Patent ID: 6541928
Filing Date: 2003-04-01
Classification: G11B

Abstract:
A method of controlling the velocity of a polyphase motor, comprising:energizing the polyphase motor in a first predetermined commutation phase; detecting whether a zero crossing of a back electromotive force (bemf) signal corresponding to the first predetermined commutation phase occurs; sensing whether the polyphase motor advanced to a next successive commutation phase immediately following in succession the first predetermined commutation phase; following the step of sensing, energizing the polyphase motor in a second predetermined commutation phase immediately following in succession the first predetermined commutation phase; detecting whether a zero crossing of a bemf signal corresponding to the second predetermined commutation phase occurs; sensing whether the polyphase motor advanced to a next successive commutation phase immediately following in succession the second predetermined commutation phase; and performing an acceleration procedure to accelerate the speed of the polyphase motor towards a desired speed based upon a detected zero crossing of the bemf signals in response to each of the steps of energizing and an affirmative determination that the polyphase motor advanced to the next successive commutation phase immediately following the first predetermined commutation phase in response to the step of energizing in the first commutation phase and immediately following the second predetermined commutation phase in response to the steps of energizing in the second commutation phase.