Patent ID: 8198843

Claim:
A motor control apparatus for an electric motor, comprising: a determining means for determining at least one characteristic of a drive command signal, which is pulsed and specifies a target rotational speed of the electric motor, by comparing a level of the drive command signal with a plurality of threshold values; a control signal generating means for generating a control signal based on the at least one characteristic of the drive command signal, which is determined by the determining means; and a drive means for driving the electric motor based on the control signal, which is generated by the control signal generating means, wherein: the determining means includes: a first duty ratio computing means for computing a first duty ratio of the drive command signal as the at least one characteristic of the drive command signal by comparing the level of the drive command signal with a first threshold value, which is one of the plurality of threshold values and is preset for an undisturbed state where the level of the drive command signal is normal; and a second duty ratio computing means for computing a second duty ratio of the drive command signal as the at least one characteristic of the drive command signal by comparing the level of the drive command signal with a second threshold value, which is another one of the plurality of threshold values set to be smaller than the first threshold value and is for a disturbed state where the level of the drive command signal is reduced from that of the undisturbed state; and the control signal generating means generates the control signal, which has a pulse at a motor control duty ratio that corresponds to one of the first duty ratio and the second duty ratio, wherein the control signal generating means generates the control signal at the first duty ratio when a high level of the drive command signal is larger than the first threshold value, and the control signal generating means generates the control signal at the second duty ratio when the high level of the drive command signal is smaller than the first threshold value and is larger than the second threshold value while a low level of the drive command signal is smaller than the second threshold value.