With the emergence of the Industry 4.0 concept, machine vibration monitoring and diagnostics systems based on the so-called smart vibration sensors using MEMS accelerometers become very popular on the market. Many automation companies use specifically designed for CbM industrial vibration sensors based on electronic chips with enclosed MEMS accelerometers. However, in the commercial vibration sensors datasheets very often are not provided detailed metrological parameters like frequency response in the declared frequency band. The article presents the results of research concerned to identification of frequency response of an exemplary available on market digital accelerometer dedicated to machines condition monitoring. The determined characteristics indicate that the sensor can be used for basic diagnostics of machines in accordance to the series of vibration standards ISO 10816 and ISO 20816. On the basis of the determined characteristics, it can be concluded that there are some non-linarites of the frequency response functions at the boundaries of the declared measurement band. It shows that application of that sensor to precise measurements conducted during scientific research could be limited.
In this paper, a procedure for MEMS accelerometer static calibration using a genetic algorithm, considering non-orthogonality was presented. The results of simulations and real accelerometer calibration are obtained showing high accuracy of parameters estimation.
Condition monitoring of vehicles with internal combustion engine is of immense importance due to high number of vehicles with such engines and their importance to transport and economy. As many persons use a vehicle which is old and inexpensive, a condition monitoring system designed for such vehicles cannot be expensive. Unfortunately, condition monitoring of engines is usually based on the use of vibration signals, which are acquired by accelerometers. Piezoelectric accelerometers are the most commonly used for this purpose, and such accelerometers are not cheap. However, an alternative exists in the form of microelectromechanical systems (MEMS) accelerometers, which are much cheaper, but have narrower frequency characteristics. This paper describes preliminary results of a research on feasibility of use of MEMS accelerometers for condition monitoring and failure detection in internal combustion engines.
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We present kinematic structure of measurement arm along with its construction restrains originating from using only accelerometers for determining relative positions of links. Method of calculating position of arm's end in relation to its base basing on orientation of individual links is presented. Accuracy and repeatability tests were performed using custom made test stand. The description of test stand, measurements procedures for last link changing its position in Cartesian directions and orientation in vertical axis is also included in the paper. These changes were justified in context of links orientation in relations to global coordinate system. Obtained tests results are presented and analyzed.
Aim of the paper is to assess uncertainty associated with determination of velocity using MEMS accelerometer. Two MEMS accelerometers are evaluated from the point of view of measurement characterized by short duration and possibility of repetitions in unchanged environment. Mathematical model of measurement of velocity is presented with its accompanying uncertainty. The accelerometers were first subjected to calibration and testing of nonlinearity of their scale factors, then fixed to a wheeled robot which performed repeated manoeuvres of straight line movement on laboratory ground. Standard uncertainty of velocity measured using the examined accelerometers was at the level of 0.02–0.04 m/s for run duration of about 1.5 s and averaged data from 12 runs. MEMS accelerometers can be recommended for velocity measurements characterised by short duration and possibility of repetitions, if uncertainties of calibration and of measurement of vehicle tilt angle during motion are minimized.
PL
W artykule poruszono problem pomiaru bezwładnościowego parametrów ruchu pojazdów. Celem pracy jest ocena niepewności pomiaru związanej z wyznaczaniem prędkości metodą całkowania przyspieszenia zmierzonego akcelerometrem typu MEMS. Dwa akcelerometry typu MEMS zostały poddane ocenie z punktu widzenia zastosowania charakteryzującego się krótkim czasem trwania pomiaru oraz możliwością jego powtarzania w niezmienionych warunkach. Zaprezentowano model matematyczny pomiaru prędkości wraz z towarzyszącą mu niepewnością. Akcelerometry zostały poddane procedurze kalibracji oraz wyznaczono nieliniowości dla ich współczynników skali dzięki wykorzystaniu urządzenia Tira-VIB do wygenerowania przyspieszeń o zmiennych wartościach. Czujniki zostały zamontowane na robocie kołowym, który wykonał w sposób powtarzalny manewr jazdy prostoliniowej na tej samej nawierzchni. Otrzymano niepewność standardową prędkości zmierzonej przy użyciu badanych akcelerometrów na poziomie 0,02–0,04 m/s dla przebiegu trwającego ok. 1,5 s, przy uśrednieniu danych z 12 przebiegów. Na podstawie wykonanej pracy można rekomendować tanie akcelerometry MEMS do pomiarów prędkości charakteryzujących się krótkim czasem trwania oraz możliwością powtarzania pomiarów. Należy zwrócić uwagę na minimalizację niepewności związanych z kalibracją instrumentów oraz pomiarem zmiennego kąta przechyłu pojazdu podczas ruchu.
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The most significant methods of increasing accuracy of tilt measurements have been presented in the paper. The measurements referred to are to be performed under quasi-static conditions by means of miniature tilt sensors built of MEMS accelerometers. Some of the methods consist in modifications of the existing MEMS accelerometers, whereas the other can be useful while using other types of commercially available accelerometers, including those manufactured with application of conventional technologies.
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