes that were noticed during the visualinspection, those pipes are to be polished with a brush toremove burrs. Immediately afterwards, the edges are heldwith both hands to check its condition after polishing.
The step after polishing the edge for approx. 2.0
second was slightly longer than the step before polishingwith a gaze period of 0.902s as shown in Figure 4. Thisphenomenon is understandable as it is a check on
workmanship.

Date: Tuesday, August 3, 2021
Workers: 1 experienced worker (the most skilledworker) and 1 novice worker as a beginner
As mentioned above, the object of the quality
inspection is the piping of the fuel cell, and the final
product is the eco-cute. We paid attention to the edge
where the notes on the test were written and observed
carefully while playing back the gaze measured video. Inorder to capture changes in a particularly short period oftime, the video was played back at 1/16th the normal
speed.
4. Result

The pipes used in household fuel cells are long andnarrow. Since the pipes are bent at several points, thequality inspection has to be done manually (Figure 1). In
other words, inspection by machine is currently difficult.
The fittings at the edge of the pipe and the exterior are
inspected for scratches, dents, deformations, and otherabnormalities. In this process, the bent parts are inspected
for wrinkles, and the fittings of both edge sides of thepipe in particular are slightly protruding, making themdifficult to see from some angles. For this reason, we lookat the edges from various angles to see if there are burrs,
scratches, dirt, etc., and if so, we polish them with a fileor brush. Once the five products that have passed theappearance inspection are assembled, they are placed ina neat row and inspected again for comparison ofappearance.

Figure 1: Image of piping (actually 3D instead of 2D)
In this paper, with the cooperation of Nihon Pipe
System Co., Ltd. the workers of visual inspection of fuelcell piping were asked to wear glasses for eyemeasurement and to perform ordinary quality inspectionwork.
3. Methods
The gaze measurement experiment was carried out asfollows.
•Location: The factory of Nihon Pipe System Co., Ltd.
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epolishing (Figure 5), the time taken was 881ms, which isnearly the same period as for the skilled worker, but its
amplitude seems to be narrowly staring. Viewing fromthe side (Figure 6), however, it was found to take
2,143ms, which is more than twice as long as for theskilled worker. Also, we found that the degree ofreciprocating is considerably less than that of the skilledworker.
Since the time required for the inspection was very
short, it turned out that the workers themselves were so
unconscious that they were not even aware that they werereciprocating gazes.
Figure 2: Experiences worker's inspection of edges
before polishing (The duration is 521ms)

Figure 5: Edge inspection of beginner after polishing(The duration is 881m)

Figure 3: Edge inspection of experienced worker
before polishing (The duration is 181ms)

Figure 6: Edge inspection of beginner after polishing(The duration is 2,143ms)

Figure 4: Edge inspection of experienced worker
after polishing (The duration is 902ms)

5. Discussion
In any case, the phenomenon that skilled worker
reciprocate remains the same, whether before or after
polishing the edge.
Now, let us look at the trajectory of the beginner's
gaze. When viewed from the front of the edge after

Looking at the gaze trajectory of the skilled worker andthe beginner, there are certain differences in thereciprocating features as mentioned in the previous
section. That is, skilled worker reciprocates whileinspecting, but beginner does not. The reasons for this387

ecannot be determined from this experiment, as they arehidden in ones’ unconscious. However, the beginner may
be "an inspection is to stare intently" and may becommitted to a single point of concentration. Skilledworker, on the other hand, may subconsciously be more
intent on "finding defects" than on staring.
There is another interesting difference between thetwo. That is, when looking at the edge, either from theside or from the front, the "length" of the gaze time isreversed, i.e., beginner spends more time on the side thanfront, while skilled worker spends more time on the front.
It is assumed that it is easier to find burrs from the front,
although the side can be seen over the entire edge, wherebeginner tends to unconsciously looking at. However, theskilled worker might have the habit of looking at the front
as an experience of the workmanship checkpoints.
The above discovered hypotheses are simply
represented in an imaginary diagram as shown in Figure
7, where the inspection time is likely to be convex
upwards and steadily decreasing, and is expected to
become shorter, since knowledge is gradually
accumulated through one’s experience. The way in which
they stare is thought to be a gradual, unconscious effectof reciprocal movement through experience, whichwould be truly tacit knowledge. This suggests that thedegree of reciprocal motion would be a convex
downward and right upward shift.

Figure 8: Key points of quality inspection at Denso(citing inspected images from [4]The above interpretation might support the following
four points which could be inferred.
First, since the act of searching for a problem is a partof the normal inspection process, the pattern ofconcentrating on a fixed point may not be possible.
Rather, the fixed pointed gazing pattern may occur aftera flaw as an example is found in a quality inspection.
Second, the remarkable factor is the reciprocating
motion. At first glance, it appears as if the subject is going
through a trial-and-error process of looking at the target
and then checking it again while slightly moving
backward. However, since this is done in a very shortperiod of time, less than one second, it can be inferredthat the reciprocating motion of the eye itself isunconsciously performed.
Third, the question is whether the reciprocal motionof the eye is left-right, up-down, or diagonal forexperienced worker. In Figures 3 and 4, the eye
movements are generally left-right, although there aresome angular variations in the eye movements. On theother hand, in Figure 2, the gaze is up and down, and thereciprocating motion is quite short. This may be due tothe difference in the shape of the object and the angle atwhich the gaze flows.
Fourth, with regard to inspecting the edge of the pipe
viewing from the front of the edge as if you were looking
at the cross section of the pipe, it takes more time thansetting the pipe on its side looking across the edge, asmentioned in the section of result. The cross section ischecked against the circumference of pipe, while the side
is in a sense a straight line. This may have an effect on
the speed. In addition, it is easy to understand that it takes
more time to brush the same section after than before.
The reciprocating motion of the eye in this paper may
be Tremor, Microsaccade, or Drift, but it needs to be

Figure 7: Image of trajectory depending on years ofexperiences
Here, let us consider the reason for the reciprocatingmotion of the eyes in quality inspection. Denso
Corporation is using eye tracking for inspection at somemanufacturing sites called Nishio-Seisakujo, where thekey point of the test is to let the gaze flow as if spellingout the letter "2" as shown in Figure 8 [7]. It can bebroadly interpreted as a reciprocal motion of the eyes.

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further explored in the future. The fact that thereciprocating direction of Gaze is not up and down but
left to right and back and forth, may be due to humanphysiological factors. This is an issue for future research.
In this paper, we focused on the edge of the pipe, but
we also observed large reciprocal eye movements such as①→②→③ and ③→②→① when we viewed the pipe
from the side as shown in Figure 1.
The most interesting feature of these reciprocating
movements of the eye is that even in a very short time,decision-making could be executed to evaluate the test
results. That means, even though the reciprocating
movements are unconscious, judgments are madeconsciously by individual. This might be similar todriving a car, where instantaneous judgement, its
evaluation and one’s decision-making, are carried out
simultaneously.
6.

This paper has been supported by Grant-in-Aid for
Scientific Research (JSPS KAKENHI Grant Number
17K03872 and 19K03062) and Grant-in-Aid forSpecially Promoted Research from Chuo University.
References
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21st Pacific Asia Conference on Information Systems(PACIS), Langkawi, Malaysia, 2017.
3. M. Hashimura, H. Iizuka, J. Lee, “Special Issues No.3:
Measurement Technique for Ergonomics, Section 4:
Measurements and Analyses of Bioelectric Phenomena
and Others (2) Measurement of Eyeball Movement”, TheJapanese journal of ergonomics, Vol. 51, No. 6, pp.406410, 2015. (In Japanese)
4. https://www.tobiipro.com/product-listing/tobii-proglasses-3/
5. S. Martinez-Conde, L. Stephen, D. Macknik, H. Hubel,“The role of fixational eye movements in visualperception”, Nature Review Neuroscience, Vol. 5, No. 3,pp. 229-240, 2004.
6. T. W. Cornsweet, “Determination of the stimuli for
involuntary drifts and saccadic eye movements”, Journalof the Optical Society of America, Vol. 46, No. 11, pp.
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Conclusion

In this paper, we visualized and discussed the eyemovements during the quality inspection of piping.
Reciprocating eye movements were found during thequality inspection, although unconsciously, and thefactors behind them were discussed. The analysis isbased on the measurement results of only one
experienced worker and one beginner, and the limitationis unavoidable. The bottleneck is that it is not possible toobtain a large number of samples due to the limited
number of workers for quality inspection. However, asstated at the beginning of this paper, SMEs do not haveenough human resources and have to make the mosteffective use of their limited management resources,particularly employees. Therefore, further study intends
to increase the number of inspections in the future to
make skilled worker as benchmark, and to consider
modelling based on Figure 5 to assess skills morequantitatively.
We would like to address research on thevisualization and analysis of the differences between
experienced and beginner workers by means ofmodelling the gaze movement, which we expect to leadto the skill transfer.

Authors Introduction
Dr. Jun Nakamura
He is a Professor of Faculty of
Global Management at Chuo
University in Japan. He graduatedfrom the Department of Technology
Management for Innovation, Schoolof Engineering, University of Tokyo,
with highest honors. His area ofresearch is Cognitive Sciences.
Dr. Nozomi Komiya
She is a Guest Researcher of Instituteof Policy and Cultural Studies, Chuo
university. She graduated from
University of Tsukuba (DoctoralProgram in Risk and Resilience
Engineering). The area of her
research are Intelligent Information
and Cognitive Science.

Acknowledgements
This paper was made possible with the understanding andcooperation of Mr. Tano, President of Nihon Pipe System
Co., Ltd. We would like to express our sincere gratitude
to all of them including the subjects.
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