Patent ID: 8552671

Claim:
A method comprising: determining a current commutation state of a brushless direct current (DC) motor, wherein the current commutation state is one of a plurality of commutation states; calculating a derivative of an inductive rise time for the brushless DC motor based at least in part on a measurement of the inductive rise time; and advancing the brushless DC motor to a next commutation state based at least in part on the magnitude of the derivative, wherein the inductive rise time further comprises a first inductive rise time and a second inductive rise time, and wherein step of calculating further comprises: determining the first inductive rise time for a first interval; determining the second inductive rise time for a second interval, wherein each of the first and second intervals have a predetermined duration; calculating a difference between the first and second inductive rise times; and dividing the difference between the first and second inductive rise times by the predetermined duration.