Vpliv statične in dinamične ekscentričnosti magnetnega senzorja RM44 na napako v signalu kota

ALIČ, MITJA (author), Nemec, Mitja (mentor)

Za regulacijo pogonov se v industriji uporablja dajalnike zasuka. Primer dajalnika zasuka je magnetni enkoder. Magnetni enkoder je zaradi svoje robustnosti primeren za delovanje v takem okolju. S Hallovimi sonadmi enkoder meri Z-komponento magnetnega polja magneta, ki se nahaja na rotirajočem delu pogona. Iz signalov Hallovih sond enkoder pridobi signala v obliki sinusa in kosinusa. Preko matematičnega algoritma se izračuna kot zasuka. Algoritem predstavlja izračun matematične funkcije atan2(). Ob nepravilni montaži enkoderja ali magneta, se prostorski zajem signalov sinusne in kosinusne oblike spremeni. Posledično se v izračunanem kotu pojavi napaka. Napaka kota se izrazi glede na nepravilno zajeto magnetno polje. V magistrskem delu je predstavljeno spreminjanje zajemanja magnetnega polja posamezne Hallove sonde v odvisnosti od nepravilne montaže. Napako zaradi nepravilne montaže, se najlažje razbere iz signalov Hallovih sond. Izhod enkoderja je le podatek o zasuku. Ker se za izračun kota potrebuje funkcijo atan2(), je v delu izpeljano, kako napaka v vhodnih signalih rezultira v napaki izhoda funkcije. V programu MATLAB je bil sestavljen simulacijski model za merjenje napake enkoderja v odvisnosti od nepravilne montaže. Simulacije so bile opravljene na linearno aprokismirani Z-komponenti gostote magnetnega polja in na numerično izračunanem polju realnega magneta. Napaka ob napačni montaži je bila analizirana v frekvenčenem prostoru in je predstavljena kot potek posameznega harmonika v odvisnosti od nepravilne montaže. Opravljene so bile meritve na enkoderju RM44, ki so bile primerjane s simulacijami. Meritve so potrdile pričakovane poteke napake predvidene s simulacijami. Na napravi je bila idealna lega določena empirično. Posledično se je to pokazalo tudi v potekih napake v odvisnosti od nepravilne montaže.

• Language: Slovenian
• Keywords: dajalnik položaja, Hallova sonda, nepravilna montaža, predvidevanje napake, arcustangens
• Work type: Master's thesis/paper
• Organization: FE - Faculty of Electrical Engineering
• Year: 2018
• PID: 20.500.12556/RUL-105878
• Publication date in RUL: 21.12.2018

Secondary language

• Language: English
• Title: Impact of static and dynamic eccentricity of magnetic RM44 sensor on error of the measured angle

Abstract

Position sensors are used for motor drive controls. Usage of magnetic encoder is appropriate for sensing position in robust industrial environment. Magnetic encoder senses the angular position of a permanent magnet placed above the sensor. The permanent magnet must be diametrically polarized and of cylindrical shape. Encoder uses Hall sensors to detect magnetic flux density. Signals from Hall sensors are then converted to signals in shape of sine and cosine. From sine an cosine signal, an angle calculation algorithm is performed. Algorithm could be presented by mathematical function of atan2(). Incorrect installation of sensor or magnet, causes error in output angle. This work presents, how incorrect installation of sensor or magnet impact to measured magnetic field by Hall sensor. Incorrect installation can be recognized from field measured by Hall sensors. Encoders output signal is only angle. In this thesis is demonstrated how to recognize changes of signals from Hall sensors, by knowing encoder output only. The basic simulation model was built in MATLAB. Simulations were made by linear approximation of Z-component of magnetic field and numerical calculations by magnet model. Encoders error was analyzed in frequency spectrum. Simulations have been compared to the encoder RM44 measurements. Simulation results of error has been confirmed by measurements. Best installation of sensor was determined empirically. Empirical determination of installation, has been resulting in the output error.

• Keywords: position encoders, Hall effect sensor, superficial implementation, anticipating an error, arcustangens