Leteči zagon brezsenzorskega BLDC stroja

PRAJNDL, ŽIGA (author), Nemec, Mitja (mentor)

V nalogi sem obravnaval delovanje elektronsko komutiranega stroja brez uporabe senzorja kota. Ker zagon stroja predstavlja težavo, sem izdelal algoritem za leteči zagon. V teoretičnem uvodu je predstavljeno vodenje elektronsko komutiranega stroja in osnovno delovanje s pomočjo senzorja kota. Nato so predstavljene možne metode za brezsenzorsko obratovanje z opazovanjem inducirane napetosti. Podrobneje sem preučil dve: direktno z zaznavanjem prehoda inducirane napetosti neaktivne faze preko ničle in indirektno z integracijo inducirane napetosti. Ker je vzorčenje inducirane napetosti potrebne za brezsenzorsko delovanje tesno povezano s proženjem močnostne stopnje, sem preizkusil tri različne strategije delovanja. Cilj za izbiro najprimernejše je bilo zanesljivo delovanje pri zelo nizkih vrtilnih hitrostih v brezsenzorskem načinu. Najbolje se je obneslo bipolarno proženje tranzistorjev ob uporabi integracijske metode, sploh kadar se je ob nizkih hitrostih na gredi stroja pojavilo nepričakovano dodatno breme. Za boljše dinamične lastnosti in nadzor stroja sem realiziral navorno in hitrostno regulacijo. Hitrostna regulacija zahteva nekaj več pozornosti, saj se časovna konstanta osveževanja njene vrednosti spreminja s hitrostjo vrtenja. Stabilno zaprtozančno obratovanje je zelo pomembno tudi za zagon stroja. Največja težava je, ker mirujoči stroj preko inducirane napetosti ne ponuja informacije o legi rotorja in ker imamo ob zagonu nepredvidljiv bremenski navor. Rešitev sem izdelal z ročnim premagovanjem neznanega bremenskega navora ob zagonu ter nato pri čim nižji hitrosti preklopil na zanesljivo zaprto-zančno delovanje. Ustvarjeno programsko kodo sem poganjal in testiral na že izdelanem testnem sistemu.

• Language: Slovenian
• Keywords: elektronsko komutirani (BLDC) motor, brezsenzorsko delovanje, leteči zagon, gibalna inducirana napetost, bipolarno proženje
• Work type: Master's thesis/paper
• Organization: FE - Faculty of Electrical Engineering
• Year: 2017
• PID: 20.500.12556/RUL-92992
• Publication date in RUL: 12.07.2017

Secondary language

• Language: English
• Title: Flying start of sensorless BLDC machine

Abstract

This thesis presents sensorless control of the brushless (BLDC) motor. The start of a sensorless motor is accomplished with a flying start algorithm. In the theoretical introduction the basic sensor control BLDC technique is presented. This is followed with description of sensorless methods based on the back-EMF voltage sensing. The direct zero crossing detection and the indirect back-EMF integration methods are analyzed. The back-EMF voltage sampling for the sensorless application is closely connected with the inverter PWM switching. For that reason three different switching strategies were developed and tested. The goal was to choose the one working reliably at very low speeds in the sensorless mode. The bipolar switching by using the back-EMF integration technic performed the best, especially at low speeds when an unexpected load appeared on the motor shaft. Furthermore open loop operation was upgraded with a torque and a speed controller. The speed control mode requires a bit more attention at design, since the time constant of refreshing the shaft speed depends on the actual speed. A reliable closed-loop operation is very important for the motor starting procedure. At standstill the back-EMF voltage is not generated thus the position of the shaft cannot be determined. The unknown starting torque presents an additional problem. The implemented solution is based upon manual acceleration until the motor reaches the required minimum speed and only then the drive is switched into the closed-loop control. The program code is written and tested with the already established laboratory system.

• Keywords: BLDC, sensorless, flying start, back-EMF, bipolar switching