Portable laser vibration measurement

From field to lab: Young researchers and explorers

Polytec empowers today’s students with state-of-the-art sensor systems for vibration measurement in the education sector, in universities or summer schools. The goal is to inspire and educate students and provide educational institutions, such as schools, colleges, and universities, the ability to enhance their classes and laboratories by using the latest optical metrology techniques. Contact your local sales engineer to see whether your region qualifies for any special offers.

PolyLab* 

^{* shows offers for inquiries from the US and Germany}

Preventive maintenance on bearings in opencast mining

In opencast mining conveyor belts, some of which are kilometers long, move in conveyor roller garlands, which are made up of several idlers with roller bearings. Regular monitoring is already a challenge due to the dimensions and distances involved. The bearings are exposed to dynamic loads, resulting in increasing wear over the period of use. A typical indication of wear is an increase in noise. Precise identification of the damage source is not possible with airborne sound measurements. By means of structure-borne sound measurements, the noises increasing near the bearings can be measured well.

The spectral signature of the defect is transmitted to the measuring point, as the vibrometer is sensitive enough. Defective idlers can thus be identified. A final evaluation in the broadband frequency spectrum, which can also be automated, then provides information about the condition of the bearings. The spectral signatures of good bearings and bearings with various degrees of damage are usually determined in preliminary tests on a test rig. Condition monitoring, which has to be carried out in many places, should be done as quickly as possible. Therefore, the mobile application possibility is an important requirement here.

The ladie's choice

Vibrational signals are well-known to play a key role in mating (Hill, 2008) and even though many bee species are known to emit vibrational signals during mating, there are almost no studies on the function of these vibrations (Wcislo & Buchmann, 1995). Mason bees use thoracic vibrations in their precopulatory mating behavior before the female chooses a male (Seidelmann, 2001). According to Peters (1978), there are two subspecies of the red
mason bee in Europe – one on the borders of Europe (England, Skandinavia and Spain) and one in Central Europe. In Denmark, the two are supposed to overlap. Previous studies have already shown that German females prefer mating with German males over males from England.*

1. Is the female bee's choice influenced by the male vibrations?
   Yes! Females indeed use vibrations for female choice while choosing the male with longer vibration bursts (Conrad et al, 2010).
2. Do “dialects” and different “languages” within species and between species exist?
   Yes! The thorax vibrations really express a species very specific communication and even differ between subspecies.
3. How does changing the male’s vibrations influence the females’ choice?
   The bioassays clearly showed that the females do indeed use characteristic vibrational signals to distinguish between males from different countries. Changing the male’s vibrations influences their choice.

_{* Source: Conrad et al 2015 - The role of vibrations in population divergence in the red mason bee, Osmia bicornis, Current Biology}

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Autonomous condition monitoring

The autonomous robot ANYmal enters certain spaces, so humans don’t need to. The ANYmal navigates independently through complex and even multi-story environments on dedicated missions. Once guided through the environment – often critical or hazardous – the robot remembers every detail and finds the fastest way to complete its task. During operation, the robotic system safely avoids obstacles and reliably moves over rough terrain. This robot – depending on the installed sensors, metrology and other potential features – can determine operating conditions in confined or hazardous environments. Here, equipped with a portable laser vibration sensor, he inspects a roller mount in a narrow, dusty mining tunnel for abnormalities. Recording hours of measurement data, he brings home valuable insights for a subsequent processing and analysis.

Courtesy: ANYbotics AG, Switzerland

Understanding insect communication for pest control

The bacterium Xylella fastidiosa causes various serious diseases in a large number of crop plants. Among other things, the plant pathogen is responsible for a devastating disease in grape vines in California and South America, which costs the Californian economy alone around 104 million USD every year. In a unique research project, scientists analyzed the courtship communication of insects as vectors like the glossy winged sharpshooter, a small cicada species measuring approximately 1 cm, with the aid of optical laser vibration measurement. They found a new method of pest control that has no adverse affects on the ecosystem, unlike existing measures such as the use of pesticides. This creates hope and optimism for farmers in Europe, where the bacterium has been spreading since 2013.

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How portable vibrometry kept the clearance crews safe

In order to protect the clearance crews during rescue operation of the World Trade Center on 9/11, building 4 was monitored with portable vibration sensors from Polytec. Professor Jim Sabatier's dynamic measurements were of great support of the assessment of the collapse hazard during rescue missions. See the reprinted original article by Dr. Sabatier, providing details about the metrological implementation of laser-based stand-off condition monitoring and vigilating the structural integrity.

Article Vibration sensing at Ground Zero

Remote inspection in hazardous areas

Access even for expert staff can be difficult when working in hazardous industrial environments. Here, the possibility of taking a very close look on test structures with a laser from a safe distance can be a crucial argument. Noise analysis e.g. on condensors, machine parts and more can be conducted with a VibroGo® portable laser vibration sensor. With environmental excitation through the wind, technical systems in the open space can reveal much about their condition. The detected movement of the structure under test is useful to study and check power plants or technical installations, look for loose parts or detached joints, worn gear wheels, pumps or fans and monitor condition, or indicate that maintenance or exchange is due.

• Measure structure-borne noise and vibration from a safe distance up to 30 m with a laser
• On-board data recording and analysis
• Detect vibro-acoustic signature on a large frequency bandwidth from DC to 320 kHz

Condition monitoring in industrial plants

Production quality in industrial manufacturing processes highly depends on reliable and reproducible machining processes such as grinding, drilling, milling or cutting. For calibration or potential failure analysis, portable laser vibrometers like the VibroGo^® allow an entirely remote inspection from comfortable and safe distances, measuring the out-of-plane motion of the milling head, analyzing the noise on pumps and compressors and more. Here, the laser sensors reliably detect noise on a wide frequency bandwidth and monitor the component's condition for a flexible and simplified preventive maintenance.

Listening to the songs of cicades

The planthopper (lat. Hyalesthes obsoletus) is a species, that represents a vector of a plantdisease in vineyards and therefore of scientific and economic interest. Cicadas, leafhoppers, planthoppers, and spittlebugs (also called Auchenorrhyncha) are a very diverse group of animals within the insect world. Nevertheless, relatively little is known about their behavior and phylogeny. Vibrational signals play an important role in species recognition and mating behavior. Here, the use of laser vibrometer is extremely helpful. Laser vibrometer measurements and complementary microphone recordings show a clear vibrational signal from a maleplanthopper. The below signal shows simultaneously recordedairborne sound close to the animal, transmitted through the host plant.

Article Measuring insect communication with laser vibrometers

Quality inspections on old but gold precision parts

Have you ever lost important photos or documents due to a defective hard drive? We want all our data, personal or work-related, to be stored safely and reliably. Hard disk drives – with their ever growing storage densities and shorter access times – require an extremely high level of stability as regards the read/write head’s positioning above the disk surface. Its flying height of just a few nanometers is a compromise between high data density and risk of collision. The resonances of the aerodynamic bearing depend on the ambient pressure and thus can cause instabilities.

Since laser vibrometers measure in a non-contact and non-intrusive way, they provide the only method of inspecting the response behaviour of the read/write head including its suspension following dynamic excitation as a function of the ambient pressure. Such resonance tests are used to identify critical conditions and then derive design improvements to develop precision mechanics that respond robustly to resonances caused by aerodynamic excitation.