Rotational speed estimation method and control device for brushless dc motor

A rotational speed estimation method for a brushless DC motor for estimating an actual rotational speed of a rotor by passing an output of a plurality of magnetic sensors configured to detect magnetic poles of the rotor through a filter, the rotational speed estimation method comprising:

• an extended particle filter setting step of using an extended particle filter to which a plurality of likelihoods is capable of being set as the filter, and setting, as the plurality of likelihoods, at least a first likelihood and a second likelihood selectively applied based on whether a change occurs in the output of the plurality of magnetic sensors to the extended particle filter, the first likelihood being adapted to a case where no change occurs in the output of the plurality of magnetic sensors and the second likelihood being adapted to a case where a change occurs in the output of the plurality of magnetic sensors;
• a detection pulse signal acquisition step of acquiring a detection pulse signal output from each of the plurality of magnetic sensors at a predetermined sampling period;
• a signal processing step of obtaining a continuous pulse by exclusive-ORing (XORing) the detection pulse signal acquired at each sampling time;
• and
• a rotational speed estimation step of using the extended particle filter to which the plurality of likelihoods is set, applying the first likelihood as a likelihood of the extended filter when no change occurs in the continuous pulse and applying the second likelihood as the likelihood of the extended particle filter when a change occurs in the continuous pulse, and estimating a rotational speed of the rotor.