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InFocusIssue 02 | 2012
Optical Measurement Solutions
Simulation and Modal Analysis in Product Development
Identification and Simulation of a Milling Robots Flexibility
Behavior
Page 4
Design of a Novel Longi t udinal-torsional Ultrasonic
Transducer
Page 6
Vibration Measurement During Milling Operations
Page 10
Laser Vibrometers Meas ure Where no Other
Instruments Can Reach (Interview)
Page 15
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Dr. Hans-Lothar Pasch
Dear Reader,Industrial product development relies heavily on
computer-based, highly
efficient design and simulation tools. But how close will a
model approach
reality with regard to the functionality of the product or
component? This
can only be revealed by testing, where fast and precise tools
are necessary to
provide the experimental data needed for the assessment and
optimization
of the model.
Regarding vibration and acoustic testing, our customers have
trusted
Polytecs Scanning Vibrometers for 20 years. The PSV-500 is the
newest,
and the 5th generation of our renowned full-field vibration
sensors, again
setting new standards in performance, flexibility and user
friendliness.
We invite you to celebrate this milestone with us. Your steady
input of
suggestions and demands has contributed a lot to both our
development of
new products and our ability to remain the clear market leader,
an achieve-
ment that began 25 years ago with the first fiber-optic
vibrometer.
In this issue wed like to present you many interesting
applications from
our customers, such as simulation studies on industrial robots,
ultrasonic
drilling tools and machining equipment. You will also find an
interview
about using industrial vibrometers on the production line and
learn more
about our latest products.
Have fun reading!
Editorial
Eric Winkler
Eric WinklerOptical Measurement Systems
Dr. Hans-Lothar PaschManaging DirectorPolytec GmbH
Polytec News Page 3
Special Feature:Simulation and Modal Analysis
Identification and Simulation of a Milling Robots Flexibility
BehaviorPage 4
Design of a Novel Longitudinal-torsional Ultrasonic
TransducerPage 6
Thermomechanical Characterization of Materials under Extreme
Conditions Page 8
Vibration Measurement During Milling OperationsPage 10
R&D and Production Applications
Vibration Imaging on Facial Surfaces During PhonationPage 12
Noise, Vibration and Harshness (NVH) Analysis at MAN in
NurembergPage 14
Laser Vibrometers Measure Where no Other Instruments Can
ReachInterview with Olaf Strama, MEDAVPage 15
Events & MediaPage 16
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Polytec News
Polytec Expanding into New Premises
Polytecs new building was finished on schedule in September
covering 8,000 square meters of ground. Polytecs manu-facturing
team was happy to move into the new premises together with their
pro-duction machinery. They were joined by
their Optical Measurement Systems sales and application
colleagues and a couple of administrative departments. Work is
ongoing at the specially designed large acoustic testing hall that
will provide robot-automated vibration measurements.
Despite the upheaval, the transition ran so smoothly that all of
our office and lab employees were able to continue support-ing
their customers seamlessly.
Polytecs PSV-500 Scanning Vibrometer will continue to meet our
customers cur-rent and future need to bridge the gap between
computer generated simu lation models and the real dynamic and
acous -tic properties of their products. Thus we have reason to
celebrate and we do it with a special edition of our InFocus
Cus-tomer Magazine where we intro duce
the innovations of the new system and say thank you to all
customers for providing generous feed back and con-tinuous support.
If you didnt receive the magazine, please down load here or order
your printed copy: www.polytec.com/InFocus
The Next Scanning Vibrometer GenerationTechnical Excellence in a
Compact Design
The RSV-150 Remote Sensing Vibro meter, designed to measure
vibration and dis-placement from remote dis tances, offers expand
ed applications when configured with the new RSV-E-150-M
Controller. The new unit extends the bandwidth to 2 MHz and the
maximum velocity to 24 m/s, which is almost the limit of the
current HSV High Speed Vibrometers (30 m/s), but with a much wider
meas -urement range and higher optical sensi-tivity. The
development was driven by applications in ultrasonic NDE, e.g. test
-ing of railroad tracks or leak detection, as well as applications
with the high speeds and ac -celerations experi e nc -ed in falling
tower and pyro shock experi ments. www.polytec.com/rsv
New RSV ControllerRemote Vibration Sensing Now at High Vibration
Velocities and Frequencies
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Robots Under ControlIdentification and Simulation of a Milling
Robots Flexibility Behavior
mine the static flexibility behavior of the gearbox, the
bearings and structural components with both high accuracy and low
measuring complexity. This meth od, which involves the precise
measurement of displacements at in -di vidual points on the robot
structure, employs a 3-D Scanning Vibrometer.
Measurement Setup
The measurements were carried out on a KR 240 R2500 prime
industrial robot made by KUKA Roboter GmbH. A mil -ling spindle is
mounted on the robots flange, on the housing of which a force in
the range of several kilonewtons can be applied via a double-action
pneumatic cylinder (fig. 1, left). The loading cycle involves both
tensile and compressive loading of the robot. To improve the
sig-nal quality of the optical measurement system, all measurement
points have reflective film attached to them. In addi-tion, a
mirror is positioned behind the robot, so that points on the
reverse side can also be measured.
The 3-D Scanning Vibrometer, supplied by Polytec, comprises
three scanning heads that are attached to a tripod. The laser beams
from all scanning heads are targeted at a point and the vibration
velocity determined in those three direc-
The tilt resistance of both the gear box and the bearings can
also be calculated using this. The processing of these para-meters
in a computation-efficient manner makes it possible to determine
the deflec-tion of the robot in real time.
Currently, machine tools are used almost exclusively for
machining work. While milling robots do indeed have many ad
-vantages, because of the high flexibility of the robot structure
such robots are only suitable for machining jobs with low accuracy
requirements and low cutting forces. To increase the accuracy
achiev-able during machining using industrial robots, the Institute
for Machine Tools and Industrial Management at the Tech-nical
University of Munich is using a model-based control system for com
-pensation of the force-induced static displacements.
The challenges in designing the simu-lation model are both the
need for an absolute real-time capability and the requirement to
precisely determine the robot flexibility parameters. In this
respect, the tilt resistance of the gear-box and bearings must be
considered.
No method has existed until now for determining the stiffness
parameters of a robot that makes it possible to deter-
tions. From knowing the positions of the scanning mirrors and
sensor heads in space, the raw data can be trigonometri-cally
transformed into the three-dimen-sional movement of that point. In
this way, the velocity vector is determined for each measurement
point during a load cycle of the robot. The displacement of all
measuring points is determined by a numerical integration of the
velocity data.
Calculation of the Stiffness Para-meters from the Measurement
Results
Fig. 2 shows the resulting displacement images for a measurement
in which the robot was only loaded in the z-axis direction.
Tilting can be seen about the gear shaft of the second and third
linkage can be seen. In addition, a rotation of the first linkage
about the y-axis is apparent which, because of the relationship of
the levers, has a marked effect on the dis-place ment of the
tool-center point (TCP). This ex am ple highlights the necessity to
also consider the bearing stiffness of the individual axles when
modeling the flexibil i ty behavior of the robot. The stiffness
para meters of the linkages are determin ed from the rota tion of
the
Simulation
This article introduces a method to identify the stiffness
parameters of an industrial robot through measurements
made using a 3-D Scanning Vibrometer.
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Vibrometer, its possible to predict in real time and therefore
compensate via robot control for the displacement of the tool
center point due to the applied force. In the next step, an
algorithm for post-processing of the measurement data will be
developed to further improve the accuracy of determining the
linkage rotation angle. This should also allow the flexibility of
the structural components of the robot to be measured and to
inte-grate this into the flexibility model.
respectively adjoining struc tural compo-nents using a calcula
tion algorithm that is not de scribed in more detail here.
Further Use of the Stiffness Parameters
The determined parameters are used in an analytical stiffness
model of the robot in order to calculate its flexibility behav -ior
in real-time. The model is coupled to the robot control so that the
actual axis position of the robot can also be consid-ered.
Depending on the calculated dis-placements, offset signals are
transmitted to the control so that force-induced dis-placements of
the robot, for example caused by milling, can be compensated in a
control-based manner.
Summary and Outlook
The work presented here has shown that, with the aid of the
PSV-400-3D Scanning
Authors Contact Oliver Rsch, Prof. Dr.-Ing. Michael F.
[email protected]
Institute for Machine Tools and Industrial Management, Technical
University of Munich (TUM), Munich, Germany
www.iwb.tum.de/en/Institute.html
Fig. 2: Deflection of the robot during tensile and compressive
loading.
0 20 40 60 s 100100
50
0
%
100
Time
Forc
e
Loading cycleIndustrial robot KR 240 R2500 prime
Milling spindleHSD ES501
Force measure-ment cell
Pneumaticcylinder
Mirror Reflectivefilm
Compressive phase
Tensile phase
Fig. 1: Measurement setup (left) and applied force curve
(right).
New Look and Feel Newly Designed PSV 9.0 and VibSoft 5.0
Software
Aside from functionality supporting the updated PSV-500
hardware, the brand new Version 9.0 Scanning Vibrometer Software
has powerful new features for all users, including those
participating in one of our software maintenance plans such as the
special university program. The newly designed user interface
pro-vides more flexibility and is customizable to meet individual
needs. The long-term user will notice that all of the familiar
func-tions necessary to perform a measurement with ease have been
retained. Shortcuts improve access to standard features for the
power user. There are many beneficial changes in core
functionality. The align-ment process for example is dramatically
improved with the High Contrast Laser Display: a machine vision
technology to avoid glare in the camera image from the laser
reflecting off shiny surfaces. The SignalProcessor post processing
feature
can now be used to instantly compare stored and live data, which
is beneficial especially when setting up excitation sig-nals for
experimental modal analysis tests. New analyzer functionality is
imple ment - ed in the presentation mode, and the ears will benefit
from the PSV-S-Audio option, listen ing to live and stored data
files to, for example, assess the tuning of the struc-ture. Version
9.0 will be the last release to support Windows XP, but near ly all
PSV models can be upgraded to the latest operating system. The new
Version 5.0 VibSoft data acquisition and analysis sys-tem for
single point systems will of course also benefit from the latest
features.
www.polytec.com/software
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Drill Tools for Earth and SpaceDesign of a Novel
Longitudinal-torsional Ultrasonic Transducer
augmenting the oscillatory displace ment amplitude provided by
an ultrasonic trans ducer. The device is necessary to effi -cient
ly transfer the acoustic ener gy from the ultrasonic transducer
into the mediumbe ing treated. The ultrasonic horn is com-monly a
solid metal rod with a round transverse cross-section and a
variable-shape longitudinal cross-section. The length of the device
must be such that there is mechanical resonance at the de -sired
ultrasonic frequency of op era tion one or multiple half wave
lengths of ultrasound in the horn material.
Efforts have been made to excite longi -tudinal-torsional
responses in devices using two different techniques; by coup-ling
the longitudinal and torsional modes,
Tool Modeling
Fig. 1: The interaction of modes as the length of an ultrasonic
step horn is incrementally altered.
Measurement of complex combinations of different vibration
modes
operating together at ultrasonic frequencies can be carried out
using
3-D laser vibrometry.
These measurements are being used to optimize the performance of
longitu di - nal-torsional (L-T) ultrasonic horns at the University
of Glasgow. L-T ultrasonic vibration has many applications includ
-ing surgical devices, industrial welding and ultrasonic motors.
Researchers at Glasgow are even developing ultra sonic drill tools
for planetary explora tion. Due
to the low gravity, traditional drilling will be difficult and
the next generation Mars landers will require low-reaction devices
for drilling into the surface.
Development of Ultrasonic Properties
An ultrasonic horn, also known as a sono-trode, is a metal bar
commonly used for
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Experimental Modal Analysis
In order to evaluate the behavior of the transducer, the
operating modal res -ponse is determined by experimental modal
analysis (EMA). The effectiveness of the transducer is
characterized by its torsionality, which is the ratio of torsional
to longitudinal vibration amplitude. The 3-D laser vibrometer was
used to meas -ure the response because it allows data to be
obtained without affecting the nat-ural frequency, mode shape, or
damp-ing, regardless of whether the device is ex cited in air
(unloaded) or under a load representing a real-world
application.
Using the 3-D laser vibrometer, responses in three orthogonal
directions are ac -quir ed at a grid of surface points on the
transducer and the modal frequencies and animated mode are
extracted using MEscope software. The results enable us to assess
the vibrational characteristics of
Authors Contact Hassan Al-Budairi, Dr. Patrick Harkness, Prof.
Margaret [email protected];
[email protected]
University of Glasgow, School of Engineering, UK
www.gla.ac.uk/schools/engineering
Fig. 3: Modelled and measured mode shapes of the transducer
represented in Simulia Abaqus and Vibrant Technologies MEscope.
and by causing the degeneration of a longitu dinal mode into a
longitudinal-torsional response by incorporating heli-cal flutes
and slits. Coupling the longitu-dinal and torsional modes of
vibration has been found to be difficult because, as the geo metry
of a typical ultrasonic horn is modified incrementally, the two
modal frequencies have been found to approach each other and then
move apart but with no crossover point where the modes are fully
coupled.
For example, using a Polytec 3-D laser vibrometer system, the
interaction of the first longitudinal mode (L1), the second
torsional mode (T2), and a bending mode (B) can be observed (fig.
1) in terms of longitudinal (L) and tangential (T) ampli-tude in a
simple titanium half-wavelength step-horn as the length of the base
sec-tion of the horn is gradually decreased.
As it is very difficult to achieve effec tive coupling between
these modes, horns exploiting this approach tend to be char
acterized by low responsiveness or, alternatively, need to
incorporate two differently poled piezoceramic stacks in the
transducer to excite the two modes. Therefore, the mode
degeneration meth -od is considered to be more promising and we
have developed a transducer (fig. 2) to take advantage of this
tech-nique. This transducer can deliver a lon-gitudinal-torsional
output when excited by the longitudinal vibration mode of a single
piezoceramic stack.
the operating mode and the frequency spacing between the desired
mode and surrounding unwanted modes of vibra-tion. The vibrometry
measurements can also be used to validate finite-element (FE)
models of the transducer (fig. 3).
Conclusion
The results show that the model can be used reliably to design
novel transducer shapes and evaluate the longitudinal-torsional
response characteristics to maxi-mize performance of devices.
Fig. 2: The new L-T transducer.
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Material Science
A new dynamic method for thermomechanical characterization of
candidate
target materials (tungsten, tantalum and molybdenum) has been
developed
as part of the program advancing high power targets for the UK
Neutrino
Factory.
The materials used in the target systems of next generation high
power particle accelerators are frequently exposed to a combination
of high stresses, high strain rates and very high temperatures. To
estimate the lifetime of target and target system components in
this environment,
the candidate materials have to be tested under extreme
conditions.
Experimental Setup
A thin wire made from the candidate material was heated and
stressed by a fast high current pulse (see fig. 1) gen -
e rated by a power supply for the ISIS syn-chrotron (Rutherford
Appleton Laborato-ry) kicker magnets. The wires were sup-ported in
a vacuum chamber to avoid oxidation and heated to 2650 C by ad
-justing the pulse rep etition rate. To allow the current to
generate a sufficient ther-mal stress, the wire had to be thin
(less than 1 mm diameter). A single-point Laser Doppler Vibrometer
(LDV) compris-ing the OFV-534 optical sensor head and OFV-5000
vibrometer control l er meas-ured the longitudinal (by sensing at
the
Metals at the LimitsThermomechanical Characterization of
Materials under Extreme Conditions using a Laser Doppler
Vibrometer
8
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Fig. 1: The experimental setup. Coaxial cables (1) carrying the
current pulse from the power supply are combined into a sin -gle
cable (2) which is connected to the test wire. The wire is
supported in a vacuum chamber (3) and its oscillations are
meas-ured by the Laser Doppler Vibrometer (4).
Fig. 3: The measured and calculated radial velocity of a 0.5 mm
diameter tungsten wire at different temperatures.
Fig. 4: Youngs modulus of tungsten compared between
experiments
Fig. 5: The yield strength versus peak temperature for tantalum,
tungsten and molybdenum wires. The characteristic strain rate
values are also shown.
wire tip) as well as radial velocities and displacements of the
wires. Three differ-ent LDV decoder units (VD-02, VD-05 and DD-300)
cover the complete range of amplitudes and frequencies of the wire
vibrations. An optical pyrometer measured the wire temperature at
the same point that was measured by the LDV.
Results and Conclusions
Fig. 3 shows the radial velocity of the tungsten wire measured
by the Laser Doppler Vibrometer at different tempe -ratures. The
current pulse began at t = 0 and the wire started to contract and
ex -pand. After about 1 s it reached a new equilibrium position and
started oscillat -ing around it. The time scale in fig. 3 begins
with t < 0 in order to illustrate a relatively low background
noise level of the LDV. The correlation between ex -periment and
finite element modeling (LS-DYNA) calculations is very good. The
radial oscillation frequency obtained was used afterwards to
extract the Youngs modulus of the wire material as a func -tion of
temperature. In fig. 4 the Youngs modulus results from the new
measure-ments are compared with earlier results.
To determine the yield strength, the current pulse amplitude in
the wire was increased in steps. This was continued until the wire
started bending or kinking. The radial surface velocity measured
by
the LDV (see fig. 3) was used to extract the strain rate during
the test. The LDV optical sensor head includes a fast cam -era for
monitoring strain in the wire. In addition, it was noticed that the
LDV radial velocity signal became very noisy when signs of plastic
deformation first appeared. This change in LDV signal quality
indicated that the wire was near its yield point. Fig. 5 shows the
stress that is needed to reach the yield point of molybdenum,
tantalum and tungsten wires.
To conclude, the candidate materials for the Neutrino Factory
target were tested under conditions expected at this accelerator. A
new dynamic method for thermomechanical characterization of
materials under extreme conditions was therefore developed that can
help test the consistency of different constitutive models.
Authors ContactDr. Goran koro, Dr. J. R. J. Bennett,Dr. T. R.
[email protected]
ISIS Facility, STFC, Rutherford Appleton Laboratory, Harwell,
Oxford, UK
www.isis.stfc.ac.uk
AcknowledgementsThis work was supported by Science and
Technology Facilities Council (UK).
Fig. 2: Photograph of a 0.75 mm diameter tungsten wire during
current pulse tests (a) and an illustration of wire clamping
(b).
9
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structures may experience regenerative lateral vibrations for
some cutting con -ditions. The inherent nature of variable dynamic
conditions of these milling and machining processes are likely to
be the culprits by which the finished parts ex -hibit poor surface
finish and lower pro-ductivity of those manufacturing process-es.
Stability lobes diagram methods are common techniques that use
dynamic information to define stability regions in which it is
possible to find the appropri -ate and desired combinations of
machin-ing parameters. With this technique, the experimental
Operational Frequency Response Functions (OFRF) and regular FRF are
required to feed the Enhanced, Multistage Homotopy Perturbation
Method (EMHPM).
In milling, structural modes of the machine tool-workpiece
system are initially excited by cutting forces. Surface finish
profiling due to oscillatory excitation left by a sec-tion of the
tooth is subsequently removed by the incoming and advancing cutting
tooth surface which causes increased struc-tural vibrations. This
self-excited cutting phenomenon can become unstable, and chatter
vibrations grow until the tool jumps out of the cut, ruins the
expected surface tolerances and can even break under excessive
cutting forces.
High speed machining is a widely used process in the
aeronautical industry to machine low stiffness structures with thin
walls and floors where high tolerances are required. Machining of
these types of
Comparison Between Laser Vibro-metry and Existing Measuring
Methods
It is well-known that accelerometer mass load on heavy
structures has neg li gible in -fluence on dynamic measurements.
How-ever, those effects are not negligible when the workpiece mass
is small. Since the accuracy of the OFRF directly affects the
stability lobes diagram, it is important to study the ac
celerometer mass loading effects over the stability diagrams to
pre-dict accu rately the dynamic behavior when milling thin walled
parts.
In order to study accelerometer mass-loading effects on thin
walled structures, we performed several impact tests at different
locations over aluminum 7075 thin-walls (1 x 35 x 50 mm) and col l
- ect ed the corresponding FRFs by using a 0.6 gram accelerometer.
We repeat -ed the measurements using a Polytec CLV-2534-2 Compact
Laser Vibrometer that allows dynamic measurements with -
Process Optimization
Chatter vibrations continue to be the major factor limiting the
increase in
material removal rates of machine tooling. Machine tool chatter
vibrations
occur due to a self-excitation mechanism in the generation of
chip thick-
ness during milling operations.
Improving Machining TechniquesVibration Measurement During
Milling Operations
MMaacchhhiiinnniiinngg TT
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Authors ContactProf. Dr. Alex Elas-Ziga, Daniel OlveraInstituto
Tecnolgico y de Estudios Superi-ores de Monterrey (ITESM),
Monterrey, Mexico.
www.topmak.com.mx
Mario Pineda, Polytec Inc.
Acknowledgements: This work was funded by Fondo Mixto Conacyt
#145045 and by Tecnolgico de Monterrey through the research chairs
in Nanotechnology and Intelligent Machines.
Parts of this article are based on the paper Experimental
Stability Analysis of Thin Wall Structures using Laser Doppler
Vibro-meter Devices, Proc. 9th Int. Conf. on High Speed Machining,
San Sebastian, Spain, March 7 8, 2012.
out adding mass to the workpiece. The dotted lines shown in fig.
1 represent the frequency response functions ac -quired using the
accelerometer and Laser Doppler Vibrometer (LDV) under the same
conditions.
Fig. 1 illustrates significant differences between the FRF
functions obtained by using the accelerometer and the laser Doppler
device. The laser vibrometer without the accelerometer attached
captures two fundamental vibrational modes with peak values at 1105
Hz and 1722 Hz. However, the measurements performed with the
accelerometer ex -hibit the same dynamic modes but with peak values
at 580 Hz and 1366Hz. These differences in the recorded FRF spectra
were noticed during experimental tests because of the sound
pressure level pro-duced by the thin wall workpiece. The 525 Hz
shift of the FRF value of the first peak mode is attributed to the
effect of the accelerometer mass.
In order to verify our experimental obser-vations, we performed
measurements by using the LDV with the accelerometer attached to
the workpiece. The results, shown by the dashed line in fig. 1, are
the same as those collected with the ac -celerometer. This
experimental test con-firmed the accelerometer mass-loading effects
over FRF values, which not only causes a shift of the frequency
value of about 48%, but also changes consider-ably the modal
damping of the system.In addition, we expect changes in the
calculat ed stiffness. As expected, the ef - fect of the accelero
meter mass in creases as 1 mm thickness of wall material is re
moved from the workpiece during the machining pro cesses.
In order to demonstrate the effects of the accelerometer
mass-loading on the dynamics of the cutting processes, we compute
the stability lobes by using the EMHPM for both accelerometer and
vibrometer measurements. The stability lobes plotted in fig. 2 are
generated for a inch diameter end mill with 2 teeth, a helix angle
of 20, and a radial depth of cut of 0.8 mm.
As we can see from fig. 2, the stable depth of cut values on the
computed
stability lobes are strongly influenced by the ac celerometer
mass load. Accelero-meter measurements produce a shift in stability
lobes not only on spindle speed direction, but also axial depth
direction in comparison with vibrometer measure-ments. For this
reason, unstable predict -ed cutting conditions are experimentally
explored by means of the LDV. The beam was aimed on the top center
of the thin wall.
For a 26,500 rpm spindle speed, the maxi-mum vibration
amplitudes were recorded up to 0.3 m/s (fig. 3), with a confirmed
stable behavior through the frequency spectrum which corresponded
to the tool passing-frequency and its harmonics. On the other hand,
an accelerometer-predict-ed unstable boundary region was explored
by LDV OFRF responses (fig. 4). In this case, the velocity
amplitude at 30,000 rpm reached 0.6 m/s. The frequency domain
exhibits a chatter frequency.
Conclusion
Fig. 5 shows a comparison between the modal parameter values
obtained by using both the FRF of the accelerometer and the laser
vibrometer recorded data.It can be clearly seen that an
accelero-meter of 0.6 grams attached to the thin wall workpiece has
a significant effect on FRF measurements.
Fig. 2: Stability diagrams for the FRF using both devices.
Fig. 3: Stable cutting at 26,500 rpm.
Fig. 4: Unstable cutting at 30,000 rpm.
Fig. 1: Laser measurements versus accelerometer measurement.
Fig. 5: First dominant frequencies measured with both laser
sensor and an accelerometer.
11
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Head-to-HeadVibration Imaging on Facial Surfaces During
Phonation
Bio Acoustics
Getting Set
The vibration patterns of head and neck surfaces, and their
contribution to the overall sound, has been inadequately studied
until now. A male (22 years of age) with no speech disorder
participat -ed in these laser vibrometry measure-ments, intended to
image vibration pat-terns that are generated by speaking.
The vibration velocity was obtained with a scanning laser
Doppler vibrometer sys-tem (Polytec PSV-400-M4). The laser
Sound from speech is radiated not
only from the mouth and nostril
openings but also from the surfaces
of the head and neck.
Japanese scientists are there fore able to use vibrometers to
study speech by meas-uring vibrations caused by phonation, taking
advantage of their ability to ana-lyze vibration for a particu lar
frequency band of interest.
Doppler vibrometer is an optical trans-ducer that senses the
frequency shift of light reflected from a vibrating sur -face
caused by the Doppler effect. It can determine the vibration
velocity and dis-placement at a certain point. The scan -ning
vibrometer can also scan and probe multiple points of a vibrating
surface automatically.
Fig. 1 shows the experimental setup. The scanning head of the
vibrometer was mounted on a tripod, perpendicular to
12
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the floor. The participant was positioned to lie directly
beneath the scanning head.
The participant was asked to articulate utterances repeatedly
while keeping his head immobile during the measurements. Speech
sounds were recorded through a microphone.
The vibration patterns of the facial surface were measured from
the frontal direction, which is perpendicular to the forehead, and
from an oblique direction, which is nearly perpendicular to the
left cheek and the left side of the nose.
In the experiment, scanning points on the facial surface were
first determined using system control software. During the
meas-urement, the vibrometer scann ed each point and determined the
vibration velo-city. It took approximately one second to probe each
point. The vibra tion velocity and speech sounds were measured up
to 5 kHz.
Results
The two upper images in fig. 2 show the vibration patterns of
the frontal facial surface during sustained phonations.
There were significant differences bet-ween the vibration
velocity patterns for the vowel (left) and nasal (right)
conso-nant. For the vowel, the facial surface around the mouth
opening vibrated the most compared to the other regions. In
contrast, for the nasal consonant, the facial sur faces of the nose
and its vicinity vibrated strongly owing to resonances in the nasal
sinuses. The forehead sur -face also vibrat ed to some extent,
pos-sibly indicating that the frontal sinuses reso nated during the
production of the nasal consonant.
The two lower images in fig. 2 show the vibration velocity
patterns of the left facial surface for the phonemes. The vibration
of the side of the nose was observed to be stronger for both
phonemes than that indicated in the upper images of fig. 2. This
means that the direction of the laser light is a significant factor
in this measure-ment method. The result also revealed that, for the
participant in the present study, the nose surface vibrated even
when the vowel, not only just the nasal consonant, was
articulated.
How Can It Be Used?
The proposed method enables us to evalu-ate the speech of
patients with cleft pal-ate or velopharyngeal insufficiency. The
vibration pattern may be helpful as visual feedback of a speaking
exercise for such patients. The vibration pattern may be easier to
relate to their somesthesis than spectra of their speech sounds.
This could also be useful for singing exercises.
In conclusion, the proposed method allows fast, non-contact and
multi-point measurements of the vibration velocity of skin
surfaces. The results will expand our knowledge of speech pro
duction. The next step that needs to be taken is to investigate the
relationship between the vibration velocity pattern of skin
surfaces and the formants and antiformants of speech sounds.
Author ContactProf. Tatsuya KitamuraFaculty of Intelligence and
Informatics, Konan University, Kobe,
Japanhttp://basil.is.konan-u.ac.jp/index_e.html
This article is based on the publication Measurement of
vibration velocity pattern of facial surface during phonation using
scanning vibrometer which can be found at
www.jstage.jst.go.jp/article/ast/33/2/33_2_126/_pdf.
AcknowledgmentsThis study was supported by JSPS KAKENHI
(21300071). The author wishes to thank Dr. Kazuhito Ito (National
Institute of Advanced Industrial Science and Techno-logy), Mr.
Francois Bouteille, Mr. Ryo Ishiyama, Ms. Shoko Wakatsuki (Polytec
Japan), and Professor Ken-ichi Sakakibara (Health Sciences
University of Hokkaido) for their generous assistance and valuable
advice.
Fig. 1: Experimental setup.
Fig. 2: Vibration velocity patterns of frontal and left facial
surface during articulation of vowel (left) and nasal (right)
consonant. The unit is m/s [dB] and 0 dB is equal to 1 m/s.
13
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of the individual engine components from the signals, with the
following aims:
Identification of engines with conspicu-ous vibration and noise
behavior.
Identification of component and assem-bly faults based on the
supplied signals
Identification of the fault for effective support of the
rework.
MAN exclusively uses Polytec laser vibro-meters as vibration
sensors, alongside microphones for airborne noise measure-ment.
To evaluate the sensor signals, ANOVIS offers comprehensive
signal processing and classification methods ranging from simple
frequency analysis and rotation-angle synchronized methods (order
analy-sis) to automatic limit value adaptation. The signal
components that arise are re lated to engine kinematics and, based
on their characteristics, are allocated to moving parts of the
engine (example in fig. 2).
The ANOVIS test system can, through its modularity, be flexibly
adjusted to match a wide variety of different engine
MAN Truck & Bus AG in Nuremberg produces a wide range of
modern com-mercial vehicle engines. Each individ u al engine is
subject to comprehensive tests before it leaves the factory,
including tests for undesirable noise and vibrations (noise,
vibration and harshness, NVH). This is where the ANOVIS system is
used, supplied by MEDAV. These vi bration and noise analyses are
effective in helping to safeguard the high quality standards of the
Nuremberg engine plant.
ANOVIS Detects Component and Assembly Faults
The NVH analysis carried out using MEDAVs ANOVIS system
constitutes an important component of the so-called engine cold
test in which engines are filled with oil and then driven by an
elec-tric motor. In comparison with other methods, this approach is
economical, ecological and simultaneously provides in-depth
testing. The ANOVIS test system (fig. 1) records noise and
vibrations at various points on the engine and deter-mines
characteristic values for assess ment
Sounds GoodNoise, Vibration and Harshness (NVH) Analysis at MAN
in Nuremberg
variants. This also refers to the selection of the sensor type.
The IVS-200 and IVS-400 laser vibrometers that are used also permit
vibration measurements on difficult-to-access measurement points or
loca tions that are in some way non-cooperative. Thus, for example,
it is in some cases necessary to measure the black-painted surfaces
of a high-pressure pump. Process-reliable signal measure-ment with
20 kHz bandwidth is also no problem here using the IVS industrial
vibrometer and intelligent speckle elimi -nation integrated into
ANOVIS, The few manual steps required as part of the maintenance,
for example, to check the position and focus, are taught in a train
-ing course to enable reliable operation during production. In this
way, ANOVIS makes it possible to detect a large num-ber of
potential types of defects, which are otherwise undetectable using
other testing methods. For example:
Damage and manufacturing deviationin the camshaft
Noise in the valve-train assembly, e.g. caused by too much
clearance
High pressure pump and other auxiliary component faults
Toothing faults, damage and geometri-cal faults on cogs,
incorrect tooth-flank backlash
Fig. 2: Sideband energy measure based on order analysis for
assessment of toothing vibrations.
voIadocsbpmpvnmm
Fig. 1: ANOVIS system variants for flexible vibration and noise
analysis in production.
Engine Cold Test
14
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Authors ContactDr. Michael Weidner, Olaf [email protected]
MEDAV GmbH, Uttenreuth, Germanywww.medav.de/?&L=2
Turbocharger faults, for example, dam age and geometrical
faults
Missing connecting rod bearing shells and for eign bodies in the
combustion chamber
Systematic errors are practically non-exis-tent in modern engine
production. The particular advantage of using ANOVIS for
vibration and noise measurements is its ability to identify
individually occurring, random errors. Additionally, the vast ex
-perience of the MEDAV division, Indus -trial & Automotive
Solutions (IAS), in engine testing allows the identification of the
cause of the faults. Also, practical tools are provided to quality
engineers for analysis and statistical evaluations,
with the help of which, production can be continuously further
optimized.
Laser Vibrometers Measure Where no Other Instruments Can
ReachInterview with Dipl.-Ing. Olaf Strama, director of Industrial
& Automotive Solutions (IAS) at MEDAV
Mr. Strama, you lead the IAS division of MEDAV. What are your
application areas?
The Industrial & Automotive Solutions Division specializes
in vibration and noise analyses, including notably the so-called
NVH test. It is used by our industrial custo-mers for such tasks as
the end-of-line test-ing of engines, gearboxes and steering
components.
How long have you been using laser vibrometers and what first
caused you to do so?
We have been using laser vibrometers for vibration measurement
since the 90s. We started with a Polytec CLV and then we purchased
a batch of IVS-200 indus-trial vibration sensors. In the meantime,
we have used its successor, the IVS-400, especially for measurement
points that are difficult to access or where a high measurement
bandwidth is required for automatic production.
The breakthrough came about 10 years ago. Since then, our ANOVIS
testing sys-tems have been equipped with an intelli-gent speckle
elimination feature. With its introduction, the number of false
meas-urements in engine production lines producing more than 1000
engines per day could be reduced to 1 2 cases per month. Measuring
with a bandwidth of
20 kHz on machined metal surfaces is reliable.
How do you view the use of laser vibrometers up until now and
what do you consider to be the essential advantages of optical
measurements when compared with the alternatives?
As already mentioned, accessibility to the optimal measurement
points is one primary criterion, as is high flexi bili ty for use
with different types of test pieces. Also, the wide bandwidth of
the laser vibrometer achievable in automat ed testing is another
argument, as some error types are only identifiable at high
frequencies. Laser vibrometers also score high because they lack
mechanical parts that wear out and do not require fre -quent
calibration.
How reliable is the laser vibrometer under harsh industrial
conditions?
Many IVS-200 units have been used daily in engine testing for
over 10 years. With many customers, maintenance is only implemented
once it becomes necessary as indicated by the signal quality, which
is statistically determined by ANOVIS.
What is the reaction of your cus -tomers and what proportion of
orders have laser vibrometers as the vibration sensor?
From our point of view, users react positively if the sensor
fulfills its task and no problems occur during daily use. The
evaluations carried out by our customer support department
regularly indicate that this is the case with laser vibrome-ters.
The IVS industrial vibration sensors have contributed significantly
to the attractiveness of the solution we offer in a considerable
number of installations.
How do you see the potential of laser vibrometers for cold and
hot testing applications in the automotive industry?
As a provider of vibration and noise meas-urement systems we
offer our customers complete testing solutions for their
pro-duction right from the start. These solu-tions consist of
optimized sensor technol-ogy for the required application, match
ing data acquisition hardware and the needed analysis and
evaluation of the defined task. The engines to be tested are
becoming more complex and, consequently, the optimal measurement
points are more difficult to access. Hence, and because of the
frequency range re quired to carry out the tasks, the choice is
increasing ly likely to be a Polytec industrial vibration
sensor.
Thank you very much for the interview, Mr. Strama!
15
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Advancing Measurements by Light
ImprintPolytec InFocus Optical Measurement SolutionsIssue 2/2012
ISSN 1864-9203 Copyright Polytec GmbH, 2012Polytec GmbH
Polytec-Platz 1-7 D-76337 Waldbronn, Germany
CEO/Publisher: Dr. Hans-Lothar Pasch Editorial Staff: Dr. Arno
Maurer, David E. Oliver,
Philipp HassingerProduction: Regelmann KommunikationImages
courtesy of the authors unless otherwise specified.
New VideoBridging Design and Real World
Did you know how precise, fast and convenient vibration
measurements can be? Please view our brand new video to learn how
the PSV-500 Scanning Vibrometer is easily applied to complex
vibro-acoustic problems: www.polytec.com/psv.
Polytec25 Years of Expertise with Laser Vibrometers
The worlds first fiber-optic vibrometer was introduced by
Polytec in 1987. Being capable of performing single point and
differential vibra-tion measurements up to 1 MHz, it soon became
obvious that this technology was extremely well suit ed for
studying the vibrational be -havior of tiny hard disk components in
the disk drive industry. Only one year later, the vibro meter was
honored with the Photonics Circle of Excellence Award the beginning
of a success story that eventually led to Polytec becoming the
accepted world leader in laser vibrometry.
Trade Shows and ConferencesDate Event Location
Nov 29, 2012 Non-Contact Topography Measurement Workshop
Loughborough University, UK
Dec 04 06, 2012 Seed Expo 2012 Hyatt Regency Chicago, USA
Dec 10 11, 2012 Netherlands MicroNano Conference 12 De ReeHorst,
Ede, The Netherlands
Jan 20 24, 2013 MEMS 2013 Taipei, Taiwan
Mar 18 20, 2013 Automotive Testing Expo Korea Seoul, Korea
May 08 10, 2013 CMMNO Condition Monitoring Conference Ferrara,
Italy
For the most up-to-date information please refer to our web
site, www.polytec.com.
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Date / Time Event
Nov 22, 201210:00 11:00 CET
Optimizing the performance of ultrasonic tools and
transducers
Nov 27, 201210:00 11:00 CET
Simplify your rotational vibration analysis: characterizing the
dynamics of rotating structures by using LDV
Dec 04, 201210:00 11:00 CET
Go ahead with optical, non-contact length and speed measurement:
LSVs for optimized reliability and minimized operational costs
Dec 13, 201210:00 11:00 CET
Accelerate your design process: optimizing NVH/Modal Testing and
FE correlations with 3-D vibration mapping system
www.polytec.com
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