CONTRIBUTION

To the New Frontier of Nano-Precision Mechanical Manufacturing
Technology (from Form Generation to Function Generation)

Professor Tsunemoto KURIYAGAWA
School of Engineering, Tohoku University

To survive in the current economic climate after Lehman Crisis and the Great East Japan Earthquake, researchand development works in manufacturing processing technology must be changed to the creation and developmentof new manufacturing principles and technologies to contribute to the competitiveness of Japanese manufacturingindustry. This report reveals one of the solutions to exploit the new frontier of manufacturing, such as nano4
precision micro/meso mechanical manufacturing (M process) for a generation of functional interface on themachined surface.
4

Key Words: micro/meso mechanical manufacturing, M process, nano-precision, functional interface

The Great East Japan Earthquake which struck on
March 11, 2011, inflicted tremendous damage to all ofJapan and drastically effected people's lives. In particular,
the disaster at Fukushima No.1 nuclear power plant led
to nuclear power plants across Japan ceasing operation,
and as a result, power supply shortage has become aserious problem. This situation presented the opportunity
to rethink energy issues. It is likely that in the future
there will be heightened interest in technologies which
utilize and store reusable energies such as solar light,
solar heat, wind, geothermal energy, etc., and accordingly
R&D activities in this space will gain more momentum.
Meanwhile, amidst heightening interest in this type ofenergy harvesting, there is also a lot of action on the
R&D front regarding energy-saving technologies. Thisis because energy-saving is relatively equivalent toproducing energy. In this way, the development of systems
and devices to solve energy issues is attracting more andmore interest as one way to revive Japan's industry in
the wake of the Lehman Crisis. As such, the questions of"What exactly is Monozukuri technology?" and "What is
the technology that can give Japan the advantage amongst
global competition?" need to be urgently addressed.
Any future discussions on Monozukuri must take into
consideration the future demographics of Japan. Figure 11), 2)
shows the forecasted Japanese population shift . As canbe seen from this figure, from last year the population
began declining from 128 million, forecast to fall below
100 million in 2050 and be only one-third of the current

2

population 100 years from now in 2100 at 48 million.
This number is almost the same as 100 years ago aroundth
the turn of the 20 century. However, the major difference
between 100 years ago and 100 years from now is thechange in the population's age structure. The percentageof the population aged 0 to 14 and the working population
aged 15 to 64 will decrease significantly. Furthermore,
the average life span in Japan is predicted to increase andbecome 84.19 years for males and 90.93 years for females2)by the year 2060 . In other words, the number of elderly
people will increase dramatically, changing the current
statistic of 1 in 4 people being over the age of 65 to 1 in
2.5 people by the year 2060, meaning that more than onethird of Japanese citizens will be 65 years old or above.

(1 million people)
150 M
Japan’s population

1. Foreword

1900
44 million

2004
127.8 million

2060
85 million

2100
48 million

65 years
old or above
0−14
years old

100 M

50 M
15−64 years old

1900

1950

2000
Year

2050

2100 (AD)Fig. 1 Demographics of Japan

JTEKT ENGINEERING JOURNAL English Edition No. 1010E (2013)

−To the New Frontier of Nano-Precision Mechanical Manufacturing Technology (from Form Generation to Function Generation)−

This changing situation surely marks the end of the
mass-production, mass-consumption style of Monozukurithat has been practiced until now and calls instead for adiversified type of Monozukuri that responds to various
values. We are right in the middle of a turning point inJapan's industrial structure and we must recognize that
now is a time to think seriously about what we will leavebehind for future generations. Consequently, when we
think about Monozukuri, we must also think about whatkind of products will be sought in the future, sufficiently
predict what will sell, and "backcast" what kind oftechnology will be needed to create such products andwhich technological issues need addressing now.

2. The Fusion of Extreme Form
Generation and Function Generation
In order for Japan's Monozukuri creative design andmanufacturing to continue to lead the world, we muststrongly promote the development of products with evenhigher accuracy and added-value to an extent that cannot
be achieved by overseas technology. Conventionally,
the evaluation criteria of a machined product were form
accuracy and surface roughness and it was sufficient aslong as these were as per design. However, when pushingprocessing accuracy to the extreme limit, a wavy patternof the nano-order remains on the machined surfaces andit is difficult to obtain a uniform machined surface. A
machining method to remove this wavy pattern and obtaina uniform machined surface is essential. This report uses
the example of aspherical grinding and introduces various
grinding methods developed with the aim of obtaining aform accuracy of 25 nm just on the ground surfaces. The
report first introduces the "Parallel Grinding Method"which improves finished surface roughness, then the"Arc Envelope Grinding Method" which improves form
accuracy and finally the "Fluctuation-free Aspherical
Grinding Method" used to obtain uniform machined
surfaces.
Currently, this sort of demand for form accuracy has
already reached its limit in the nuclear-order. Surely now
a demand will emerge for Monozukuri that comprises
ideas to create machined surfaces with new functions
through generating microscopic structures on the obtainedmachined surfaces and controlling crystal structures in
the proximity of the machined surfaces. In other words,
the fusion and advancement of a new type of monozukuri
technology which does not merely focus on form
generation, but also incorporates function generation.
That is why this paper also introduces nano-precision
micro/meso mechanical manufacturing.

JTEKT ENGINEERING JOURNAL English Edition No. 1010E (2013)

3. Nano-precision Grinding of Aspherical
Optical Components
3. 1 Parallel Grinding
Figure 2 (a) shows the conventional grinding method
currently being used for axi-symmetric asphericalsurfaces. The figure shows that machining is carried out
through 2-axial simultaneous control of the x and y axes
in a configuration whereby the wheel spindle and the3)workpiece spindle are perpendicular . The feature of thisform of grinding is that the rotational direction of theworkpiece and peripheral vector of the grinding wheel
cross at the grinding point, and grinding marks are formedin the workpiece radial direction, as shown in Fig. 3 (a).
This grinding method is known as "cross-grinding".
In many cases, cross-grinding uses an abacus ballshaped grinding stone edge that has been made into a
V-shape formation as the working surface. This method is
problematic because wheel wear and collapsed abrasive
grain is concentrated in one area due to grinding being
performed in one spot on a wheel cross-section vertical to
the grinding direction. This means that if the workpieceis high hardness material such as ceramic or has a large
diameter, it is practically impossible to grind efficiently.
That is why the grinding method shown in Fig. 2 (b)was devised, where the workpiece rotational direction
and the wheel periphery vector are parallel. This
grinding method is known as "parallel grinding". The
only difference between cross-grinding and parallel
grinding is the cutting direction of the abrasive cuttingedge. If a spherical wheel is used, the two methods canbe regarded as being completely identical geometrically4)
wise. However if grinding theory is used to calculate
finished surface roughness theoretically, a completely
different result could be obtained. In other words,
because parallel grinding has more active cutting edges
than cross-grinding, it was discovered that parallel
grinding has better surface roughness under all grinding
5)
conditions . Figure 3 (b) is a Nomarski photomicrographAxi-symmetricasphericalz

Axi-symmetricaspherical
V wheel

z
y

y
x

x
Toras wheel(a) Cross-grinding method(Conventional grinding method)(b) Parallel-grinding method(New grinding method)

Fig. 2 Comparison of aspherical grinding methods3−To the New Frontier of Nano-Precision Mechanical Manufacturing Technology (from Form Generation to Function Generation)−of ground surfaces of a carbide die. As is apparent
when a comparison is made with the cross-grinding
shown in Fig. 3 (a), despite the exact same wheel andgrinding conditions being used, the finishing surface
roughness obtained with parallel grinding is smaller byapproximately half. Parallel grinding is the grinding
method which improves ground surface roughness.

14 µm(a) Fixed grinding point. (Conventional grinding method)

1 µm(b) Moving grinding point. (New grinding method)
1mm

1mm

(a) Cross-grinding method (84 nm Ry) (b) Parallel-grinding method (44 nm Ry)

Fig. 3 Nomarski photomicrographs of ground surfaces

3. 2 Arc Envelope Grinding
As already mentioned, in the conventional grinding
method, the grinding point on the wheel cross-section
does not change, causing wear concentrates of the point
where grinding is carried out. Consequently, life between
dressings is shorter and the efficient grinding of large
workpieces is practically impossible. Even more fatal is
the fact that this triggers degradation of the aspherical form
accuracy. If the grinding point that is fixed to one spot is
moved in the wheel width direction, these problems could
be solved. In order to do that, it would be sufficient to use
a wheel with an arc cross-section as shown in Fig. 4 togenerate an aspherical surface by the envelope of that arc
6)cross-section . In such a case, the active grinding width
would be larger and wheel wear would be dispersed. As aresult, with the arc envelope grinding method it would bepossible to reduce wheel wear significantly, as shown in
Fig. 5, and greatly improve form accuracy in aspherical
grinding.
XaGrinding path

Workpiecer

Z

O

Grinding point moving range
Spherical wheel

Fig. 4 Arc-envelope grinding method

4Fig. 5 Decrease in wheel wear due to the movement ofgrinding point

3. 3 Fluctuation-free Grinding
The difficulty of aspherical grinding lies in the fact thata ground surface roughness in nano-order is demanded
at the same time as a high accuracy profile. The above
sections showed that the combination of parallel grinding
and arc envelope grinding was extremely effective insolving this problem. This solution has made it possible
to achieve a form accuracy of 50 to 100 nm and a surface
roughness of 10 to 30 nmRy. However, year after year
higher accuracy is being demanded of aspherical lenses
in order to obtain an even clearer, finer optical image.
Hence, now there is a demand for a form accuracy of
25 nm or less and a surface roughness of only a coupleof nm. In order to achieve this kind of high accuracy
grinding, the high accuracy countermeasures that have
conventionally been implemented on processing machines
is no longer sufficient. One example of this is the fact thatthe control resolution of processing machines is alreadyat 1 nm, approaching its limit. That is why it is necessary
to look at improving the accuracy of machined surfaces
from a different perspective.
The current outstanding issue with aspherical grindingis that the 3-dimensional form (form error pattern) of
the waviness which occurs on the lens machined surface
cannot be reproduced. For example, a spiral pattern shownin Fig. 6 (a), or a concentric circle pattern as in Fig. 6(b) appears, and these patterns are unstable. Throughfundamental research relating to the nano topographicalgeneration mechanism of ultra-precision ground surfaces,
the author determined that the instability of the form error
pattern was affected significantly by the unevenness ofwheelspindle and workpiece spindle rotation as well as
7)wheel unbalance . This means that due to the instability(unevenness) of processing machines it would be difficult
to achieve an even form error pattern and form accuracyof 25 nm with practically all of the commerciallyavailable ultra-precision aspherical grinding equipment.
In order to solve this problem and achieve an even form

JTEKT ENGINEERING JOURNAL English Edition No. 1010E (2013)

−To the New Frontier of Nano-Precision Mechanical Manufacturing Technology (from Form Generation to Function Generation)−(a) Spiral pattern(b) Concentric circle pattern(c) Uniform and fine patternFig. 6 Grinding marks generated on axi-symmetric aspherical ground surfaces

error pattern on machined surfaces, a form of machining
where all the parameters which affect machining results
are entirely controlled at predetermined values and do
not fluctuate, vary or waver whatsoever, in other words
fluctuation-free machining, is necessary.

3. 4 Development of a Fluctuation-free, UltraPrecision Aspherical Grinding System
Fundamental research relating to nano topographicalgeneration mechanisms showed that if the fluctuationof workpiece and wheelspindle RPM is 0.1% or less,the error form pattern would not be obvious (Fig. 6(c)). That is why a new fluctuation-free, ultra-precisionaspherical grinding system was developed which allows
the abovementioned parallel grinding (improved groundsurface roughness) and arc envelope grinding (improved
form accuracy) to be performed simultaneously at thesame time as maintaining rotation fluctuation during
grinding below 0.1%. The newly developed system isshown in Fig. 7. We used this grinding machine to grind
aspherical glass lenses (4mm dia.) for an endoscope (rigid
scope). The resulting form accuracy was ±25.5 nm andthe surface roughness was 21 nmRy, meaning that form
accuracy was improved by approximately one-fifth ofthe conventional product while surface roughness was
improved by two-thirds. Moreover, as shown in Fig. 8, theform error pattern was dramatically less than conventional
products. The author also ground a cemented carbide
concave aspherical die (die dia. = 25.0mm, lens aperture
dia. = 24.4mm) used to form aspherical glass lenses forhigh-definition digital cameras. This achieved a form
accuracy of ±25.5 nm and a surface roughness of 18
nmRy. Moreover, there were no form error patterns on themachined surfaces and results of a resolution assessmentof a sagittal image and a meridional image confirmed
improvement compared to the conventional method.

JTEKT ENGINEERING JOURNAL English Edition No. 1010E (2013)

Fig. 7 Newly-developed fluctuation-free ultra-precisionaspherical grinding machine

0.5mm

0.5mm
Nomarski photomicrograph±25.5 nm±132 nmForm error curve(a) Conventional grinding method(b) Fluctuation-free grinding method

Fig. 8 Ground aspherical glass lenses

4

4. Nano-precision M Process Technology
The last chapter introduced fluctuation-free machining
which raises form accuracy to extreme limits. This4
chapter will introduce M processes, which are one
function generation method to add even more functions.
The nano/micro/meso hybrid structure such as thatshown in Fig. 9 is one of the structures for expressing
function. This was formed by forming a micro-sized
functional microscopic structure on top of a macro-sized5−To the New Frontier of Nano-Precision Mechanical Manufacturing Technology (from Form Generation to Function Generation)−

6of material, and there are many points which cannot beclarified with the mechanical engineering approach taken
until now. In other words, rather than merely looking
at actual physical and chemical phenomena in the nanoregion from a mechanical engineering perspective, amechanical scientific approach which sees things froma quantum mechanics perspective incorporating nuclear
bonding state change and the electromagnetic or chemical
mutual effect which triggers such changes. In thisway, even more emphasis will be placed on machining
simulation technology as a common fundamental
technology and R&D of nano-precision measurement
assessment technology.
Nano structure
Pitch: Several 10 to several 100 nm
Free-form surface
Form accuracy < several nm
Finishing surface roughness < Several ÅRy

Micro structure
Pitch: Several µm
to several 10 µm

Macro structure
Free-form surface, etc:
Several mm to several 100mm

Fig. 9 Nano/micro/macro hybrid-structure−3

10
Machining accuracy, mfree-form surface (or surface) with a smooth surface inthe nm order then overlapping a further microscopic
structure of the nano size to that surface. There are
expectations that this kind of nano/micro/meso hybrid
structure will express particular functions optically,
electrically, thermally or mechanically. The generation ofsuch functions is not achievable with conventional ultraprecision mechanical machining technology, therefore
the creation of a new machining technology covering thearea shown in Fig. 10 is necessary. That is why, regarding
various mechanical machining technologies which havedeveloped and advanced independently, there is a highexpectation of micro/meso mechanical manufacturing
4(hereinafter referred to as nano-precision M processes) as
being able to machine sizes as small as several µm and at
the same time raise machining accuracy to the nano order.
4
Table 1 shows typical types of nano-precision M
processes. It is expected that the machining mechanisms
are practically the same as conventional mechanicalmachining methods however the following newchallenges will arise as a result of the machining target
getting smaller.
4
1. Development of an M processing machine/system:
It would be necessary to develop a multi-axes control
nano-precision micro processing machine which would
be capable of controlling machining force.
4
2. M process combination technology: The developmentof a unit which could support combination machining
would be necessary.
4
3. M process tool development: Because the tools would
be thinner, a new fabrication technology for such tools
would be necessary.
4
4. M process measurement assessment technology:
Because the machining force itself would get smaller,
micro-force measurement and control technology
would be necessary. Also, because the machined
profiles would be small, new profile measurement
technology would be necessary. Finally, developing
a way to assess sub-surface damage of the machined
surfaces is essential.
4
5. Clarification of M process machining mechanisms
and functionality generation mechanisms: In order tominimize the removal unit it is necessary to assess theremoval property of the material itself, and that is why
it is essential to develop new analytical methods suchas machining simulations, large-scale molecular level
simulations combining FEM and molecular dynamics
or multiphysics simulations able to comprehensively
analyze multiple physical phenomena such as material
distortion and thermal behavior.
4
Also, in this type of nano-precision M processmachining, the chips themselves are of the nano order.
Consequently, it is easily predicted that chemicalelements will also strongly affect the removal mechanism

Ultra-precision
mechanicalmachining

MEMS

−6

10

Nano-precision
M4 process−910Machining limit > Nuclear size
−12

10

−12

10

−9

10

10

−6

10

−3

−0

10

10

3

Target dimension, m

Fig. 10 Object size and machining accuracy focused in
nano-precision M4 processes

Table 1 Various types of nano-precision M4 processes

Abrasive
machining

Micro-grinding
Micro-polishing
Micro-ultrasonic machining
Micro-abrasive jet machining, etc

Cutting

Micro-cutting
Micro-milling, etc

OtherParticle jet coating
Micro-discharging
Micro-adhesion
Micro-punching
Micro-laser processing
Micro-forming, etc

JTEKT ENGINEERING JOURNAL English Edition No. 1010E (2013)

−To the New Frontier of Nano-Precision Mechanical Manufacturing Technology (from Form Generation to Function Generation)−

WC - Toshiba Tungloy - Aspheric
SD3000P150
Rbase=2.000mm, PV=0.4169 µm

PV, µm0.5

0.0

Micro Insert

1mm(a) Thin diamond grinding wheel for micro-grinding

−0.5
−0.3

1mm
(b) Micro-aspheric WC die (Diameter is 0.6mm)

−0.2

−0.1

0.0
X, mm

0.1

0.2

0.3

(c) Form accuracy of the ground die

Fig. 11 Micro-aspherical die generated by micro-grinding process

4. 1 Micro Aspherical Machining
This section will introduce micro aspherical grinding4
as an example of an M process. The targeted asphericalsurface is of submillimeter size. Phenomena which werepractically not problems with conventional machining
sizes or of the extent which could be ignored, can nolonger be ignored in machining this size. For example, if
an aspherical surface with a submillimeter sized diameter
was micro-grinded with a wheel that had a diameter of
1mm or less, no doubt the truing/dressing of a small
diameter wheel and other applied technology would
become issues. In order to solve these issues the following
would be important.
• Development of a truing/dressing method where there
would be more active cutting edges.
• Development of a grinding wheel with an ultra-highdegree of concentration.
• Development of a grinding method where wheel wear
and surface roughness become smaller.
Also, if the workpieces themselves have small
diameters, ways to make the machining force itself
smaller (such as ultrasonic grinding, etc) must be
examined.
Figure 11 shows a carbide micro-aspherical lens dieground using an SD3000P150 ultra-fine abrasive diamondwheel with a diameter of 1mm. The form accuracy was
0.4 μm and the surface roughness was 62 nm. These
are improvements of one-digit compared with grinding
results when normal size wheels are used. This is because
the number of active cutting edges becomes much smallerwhen a small-diameter wheel is used.

4. 2 Nano/Micro Structure Generation Utilizing
Hybrid-Vibration Assisted Grinding
Generally speaking, nano/micro structure generationis performed using surface generation technologies suchas nanoimprint technology or self-assembly, etc. Thesemethods have still many issues such as the difficulty ofgeneration of complicated 3-dimensional surfaces on thelarge surface, and high costs problem. Here, the author
would like to introduce a method which is relatively low
in cost and able to mechanically generate structures in the
sub-micron order on large surfaces.
Figure 12 (a) shows the principle of hybrid-vibration
assisted grinding overlapping low frequency vibration of
9),several Hz with ultrasonic vibration of several 10 kHz
10). Ultrasonic vibration in the axial direction is applied
using a special-purpose ultrasonic spindle while lowfrequency vibration and workpiece feed are executed with
NC commands from the processing machine. Figure 12(b) shows the cutting trajectory of the abrasive cuttingedges and by controlling the position where these cuttingedges overlap a fine structure such as that shown in
Fig. 12 (c) can be acquired. Figure 13 shows a periodic
structure with a 500 nm pitch generated on a zirconia
ceramic surface using an SD600 small-diameter wheelwith a diameter of 1mm. By changing feed rate, vibration
frequency and so on, it is possible to generate various
forms.

Wheel rotation
Workpiece feed
Low frequency
Wide amplitude

High frequency Control the overlapping
Small amplitude position
(a)

(b)

The remaining part willbe the fine structure(c)Fig. 12 Principle of fine structure generation utilizing
hybrid-vibration assisted grinding

JTEKT ENGINEERING JOURNAL English Edition No. 1010E (2013)7

−To the New Frontier of Nano-Precision Mechanical Manufacturing Technology (from Form Generation to Function Generation)−

6. Development of nano measurement/assessment
technology.
The author looks forward to future advancements inresearch and development.

References
Fig. 13 Periodic structure with 500 nm pitch generated byhybrid-vibration assisted grinding

5. Conclusion
This report has introduced key words thought to beimportant when contemplating Monozukuri in the future.
No doubt from here on more than mere "form generation"
will be required. "Function generation", which creates
structures possessing various functions in such surfaces
or internally, will also play an important role. This
report used the example of grinding, one mechanicalmachining method, to introduce fluctuation-free grinding
which increases form accuracy and hybrid-vibration
assisted grinding for the generation of fine structures.
However, rather than stopping at mechanical techniques
in order to generate functions, we should adopt a topdown approach of Monozukuri such as optic machiningor MEMS machining in an effective and timely manner.
Moreover, it could be said that a bottom-up approach of
Monozukuri that efficiently utilizes molecular design andself-assembly would be an effective method.
In this way, in order to realize the machining
technology foundation for Monozukuri of the future,
it will be essential to construct learning frameworkand technology achieving "Monozukuri with scientificrationality that understands the essence of phenomena of
the nano world" and research foundation for that.
In other words, it will be necessary to strongly promote
the following:
1. Clarification from a quantum-mechanical perspective
through positioning nuclear level and nano levelmechanical behavior as coupled problems withelectromagnetic phenomena and chemical reactions.
2. Scientific clarification of the various phenomena
related to nano mechanochemistry, nano material andnano processing.
3. Design and construction of micro machines, nanomachines and nano systems.
4. Establishment of material/strength reliability
assessments at a nuclear/nano-level and energy
conversion system safety assessment research.
5. D eve l o p m e n t o f m a t e r i a l d u r a b l e i n ex t r e m eenvironments and high-reliability nano machines/
systems, etc.

81)

K. Kato, Energy Self-sufficient and Symbiotic House of
LOHAS (A Hundred Year Plan for Revival), Journal of
JSME, 115, 1126 (2012) 664-667. [in Japanese]2) National Institute of Population and Social Security
Research (online), http://www.ipss.go.jp/syoushika/
tohkei/suikei07/index.asp
3) H. Suzuki, S. Kodera, S. Maekawa, N. Morita, E.
Sakurai, K. Tanaka, H. Takeda, T. Kuriyagawa and K.
Syoji, Study on Precision Grinding of Micro Aspherical
Surface (Feasibility Study of Micro Aspherical Surface
by Inclined Rotational Grinding), Journal of JSPE, 64, 4(1998) 619-623. [in Japanese]
4) S. Matsui and K. Syoji, On the Maximum Height
Roughness of Ground Surface, Technology Reports of
Tohoku University. 38, 2 (1973) 615-626.
5) M. Saeki, T. Kuriyagawa and K. Syoji, Machining ofAspherical Molding Dies Utilizing Parallel Grinding
Method, Journal of JSPE, 68, 8 (2002), 1067-1071. [inJapanese]
6) T. Kuriyagawa, T. Tachibana, K. Syoji and Y. Mori,
Nonaxisymmetric Aspheric Ceramic Mirror Machining
Using Arc Envelope Grinding Method, The Japan Societyof Mechanical Engineers (C), 63, 611 (1997) 2532-2537.
[in Japanese]
7) N. Yoshihara, K. Syoji, T. Kuriyagawa and M. Saeki,
Grinding Marks Generated on Axi-symmetric Aspherical
Surface, Journal of JSPE, 70, 7 (2004) 972-976. [inJapanese]
8) W.K. Chen, T. Kuriyagawa, H. Huang and N. Yoshihara,
Machining of micro aspherical mould inserts, Precision
Engineering, 29, 3 (2005) 315-323.
9) K. Shimada, T. Tateishi, N. Yoshihara, J. Yan and T.
Kuriyagawa, Ultrasonic-assisted micro-grinding withelectroplated diamond wheels, Journal of JSAT, 53, 1(2009) 45-48. [in Japanese]10) K. Shimada, T. Tateishi, N. Yoshihara, J. Yan and T.
Kuriyagawa, Ultrasonic-assisted micro-grinding using
electroplated diamond wheels (2nd Report : Effect ofultrasonic vibration on workpiece removal in grinding
with wheel end), Journal of JSAT, 54, 1 (2009) 37-40. [inJapanese]11) K. Shimada, Study on Vibration Grinding, A doctoral
dissertation of Tohoku University (March 27th, 2012). [inJapanese]

JTEKT ENGINEERING JOURNAL English Edition No. 1010E (2013)