Output inspection of products based on vibroacoustic diagnostics

The introduction of effective automated measurements based on vibroacoustic diagnostics enables fast and reliable 100% inspection of products on the assembly line. This ensures the quality and safety of products and at the same time minimizes the costs associated with resolving any complaints.

Depending on the type of product being inspected, different types of analyses are used. For the inspection of individual products (e.g. parts after machining), this can be, for example, modal analysis. The inspected part is excited by an automatic hammer with a so-called Dirac impulse. The response of the part is usually measured contactlessly, e.g. using a suitable microphone. The natural frequencies obtained through the analysis are then compared with the natural frequencies of the OK product (e.g. crack detection).

For the verification of more complex products, e.g. gearboxes, motors, it is necessary to ensure the operation of the tested device under load during the output check (e.g. using an external electric motor and dynamometer). The test mode should correspond to real operating conditions. Either vibration or sound pressure measurement can be used to inspect products. When using a microphone, it is necessary to acoustically isolate the measured product, for example by using a special cabin or chamber. This is of course associated with increased measurement costs. For this reason, it is usually more advantageous to measure vibrations at suitably selected measuring points. When selecting measurement locations, it is necessary to ensure the greatest possible signal-to-noise ratio in terms of measurement accuracy. To measure vibrations, it is possible to use accelerometers (automatically moved to the measured locations or permanently installed, e.g. in the locations where the tested device is placed and fixed on tester), or to use non-contact measurement using a laser vibrometer. During the measurement, it is necessary to ensure the exclusion of the influence of excitation sources that are not related to the measured device (various systems of the tester, assembly line, etc.).

To process the measured signals, it is necessary to choose an appropriate diagnostic method. Various analyses in the time and/or frequency domain are commonly used, including order analysis for testing in non-stationary regimes. The output evaluation is performed, for example, based on a comparison of the spectrum of the tested product with the so-called reference spectrum (corresponding to the spectrum of an OK product) and subsequent identification of problematic frequency components.

Today, several modular measurement systems are available on the market that can also be used in the field of automated measurements and signal analysis on the EoLT - end of line tester (see Fig. 1). These are so-called virtual measurement systems, the essence of which is to supplement the open architecture of the PC with the appropriate measurement card (e.g. using the PCI bus) and software. The application also includes, for example, a graphical user interface (programmable front panel).

In addition to the increasing level of automation, the implementation of various intelligent solutions in the field of technical diagnostics can also contribute to further increasing the efficiency of production processes, improving the quality and competitiveness of products.

List of used literature:

[1] corporate materials of SIEMENS

Internet sources:

[1]? https://youtu.be/5Rk025RuIUQ?feature=shared

Vystupná kontrola produktov na základe vibroakustickej diagnostiky

Zavedenie efektívnych automatizovanych meraní na báze vibroakustickej diagnostiky umo?ňuje rychlu a spo?ahlivú 100% kontrolu vyrobkov na montá?nej linke. Tym je zabezpe?ená kvalita a bezpe?nos? produktov a zároveň sa minimalizujú náklady spojené s rie?ením prípadnych reklamácií.

V?závislosti od druhu kontrolovaného produktu sa vyu?ívajú r?zne druhy analyz. Pre kontrolu jednotlivych vyrobkov (napr. dielov po opracovaní) to m??e by? napr. modálna analyza. Kontrolovany diel je budeny prostredníctvom automatického kladiva tzv. Diracovym impulzom. Odozva dielu je spravidla snímaná bezkontaktne napr. pomocou vhodného mikrofónu. Analyzou získané? vlastné frekvencie sa potom porovnávajú s?vlastnymi frekvenciami OK produktu (napr. detekcia trhlín).

Na overovanie zlo?itej?ích produktov, napr. prevodoviek, motorov, je potrebné pri vystupnej kontrole zabezpe?i? chod testovaného zariadenia pod za?a?ením (napr. pomocou externého elektromotora a dynamometra). Testovací re?im by mal zodpoveda? reálnym prevádzkovym podmienkam. Pre kontrolu produktov je mo?né vyu?i? bu? meranie vibrácií alebo akustického tlaku. V?prípade pou?itia mikrofónu je potrebné merany produkt akusticky odizolova? napr. pou?itím ?peciálnej kabíny alebo komory. To je samozrejme spojené s?navy?ením nákladov na meranie. Z?tohto d?vodu je oby?ajne vyhodnej?ie mera? vibrácie vo vhodne zvolenych meracích miestach. Pri vybere meranych miest je potrebné z h?adiska presnosti merania zabezpe?i? ?o najv???í odstup signálu od ?umu. Pre meranie vibrácií je mo?né pou?i? akcelerometre (automaticky prisunuté na merané miesta alebo pevne zabudované napr. v?miestach ulo?enia a?upevnenia testovaného zariadenia na testeri), príp. vyu?i? bezkontaktné meranie prostredníctvom laserového vibrometra. Po?as merania je potrebné zabezpe?i? vylú?enie vplyvu zdrojov budenia, ktoré nesúvisia s?meranym zariadením (r?zne systémy testera, montá?nej linky a?pod.).

Pre spracovanie nameranych signálov je potrebné zvoli? vhodnú diagnostickú metódu. Oby?ajne sa vyu?ívajú r?zne analyzy v??asovej a/alebo?frekven?nej oblasti, vrátane rádovej analyzy pre testovanie v?nestacionárnych re?imoch. Hodnotenie na vystupe sa vykonáva napr. na základe porovnania spektra testovaného produktu s?tzv. referen?nym spektrom (odpovedá spektru OK produktu) a?následnej identifikácii problémovych frekven?nych zlo?iek.

Dnes je na trhu k?dispozícii nieko?ko modulárnych meracích systémov vyu?ite?nych i?v?oblasti automatizovanych meraní a?analyzy signálov na EoLT - end of line tester (vi? obr. 1). Jedná sa o?tzv. virtuálne meracie systémy, ktorych podstatou je doplnenie otvorenej architektúry PC príslu?nou meracou kartou (napr. vyu?itím PCI zbernice) a softvérom. Sú?as?ou aplikácie je napr. aj grafické rozhranie k u?ívate?ovi (programovate?ny ?elny panel).??

Okrem?rastúcej úrovne automatizácie m??e k??al?iemu zvy?ovaniu efektívnosti vyrobnych procesov, zlep?ovaniu kvality a?konkurencieschopnosti produktov prispie? aj implementovanie r?znych inteligentnych rie?ení z?oblasti technickej diagnostiky.