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Ventil: Prof. Backé, it is a great honor
for our fluid power engineering jour-
nal Ventil to have an interview with
you as one of the most prominent
professors and experts in the field of
Fluid Power worldwide. In July this
year you celebrated you 80
th
birthday
anniversary. On behalf of the journal
Ventil I would like to congratulate
you on this special occassion. On
31 July 2009 there was a great event
in Aachen, a special Colloquium
to honor your birthday. It was an
extraordinary honor for me to have
been a part of this event, to which
about 160 guests from Germany and
abroad were invited and to celebrate
it with you and your respected wife
Ms. Seitz-Backé. What were your
feelings on this day and what are your
feelings now?
Prof. Backé: First of all, thank you for
your good wishes. My answer to your
question is that I felt great and I am
very proud that I could run the insti-
tute for 26 years and reached some
good results so the institute has got
a better reputation in Germany and
also globally.
A short interview with Professor Emeritus Wolfgang Backé, Dr.-Ing. Dr. h.c. mult., former Head of IFAS of RWTH 
Aachen University, on the occasion of his 80
th
 birthday celebration in Aachen on 31 July 2009 
Fluid Power Over Four Decades
em. Univ.-Prof. Dr.-Ing. Dr. h.c. mult. 
Wolfgang Backé
Ventil: You have been professor eme-
ritus for fifteen years and are still
active at the Institute IFAS where you
were a director for 26 years. How
do you see the development of the
Institute nowadays?
Prof. Backé: I am happy that the Insti-
tute IFAS is running so well under the
guidance of my successor professor
Murrenhoff.
But we have to realize that research
in the field of fluid power has be-
come more difficult today. The real
important discoveries, as for example
the proportional technique, the car-
tridge technique, the displacement
control technique and the secondary
control was introduced and much
research has already been done in
this field.
So, today the research is much more
directed to a deeper knowledge of
materials, hydrodynamics, produc-
tion possibilities and to a condition
monitoring.
Ventil: Let’s go back to the begin-
ning of your career in fluid power,
Prof. Backé. You earned your BSc in
Mechanical Engineering at RWTH
Aachen in 1955 and your PhD at the
Institute of Machine Tools at RWTH
Aachen in 1959. What were the rea-
sons for continuing your professional
career in the field of Fluid Power?
Prof. Backé: From the beginning of
my studies I was interested in fluid
power. At that time machine tools
were the main application of fluid
power. We had one ingenious lec-
turer who could explain fluid power
very well. So the signal circuit at
that time was electric but sometimes
also hydraulic or pneumatic. It was
fascinating how the automatic pro-
cedures went on, only controlled by
the electric or fluid power switches.
Ventil: After spending some years at
another university and in the industry,
you rejoined RWTH Aachen in 1968
and established the Institute for Hy-
draulics and Pneumatics (IHP), today
known as the Institute for Fluid Power
Drives and Controls (IFAS). What
were the reasons for such a step?
Prof. Backé: I think that in the field of
fluid power a few years of industrial
experience are necessary because
fluid power is quite related to an
application. But I thought that in
this field a lot of systematic work
The fi rst building of the Institute for Hydraulics 
and Pneumatics (1968 – 1972)

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was necessary. The knowledge of
the fundamentals has to be taught
to students who want to work in this
field successfully.
Ventil: Can you describe the begin-
nings of the institute IHP and the
main research interests in a bit more
detail. How big was the Institute in
the beginning?
Prof. Backé: The beginning of the IHP
was not easy. We were only a few
people and we had nearly no mea-
suring devices, so our only chance
was to write intelligent applications
to research funding organizations
and in this way increase our man
power, measuring devices and testing
stands. We made systematic tests of
all the available control devices and
displacement units.
At last we covered the whole field of
fluid power. Because of our reason-
able reports we earned good reputa-
tion and joined research projects
carried out by a group of institutes,
so we worked for instance in the field
of production technology, in the field
of medical technique, in the field of
power transmission and in the field
of robotics.
Ventil: Prof. Backé, after the es-
tablishment of the new Institute in
1968 you spent the next 26 years
as Professor and Director of Fluid
Power Transmission and Control at
the Faculty of Mechanical Engineer-
ing. During these years your Institute
became one of the world’s largest
and renowned research institutes in
the field of Fluid Power. How did
you succeed in this and what where
the main driving forces for such a
success?
Prof. Backé: There really were good
opportunities at that time. We were
the only institute that was fully work-
ing on fluid power. Other universities
employed experts from the industry
to teach the students, but that could
only give an explanation of a single
application of fluid power and not the
whole field. Our system of handling
the whole field from the fundamen-
tals to the different applications sys-
tematically seems to be the right way.
So other universities as Dresden,
Braunschweig, Hamburg, Karlsruhe
followed our system and founded
special institutes for fluid power. The
same is true for other countries like
England, Sweden, Finland, Slovenia
and Japan, to only name a few. 
Ventil: Well, this is probably only
one of the reasons why you are
called The Pope of the Fluid Power
among the “Fluid Power people” all
around the world. For your leader-
ship and distinguished contributions
to fluid power and motion control,
including the establishment of one
of the world’s largest and renowned
research institutes in the field of
fluid power, you were honored dur-
ing your professional career with
numerous national and international
recognitions, rewards and medals
like ASME medal, “Verdinstkreuz
des Verdinstordens« of the Federal
Republic of Germany etc. You also
hold honorary doctorates from the
University of Tampere, Finland, the
University of Linköping, Sweden
and the University of Bath, UK. You
were also the honorary professor at
the Technical University of Taiyuan
(1981) and the Technical University
of Hangzhou (1989) in China. What
is the secret to your success?
Prof. Backé: I have no special secrets,
but I had fun working intensively on
fluid power problems. Another point
may be that I am very interested in
special research objects, so I was
a serious discussion partner to my
students.
We have contacts with nearly all
groups working on fluid power in
Germany as well as around the world.
I am always happy to meet colleagues
on conferences and discuss present
and future developments in fluid
power.
Ventil: Your main activities as full and
emeritus professor have also included
the promotion of 122 doctorate
students, to who you were “Doktor-
vater”. Many of them, including my-
self, came from abroad to study with
you. 122 is an incredible number and
achievement!
Prof. Backé: It is my experience that
there are excellent students in any
country in the world if your institute
is well known as a forge of systems
and new ideas. I am proud that many
of my former doctorate students hold
important positions in the industry or
at universities.
Ventil: As your “Doktorsohn” I can
confirm your special feeling for
people, for their research work and
especially for the novelties in the
specific research field. You have
The handing of the Bundesverdienstkreuzes of the Federal Republic of Ger-
many by President Herzog

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JUBILEJ – INTERVJU
always found the right research idea
at the right time. Can you give some
advice in this direction to those of us,
who continue your work as university
professors in the field of Fluid Power?
Prof. Backé: I have always said that
is very necessary that a university
professor has good contacts in the in-
dustry - this means to the applications
- so he can hear and see what the real
problems in practice are. I recom-
mend that capable younger scientists
should start their way as university
professors to transmit and increase
the knowledge of fluid power.
Ventil: Your research work in Fluid
Power was very rich and innovative
the entire time during your profes-
sional career. Besides the theoreti-
cal approach you always wanted to
end the research with a prototype
and with experimental verification.
Are there any special milestones,
research fields or research achieve-
ments, which seem to you as the most
important in your career?
Prof. Backé: The theoretical approach
of the system cannot take into ac-
count all the peripherical influences.
Therefore in our field, near to appli-
cations, it is necessary to prove the
applicability of a development by ex-
periments and to correct the theoreti-
cal model after the test results. Such
corrections by unexpected influences
often happen during our tests. That is
true, for instance, for different kinds
of valves or displacement units.
Ventil: One of your important per-
sonal characteristics has always been
a special feeling for the industry.
You have succeeded in developing
and kept it active, this, so important
university-industry cooperation, not
only in Germany but also with com-
panies from abroad. How did you do
it and what are the secrets to such a
success?
Prof. Backé: It takes a lot of time for
an institute to get a good reputation
in the industry. If the institute gets a
request from a company, the com-
pany must rely on the delivery of the
report on time and get an accurate
analysis of the results. That means
that the members of the institute have
to work more or less under industrial
conditions.
Ventil: For ma-ny years you have
been the pu-blisher of the globally
known journal O+P, which has been
a very important source of informa-
tion and research ideas for research-
ers and industrial environment all
over the world. Also our journal
Ventil has followed it as a model. You
have also started to organize a scien-
tific conference AFK, now IFK and
initialized and moderated numerous
so called “O+P Gespraeche” – O+P
discussions. All these activities prove
that you have a special feeling for
research and especially for the re-
sponsibility to transfer this knowledge
to the industry and vice versa.
Prof. Backé: I think that it is an im-
portant task of university institutes to
spread the knowledge of their field
and to stimulate innovations. For this
purpose we used all the possibilities
you mentioned: a journal with appli-
cable and innovative articles, confe-
rences and discussions.
Ventil: How do you see nowadays
the position and the development
of fluid power in Germany and also
globally?
Prof. Backé: We have to realize that
fluid power has got a strong competi-
tor in electricity. The introduction of
microelectronics in the signal path of
systems has strengthened the position
of fluid power.
But electricity is also trying to enter
the energy path of systems. Because
of the lower force density, until now
only low force applications have
been possible. In this area, whether
electric or fluid power means are
used often depends on the price. But
we must see that it is a tendency to
use electrical systems mainly to avoid
oil losses.
That is the reason why the research
in the sealing technique is so impor-
tant. Until now there has been an
increase of fluid power production
in spite of the competition by elec-
tric systems, but that can change if
electric drives or fuel cells are further
developed.
Ventil: Prof. Backé, in the last few
years your focus has been perhaps
a bit more in pneumatics, which is
becoming increasingly important
and already takes almost 50% of the
market in comparison to hydraulics.
In your opinion, what, is the reason
for such a growth and where do you
see the most important advantages of
pneumatics?
Prof. Backé: This higher annual in-
crease of pneumatics in comparison
IFAS today – Main building

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JUBILEJ – INTERVJU
to hydraulics is astonishing. I found
that this fact does not only have one
single reason but several. The main
reason may be that a pneumatic
system can be used anywhere: in
production engineering, handling,
packaging or in process engineering.
There are companies which offer
prefabricated components. So there
is no need for the components to
be designed and produced, but the
user can select them out of the cata-
log and build up complete systems.
Furthermore, he can insert desired
functions into the components: as ac-
celeration and deceleration charac-
teristics, speed behavior, generation
of desired forces and so on.
The energy costs are higher in pneu-
matics but on the other side the
investment and maintenance costs
can be much lower. So, for a long
working period the overall costs of a
pneumatic system can be lower than
of an electric or hydraulic drive.
Ventil: What is your opinion on the
future development of fluid power?
Prof. Backé: I think that the devel-
opment by permanent innovations
will continue in the future. They will
strengthen fluid power. But the inno-
vations, which open wide new fields
will are becoming rarer. The competi-
tion with electricity will become more
severe, that is sure, so it is necessary
to find new applications where the
special advantages of fluid power are
used and are not replaceable.
Until now hydraulic drives have do-
minated the mobile machinery. The
hydraulic high force cylinder cannot
be easily replaced by an electric de-
vice. But high torque electric motors
can perhaps become a strong compe-
tition. That is especially true if the fuel
cells can one day replace the diesel
engine. But that will take decades.
Ventil: And the last question, Prof.
Backé. What are your plans for your
future professional activities?
Prof. Backé: I have just moved out of
my cabinet in IFAS. Combined with
this is the decision to stop profes-
sional activities. Young people must
have the chance to gain reputation
in the field of fluid power. I am still
interested in publishing articles in
different magazines. Anyhow, if
someone asks a question, I will still
try to find an adequate answer. 
But I am happy to have some more
time to read historical books. I am
mainly interested in historical de-
scriptions and biographies. Events, to
which I have direct personal connec-
tions often attract my attention. The
history of Aachen and surroundings
offers many such possibilities.
Ventil: Prof. Backé, in the name of
our journal Ventil and in my per-
sonal name I thank you very much
for your answers and the time you
took for us. I also wish you many
fruitful activities and happy years
with your wife Frau Seitz-Backé in
the time to come.
For journal Ventil:
Niko HerakoviÏ
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