Detection of starting motor position in a brushless DC motor

摘要: A microprocessor-controlled-circuit applies pulses to a standing motor whose rotor position is be determined. The time required for the injected current reach predetermined threshold in comparator measured. are long enough effectuate an accurate measurement, but not so that moves. pulse applied twice each phase, once with positive polarity and negative polarity, total of six measurements. rise times subtracted from other determine whether or was greater. Based upon differences readings all phases, known. There which difference zero negligible. at least two methods when there ambiguities sign difference. In one method, combination its absence plus magnitude can used along look-up tables position. Another method resolve uncertainty by changing effective This done pulsing three phases actively. Instead leaving phase open during pulsing, third tied high low. Once start-up resolved, control acceleration stand-still through medium speed constant, nominal provided.